WO2025027530A1

WO2025027530A1 - Circulatory assist from systems with axial flow

Info

Publication number: WO2025027530A1
Application number: PCT/IB2024/057381
Authority: WO
Inventors: Florian Niklas Ludwig; Daniël Immanuel Michaël VAN DORT; René Cornelis Henricus VAN DER BURGT; Ferry VAN DER LINDE; Jasper Gerhard TOEBES; Patrick Griffin; David O'reilly; Shane MULDERRIG; Anisia LAUDITI; Damián SUASSO DE LIMA DE PRADO
Original assignee: Cardiacbooster BV
Current assignee: Cardiacbooster BV
Priority date: 2023-07-31
Filing date: 2024-07-30
Publication date: 2025-02-06
Anticipated expiration: 2026-01-31

Abstract

Circulatory assist systems, devices, and methods are disclosed herein. In some variations, a circulatory assist system may include a pump body including a conduit having a longitudinal flow axis extending between the inlet and the outlet and a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase. The circulatory assist system may also include an inlet valve configured to receive a fluid along the flow axis. The pump body may be configured to convey the received fluid through the outlet during both the expansion phase and the contraction phase, such as at least partially due to sustained momentum of fluid during at least a portion of the expansion phase and at least a portion of the contraction phase.

Description

CIRCULATORY ASSIST FROM SYSTEMS WITH AXIAL FLOW

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority to U.S. Provisional Patent Application 63/516,792, filed July 31, 2023, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The present technology relates to a circulatory assist system.

BACKGROUND

[0003] For patients suffering from cardiogenic shock, or those undergoing high-risk percutaneous coronary interventions (PCI), a patient's heart function may be compromised such that the use of circulatory assist devices may be required to maintain adequate blood flows through the circulatory system. Although there is some variation depending on patient size and condition, circulatory assist devices for patients undergoing high risk PCI typically must produce blood flows of least 3 L/min to maintain adequate circulation, while for patients in cardiogenic shock, a minimum of 5 L/min is generally considered necessary.

[0004] The most common types of circulatory assist devices are intra-aortic balloon pumps (IABP), extra-corporeal membrane oxygenation (ECMO) systems, and impeller-based blood pumps. IABPS are catheters having an inflatable balloon which can be placed in the descending aorta and cyclically inflated to displace the blood. ECMO systems include a venous catheter for removing deoxygenated blood from the venous system, an extracorporeal oxygenator and pump, and an arterial catheter for returning the blood to the arterial system, thus bypassing the heart. Impeller pump systems have a rotary impeller that can be placed in a chamber of the heart or in a major vessel and rotated at relatively high speed to propel blood through the circulatory system.

[0005] While offering some benefit in increasing blood flow and reducing load on the heart, currently available circulatory assist devices suffer from certain drawbacks. IABPs may not improve flows adequately to support the patient when the heart is significantly compromised, such as during cardiogenic shock. ECMO systems may have higher morbidity associated with multiple catheterizations including bleeding, thrombus, and infection, as well as problems associated with membrane oxygenation including cognitive deficit and stroke. In addition, they increase afterload which is generally regarded as counterproductive. Impeller pump systems, if operated at higher speeds in order to produce higher flows, can result in excessive hemolysis; further, if impeller pumps are made larger to produce higher flows, the profile of such devices can be undesirably large, inhibiting percutaneous delivery, and increasing the risk of injury to cardiovascular structures and/or causing limb ischemia. As a result, current impeller-type pumps which are capable of providing the high flows necessary for patients in cardiogenic shock, are often too large for endovascular delivery thus requiring surgical placement, and further produce undesirable levels of hemolysis. What is needed, therefore, are improved circulatory support systems and methods.

SUMMARY

(0006] The subject technology is illustrated, for example, according to various aspects described below, including with reference to FIGS. 1-13. Various examples of aspects of the present technology are described as numbered examples (Al, A2, A3, etc.) for convenience. These are provided as examples and do not limit the present technology.

(0007| Example Al. A blood pump system comprising: a pump body comprising: a conduit having an inlet, an outlet, and a longitudinal flow axis extending between the inlet and the outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive blood into the conduit substantially along the flow axis, wherein the pump body is configured to convey the received blood through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase.

(0008] Example A2. The system of example Al, wherein the portion of the conduit between the volume displacement member and the outlet is valveless.

[0009] Example A3. The system of example Al or A2, wherein the outlet of the conduit comprises a valve.

[0010] Example A4. The system of any one of examples A1-A3, wherein the conduit comprises a membrane. [0011] Example A5. The system of any one of examples A1-A4, wherein the conduit further comprises an expandable support, wherein the membrane is adjacent to a surface of the expandable support.

[0012] Example A6. The system of example A5, wherein the expandable support is self-expandable.

[0013] Example A7. The system of any one of examples A1-A6, wherein the conduit comprises a distal inflow region comprising the inlet, a proximal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

[0014] Example A8. The system of any one of examples A1-A6, wherein the conduit comprises a proximal inflow region comprising the inlet, a distal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

[00.1.5] Example A9. The system of example A7 or A8, wherein the conduit comprises a membrane covering at least a portion of the intermediate region.

[0016] Example Al 0. The system of example A9, wherein the membrane covers a portion of the inflow region.

[0017] Example Al l. The system of example A10, wherein the covered portion of the inflow region is flared radially outward.

[0018] Example A12. The system of example A10, wherein the covered portion of the inflow region is tapered radially inward.

[0019] Example A13. The system of any one of examples A10-A12, wherein the inlet valve is arranged inside the covered portion of the inflow region.

[0020] Example A 14. The system of any one of examples A9-A13, wherein the membrane covers a portion of the outflow region.

[0021] Example A15. The system of example A14, wherein the covered portion of the outflow region is flared radially outward.

[0022] Example A16. The system of example A14, wherein the covered portion of the outflow region is tapered radially inward. [0023] Example Al 7. The system of any one of examples A7-A16, wherein at least one of the inflow region or the outflow region has a maximum diameter larger than a diameter of the intermediate region.

[0024] Example A18. The system of any one of examples A7-A17, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

[0025] Example Al 9. The system of any one of examples A7-A16, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0026] Example A20. The system of any one of examples A7-A18, wherein the inlet valve is arranged in the conduit between the inlet and the volume displacement member.

[0027] Example A21. The system of any one of examples A7-A20, wherein the intermediate region is tubular.

[0028] Example A22. The system of any one of examples A1-A21, wherein the inlet valve is configured to convey the received blood to a volume in the conduit outside of the volume displacement member.

[0029] Example A23. The system of any one of examples A1-A22, wherein the inlet valve is a one-way valve.

[0030] Example A24. The system of example A23, wherein the one-way valve comprises a multi-leaflet valve.

[0031] Example A25. The system of any one of examples A1-A24, wherein the volume displacement member comprises a balloon.

[0032] Example A26. The system of any one of examples A1-A25, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a total member volume in the expansion phase, and wherein a distal portion of the member volume ranging between up to about 5% and about 50% of the total member volume is located along a distalmost third of the conduit length.

[0033] Example A27. The system of any one of examples A1-A26, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a member length extending along the flow axis, and wherein a distal portion of the member length ranging between about the distalmost 5% of the member length and about the distalmost 15% of the member length is located along a distalmost third of the conduit length.

[0034] Example A28. The system of any one of examples A1-A27, further comprising: an inflation member in fluidic communication with the volume displacement member; and a pump configured to operate the balloon in the expansion phase and the contraction phase via the inflation member.

[0035] Example A29. The system of example A28, wherein the pump is configured to transition the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

[0036] Example A30. The system of any one of examples A1-A29, wherein the pump body is configured to convey received blood through the outlet at least partially via momentum of the blood during both the expansion phase and the contraction phase.

[0037] Example A31. The system of any one of examples A1-A30, wherein the pump body is configured to convey blood through the outlet with a flow rate of at least about 5 L/min.

[0038] Example Bl. A method comprising: positioning a pump device in the circulatory system of a patient, the pump device comprising: a pump body comprising: a conduit having an inlet, an outlet, and a longitudinal flow axis extending between the inlet and the outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive a fluid into the conduit substantially along the flow axis; cyclically operating the volume displacement member in the expansion phase and the contraction phase; and allowing received fluid to exit the conduit through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase.

[0039] Example B2. The method of example Bl, wherein positioning the pump device comprises positioning at least a portion of the pump body in a left ventricle of the patient. [0040] Example B3. The method of example B 1 or B2, wherein positioning the pump device comprises positioning a distal portion of the pump body in the left ventricle and a proximal portion of the pump body in an aorta of the patient.

[0041] Example B4. The method of any one of examples B 1-B3, wherein positioning the pump device comprises positioning a majority of the pump body in the left ventricle of the patient.

[0042] Example B5. The method of example Bl, wherein positioning the pump comprises positioning a proximal portion of the pump body in the right ventricle and a distal portion of the pump body in a pulmonary artery of the patient.

[0043] Example B6. The method of example Bl, wherein positioning the pump device comprises positioning the entire pump body in a blood vessel.

[0044] Example B7. The method of any one of examples B 1-B6, wherein the volume displacement member comprises a balloon.

[0045] Example B8. The method of example B7, wherein cyclically operating the balloon in the expansion phase and the contraction phase comprises controlling fluid flow in a catheter fluidically coupled to the balloon.

[0046] Example B9. The method of any one of examples B1-B8, wherein cyclically operating the volume displacement member comprises transitioning the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

[0047] Example B10. The method of any one of examples B1-B9, wherein the method comprises allowing received fluid to exit the conduit through the outlet at least partially via momentum during both the expansion phase and the contraction phase.

[0048] Example Bl l. The method of any one of examples B1-B10, wherein the portion of the conduit between the volume displacement member and the outlet is valveless.

[0049] Example B12. The method of any one of examples Bl-Bl 1, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter larger than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0050] Example B13. The method of example B12, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape. [0051] Example B14. The method of any one of examples B1-B13, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0052] Example Cl. A blood pump system comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive blood into the conduit, wherein the pump body is configured to convey the received blood through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase, and wherein the portion of the conduit between the volume displacement member and the outlet is valveless.

[0053] Example C2. The system of example Cl, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during the entire expansion phase and the entire contraction phase.

[0054] Example C3. The system of example C 1 or C2, wherein the conduit comprises a membrane.

[0055] Example C4. The system of any one of examples C1-C3, wherein the conduit further comprises an expandable support, wherein the membrane is adjacent to a surface of the expandable support.

[0056] Example C5. The system of any one of examples C1-C4, wherein the conduit comprises a distal inflow region comprising the inlet, a proximal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

[0057] Example C6. The system of any one of examples C1-C4, wherein the conduit comprises a proximal inflow region comprising the inlet, a distal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region. [0058] Example C7. The system of example C5 or C6, wherein the conduit comprises a membrane covering at least a portion of the intermediate region.

[0059] Example C8. The system of example C7, wherein the membrane covers a portion of the inflow region.

[0060] Example C9. The system of example C8, wherein the covered portion of the inflow region is flared radially outward.

[0061] Example CIO. The system of example C8, wherein the covered portion of the inflow region is tapered radially inward.

[0062] Example Cl l. The system of any one of examples C8-C10, wherein the inlet valve is arranged inside the covered portion of the inflow region.

[0063] Example Cl 2. The system of any one of examples C7-C11, wherein the membrane covers a portion of the outflow region.

[0064] Example C13. The system of example Cl 2, wherein the covered portion of the outflow region is flared radially outward.

[0065] Example C14. The system of example C12, wherein the covered portion of the outflow region is tapered radially inward.

[0066] Example C15. The system of any one of examples C5-C14, wherein at least one of the inflow region or the outflow region has a maximum diameter larger than a diameter of the intermediate region.

[0067] Example Cl 6. The system of any one of examples C5-C15, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

[0068] Example C17. The system of any one of examples C5-C14, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0069] Example Cl 8. The system of any one of examples C5-C17, wherein the inlet valve is arranged in the conduit between the inlet and the volume displacement member.

[0070] Example Cl 9. The system of any one of examples C5-C18, wherein the intermediate region is tubular. [0071] Example C20. The system of any one of examples C1-C19, wherein the inlet valve is configured to convey the received blood to a volume in the conduit outside of the volume displacement member.

[0072] Example C21. The system of any one of examples C1-C20, wherein the inlet valve is a one-way valve.

[0073] Example C22. The system of any one of examples C 1-C21 , wherein the volume displacement member comprises a balloon.

[0074] Example C23. The system of any one of examples C1-C22, wherein the conduit has a conduit length extending along the flow axis and the volume displacement member has a total member volume in the expansion phase, and wherein a distal portion of the member volume ranging between about 5% and about 50% of the total member volume is located along a distalmost third of the conduit length.

[0075] Example C24. The system of any one of examples C1-C23, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a member length extending along the flow axis, and wherein a distal portion of the member length ranging between about the distalmost 5% of the member length and about the distalmost 15% of the member length is located along a distalmost third of the conduit length.

[0076] Example C25. The system of any one of examples C1-C24, further comprising: an inflation member in fluidic communication with the volume displacement member; and a pump configured to operate the balloon in the expansion phase and the contraction phase via the inflation member.

[0077] Example C26. The system of example C25, wherein the pump is configured to transition the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

[0078] Example C27. The system of any one of examples C1-C26, wherein the pump body is configured to convey received blood through the outlet at least partially via momentum of the blood during both the expansion phase and the contraction phase.

[0079] Example C28. The system of any one of examples C1-C27, wherein the pump body is configured to convey blood through the outlet with a flow rate of at least about 5 L/min. [0080] Example DI . A method comprising: positioning a pump device in the circulatory system of a patient, the pump device comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive fluid into the conduit, wherein the portion of the conduit between the volume displacement member and the outlet is valveless; cyclically operating the volume displacement member in the expansion phase and the contraction phase; and allowing received fluid to exit the conduit through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase.

[0081] Example D2. The method of example DI, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during the entire expansion phase and the entire contraction phase.

[0082] Example D3. The method of example D 1 or D2, wherein positioning the pump device comprises positioning at least a portion of the pump body in a left ventricle of the patient.

[0083] Example D4. The method of any one of examples D1-D3, wherein positioning the pump device comprises positioning a distal portion of the pump body in the left ventricle and a proximal portion of the pump body in an aorta of the patient.

[0084] Example D5. The method of any one of examples D1-D3, wherein positioning the pump device comprises positioning a majority of the pump body in the left ventricle of the patient.

[0085] Example D6. The method of any one of examples D1-D3, wherein positioning the pump device comprises positioning a proximal portion of the pump body in the right ventricle and a distal portion of the pump body in a pulmonary artery of the patient.

[0086] Example D7. The method of example D 1 or D2, wherein positioning the pump device comprises positioning the entire pump body in a blood vessel. [0087] Example D8. The method of any one of examples D1-D7, wherein the volume displacement member comprises a balloon.

[0088] Example D9. The method of example D8, wherein cyclically operating the balloon in the expansion phase and the contraction phase comprises controlling fluid flow in a catheter fluidically coupled to the balloon.

[00891 Example D10. The method of any one of examples D1-D9, wherein cyclically operating the volume displacement member comprises transitioning the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

[0090] Example Dl l. The method of any one of examples DI -D10, wherein the method comprises allowing received fluid to exit the conduit through the outlet at least partially via momentum during both the expansion phase and the contraction phase.

[0091 ] Example D12. The method of any one of examples Dl-Dl 1, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter larger than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0092] Example D13. The method of example D12, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

[0093] Example D14. The method of any one of examples Dl-Dl 1, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0094] Example El. A blood pump system comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit having a first member volume Vc in a contracted state and a second member volume Ve in an expanded state, wherein the volume displacement member is operable between the contracted and expanded states at a pump frequency/; and an inlet valve configured to receive blood into the conduit, wherein the pump body is configured to convey the received blood through the outlet at a volumetric flow rate that is greater than (Ve - Vc) */when /is greater than about 5 Hz.

[0095] Example E2. The system of example El, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during an entire expansion phase and an entire contraction phase of the volume displacement member.

[0096] Example E3. The system of example El or E2 wherein the conduit comprises a membrane.

[0097] Example E4. The system of any one of examples E1-E3, wherein the conduit further comprises an expandable support, wherein the membrane is adjacent to a surface of the expandable support.

[0098] Example E5. The system of any one of examples E1-E4, wherein the conduit comprises a distal inflow region comprising the inlet, a proximal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

[0099] Example E6. The system of any one of examples E1-E4, wherein the conduit comprises a proximal inflow region comprising the inlet, a distal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

[0100] Example E7. The system of example E5 or E6, wherein the conduit comprises a membrane covering at least a portion of the intermediate region.

[0101] Example E8. The system of example E7, wherein the membrane covers a portion of the inflow region.

[0102] Example E9. The system of example E8, wherein the covered portion of the inflow region is flared radially outward.

[0103] Example E10. The system of example E8, wherein the covered portion of the inflow region is tapered radially inward.

[0104] Example El l. The system of any one of examples E8-E10, wherein the inlet valve is arranged inside the covered portion of the inflow region. [0105] Example E12. The system of any one of examples E7-E11, wherein the membrane covers a portion of the outflow region.

[0106] Example E13. The system of example E12, wherein the covered portion of the outflow region is flared radially outward.

[0107] Example E14. The system of example E12, wherein the covered portion of the outflow region is tapered radially inward.

[0108] Example E15. The system of any one of examples E5-E14, wherein at least one of the inflow region or the outflow region has a maximum diameter larger than a diameter of the intermediate region.

[0109] Example E16. The system of any one of examples E5-E15, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

[0110] Example E17. The system of any one of examples E5-E14, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0111] Example E18. The system of any one of examples E5-E17, wherein the inlet valve is arranged in the conduit between the inlet and the volume displacement member.

[0112] Example E19. The system of any one of examples E5-E18, wherein the intermediate region is tubular.

[0113] Example E20. The system of any one of examples E1-E19, wherein the inlet valve is configured to convey the received blood to a volume in the conduit outside of the volume displacement member.

[0114] Example E21. The system of any one of examples E1-E20, wherein the inlet valve is a one-way valve.

[01.1.5] Example E22. The system of any one of examples E1-E21, wherein the volume displacement member comprises a balloon.

[0116] Example E23. The system of any one of examples E1-E22, wherein the conduit has a conduit length extending along the flow axis and the volume displacement member has a total member volume in the expansion phase, and wherein a distal portion of the member volume ranging between about 5% and about 50% of the total member volume is located along a distalmost third of the conduit length.

[0117] Example E24. The system of any one of examples E1-E23, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a member length extending along the flow axis, and wherein a distal portion of the member length ranging between about the distalmost 5% of the member length and about the distalmost 15% of the member length is located along a distalmost third of the conduit length.

[0118] Example E25. The system of any one of examples E1-E24, further comprising: an inflation member in fluidic communication with the volume displacement member; and a pump configured to operate the balloon in the expansion phase and the contraction phase via the inflation member.

[0119] Example E26. The system of example E25, wherein the pump is configured to transition the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

[0120] Example E27. The system of any one of examples E1-E26, wherein the pump body is configured to convey blood through the outlet with a flow rate of at least about 5 L/min.

[0121 ] Example Fl. A method comprising: positioning a pump device in the circulatory system of a patient, the pump device comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit having a first member volume Vc in a contracted state and a second member volume Ve in an expanded; and an inlet valve configured to receive blood into the conduit; cyclically operating the volume displacement member between the contracted and expanded states at a pump frequency /; and conveying the received fluid to exit the conduit through the outlet at a volumetric flow rate that is greater than (Ve - Vc) * f.

[0122] Example F2. The method of example Fl, wherein /is at least about 5 Hz. [0123] Example F3. The method of example Fl or F2, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during an entire expansion phase and an entire contraction phase of the volume displacement member.

[0124] Example F4. The method of any one of examples F1-F3, wherein positioning the pump device comprises positioning at least a portion of the pump body in a left ventricle of the patient.

[0125] Example F5. The method of any one of examples F1-F4, wherein positioning the pump device comprises positioning a distal portion of the pump body in the left ventricle and a proximal portion of the pump body in an aorta of the patient.

[0126] Example F6. The method of any one of examples F1-F5, wherein positioning the pump device comprises positioning a majority of the pump body in the left ventricle of the patient.

[0127] Example F7. The method of any one of examples F1-F4, wherein positioning the pump device comprises positioning a proximal portion of the pump body in the right ventricle and a distal portion of the pump body in a pulmonary artery of the patient.

[0128] Example F8. The method of any one of examples F1-F3, wherein positioning the pump device comprises positioning the entire pump body in a blood vessel.

[0129] Example F9. The method of any one of examples F1-F8, wherein the volume displacement member comprises a balloon.

[0130] Example F 10. The method of example F9, wherein cyclically operating the balloon in the expansion phase and the contraction phase comprises controlling fluid flow in a catheter fluidically coupled to the balloon.

[0131] Example Fl 1. The method of any one of examples F1-F10, wherein cyclically operating the volume displacement member comprises transitioning the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

[0132] Example F12. The method of any one of examples Fl-Fl 1, wherein the method comprises allowing received fluid to exit the conduit through the outlet at least partially via momentum during both the expansion phase and the contraction phase. [0133] Example F13. The method of any one of examples F1-F12, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter larger than a diameter of an intermediate region extending between the inflow region and the outflow region.

[0134] Example F14. The method of example F13, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

[0135] Example F15. The method of any one of examples F1-F14, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0136] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure.

[0137] FIG. 1 A is an illustrative schematic of an example circulatory assist device, in accordance with the present technology.

[0138] FIG. IB is an illustrative schematic of an example circulatory assist device positioned in a patient, in accordance with the present technology.

[0139] FIG. 1C is an illustrative schematic of an example circulatory assist device positioned in a patient, in accordance with the present technology.

[0140] FIGS. 2A and 2B are illustrative schematics of an example circulatory assist device during operation, in accordance with the present technology.

[0141] FIGS. 3A-3C are illustrative schematics of cross-sectional views of various example supports in a circulatory assist device, in accordance with the present technology.

[0142] FIG. 4A is an illustrative schematic of an example circulatory assist device, in accordance with the present technology.

[0143] FIG. 4B is an illustrative schematic of an example circulatory assist device, in accordance with the present technology.

[0144] FIG. 4C is an illustrative schematic of an example circulatory assist device, in accordance with the present technology. [0145] FIG. 5A is an illustrative schematic of a side view of an example circulatory assist device according to the present technology placed through a delivery sheath.

[0146] FIGS. 5B-5F are illustrative schematics of cross-sectional views of the circulatory assist device of FIG. 5 A at various axial locations along the length thereof.

[0147] FIG. 6 is a schematic diagram of an example control unit of a circulatory assist device in accordance with the present technology.

[0148] FIGS. 7A-7E are illustrative schematics of various phases of operation of an example circulatory assist device, in accordance with the present technology.

[0149] FIG. 8 is an illustrative schematic of an experimental setup including an example mock circulatory assist device in accordance with the present technology.

[0150] FIG. 9 is a plot illustrating pressure and flow patterns of an example mock circulatory assist device in accordance with the present technology.

[0151 J FIG. 10 is a plot illustrating fluid outflow of various example circulatory assist devices in accordance with the present technology.

[0152] FIG. 11 A is an illustrative schematic of an example circulatory assist device, in accordance with the present technology.

[0153] FIG. 1 IB is an illustrative schematic of a radial inlet valve arrangement in an example circulatory assist device, in accordance with the present technology.

[0154] FIGS. 12 and 13 are illustrative schematics of example volume displacement members in a circulatory assist device, in accordance with the present technology.

DETAILED DESCRIPTION

[0155] The present technology relates to circulatory assist systems and methods. Some aspects of the present technology, for example, are directed to cardiac assist devices and methods. Such devices can, for example, be delivered percutaneously into a cardiovascular lumen and are capable of pumping blood at flows high enough to support patients in cardiogenic shock, acute myocardial infarction, acute heart failure or during high-risk percutaneous coronary interventions, or other situations requiring hemodynamic support with reduced levels of hemolysis. Specific details of several aspects of the technology are described below with reference to FIGS. 1-13. [0156] As used herein, the terms “proximal” and “distal” (and derivatives thereof) are used primarily within a frame of reference of a user placing a circulatory assist device within a patient, unless otherwise specified. For example, “proximal” primarily refers to a direction closer to the user, while “distal” primarily refers to a direction farther from the user.

[0157] The circulatory assist devices and systems of the present technology may be used to provide circulatory assistance (e.g., cardiac assistance) in a variety of procedures and to address a variety of patient conditions. For example, the circulatory assist devices and systems may be used for cardiac assist during high-risk percutaneous coronary interventions (PCI) including angioplasty and stenting. Furthermore, the circulatory assist devices and systems may be used to provide cardiac support for patients experiencing cardiogenic shock. Furthermore, the circulatory assist devices and systems may be used to provide cardiac support for patients experiencing acute myocardial infarction. Generally, for such procedures, the heart assist devices will be configured for placement at least partially in the left ventricle. However, placement at various other cardiovascular lumen sites is also possible, including at least partially in the ascending or descending aorta, the right atrium, right ventricle, or pulmonary artery.

I. Circulatory assist systems

[0158] In some variations, a circulatory assist system includes a circulatory assist device that is positionable in a patient (e.g., in a cardiovascular lumen, such as a blood vessel and/or heart chamber). For example, the circulatory assist device can function as a percutaneous ventricular assist device (pVADs), a transvalvular pVAD, or an intra-vascular and intra-ventricular blood pump, though other uses of the circulatory assist device are contemplated.

[0159] In some variations, the circulatory assist device can include a pump body having a conduit, at least one inlet valve, and a volume displacement member arranged in the conduit. The conduit may have an inlet, an outlet, and a longitudinal flow axis extending between the inlet and the outlet. The inlet valve may be configured to receive a fluid (e.g., patient body fluid such as blood) along the flow axis. Furthermore, in some variations, the portion of the conduit between the volume displacement member and an outlet of the conduit may be valveless (e.g., the circulatory assist device may include only one or more inlet valves). The fluid column traveling in an axial direction in the conduit may have particular advantages, as described below. The volume displacement member may be operable in an expansion phase and a contraction phase, and the pump body may be configured to convey fluid through the outlet during both at least a part of the expansion phase and at least a part of the contraction phase of the volume displacement member. In some variations, the pump body may be configured to substantially continuously convey fluid through the outlet during both at least a part of the expansion phase and at least a part of the contraction phase of the volume displacement member. Additionally or alternatively, the pump body may be configured to convey received fluid through the outlet at a volumetric flow rate that is greater than (Ve - Vc) * f where Vc is the volume of the volume displacement member in its contracted state (e.g., fully contracted state), Ve is the volume of the volume displacement member in its expanded state (e.g., fully expanded state), and f is a pump frequency at which the volume displacement member is operable between the contracted and expanded states. In some variations, this enhanced volumetric flow rate outputted by the pump body may be possible when the volume displacement member is operated at a frequency f of at least about 5 Hz (e.g., an inflation or expansion time of about 0.1s).

[0160] For example, in some variations, as shown in FIG. 1A, a circulatory assist device 100 can include a pump body 120 configured to receive a fluid (e.g., blood) when placed in a cardiovascular lumen of a patient and convey the fluid back to the cardiovascular lumen for circulatory assistance. The pump body 120 may include a conduit with a distal inflow region 120a, a proximal outflow region 120c, and an intermediate region 120b between the inflow region 120a and the outflow region 120c. Generally, the pump body 120 (at least the intermediate region 120b, for example) may have an elongated shape (e.g., cylindrical or elongated with an elliptical cross-section), such as a tubular or pipe-like shape. However, in some variations the pump body 120 may have an elongated shape with a varying cross-section (e.g., the pump body 120 may be bulbous or hourglass-shaped) along the conduit length. The conduit may have a longitudinal flow axis extending between an inlet of the inflow region 120a and an outlet of the outflow region 120c. The flow axis may generally follow a longitudinal axis of the conduit of the pump body 120, which may be at least partially linear and/or at least partially curved. As such, the flow axis between the inlet and the outlet may be linear, may be curved, or may have one or more portions that are linear and one or more portions that are curved. Furthermore, the exact path of the flow axis may change dynamically depending on, for example, the shape of the pump body 120 during any given point in time during operation (e.g., a linear portion of the flow axis may become more curved, a curved portion of the flow axis may become more linear, the contour of a curved portion of the flow axis may change, etc.). For example, as the pump body 120 is operated, the exact relative positions of the inlet and the outlet of the conduit may change.

[0161] As further described below, the pump body 120 may further include an inlet valve 140 configured to receive a fluid through the inlet of the conduit along the flow axis, and a volume displacement member 130 (e.g., balloon) arranged in the conduit. The volume displacement member 130 may be operable in an expansion phase and a contraction phase. For example, in variations in which the volume displacement member 130 includes a balloon, the balloon may be inflated in the expansion phase, and deflated in the contraction phase. In operation, as further described below, the pump body 120 may be configured to convey the received fluid through an outlet of the outflow region 120c during both at least a part of the expansion phase and at least a part of the contraction phase of the volume displacement member 130. In some variations, such conveyance of fluid through the outlet may be sustained at least partially due to momentum of a fluid column along the flow axis of the conduit, where such momentum of the fluid column is created and maintained by the circulatory assist device during its operation, as further described below.

[0162] In some variations, the pump body 120 may be coupled to or otherwise arranged on a catheter 110, which can be used to position the pump body 120 in the patient and/or facilitate operation of the volume displacement member 130 in the expansion phase and the contraction phase. For example, the pump body 120 may be coupled to a distal portion of the catheter 110, while a proximal portion (not shown in FIG. 1A) of the catheter 110 may be outside the patient and coupled to a control system and/or actuator for controlling the volume displacement member 130 in the expansion phase and the contraction phase.

[0163] FIGS. 2A and 2B are schematic illustrations of an example circulatory assist device 100 during selected timepoints during its operation. Further details regarding operation of the circulatory assist device 100, including additional stages of fluid flow through the circulatory assist device 100, are described herein (e.g., with respect to FIGS. 7A-7E). In the example device shown in FIGS. 2A and 2B, the volume displacement member 130 includes a balloon that is cyclically inflated and deflated within the pump body 120. The balloon is shown as partially deflated in FIG. 2A (e.g., near the end of its contraction phase), and partially inflated in FIG. 2B (e.g., near the end of its expansion phase). As further described below, inflation and deflation of the balloon may be controlled at least in part by introducing and removing fluid from the balloon via the catheter 110 or other suitable element. Furthermore, the inlet valve 140 includes a one-way valve that opens to permit flow of fluid in a first direction through the inflow region 120a (FIG. 2 A) into the pump body 120 toward the outflow region 120c, and closes to substantially prevent flow in a second direction opposite the first direction, out of the pump body 120. In some embodiments, as further described below, the inlet valve 140 may be a passive valve that opens and closes in response to pressure difference between both sides of the inlet valve. For example, the passive valve may be biased toward a closed position, such that it may open in response to a threshold pressure difference but return to a closed position (e.g., via elastic recovery) in the absence of the threshold pressure difference. As another example, the passive valve may be biased toward an open position, such that it may close in response to a threshold pressure difference but return to an open position (e.g., via elastic recovery) in the absence of the threshold pressure difference. As yet another example, the passive valve may lack a particular bias toward a closed position or open position, such that it may open and close largely in response to the nature of the pressure difference. In some variations, the circulatory assist device 100 may additionally or alternatively include one or more inlet valves 140 that are actively controlled with a suitable actuator.

[0164] As shown in FIG. IB, in some variations, the circulatory assist device 100 may be configured for placement at least partially in the left ventricle (LV) and/or the ascending aorta (AA). For example, in some variations, the pump body 120 can placed across the aortic valve (AV) such that a first portion of the pump body 120 (including the distal inflow region) is in the left ventricle, and a second portion of the pump is in the ascending aorta. Furthermore, in some variations a portion of the pump can extend into the aortic arch (and optionally, into the descending aorta). Although the pump body 120 is shown in FIG. IB as having approximately half of its length in the left ventricle and half of its length in the ascending aorta, it should be understood that placement of the pump body 120 may vary. For example, in some variations the pump body 120 can be placed such that less of its length (e.g., about 20%, 30%, 40% of the pump body length) is in the left ventricle than the length (e.g., about 80%, 70%, 60%) that is in the ascending aorta. In some instances, it may be beneficial to reduce the volume of the pump body 120 that is placed in the left ventricle, as this positioning limits the amount of potentially adverse interaction between the pump body 120 and the heart muscle and valves (e.g., reduce risk of obstruction of the mitral valve). However, in some variations any suitable portion of the pump body 120 can be placed in the left ventricle. For example, the pump body 120 can be placed such that more of its length (e.g., about 80%, 70%, 60%) of the pump body length is in the left ventricle than the length (e.g., about 20%, 30%, 40%) that is in the ascending aorta. In some variations, the pump body 120 is placed such that a portion of its intermediate region 120b (such as somewhere along the conduit length including the volume displacement member 130) crosses the aortic valve (e.g., is located at the plane of the aortic valve). In some variations, the pump body 120 is placed such that a portion of its outflow region 120c crosses the aortic valve (e.g., is located at the plane of the aortic valve).

|0165| In some variations, the circulatory assist device 100 may be configured for placement at least partially in the right ventricle (RV) and/or the pulmonary artery (PA). For example, in some variations the pump body 120 can be placed such that less of its length (e.g., about 20%, 30%, 40% of the pump body length) is in the right ventricle than the length (e.g., about 80%, 70%, 60%) that is in the pulmonary artery. In some instances, it may be beneficial to reduce the volume of the pump body 120 that is placed in the right ventricle, as this positioning limits the amount of potentially adverse interaction between the pump body 120 and the heart muscle and valves (e.g., reduce risk of obstruction of the pulmonary valve). However, in some variations any suitable portion of the pump body 120 can be placed in the right ventricle. For example, the pump body 120 can be placed such that more of its length (e.g., about 80%, 70%, 60%) of the pump body length is in the right ventricle than the length (e.g., about 20%, 30%, 40%) that is in the pulmonary artery. In some variations, the pump body 120 is placed such that a portion of its intermediate region 120b (such as somewhere along the conduit length including the volume displacement member 130) crosses the pulmonary valve (e.g., is located at the plane of the pulmonary valve). In some variations, the pump body 120 is placed such that a portion of its outflow region 120c crosses the pulmonary valve (e.g., is located at the pulmonary of the aortic valve).

[0166] Furthermore, in some variations the circulatory assist device 100 may be configured for placement in any suitable blood vessel.

[0167] As described above, the circulatory assist device 100 is characterized by axial, flow between the inlet and the outlet of the conduit. In other words, in some variations, fluid pumped by the circulatory assist device 100 travels from the inlet to the outlet substantially entirely or predominantly axially along (e.g., aligned with) the flow axis of the conduit. In some variations, the fluid flow in the conduit has limited to no radial flow component., and/or limited to no circumferential flow component. The flow axis of the conduit may be substantially coincident with a longitudinal axis of the conduit, for example, though it should be understood that axial flow includes both flow of fluid coincident with the longitudinal axis and flow of fluid generally parallel to the longitudinal axis. The circulatory assist device 100 with axial flow may have a number of advantages. For example, because forces acting on the fluid within the pump body are generally oriented in the same direction, the fluid travels in a linear path through the circulatory assist device 100 and experiences less turbulence, thereby resulting in less disturbance in components of the fluid itself (e.g., less hemolysis in blood pumped by the circulatory assist device 100). Additionally, since flow occurs all in the same general axial direction (e.g., with little to no radial flow component), the kinetic behavior of the pump body (e.g., expansion and contraction of the volume displacement member, such as inflation and deflation of a balloon) can be more streamlined and energy efficient.

[0.168] Other aspects of the present technology may have additional benefits. For example, the pump body 120 can have an elongated shape that is well-suited for axial flow, which can be advantageous because increased length of the pump body 120 provides a longer landing zone that can be placed within and against leaflets of a valve (e.g., native leaflets of an aortic valve between the left ventricle and the ascending aorta). Accordingly, an elongated circulatory assist device 100 can be delivered to a transvalvular position with greater ease, as less precision is required for the circulatory assist device 100 to be placed in a suitable position across a valve (e.g., aortic valve, pulmonary valve).

[0169] Further details of the circulatory assist device 100, and methods of treatment using the circulatory assist device 100, are described below.

A. Pump body

[0170] As described above, the circulatory assist device 100 may include a pump body 120 that functions to receive a fluid (e.g., blood) when placed in a cardiovascular lumen and pump the fluid to provide circulatory assistance. Generally, the pump body 120 may be sized to fit the intended anatomy without causing obstruction of fluid flow. For example, in some variations, the pump body 120 in an expanded state may have a diameter of about 12 mm or less (e.g., at least in the outflow region 120c). In some variations, the pump body 120 in the expanded state may be configured (e.g., sized and shaped) to extend through a native cardiac valve such as an aortic valve. In some variations, the pump body 120 may be flexible (or preformed with a suitable contour or other shape) to conform to surrounding anatomy and avoid tissue trauma.

[0171] In some variations, the pump body 120 may include a conduit with an expandable support 122 and at least one fluid impermeable membrane 124 adjacent to the expandable support. The pump body 120, for example by virtue of the geometric and/or material properties of the support 122 and/or the membrane 124, may be non-compliant (e.g., stiff) enough so as to resist deformation during the expansion and contraction cycles of the volume displacement member 130, yet compliant (e.g., flexible) enough to avoid excessive pressure in the pump body 120 as the volume displacement member 130 is expanded. Furthermore, the conduit may have a circular, ellipsoidal, or other suitable curved wall, so as to help the conduit (and the overall pump body 120) be more resistant to failure in response to internal pressure (i.e., positive and/or negative pressure). Additionally, the curved wall of the conduit may help facilitate suitable clearance between the outer surface of the volume displacement member 130 and the conduit, as further described herein.

101721 The support 122 functions at least in part to provide structural support to the pump body 120. For example, the support 122 may help the conduit to be resistant against diametrical expansion in response to increased pressure when filled with blood and during expansion of the volume displacement member. Such non-distensibility allows spacing to be maintained between the pump body 120 and the ventricular wall to minimize trauma to heart tissue and also increases pump efficiency. Additionally, the support 122 may help the conduit be resistant against collapsing in response to decreased pressure (e.g., during contraction of the volume displacement member). In some variations, the support 122 may be configured to be collapsible or crimpable into a lower profile transport state during delivery to the target placement location (e.g., left ventricle and/or ascending aorta), and/or when subject to sufficient external forces to allow for endovascular delivery and retrieval. The support 122 may further be configured to expand into a deployed state, such as by self-expansion and/or expansion with another device (e.g., balloon-expandable). In some variations, the support 122 may include a frame or skeleton of a resilient metal such as nickel -titanium alloy, cobaltchrome, chromoly steel, or stainless steel, etc., or a suitable polymeric material such as nylon. The support 122 may, for example, include woven wires, mesh, a basket, laser-cut material, or a monolithic tube having an arrangement of openings, slits, or cells which allow expansion in at least one dimension from the transport state to the deployed state. For example, the support 122 can include a plurality of struts or cells arranged in a radially-expandable geometry. The support 122 can include a single continuous body, or can include multiple bodies coupled together (e.g., nested mesh tube structures with overlapping walls).

[0173] In some variations, at least a portion of the support 122 may have a generally tubular shape. For example, at least the portion of the support 122 forming the intermediate region 120b can be tubular. The portion of the support 122 forming the intermediate region can have any suitable cross-sectional shape, such as circular, elliptical, multi-sided (e.g., hexagonal, octagonal, other regular or irregular polygon shape, etc.) with regular or , etc. The cross-sectional shape may be symmetrical (e.g., radially symmetrical, bilaterally symmetrical, etc.) or asymmetrical. In some variations, at least a portion of the support 122, such as at least the portion of the support 122 forming the intermediate region 120b, can be tubular with a constant cross-sectional shape (e.g., cylindrical) or a varying profile shape along its length (e.g., bulbous, hourglass-shaped). The support 122 can have at least one closed end. For example, as shown in FIG. 1A, in some variations the distal end of a generally tubular support 122 (e.g., the distal end of the inflow region 120a) may be closed by a connector 126 (e.g., crimp, tube, etc. that may connect free ends of wires forming the support 122) or other suitable mechanical fastener(s), and/or joined in any other suitable manner such as welding, etc. Furthermore, in some variations the proximal end of the support 122 (e.g., the proximal end of the outflow region 120c) may be closed through integral formation, such as by virtue of the pattern of weaving, mesh, laser-cutting, etc. It should be understood that in some variations, either or both of the distal end of the support 122 and the proximal end of the support 122 may additionally or alternatively be closed through integral formation, mechanical fastener(s), welding, and/or the like. Furthermore, in some variations, the distal end of the support 122 and/or the proximal end of the support 122 may instead be open. Other geometric features of the support 122, such as profile of the inflow region 120a and the outflow region 120c, are described in further detail below.

(0174] In some variations, the pump body 120 may include one or more features to aid repositioning or retrieval of the pump body 120 from the patient (e.g., after circulatory assistance is no longer needed, or if the pump body 120 is to be swapped with another circulatory assist device). For example, a pigtail connector may be coupled to or integrally formed with a distal end of the pump body 120, such as coupled to or integrally formed with the support 122 at distal inflow region 120a. In some variations, the pigtail connector may be compliant such that the pigtail connector can straighten out to a lower-profile configuration (e.g., during device loading in a catheter, during repositioning, etc.).

(0175] In some variations, the pump body 120 may include at least one fluid impermeable membrane 124 adjacent to a surface of the support 122. The membrane 124 may extend along at least a portion of the length of pump body 120. For example, as shown in FIG. 1A, the membrane 124 may extend along at least the intermediate region 120b of the pump body 120. The membrane 124 may further extend along at least a portion of the inflow region 120a and at least a portion of the outflow region 120c. In some variations, at least a portion of the inflow region 120a and/or the outflow region 120c may remain uncovered by the membrane 124 so as to permit passage of fluid through the support 122 in and/or out of the conduit (e.g., through open and uncovered cells of the support 122). The membrane 124 may include one continuous layer of material, or may include multiple segments of material that are coupled to one another (e.g., radial or longitudinal strips sealed to one another, such as by heat welding).

[0176] The pump body 120 may include at least one membrane 124 adjacent to an inner surface and/or an outer surface of the support 122. In some variations, one or more membranes 124 may be adjacent to an inner surface and/or an outer surface of the support 122. That is, the one or more membranes 124 may include an inner membrane 124a and/or an outer membrane 124b. For example, as shown in the cross-sectional view depicted in FIG. 3A, the pump body 120 may include an inner membrane 124a coupled to an inner surface of the support 122.

[0177] As another example, as shown in the cross-sectional view depicted in FIG. 3B, the pump body 120 may include an outer membrane 124b adjacent to an outer surface of the support 122. In this example of FIG. 3B, the outer membrane 124b may be coupled to the outer surface of the support 122, or may be unattached from the outer surface of the support 122. In variations in which the outer membrane 124b is not attached to the outer surface of the support 122, the outer membrane 124b may overlie the outer surface of the support 122 such that the outer membrane 124b is configured to expand in tandem with the support 122 when the support 122 is expanded. In these variations similar to the example of FIG. 3B, the outer membrane 124b may help contain radially outward pressure in the pump body 120, while the support 122 may help prevent collapse of the pump body 120 by providing outward support against negative (e.g., inward) pressure.

[0178] As yet another example, as shown in the cross-sectional view depicted in FIG. 3C, the pump body 120 may include both an inner membrane 124a and an outer membrane 124b, such that at least a portion of the support 122 is sandwiched between membrane layers. In some variations, the inner membrane 124a may be coupled to an inner surface of the support 122 and/or the outer membrane 124b may be coupled to an outer surface of the support 122. Alternatively, in some variations neither the inner membrane 124a nor the outer membrane 124b is coupled to the support 122, but the inner membrane 124a and the outer membrane 124b may be coupled to each other (e.g., through open regions or cells of the support), thereby securing the support 122 therebetween. Furthermore, the pump body 120 may include more than one layer of an inner membrane 124a (e.g., two or more inner membrane layers), and/or more than one layer of an outer membrane 124b (e.g., two or more outer membrane layers). In variations in which the pump body 120 includes both an inner membrane 124a and an outer membrane 124b, the inner membrane 124a and the outer membrane 124b may extend over the same portions of the support 122, or may extend over different portions of the support 122.

[0179] The inner membrane 124a and/or the outer membrane 124b may be coupled to the support (and/or the inner membrane 124a and the outer membrane 124b may be coupled to each other) in any suitable manner, including, for example, spray lamination, welding, bonding, and/or adhesive. Furthermore, in some variations, the support 122 may be at least partially embedded within a fluid impermeable membrane 124 (e.g., via overmolding or other suitable technique). In some variations, the one or more membranes 124 may be coupled to the support 122 continuously along the inner and/or outer surfaces of the support 122. However, in some variations, at least some of the one or more membranes 124 may be coupled to the support 122 at only a portion of the inner and/or outer surfaces of the support 122, such as only along certain selected axial locations of the support 122 and/or certain selected radial locations around the support 122).

[0180] In some variations, the material of the one or more membranes 124 may be flexible and durable, such as nylon or polyurethane with high durometer values. This can be achieved by using a polymer with high tensile modulus. For example, the membrane may comprise a TPU such as pellathane or tecothane. In one example, the membrane can include tecothane in a durometer of approximately 72D, which may accommodate the stress placed on the conduit during operation of the circulatory assist device 100, without undergoing plastic deformation. As another example, the membrane may include oriented ePTFE that is oriented to accommodate stretching of the membrane in an axial direction but is stiffer in a radial direction to resist radial stretching. In some variations, the one or more membranes 124 may include an inelastic (e.g., non-compliant) material. For example, an inelastic material for the one or more membranes 124 may be suitable in variations in which the membrane(s) 124 are coupled to the support 122 at only a portion of the inner and/or outer surfaces of the support 122.

[0181] In some variations, any of the one or more membranes 124 may applied to the support 122 as a coating. For example, in some variations at least a portion of the support 122 can include an electro-spun coating comprising a suitable material (e.g., polymer) that provides a surface on or over the membrane(s) 124 that is substantially impervious to fluid. In some variations, such a coating may form a matrix structure that is sufficiently flexible to accommodate stress placed on the conduit during operation of the circulatory assist device 100, without undergoing plastic deformation. Furthermore, in some variations, the electro-spun coating can comprise an additional hydrogel and/or polymer overspray to improve its imperviousness to fluid (e.g., blood) passing through the membrane(s) 124 and/or adhering to the membrane(s) 124 (e.g., thrombus).

[0182] In some variations, any of the one or more membranes 124 may include at least one geometric feature configured to increase radial stiffness of the pump body 120 when expanded beyond an intended working expanded diameter. For example, at least one membrane 124 may include one or more circumferential regions (e.g., arc, ring) having a greater thickness so as to resist stretching in a radial direction. As another example, at least one membrane 124 may additionally or alternatively include one or more circumferential regions (e.g., arc, ring) comprising a material with a higher Young’s modulus compared to other regions of the membrane (e.g., different axial segments of the conduit may include different membrane materials with different durometers). As another example, at least one membrane 124 may additionally or alternatively include one or more circumferential regions (e.g., arc, ring) in which the membrane material includes localized cross-linking to selectively stiffen the polymer modulus in those circumferential regions (e.g., via radioactive irradiation or light treatment).

[0183] In some variations, the pump body 120 may also include one or more circumferential fibers of a material with a high tensile strength, which function to further limit the distensibility of the support 122 beyond its desired size, while still allowing the pump body 120 to be radially collapsed into a transport state (e.g., for insertion and removal). Such circumferential fibers may be arranged, for example, circumferentially around at various axial locations along the intermediate region 120b of the pump body 120. The circumferential fibers can include any suitable material such as Kevlar, spectra, carbon nanotubes, and/or other such materials that are attached, embedded within, or woven into the support 122 and/or membrane 124.

[0184] In some variations, the pump body 120 may have substantially uniform radial stiffness (or compliance) along its length. However, in some variations, the pump body 120 may have varying radial stiffness along its length. For example, in some variations, the pump body 120 may generally have greater radial stiffness at an inflow region of the pump body 120 (e.g., around the inlet valve of the pump body 120 and/or where the volume displacement member has a maximum diameter along its length) compared to an outflow region of the pump body 120. The radial stiffness of the pump body 120 may decrease (e.g., generally linearly or step-wise) from the inflow region toward the outflow region. Radial stiffness of the pump body may be controlled, for example, by varying the thickness of the one or more membranes 124 (e.g. thickness of one or more membranes, varying the number of membranes at a particular axial location along the pump body, etc.), and/or varying the material type and/or other material characteristics of the one or more membranes 124 (e.g., via any of the features or treatments described above with respect to controlling radial stiffness of one or more circumferential regions in the membrane(s) 124). Additionally or alternatively, radial stiffness of the pump body 120 may be controlled by varying stiffness of the support 122, such as by varying material type of the support 122, varying the cell or mesh pattern that may be present in the support 122 (e.g., smaller cells may increase radial stiffness of the support 122 at selected regions), and/or varying the width and/or thickness of the struts that may be present in the support 122 (e.g., wider or thicker struts may increase radial stiffness of the support 122 at selected regions). As described above, the pump body 120 may further include at least one inlet valve 140 configured to receive fluid along the flow axis of the conduit. In this manner, flow entering the pump body 120 may travel in an axial flow direction, with little to no radial flow component orthogonal to the flow axis. The inlet valve 140 may be a one-way valve with a preferential flow direction, where the one-way valve permits flow into the pump body 120 through the inflow region 120a, while substantially preventing flow out of the pump body 120 through the inflow region 120a. For example, the inlet valve 140 may include a duckbill valve, or a valve with multiple leaflets (e.g., bicuspid valve, tricuspid valve, etc.). In some variations, the inlet valve 140 may be a passive valve configured to open and close in response to pressure change, though in some variations the inlet valve 140 may additionally or alternatively be an active valve whose opening and closure may be controlled by a suitable actuator.

[0185] In some variations, the valve cracking pressure of the inlet valve 140 (the minimum pressure at which flow through the inlet valve 140 is permitted) may be lower than the pressure differential created across the inlet valve 140 that is created by momentum of fluid exiting the pump body 120. The movement of exiting fluid reduces the internal pressure of the pump body 120 relative to pressure external to the pump body 120, and a lower valve cracking pressure is configured to permit entrainment of flow. When open, the inlet valve 140 may be configured to be non-obstructive (e.g., little to no restriction of flow when open).

[0186] The inlet valve 140 may be configured to withstand opening and closing at a high frequency over a sustained period of time (e.g., high fatigue resistance). For example, in some variations, the inlet valve 140 may be configured to have a fast closure response time, such as about 4 milliseconds or less, about 3 milliseconds or less, about 2 milliseconds or less, about 1.5 milliseconds or less, or about 1 millisecond or less.

[0187] The inlet valve 140 may be positioned in a portion of the conduit that is covered by the membrane 124. The inlet valve 140 may be in or proximate to the inflow region 120a of the conduit of the pump body 120. For example, in some variations, the inlet valve 140 may be arranged in a portion of the inflow region 120a that is covered by the membrane 124. As another example, the inlet valve 140 may be arranged in a covered portion of the intermediate region 120b, such as at an axial location between the volume displacement member 130 and the inlet of the pump body 120 (e.g., portion of the inflow region 120a that is not covered by the membrane 124, or at an open end of the support 122).

[0188] In variations in which the inlet valve 140 is arranged to permit axial flow of fluid into the conduit, such an axial orientation of the inlet valve 140 may be advantageous for reducing the diameter of the pump body 120 in the collapsed (e.g., crimped) configuration. For example, as described above, the inlet valve 140 may be arranged at an axial location between the volume displacement member 130 and the inlet of the pump body 120, such that the inlet valve 140 does not overlie the volume displacement member 130 and thus does not add additional radial bulk to the profile of the pump body 120 in the collapsed configuration. Furthermore, in some variations the axial inlet valve 140 may itself be low-profile, thereby further contributing to a smaller profile of the pump body 120 in the collapsed configuration.

[0189] Although FIG. 1A depicts a circulatory assist device 100 including one inlet valve 140, it should be understood that in some variations, the circulatory assist device 100 may include multiple (e.g., two or more) inlet valves.

[0190] Furthermore, in some variations, in addition to or as an alternative to an inlet valve receiving fluid in a direction aligned with the flow axis of the conduit, the circulatory assist device 100 may include one or more inlet valves configured to receive fluid in a direction not aligned with the flow axis of the conduit. For example, as shown in FIG. 11 A, in some variations, a circulatory assist device 1100 may be similar to the circulatory assist device 100, except that the circulatory assist device 1100 includes one or more inlet valves 140' configured to receive fluid in a radial direction. The inlet valves 140' may, for example, be a flap valve configured as a one-way valve, and may include an aperture formed in a wall of the conduit of the pump body 120, and a flap (e.g., coupled to or integrally formed with the membrane 124). The flap may be configured to alternate between exposing the aperture (thereby permitting fluid flow into the conduit) and covering the aperture (thereby substantially preventing fluid flow from exiting the conduit). An example variation of an inlet flap valve 140' is shown in FIG. 1 IB. As shown in FIG. 1 IB, an inner membrane 124a may be arranged on an inner surface of the support 122, and an outer membrane 124b may be arranged on an outer surface of the support 122. The inner membrane 124a and the outer membrane 124b may have respective apertures 142a and 142b that at least partially overlie each other (and at least partially overlie an opening of the support 122). A flap 144, which may be attached to the inner membrane 124a at a connection 146 on one side of the flap 144 (or alternatively may be integrally formed with the inner membrane 124a, such as cut out from the inner membrane 124a) is configured to overlie the apertures 142a and 142b. Pressure differential between inside and outside the pump body 120 may cause movement of the flap 144 relative to the apertures 142a and 142b. For example, movement of the flap 144 away from the inner membrane 124a may allow fluid to enter the conduit in a radial direction. Conversely, movement of the flap 144 toward the inner membrane 124a may substantially prevent fluid from exiting the conduit. Although FIG. 1 IB illustrates one variation of an inlet flap valve 140', other variations of flap valves (and other kinds of radial valves) may be constructed in accordance with the present technology. For example, pump body 120 may include only an inner membrane 124a with at least one aperture 142a, or only an outer membrane 124b with at least one aperture 142b. Additionally or alternatively, the flap 144 may be arranged internal to the support 122, or external to the support 122. Other variations of suitable flap valves are described in greater detail in International Patent Application No. PCT/EP2023/059293, which is incorporated herein in its entirety by this reference.

[0191] Furthermore, in some variations, the circulatory assist device may include one or more outlet valve. For example, as shown in FIG. 1C, a circulatory assist device 100c (similar to circulatory assist device 100 except including at least one outlet valve) may include one or more outlet valves 141 arranged at or near the outflow region 120c of the pump body. The outlet valve(s) may, for example, help regulate the exit of fluid from the pump body by substantially occluding fluid flow out of the pump body during certain phase(s) of operation. However, in accordance with the aspects of the present technology (e.g., as further described herein), when momentum is strong enough to overcome resistance and afterload, there may be a reduced need for an outlet valve. For example, in some variations the circulatory assist device 100 may lack an outlet valve (e.g., between the volume displacement member 130 and the outlet), such that the conduit remains permissive (open) to outflow of fluid during an entire cycle of expansion/contraction of the volume displacement member 130. The absence of an outlet valve may have certain advantages. For example, the absence of an outlet valve may reduce the outward resistance of flow from the conduit, may result in less disturbance of the flow path, and may result in less fluid turbulence. As such, the absence of an outlet valve may increase preservation of fluid momentum (and output efficiency) of the circulatory assist device 100, as well as reduce the likelihood of hemolysis and/or thrombogenicity. Additionally, the absence of an outlet valve may allow the volume displacement member 130 to be expandable even at low pressures during pump operation, since there is no need for pressure within the pump body 120 to be at least a threshold valve cracking value for opening an outflow valve.

[0192] As described herein, the circulatory assist device 100 may include at least one volume displacement member 130. The volume displacement member 130 functions to help create and maintain momentum in the fluid column through the conduit of the pump body 120, thereby drawing fluid into the conduit through the inlet valve 14 and enabling flow of fluid through the outlet of the conduit.

[0193] The volume displacement member 130 may include any of various types of mechanisms capable of displacing a volume of fluid in a cyclical, repeating manner. In some variations, the volume displacement member 130 may include an inflatable balloon that can be inflated with a fluid to an expanded, high-volume state and deflated partially or completely to a contracted, low-volume state. Suitable fluids include, for example, helium, carbon dioxide, etc. In other variations, a piston, bellows, accordion-style expandable body, and/or other type of volume displacement member may be used. The volume displacement member is capable of moving cyclically between the contracted low-volume state in which it occupies a smaller portion of the conduit, to an expanded high-volume state, in which it occupies a substantially larger portion of the conduit, thus displacing blood therefrom. The volume displacement member 130 may be configured to cyclically move between these contracted and expanded states at a high frequency, such as at least about 300 beats per minute, at least about 500 beats per minute, at least about 1000 beats per minute, or at least about 1200 beats per minute, at least about 1500 beats per minute, at least about 2000 beats per minute, at least about 2500 beats per minute, at least about 3000 beats per minute (e.g., between about 1000 beats per minute and about 3000 beats per minute). In some variations, the frequency of the contract! on/expansi on cycle of the volume displacement member 130, in combination with the features (e.g., dimensions) of the rest of the pump body 120, is controlled such that the pump body is configured to convey fluid through the outlet with a flow rate of at least about 5 L/min. [0194] When in the fully expanded state, the volume displacement member 130 may have a maximum diameter that is smaller than the inner diameter of the support 122, thereby allowing the outer surface of the expanded volume displacement member 130 to be spaced apart from the support 122, which provides clearance for fluid to move through the conduit between the inlet and the outlet even when the volume displacement member 130 is fully expanded. Such clearance may, in some instances, further function to help limit hemolysis during high frequency operation of the volume displacement member 130. For example, in some variations, when the volume displacement member 130 is fully expanded, a spacing of at least about 0.05 mm, or at least about 1.0 mm-5.0 mm (e.g., about 1.0 mm-3.0 mm) may be maintained between the volume displacement member 130 and an interior surface of the support 122. In some variations, the volume displacement member 130 may be generally axially centered within the pump body 120 (e.g., along a longitudinal axis of the pump body 120, or along the flow axis) such that the volume displacement member 130 may be equally spaced apart from the interior surface of the support 122 on all sides of the volume displacement member 130. In some instances of operation, the volume displacement member 130 may remain generally axially centered within the pump body 120 as the volume displacement member 130 cycles between expansion and contraction. However, in some variations, the volume displacement member 130 may operate in an eccentric manner relative to the pump body 120, such that during part of the expansion/contraction cycle, the spacing between a first side of the volume displacement member 130 and the interior surface of the support 122 may be greater than the spacing located on a second side of the volume displacement member 130 (e.g., where the second side is opposite the first side). For example, in some variations the volume displacement member 130 may be biased to expand more on one side of the volume displacement member 130 than the other. This may occur, for example, due to the natural movement (e.g., flexure) of the guidewire lumen caused by position of the device in anatomy, where the device position causes lateral bending of the guidewire lumen and accordingly a bend or bias of the volume displacement member 130 mounted on or over the guidewire lumen.

[0195] Additionally or alternatively, in some variations, at least a portion of the volume displacement member 130 may be intentionally placed radially offset (and/or radially asymmetrically constructed) so as to be positioned offset from the axial center of the pump body 120 (e.g. the longitudinal axis of the pump body 120, or flow axis) so as to operate in an eccentric manner relative to the pump body 120. For example, similar to that described above, on a first side of the volume displacement member 130, the spacing between the volume displacement member 130 and the interior surface of the support 122 may be greater than that located on a second side of the volume displacement member 130 (e.g., where the second side is opposite the first side). In some variations in which the volume displacement member is in an eccentric position relative to the support 122, the volume displacement member 130 may be constantly or typically touching the support 122, such that flow within the pump body 120 does not pass entirely around the circumference of the volume displacement member 130. For example, one side of the volume displacement member 130 may be coupled with the support 122 at one or more axial locations (e.g., coupled along a seam running the length of the volume displacement member 130, or tacked at an end or at one or more locations along the length of the volume displacement member 130), such as with mechanical fastening, thermal joining processes, and/or the like.

[0196] In some variations, the volume displacement member 130 may have a tapered profile, such that a first portion of the volume displacement member 130 has a first diameter that is larger than a second diameter of a second portion axially displaced from the first portion. For example, in some variations, a distal portion (e.g., near an inflow region 120a, in a variation in which the circulatory assist device is configured for placement in a left ventricle) may be larger in diameter than a proximal portion (e.g., near an outflow region 120c). In some variations, the diameter of the volume displacement member 130 may transition from the first diameter to the second diameter in a linear manner. An illustrative example of a volume displacement member 1230 (which is an example of volume displacement member 130) with a single taper is shown in FIG. 12. As shown in FIG. 12, the volume displacement member 1230 includes an inflow member region 1232a, and outflow member region 1232c, and an intermediate member region 1232b therebetween. The volume displacement member 1230 may include a single taper extending generally along at least a portion of the intermediate member region 1232b, with the diameter of the volume displacement member 1230 decreasing from the inflow member region 1232a to the outflow member region 1232c at a taper angle 0. The taper angle 9 may range, for example, between about 2 degrees and about 5 degrees (e.g., between about 2.5 and about 4.5 degrees).

[0197] In some variations, the volume displacement member may include multiple tapered regions. For example, an illustrative example of a volume displacement member 1330 (which is an example of volume displacement member 130) with dual tapers is shown in FIG. 13. As shown in FIG. 13, the volume displacement member 1330 includes an inflow member region 1332a, and outflow member region 1332c, and an intermediate member region 1332b therebetween. The volume displacement member 1330 may include a maximum diameter in a maximum diameter region 1334, and may include a first taper extending from the maximum diameter region 1334 to the inflow region 1332a at a first taper angle a, and a second taper extending from the maximum diameter region 1334 to the outflow region 1332c at a second taper angle p. In some variations, the first taper angle a may, for example, range between about 10 degrees and about 30 degrees, between about 15 degrees and about 25 degrees, or between about 10 degrees and about 20 degrees, or between about 20 degrees or about 30 degrees. Additionally or alternatively, the second taper angle P may, for example, range between about 2 degrees and about 10 degrees, or between about2.5 degrees and about 9.5 degrees, or between about 2 degrees and about 5 degrees, or between about 5 degrees and about 10 degrees.

[0198] As further described below with respect to the catheter 110, the volume displacement member 130 may be coupled to a shaft of the catheter 110. Additionally or alternatively, in some variations, the volume displacement member 130 may be coupled to the conduit of the pump body 120 (e.g., support 122 and/or membrane 124), which may help to anchor the volume displacement member 130 in a fixed position relative to the pump body 120, thereby minimizing movement of the volume displacement member 130 relative to the pump body 120 (other than from inflation) and reducing vibration of pump body 120.

[0199] In variations in which the volume displacement member 130 is a balloon, it may include a durable material such as polyurethane or nylon. The balloon may be formed of a single, thin wall of such material. For example, in one illustrative variation, the balloon may be made of pellethane 55D (or a material with similar mechanical properties). The balloon may have a single wall thickness of between about 20 pm and 150 pm, or between about 60 pm and about 100 pm (e.g., about 80 pm). As shown in FIG. 1A, the balloon may have a generally elongated shape and extend longitudinally along a portion of the length of the pump body 120. For example, the balloon in its expanded state may have a generally ellipsoidal shape. Other features of the volume displacement member 130 are described in further detail herein (e.g., with respect to FIGS. 4A-4C).

[0200] FIGS. 7A-7E illustrate various phases of operation in which fluid may be allowed to exit the conduit of the pump body via maintained momentum during the expansion phase and at least a part of the contraction phase of a volume displacement member 130. Although the volume displacement member 130 is primarily shown and described below as a balloon, it should be understood that the same principles of operation apply with respect to other variations of circulatory assist devices that include different kinds of volume displacement members 130.

[0201] FIG. 7A illustrates a pump body 120 that has received fluid (e.g., blood) through the inlet valve 140, and has a volume displacement member 130 in the process of being inflated to expand within the pump body 120. As the volume displacement member 130 inflates, it displaces surrounding fluid, thereby pushing fluid both distally toward the inflow region 120a and proximally toward the outflow region 120c. Fluidic pressure causes the inlet valve 140 to close, while also urging fluid to exit the pump body 120. As shown in FIG. 7B, when the inlet valve 140 is fully closed, all of the fluid volume in the pump body 120 exits through the outlet of the outflow region 120c.

[0202] Inflation of the volume displacement member 130 also helps generate momentum of the fluid column traveling toward the outflow region 120c in the pump body 120. FIG. 7C illustrates when the volume displacement member 130 is at an end portion of the expansion phase, and the volume displacement member 130 is inflated to a maximum volume. At this stage of operation, the fluid mass in the pump body 120 has momentum (imparted by the volume displacement member 130) toward the outflow region 120c to exit the pump body 120 through the outlet, and such movement of the fluid mass results in a negative pressure within the pump body 120 (relative to pressure outside of the pump body 120, such as left ventricular pressure if the pump body 120 is placed in the left ventricle, or right ventricular pressure if the pump body 120 is placed in the right ventricle). Under such momentum and negative pressure within the pump body 120, the inlet valve 140 opens and additional fluid is pulled into the pump body 120 through the open inlet valve 140 in the axial flow direction, as shown in FIG. 7C. In some variations, the volume displacement member 130 can be held in a state of maximum expansion for a limited period of time while the momentum transfer imparted on the fluid continues to generate flow into the pump body 120. In some variations, a negative pressure peak in the fluid provides for this extended duration of the inflation, as the volume displacement member’s expanded state is the result of pressure difference between its inflation fluid and fluid between the volume displacement member and conduit wall. As one example, when operated at a pumping frequency of about 1500 bpm (25 Hz, or cycle time about 40 ms), the volume displacement member 130 can be temporarily held in its maximum expanded state for about 10 ms. As another example, when operated at a pumping frequency of about 600 bpm (10 Hz, or cycle time about 100 ms), the volume displacement member 130 can be temporarily held in its maximum expanded state for about 30 ms. The period of time in which the volume displacement member 130 is maintained in its maximum expanded state can be considered to scale roughly inversely proportional between these examples.

[0203] As shown in FIG. 7D, when the volume displacement member 130 enters its contraction phase and begins to deflate, the fluid momentum continues, and additional fluid is pulled into the pump body 120 in the axial flow direction through the open inlet valve 140. In some instances, the amount of fluid momentum may decrease at this stage if additional fluid is also pulled into the pump body 120 through the outflow region 120c. However, in these instances, the momentum (and volume) of fluid pulled through the inflow region 120a is greater than that of fluid pulled distally through the outflow region 120c. Accordingly, fluid momentum may slow, but still continues in the direction from the inflow region 120a toward the outflow region 120c, thereby drawing in additional fluid into the pump body 120 for further pumping.

[0204] FIG. 7E illustrates when the volume displacement member 130 is at an end portion of the contraction phase, and the volume displacement member 130 is deflated to a minimum volume. At this stage of operation, the fluid mass continues to have momentum in the proximal direction toward the outflow region 120c, and fluid continues to exit the pump body 120 through the outlet of the conduit. Following the contraction phase, the volume displacement member 130 returns to its expansion phase, and the above-described cycle of expansion and contraction (with continued momentum and fluid conveyance through the conduit outlet, as shown in FIGS 7A-7E) may repeat.

[0205] The momentum of fluid in the pump body 120 during operation can be characterized by the Navier-Stokes momentum equation (Equation 1):

where is the time derivative of flow velocity u, p is the mass density of the fluid, V is the divergence, p is the fluid pressure, T is the deviatoric stress tensor, and g is the gravitational acceleration constant.

[0206] The amount of fluid momentum generated depends on various factors. For example, one factor that can increase the momentum of fluid in the pump body 120 is increased volume available in the pump body 120 for the fluid to occupy, as greater available fluid volume allows greater fluid mass (and hence greater inertia as the fluid mass moves). The volume available in the pump body 120 for fluid can be at least partially dependent on the internal volume of the conduit itself, the volume of the volume displacement member 130 in its contracted state and in its expanded state, the volume in the conduit that is proximal to the volume displacement member 130 (e.g., volume of the long nozzle), and closing speed and sealing capacity of the inlet valve 140.

[0207] Additionally, the speed at which the volume displacement member 130 completes its expansion phase (e.g., speed of inflation) may affect momentum, as increased expansion speed may increase fluid momentum in the pump body 120.

[0208] Another factor that may affect momentum is whether the direction of expansion and the direction of contraction of the volume displacement member 130 are aligned, as such alignment may have a positive impact on fluid momentum. Accordingly, design of the expansion and contraction mechanics of the volume displacement member 130 (e.g., inflation and deflation) can be configured to increase the attainable fluid momentum.

[0209] Additionally, because high compliance in the volume displacement member 130 and/or the conduit of the pump body 120 may have a damping effect on momentum (e.g., because energy is dissipated in deforming the conduit instead of driving fluid flow), the volume displacement member 130 and/or the pump body 120 may be designed to have relatively low extensibility. For example, material of the volume displacement member 130, the support 122, and membrane 124 may be configured with low extensibility and low compliance, so as to increase fluid momentum.

[0210 ] Loss of fluid momentum in the pump body 120 can be partially due to resistance through the inlet valve 140 and/or reduced clearance between the volume displacement member 130 and the wall of the conduit. Furthermore, in some variations, afterload (the aortic blood pressure, or the pressure boundary condition at the outflow of the pump body 120) may have a damping effect on fluid momentum within the pump body 120. For example, the afterload may counter the fluid momentum in the pump body 120 by pushing from outside the pump device onto the fluid, thereby decelerating the fluid exiting the pump body 120. If this effect of the afterload overcomes the fluid momentum in the pump body 120, backflow will occur (and the higher the afterload, the stronger the backflow). However, the damping effect of resistance and afterload may be limited, for example, by configuring the inlet valve 140 with low flow resistance and ensuring that the pump body 120 has suitable spacing between the volume displacement member 130 and the conduit wall, as described above. Additionally or alternatively, the damping effect may further be limited by increasing the impedance (e.g., resistance and/or inertance) of the outflow region, such as by including a longer and/or more narrow outflow nozzle, as further described herein. Accordingly, configuring the pump body 120 (and its components) and parameters of the expansion and contraction of the volume displacement member 130 to achieve a sufficiently strong momentum for continued fluid movement out of the outflow region 120c of the conduit, in accordance with the present technology.

10211] Further design considerations of example variations of the circulatory assist device 100 for improving fluid flow within the conduit, including structural features of the pump body 120, are further described below with reference to FIG. 4A and elsewhere herein. FIG. 4A is a schematic illustration of an example circulatory assist device 300, which may be similar to the circulatory assist device 100 as described herein, except with further geometrical features as described below. The circulatory assist device 300 may operate under the same principles as circulatory assist device 100, such as that described herein with respect to FIGS. 7A-7E. Similar to the circulatory assist device 100, the circulatory assist device 300 may include an inflow region 120a, an outflow region 120c, and an intermediate region 120b arranged between the inflow region 120a and the outflow region 120c. A proximal portion (B) of the inflow region 120a is covered by the membrane 124, while a distal portion (A) of the inflow region 120a is not covered by the membrane 124 and thus allows passage of fluid therethrough. A distal portion (F) of the outflow region 120c is covered by the membrane 124, while a proximal portion (G) of the outflow region 120c is not covered by the membrane 124 and thus allows passage of fluid therethrough.

[0212] In some variations, at least a portion of the volume displacement member 130 may be arranged within the conduit in the intermediate region 120b of the conduit. For example, the entire volume displacement member 130 may be arranged in the intermediate region 120b of the conduit. The inlet valve 140 may be positioned within the conduit in the covered portion (B) of the inflow region 120a as shown in FIG. 4A, or may be otherwise between an inlet of the pump body 120 and the volume displacement member 130.

|0213j The inflow region 120a may, in some variations, have a generally rounded or bulbous shape (e.g., spherical, ovate, lanceolate, etc.) as shown in FIG. 4A. Curvature of this inflow region may help improve the pressure resistance of the valve (e.g., compared to a cylinder). Furthermore, a bulbous shape for the inflow region may help prevent lateral tissue contact from impeding flow into the inlet of the pump body, as the wider diameter of the bulbous shape may function as a standoff to generate spacing between the inlet and adjacent tissue surfaces. The uncovered portion (A) of the inflow region 120a may be closed with a rounded, atraumatic distalmost end, which may, for example, help reduce harm to tissue (e.g., endocardium and valve(s)) both during delivery and placement of the pump body 120 in a patient). The uncovered portion (A) has sufficient inflow area (e.g., in open cells of a support 122) to convey fluid through the inlet valve 140 and into the conduit of the pump body 120. Furthermore, in some variations, a pigtail connector other suitable feature may be coupled to or integrally formed with the support 122 at the inflow region 120a, which may be used, for example, in retrieving the pump body 120 from the patient. The distal end of the inflow region 120a may be atraumatic (e.g., include a pigtail or other curved, flexible structure) so as to permit atraumatic contact of the distal end of the pump body 120 with tissue (e.g., cardiac tissue, such as in the left ventricle). In some variations, the inflow region 120a, as integrally formed with or coupled to the intermediate region 120b of the pump body 120, may help provide supporting strength to the intermediate region 120b (e.g., to resist deformation under high pressure fluctuations).

[0214] In some variations, the covered portion (B) of the inflow region 120a may be outwardly (radially) flared with a certain angle of divergence (H), which may help to promote laminar flow of fluid entering pump body 120. Such laminar flow may, for example, improve fluid momentum and pump efficiency, as well as reduce turbulence that may cause increased likelihood of hemolysis and/or thrombogenesis. In some variations, the inflow region 120a may have a maximum diameter that is larger than a diameter of the intermediate region 120b. Furthermore, in variations in which the inlet valve 140 is at least partially located in the covered portion (B) of the inflow region 120a, the covered portion (B) may have high radial strength and suitable attachment area(s) for permitting fluid-tight and durable coupling or mounting of the inlet valve 140. Additionally or alternatively, in variations in which the inlet valve 140 is at least partially located in the covered portion (C) of the intermediate region 120b between the volume displacement member 130 and the inflow region 120a, the covered portion (C) may similarly have high radial strength and suitable attachment area(s) for the inlet valve 140.

[0215] In some variations, intermediate region 120b and/or the inflow region 120a may have a tapered, narrower inflow opening. For example, FIG. 4B is a schematic illustration of an example circulatory assist device 300', which is substantially similar to the circulatory assist device 300 except as described below. In the circulatory assist device 300', at least the covered portion (B) may be inwardly (radially) narrowed with a certain angle of convergence (H). A tapered, narrower diameter of the intermediate region 120b and/or inflow region 120a may, for example, allow for a smaller size inlet valve 140 which may reduce the overall profile of the device 300' in the collapsed (e.g., crimped) configuration. Additionally or alternatively, a tapered or narrowed intermediate region 120b and/or inflow region 120a may contribute to reducing the diameter of the portion of the device 300' that crosses the plane of a native valve (e.g., aortic valve). Accordingly, in some variations, a tapered or narrowed intermediate region 120b and/or inflow region 120a may ease placement of the device 300' in a patient (e.g., enable use of a smaller diameter delivery sheath) and/or result in lower risk of complications with native anatomy.

|0216j Like the inflow region 120a, the outflow region 120c may, in some variations, have a rounded or bulbous shape (e.g., spherical, ovate, lanceolate, etc.) as shown in FIG. 4 A. The outflow region 120c may be closed with a rounded, atraumatic proximalmost end, which may, for example, help reduce harm to tissue in the patient. The covered portion (F) may be outwardly (radially) flared with a certain angle of divergence (I). This angle of divergence (I) may help to decelerate flow and decrease the difference in flow velocity between the outflow and the inflow of fluid in the pump body 120, thereby advantageously decreasing shear and/or turbulence, and hence reduce likelihood of hemolysis and/or thrombogene sis. For example, in some variations, the angle of divergence may be between about 10 degrees and about 20 degrees (e.g., about 15 degrees). In some variations, the outflow region 120c may have a maximum diameter that is larger than a diameter of the intermediate region 120b. The uncovered portion (G) of the outflow region 120c has sufficient outflow area (e.g., in open cells of a support 122) to convey fluid through the outlet of the pump body 120 without obstruction. Furthermore, in some variations, the outflow region 120c, as integrally formed with or coupled to the intermediate region 120b of the pump body 120, may help provide supporting strength to the intermediate region 120b (e.g., to resist deformation under high pressure fluctuations). In some variations, at least a portion of the outflow region 120c (e.g., uncovered portion (G) of the outflow region 120c) may be engaged with a retrieval tool (e.g., hook) for retrieval and/or repositioning of the pump body 120.

[0217] In some variations, the outflow region 120c may converge or taper to a narrower outflow opening. For example, FIG. 4C is a schematic illustration of an example circulatory assist device 300", which is substantially similar to the circulatory assist device 300 except as described below. In the circulatory assist device 300", at least a portion of the covered portion (F) may be inwardly (radially) narrowed with a certain angle of convergence (I). This angle of convergence (I) may help to increase (e.g., maximize) outflow nozzle pressure, thereby helping to maintain fluid momentum. In other words, a tapered or narrowed outflow region 120c may help to increase inertia of the fluid, with a shorter outflow region length. In some variations, the outflow region 120c of circulatory assist device 300" has a maximum diameter that is equal to or smaller than a diameter of the intermediate region 120b. Like in the circulatory assist device 300 described herein with respect to FIG. 4 A, the uncovered portion (G) of the outflow region 120c in the circulatory assist device 300" has sufficient outflow area (e.g., in open cells of a support 122) to convey fluid through the outlet of the pump body 120 without obstruction. Furthermore, in some variations, the outflow region 120c, as integrally formed with or coupled to the intermediate region 120b of the pump body 120, may help provide supporting strength to the intermediate region 120b (e.g., to resist deformation under high pressure fluctuations).

[0218] Although FIGS. 4A-4C separately illustrate a number of variations of a circulatory assist device, it should be understood that in some variations of a circulatory assist device, various features of the circulatory assist device 300, 300', and/or 300" may be combined in any suitable manner. For example, a circulatory assist device may include both a tapered inflow region 120a (As shown in FIG. 4B) and a tapered outflow region 120c (as shown in FIG. 4C). As another example, any of the circulator assist devices in accordance with the present technology may include an inlet valve 140 in the intermediate region 120b (as shown in FIG. 4C), whether in combination with an inflow region 120a that is tapered, bulbous, or any suitable shape, etc.

[0219] Overall axial positioning and/or shape of the volume displacement member 130 may be further configured to promote fluid momentum in the pump body 120. For example, a greater distance (E) between the volume displacement member 130 and the outflow region 120c increases the mass of fluid in motion, thereby increasing fluid momentum and outflow of fluid from the pump body 120. In some variations, the axial position of the volume displacement member 130 relative to the conduit can be selected such that the volume displacement member 130 is located as close as possible (measured along the flow axis) to the intlet valve without physically overlapping with the inlet valve. Length (D) and/or diameter of the volume displacement member 130 contribute to overall volume of the conduit available for fluid in the conduit, which can be configured as described above for increasing fluid mass and hence fluid momentum in the pump body 120. In some variations, for example, a distal portion of the volume displacement member 130 (e.g., distal portion ranging between about 5% distal most length and about 15% distalmost length of the length of the volume displacement member) may be located in the distalmost third of the overall length of the conduit or pump body (e.g., at least the portion of the conduit covered by the membrane). For example, up to the distalmost 9%, 10%, or 11% of the length (D) may be located in a third of the sum of (B), (C), (D), (E), and (F). Additionally or alternatively, a distal volumetric portion of the volume displacement member 130 (e.g., up to a distal portion of the member volume of more than about 50%, or ranging between about 5% and about 50%, between about 10% and about 45%, between about 15% and about 40%, or about 10% of the total member volume measured when the member 130 is in the expanded state or phase) may be located in the distalmost third of the overall length of the conduit or pump body (e.g., at least the portion of the conduit covered by the membrane). Additionally or alternatively, the volume displacement member 130 may be tapered (at least at its proximal end, toward the outflow region 120c) so as to increase the flow speed of fluid proximal to the volume displacement member, which may help contribute to the creation of fluid momentum.

[0220] Additionally or alternatively, overall length of the pump body 120 or a portion thereof may affect the outflow of fluid from the pump body 120. For example, in some variations, the outflow region 120c may include a covered portion (F) configured to function as an outflow nozzle. The covered portion (F) may be contoured as described above, and/or have an elongated length to further increase the distance between the volume displacement member 130 and an outlet (e.g., adding to the outflow travel distance downstream of the volume displacement member beyond the distance (E) shown in FIG. 4 A). This increased nozzle length further increases the fluid mass that is in motion during pump operation, thereby increasing momentum of the fluid within the pump body 120 and improving efficiency, etc.

B. Catheter

[0221] The catheter 110 may have specific features allowing or enhancing the high frequency operation of the circulatory assist device 100, and/or to optimize inert flow for the volume displacement member 130 (e.g., in variations in which the volume displacement member 130 is a balloon).

[0222] FIGS. 5A-5F depict an example variation of a catheter 110 that is suitable for use with a volume displacement member 130 including a balloon. In some variations, as shown in FIG. 5 A which shows the catheter 110 extending through a delivery sheath 36, the catheter 110 may include a balloon shaft 54 having an inflation lumen 56. The inflation lumen 56 may, for example, have a cross-sectional flow area of between 1 mm² and 20 mm². This corresponds to an inner diameter of generally between about 0.5 mm and about 5 mm, which allows a proper balance between flow resistance for the inert fluid and further characteristics of the catheter parts, such as bending radius, kinking resistance, etc. In some variations, the inflation lumen 56 is not subdivided, since the resistance will go up when the cross-sectional area is distributed over different channels. The shape of the inflation lumen 56 may be configured to have the lowest resistance possible, while leaving room in the catheter for a potential guidewire, pull wires for device retrieval, and/or any potential sensors.

(0223] In some variations, as shown in FIGS. 5B-5E, the balloon shaft 54 includes three or more lumens, including an inflation lumen 56 (which may be largest in diameter among the lumens), a guidewire lumen 58, and one or multiple wire lumens 60 for pull wire(s) 62 for retrieval of the pump body 120. The catheter 110 may include one or more sensors at or near its distal end. For example, the catheter 100 may include one or more pressure sensors (e.g., pressure transducers, optical pressure sensors) for measuring pressures within the conduit of the pump body 120, or in the heart outside the pump body 120, electrical sensors such as ECG or heart rate sensors, and/or or other sensors. The balloon shaft 54 may include lumens for wires to any such sensors.

[0224] In some variations, a distal section of the catheter 110 may have a wider diameter than a proximal section of the catheter, the proximal section of the catheter being farther from the balloon-based volume displacement member 130 than the distal section of the catheter. This may allow the inflation lumen to be larger in the distal section of the catheter 110 than in the proximal section of the catheter 110, and thereby may lower friction of the inert inflation fluid passing through the larger distal section of the catheter 110. The distal section may also be configured to be positioned in the larger vessels closer to the heart relative to the point of percutaneous introduction, such as in the aorta. As an illustrative example, a distal section of the catheter 110 may be 60 mm long with a diameter of about 2.5 mm, and a proximal section of the catheter (in the aorta, femoral area, and outside the patient) may be about 1200 mm long and a diameter of about 2.2 mm or less. In some variations, the overall insertable length of the catheter 110 may be configured to extend from a femoral puncture site (e.g., from an insertion site at the femoral artery) of the patient, through the aorta, and into the left ventricle.

[0225] In some variations, the catheter 110 may include a plurality of catheter sections with different diameters. The wider diameter sections may, for example, be configured for placement in areas where blood flow is not obstructed (e.g., peripheral arteries) or where they remain outside of a patient during operation. In an illustrative example, a first section (within the pump body 120) is about 60 mm long with a diameter of 2.2 mm, a second section (in the aorta area) is 800 mm long with a diameter of 3 mm, a third section (in the femoral area) is 400 mm long and a diameter of 2.5 mm, and a fourth section (outside the patient) has a length of 750 mm and a diameter of 4mm. Additionally or alternatively, the catheter 110 may have a necked or narrower diameter in the region where the catheter 110 overlaps with (e.g., is arranged within) the pump body 120, so as to lower the overall crimp profile of the pump body 120 in the radially collapsed state (e.g., for transport).

[0226] In some variations the catheter 110 may include a stiff material selected to provide a low flow resistance (i.e., a low impedance to the inflation and deflation pressures during operation) as well as kink resistance. For example, in some variations the catheter may include a nylon material with a wall thickness of between 0.1 mm and 0.3 mm (e.g., 0.2 mm). Dedicated catheter material and dimension choices allow preservation of the radial shape, while being sufficiently flexible in the longitudinal direction. The shaft may have a high radial stiffness, achieved by high durometer material such as nylon 12 Pebax or polyimide of 72D or higher wall thickness, which may be reinforced with a braid or coil (e.g., wire or ribbon). The high durometer may, for example, help to facilitate rapid transport of helium. The durometer may vary over the shaft length to accommodate the curvature of the vasculature or ascending aorta.

[0227] Furthermore, in some variations the catheter 110 may include a thermally insulative coating layer over its exterior. This may help to maintain the (relative) low temperature of the inert fluid, such as helium, thereby giving it higher density and allowing higher flow velocities. Additionally or alternatively, the control system 2 (further described below) may be provided with an active cooling subsystem for controlling the temperature of the inert fluid delivered to the catheter 110 during operation. In some variations, the inflation fluid may be cooled and maintained at a temperature between -20 degrees Celsius and 20 degrees Celsius.

[0228] The catheter 110 and/or the pump body 120 may be configured to minimize vibration or oscillation when operated at high frequency. When fluid exits the pump body 120, the resulting thrust may lead to a force in the opposite direction, which is a counterforce that can potentially move the pump body 120 from its equilibrium position to a position deeper into the left ventricle. Once the pump stroke has been completed, the pump body 120 may seek to return into its equilibrium position, driven by the pull from the catheter 110 and the push from the distal tip of the circulatory assistance device 100. The size, geometry, and stiffness of balloon shaft 54 may be selected such that it acts to dampen this motion of the pump body 120. Further, by operating the volume displacement member 130 (e.g., balloon) at a sufficiently high frequency, the next pump stroke will happen before the pump body 120 has time to relax and return to its equilibrium position. In this case, the device will be "trapped" in a position away from its equilibrium position. The higher the frequency, the less time the pump body 120 has to move back towards its equilibrium position, and the more stable the device tip will be.

C. Control system

[0229] FIG. 6 shows a schematic diagram of details of an example control unit 2 of a circulatory assist system 10 according to the present technology. The control unit 2 may be configured to operate a balloon-style volume displacement member that is operable in an inflation phase and a deflation phase. For example, the control unit 2 may be configured to deliver an inflation fluid and regulate pumping parameters to provide the desired high blood flow rates from a very compact pump. The control unit may be configured to deliver any one or more selected inflation fluids at pressures and temperatures selected to allow cyclical expansion of the volume displacement member at a high frequency. For example, the control unit 2 may cyclically expand the volume displacement member 130 at a frequency of at least about 300 beats per minute, at least about 1000 beats per minute, at least about 1500 beats per minute, at least about 2000 beats per minute, at least about 2500 beats per minute, at least about 3000 beats per minute, at least about 5000 beats per minute, or between about 1000 beats per minute and about 10,000 beats per minute (e.g., between about 1500 and about 3,000 beats per minute). In some variations, the inert fluid may be a low viscosity fluid such as helium or carbon dioxide gas, to minimize friction with inside walls of the catheter assembly. Helium has the additional advantage of having a low density, therefore a lower mass inertia, allowing higher inflation frequencies.

[0230] In some variations, the control unit may allow user adjustment or tuning of the frequency of cyclical expansion of the volume displacement member so that an appropriate frequency can be selected by the user for a particular patient and procedure, or the frequency can be changed during a procedure according to the patient's needs. Additionally, the control unit 2 may allow for adjustment of the volume displaced by the volume displacement member (e.g., its volume in the fully contracted low-volume state, in the fully expanded high-volume state, or both). [0231 ] In some variations, the volume change of the volume displacement member may be generated by changing the pressure of the volume enclosed by volume displacement member, such as an inflatable balloon. This may be achieved by pressurizing and depressurizing the enclosed volume through the connecting inner lumen of the catheter shaft. Accordingly, in some variations, the control unit 2 may include a high-pressure pump arrangement 21, a low-pressure pump arrangement 22, and a switching arrangement 23 connected to the high-pressure source 21. The low-pressure pump arrangement 22, the catheter 110, and the switching arrangement 23 may be arranged to alternately connect the high- pressure source 21 and the low-pressure source 22 to the catheter assembly 3. This may allow the control unit 2 to use suitable hydraulic/pneumatic control components, with reliable and robust (bedside) operation. As shown in FIG. 6, the high-pressure source 21 may be implemented as a combination of a high-pressure buffer 2 Id, high pressure compressor 21a and regulator 21c (and optionally high-pressure sensor 21b). The low-pressure source 22 may be implemented as a combination of a vacuum buffer 22c, vacuum pump 22a and low-pressure sensor 22b. The switching arrangement 23 may be implemented as a combination of a 3 -way valve unit 23 d controlled via switch valve 23a using, e.g., a controller 23c. The controller 23c receives signals from the high-pressure sensor 21b, low pressure sensor 22b, and switch pressure sensor 23b, in order to properly drive the switch valve 23a. Connection to the catheter assembly 3 is implemented via a safety driver 24. To allow high frequency operation of the 3- way valve unit 23d, a valve design may be selected to have an optimal flow through the valve, with minimal turbulence, high switch speed and low leak rate.

[0232] In some variations, the control unit 2 may further include a safety driver 24 having a source side chamber 25 and a catheter side chamber 26 separated by a safety diaphragm 27. This may allow the use of a pneumatic/hydraulic part of the control unit 2, separated from an inert gas side part of the control unit 2, to be connected to the catheter assembly 3, minimizing the volume of inert gas needed in the heart assist system 100. The safety driver 24 accommodates the actuation of the inert gas circuit, by compressing and expanding the inert gas circuit at the catheter side chamber 26 of the safety driver 24. The actuation speed of the safety driver is sufficient to e.g., provide a pressure difference between +800 to -760 mmHg, in a volume of, e.g., 20 ml (typical range is 5-70ml) within 5-200ms.

[0233] In some variations, the control unit 2 may be arranged to connect the high- pressure pump arrangement 21 to the catheter 110 during an inflation phase and to connect to the low-pressure pump arrangement 22 during a deflation phase. This duty cycle may be altered with variable counterpressure. With higher counterpressure, there may be a need for more inflation time, while the deflation may be faster, when the environmental pressure also reduces the balloon volume.

[0234] The control unit 2 furthermore may be arranged to respond to sensor data or user input. For example, the control unit 2 may be responsive to certain sensed pressures (e.g., sensed left ventricular pressure, aortic pressure, etc.), or simply to create an additional pulsatile flow, by altering the speed of the inflation. For example, the control unit 2 may respond to ECG triggers by switching between a lower frequency (e.g., 300 beats per minute) and a higher frequency (e.g., 5000 beats per minute), operating the circulatory assist device 100 only during diastole or only during systole, or briefly pausing inflation or deflation at a specific detected moment in the cardiac cycle.

[0235] In some variations, the safety driver 24 (or safety chamber) may be sized relative to the total volume of the inert gas (e.g., helium) circuit. The safety diaphragm 27 may be movable so as to alter the volume of the inert gas circuit. For example, by moving the safety diaphragm 27 into the source side chamber 25, the total volume of the inert gas circuit can be enlarged, thus depressurizing the inert gas circuit. Furthermore, by moving the safety diaphragm 27 in the opposite direction, the total volume of the inert gas circuit may be reduced, and thereby pressurized. With this actuation, pressures can be obtained in the inert gas circuit of, for example, between 600mmHg and -600mmHg in a 130cm long catheter assembly 3 with a cross section area of, e.g., 3mm² in order to inflate and deflate the volume displacement member within 10 ms.

[0236] To further optimize the translation of pressure from the safety diaphragm 27 to the volume displacement member 130, the length of catheter assembly 3 can be minimized. Therefore, the safety diaphragm 27, and other components of the control unit 2 may be adapted to be included in a bedside control unit, such as by using external versions of the high-pressure source 21 and low-pressure source 22. The bedside control unit can then be mounted to the bed at a distance of 20-100 cm away, in some cases less than 30 cm away, from the vascular access site on the patient.

[0237] In some variations, as shown in FIG. 6, the inert gas circuit between the safety diaphragm 27 and the volume displacement member 130 may be provided with an inert gas pressure sensor 26b, the signal of which can be provided to the controller 23c for user information, driver control and/or failure detection functions. For example, in the control unit, a continuous check for the pressure waveforms may be applied, such as to detect a gas leak or kinking/obstruction of the catheter 110. For example, a pressure drop below a predetermined value may indicate a possible inert gas leak, in which case the circulatory assist device 100 may be stopped or switched to a vacuum/low pressure control mode. As another example, a pressure drop above a predetermined valve may indicate possible kinking of the catheter or other obstruction of flow in the catheter. Suitable alerts or notifications may be communicated to a user (e.g., on a display, audio alerts, etc.) to prompt suitable remedial actions. More advanced software may be used in the control unit to determine the ventricular pressure from the inert gas (balloon) pressure.

[0238] Furthermore, in some variations, the safety driver 24 may be cooled/heated (e.g., to about 10 degrees Celsius) in order to preserve the material properties, safety, and/or inert gas flow speed. As an alternative to this indirect temperature control of the inert fluid in the catheter 110 during operation, the inert fluid temperature may be controlled using an active fluid cooling subsystem. In some variations, the inert gas circuit may be provided with an automatic filling system. For example, to ensure stable helium concentration, every two hours (or periodically with an interval between 30 min and 4 hours) the helium system may be emptied and replaced with an automatic injection of a new volume of helium.

II. Methods of operation

[0239] In some variations, a method for providing circulatory assistance includes positioning a pump body in the circulatory system of a patient, where the pump body includes a conduit, an inlet valve configured to receive a fluid along a longitudinal flow axis of the conduit, a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase. In some variations, the pump body may be substantially similar to that described herein (e.g., pump body 120, such as with respect to FIG. 1 A, FIG. 4 A, FIG. 4B, and/or FIG. 4C). The method may further include cyclically operating the volume displacement member in the expansion phase and the contraction phase, and allowing received fluid to exit the conduit through the outlet during both the expansion phase and the contraction phase. Furthermore, in some variations, the method may include allowing the conduit to concurrently receive fluid through the inlet valve and convey fluid through the outlet, including but not limited to during the end of the expansion phase and during the end of the contraction phase. Additionally or alternatively, in some variations, the method may include conveying the received fluid to exit the conduit through the outlet at a volumetric flow rate that is greater than (Ve - Vc) * f where Vc is the volume of the volume displacement member in its contracted state (e.g., fully contracted state), Ve is the volume of the volume displacement member in its expanded state (e.g., fully expanded state), and f is a pump frequency at which the volume displacement member is operable between the contracted and expanded states. In some variations, this enhanced volumetric flow rate outputted by the pump body may be possible when the volume displacement member is operated at a frequency f of at least about 5 Hz (e.g., an inflation or expansion time of about 0.1s).

(0240] For example, in some variations (e.g., as shown in FIG. IB), the method may include positioning at least a portion of the pump body in a left ventricle of the patient. For example, a distal portion of the pump body (e.g., including an inflow region 120a of the pump body) may be positioned in the left ventricle of the patient and a proximal portion of the pump body (e.g., including an outflow region 120c of the pump body) in an ascending aorta of the patient. Accordingly, in this example, the pump body may be positioned through or across the aortic valve of the patient. As another example, in some variations, the method may include positioning the pump body in a blood vessel of the patient (e.g., aorta). Cyclical operation of the volume displacement member in the expansion phase and the contraction phase may, in some variations in which the volume displacement member is a balloon, be substantially similar to that described herein with respect to cyclically inflating the balloon via a catheter having an inflation lumen (e.g., described herein with respect to FIG. 6).

III. Examples

[0241] FIG. 8 illustrates an example experimental setup 80 of a mock circulatory assist device 800 in accordance with the present technology. Fluid flow in the circulatory assist device 800 is directed left-to-right in the direction denoted with arrow (F). Similar to the circulatory assist devices described herein (e.g., circulatory assist devices 100, 300), the mock device 800 includes a pump body 820 having an inflow region 820a with an inlet valve 840 arranged therein, an outflow region 820c, and an intermediate region 820b between the inflow region 820a and the outflow region 820c. A balloon 830 is arranged in the intermediate region 820b of the pump body 820, and is connected via a catheter to a helium pump (not shown) that is operable to cyclically inflate and deflate the balloon 830. The pump body 820 in this mock device 800 includes a rigid polymer pipe that is coupled to a fixture and in fluidic communication with a fluid pump (not shown) for receiving fluid. A distal pressure port 860a is fitted with a pressure sensor configured to measure the pressure in the pump body 820 between the inlet valve 840 and the balloon 830. A proximal pressure port 860b is fitted with a pressure sensor configured to measure the pressure in the pump body 820 between the balloon 830 and the outlet of the pump body 820.

[0242] FIG. 9 depicts a de-noised plot of pressure patterns in the circulatory assist system including the mock circulatory assist device 800 described above with respect to FIG. 8, over time across various phases of device operation when the balloon 830 is cyclically inflated and deflated. Specifically, FIG. 9 illustrates variance in pressure at the distal pressure port 860a (“distal pressure”), pressure at the proximal pressure port 860b (“proximal pressure”), and pressure within the catheter (“catheter (He)”) as measured at a proximal portion of the catheter near the helium pump. Also pictured in the plot of FIG. 9 is an overlay of volumetric flow through the pump body 820 over time as the balloon 830 is cyclically inflated and deflated. In general, there may be a phase shift between the catheter pressure signal and the balloon inflation/deflation cycle, corresponding to a time lag associated with travel time of helium to inflate or deflate the balloon 830. For example, maximum balloon inflation may occur some time even after catheter pressure begins to decrease, while maximum balloon deflation may occur some time even after catheter pressure begins to increase. Various specific timepoints in the phases of device operation are labeled as timepoints (a) through (e) and are described below.

[0243] Timepoint (a) generally corresponds to the state of the circulatory assist device 800 similar to that shown in FIG. 7A, where the balloon 830 is in the process of being inflated (indicated by a rising catheter pressure). Continued inflation of the balloon 830 pushes fluid both distally toward the inlet (thereby causing an increase in distal pressure) and proximally toward the outlet (thereby causing an increase in proximal pressure). As the balloon 830 continues to inflate, an increase in the fluid flow out of the outlet is seen. In other words, fluid momentum in a flow direction along the axis of the flow body 820 is created and maintained as the balloon 830 inflates.

[0244] Timepoint (b) generally corresponds to the state of the circulatory assist device 800 similar to that shown in FIG. 7B, where the inlet valve 840 has closed as a result of distal pressure above a threshold value. At timepoint (b), the catheter pressure has its peak positive value for balloon inflation, and the distal pressure is at or near its respective peak positive value while the distal inlet valve 840 is closed. With the distal inlet valve 840 closed and balloon 830 fully inflated, momentum further carries fluid to exit the pump body 820 through the outlet. [0245] Timepoint (c) generally corresponds to the state of the circulatory assist device 800 similar to that shown in FIG. 7C, where fluid momentum results in negative pressure within the pump body 820 (including both distal pressure and proximal pressure). The catheter has ceased to supply inflation fluid to the balloon 830 and is about to begin deflation, as seen by the drop in catheter pressure at timepoint (c). In response to the negative pressure and in view of the continued fluid momentum within the pump body 820, the inlet valve 840 opens.

[0246] Timepoint (d) generally corresponds to the state of the circulatory assist device 800 similar to that shown in FIG. 7D, where additional fluid is pulled into the pump body 820 through the open inlet valve 840 as the balloon deflates. At timepoint (d), fluid flow through the pump body 820 may be near its peak. While the balloon 830 continues to deflate following timepoint (d), outflow through the pump body 820 continues, but may be with reduced fluid momentum as additional fluid is pulled into the pump body 820 under negative distal and proximal pressure.

[0247] Timepoint (e) generally corresponds to the state of the circulatory assist device 800 similar to that shown in FIG. 7E, where the balloon 830 is fully deflated (indicated by a minimum catheter pressure). Following timepoint (e), the inflation phase of the balloon 830 begins again, causing distal and proximal pressure to rise as fluid is displaced. The pressure and flow cycle continue as the balloon 830 is inflated, returning to timepoint (a) as described above.

[0248] FIG. 10 depicts a plot of measured pump output (L/min) of various example mock circulatory assist devices having different pump body lengths (e.g., different lengths of outflow region). The example mock circulatory assist devices are similar to the mock circulatory assist device 800 described above with respect to FIG. 8, except with varying lengths. Specifically, three different lengths of a 12 mm-diameter pump body for the mock circulatory assist device were tested: 90 mm length, 180 mm, and 270 mm. Each mock circulatory assist device 800 was controlled to operate at a variety of pumping frequencies (i.e., variety of frequencies at which the balloon 830 was cyclically inflated and deflated) between about 1000 beats per minute and about 1800 beats per minute, and the resulting pump output was measured across these frequencies for each device.

[0249] As shown in FIG. 10, it was observed that pump output of the pump body generally increases when the length of the pump body increases, at least for all observed operating frequencies of at least about 1000 beats per minute. For example, in the test set-up used, pump output for the 90 mm length pump body (“lx length”) was generally between about 2 L/min and about 3 L/min, while the pump output for the 180 mm length pump body (“2x length”) was generally higher at between about 3 L/min and about 4 L/min. Pump output for the 270 mm length pump body (“3x length”) was generally the highest of the three devices, with a pump output of at least about 4 L/min. Accordingly, this example indicates that a longer pump body (e.g., a longer outflow nozzle) may help increase the outflow and pumping capabilities of a circulatory assist device including such a longer pump body.

Conclusion

[0250] Although many of the variations are described above with respect to systems, devices, and methods for circulatory assistance, the technology is applicable to other applications and/or other approaches. Moreover, other variations in addition to those described herein are within the scope of the technology. Additionally, several other variations of the technology can have different configurations, components, or procedures than those described herein. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other variations with additional elements, or the technology can have other variations without several of the features shown and described above with reference to FIGS. 1A-13.

[0251] The descriptions of variations of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform steps in a different order. The various variations described herein may also be combined to provide further variations.

[0252] As used herein, the terms “generally,” “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent variations in measured or calculated values that would be recognized by those of ordinary skill in the art.

[0253] Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term "comprising" is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. It will also be appreciated that specific variations have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with certain variations of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all variations need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other variations not expressly shown or described herein.

Claims

CLAIMS I/We claim:

1. A blood pump system comprising: a pump body comprising: a conduit having an inlet, an outlet, and a longitudinal flow axis extending between the inlet and the outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive blood into the conduit substantially along the flow axis, wherein the pump body is configured to convey the received blood through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase.

2. The system of claim 1, wherein the portion of the conduit between the volume displacement member and the outlet is valveless.

3. The system of claim 1 or 2, wherein the outlet of the conduit comprises a valve.

4. The system of any one of claims 1-3, wherein the conduit comprises a membrane.

5. The system of any one of claims 1-4, wherein the conduit further comprises an expandable support, wherein the membrane is adjacent to a surface of the expandable support.

6. The system of claim 5, wherein the expandable support is self-expandable.

7. The system of any one of claims 1-6, wherein the conduit comprises a distal inflow region comprising the inlet, a proximal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

8. The system of any one of claims 1-6, wherein the conduit comprises a proximal inflow region comprising the inlet, a distal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

9. The system of claim 7 or 8, wherein the conduit comprises a membrane covering at least a portion of the intermediate region.

10. The system of claim 9, wherein the membrane covers a portion of the inflow region.

11. The system of claim 10, wherein the covered portion of the inflow region is flared radially outward.

12. The system of claim 10, wherein the covered portion of the inflow region is tapered radially inward.

13. The system of any one of claims 10-12, wherein the inlet valve is arranged inside the covered portion of the inflow region.

14. The system of any one of claims 9-13, wherein the membrane covers a portion of the outflow region.

15. The system of claim 14, wherein the covered portion of the outflow region is flared radially outward.

16. The system of claim 14, wherein the covered portion of the outflow region is tapered radially inward.

17. The system of any one of claims 7-16, wherein at least one of the inflow region or the outflow region has a maximum diameter larger than a diameter of the intermediate region.

18. The system of any one of claims 7-17, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

19. The system of any one of claims 7-16, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

20. The system of any one of claims 7-18, wherein the inlet valve is arranged in the conduit between the inlet and the volume displacement member.

21. The system of any one of claims 7-20, wherein the intermediate region is tubular.

22. The system of any one of claims 1-21, wherein the inlet valve is configured to convey the received blood to a volume in the conduit outside of the volume displacement member.

23. The system of any one of claims 1-22, wherein the inlet valve is a one-way valve.

24. The system of claim 23, wherein the one-way valve comprises a multi-leaflet valve.

25. The system of any one of claims 1-24, wherein the volume displacement member comprises a balloon.

26. The system of any one of claims 1-25, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a total member volume in the expansion phase, and wherein a distal portion of the member volume ranging between up to about 5% and about 50% of the total member volume is located along a distalmost third of the conduit length.

27. The system of any one of claims 1-26, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a member length extending along the flow axis, and wherein a distal portion of the member length ranging between about the distalmost 5% of the member length and about the distalmost 15% of the member length is located along a distalmost third of the conduit length.

28. The system of any one of claims 1-27, further comprising: an inflation member in fluidic communication with the volume displacement member; and a pump configured to operate the balloon in the expansion phase and the contraction phase via the inflation member.

29. The system of claim 28, wherein the pump is configured to transition the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

30. The system of any one of claims 1-29, wherein the pump body is configured to convey received blood through the outlet at least partially via momentum of the blood during both the expansion phase and the contraction phase.

31. The system of any one of claims 1-30, wherein the pump body is configured to convey blood through the outlet with a flow rate of at least about 5 L/min.

32. A method comprising: positioning a pump device in the circulatory system of a patient, the pump device comprising: a pump body comprising: a conduit having an inlet, an outlet, and a longitudinal flow axis extending between the inlet and the outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive a fluid into the conduit substantially along the flow axis; cyclically operating the volume displacement member in the expansion phase and the contraction phase; and allowing received fluid to exit the conduit through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase.

33. The method of claim 32, wherein positioning the pump device comprises positioning at least a portion of the pump body in a left ventricle of the patient.

34. The method of claim 32 or 33, wherein positioning the pump device comprises positioning a distal portion of the pump body in the left ventricle and a proximal portion of the pump body in an aorta of the patient.

35. The method of any one of claims 32-34, wherein positioning the pump device comprises positioning a majority of the pump body in the left ventricle of the patient.

36. The method of claim 32, wherein positioning the pump comprises positioning a proximal portion of the pump body in the right ventricle and a distal portion of the pump body in a pulmonary artery of the patient.

37. The method of claim 32, wherein positioning the pump device comprises positioning the entire pump body in a blood vessel.

38. The method of any one of claims 32-37, wherein the volume displacement member comprises a balloon.

39. The method of claim 38, wherein cyclically operating the balloon in the expansion phase and the contraction phase comprises controlling fluid flow in a catheter fluidically coupled to the balloon.

40. The method of any one of claims 32-39, wherein cyclically operating the volume displacement member comprises transitioning the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

41. The method of any one of claims 32-40, wherein the method comprises allowing received fluid to exit the conduit through the outlet at least partially via momentum during both the expansion phase and the contraction phase.

42. The method of any one of claims 32-41, wherein the portion of the conduit between the volume displacement member and the outlet is valveless.

43. The method of any one of claims 32-42, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter larger than a diameter of an intermediate region extending between the inflow region and the outflow region.

44. The method of claim 43, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

45. The method of any one of claims 32-44, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

46. A blood pump system comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive blood into the conduit, wherein the pump body is configured to convey the received blood through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase, and wherein the portion of the conduit between the volume displacement member and the outlet is valveless.

47. The system of claim 46, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during the entire expansion phase and the entire contraction phase.

48. The system of claim 46 or 47, wherein the conduit comprises a membrane.

49. The system of any one of claims 46-48, wherein the conduit further comprises an expandable support, wherein the membrane is adjacent to a surface of the expandable support.

50. The system of any one of claims 46-49, wherein the conduit comprises a distal inflow region comprising the inlet, a proximal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

51. The system of any one of claims 46-49, wherein the conduit comprises a proximal inflow region comprising the inlet, a distal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

52. The system of claim 50 or 51, wherein the conduit comprises a membrane covering at least a portion of the intermediate region.

53. The system of claim 52, wherein the membrane covers a portion of the inflow region.

54. The system of claim 53, wherein the covered portion of the inflow region is flared radially outward.

55. The system of claim 53, wherein the covered portion of the inflow region is tapered radially inward.

56. The system of any one of claims 53-55, wherein the inlet valve is arranged inside the covered portion of the inflow region.

57. The system of any one of claims 52-56, wherein the membrane covers a portion of the outflow region.

58. The system of claim 57, wherein the covered portion of the outflow region is flared radially outward.

59. The system of claim 57, wherein the covered portion of the outflow region is tapered radially inward.

60. The system of any one of claims 50-59, wherein at least one of the inflow region or the outflow region has a maximum diameter larger than a diameter of the intermediate region.

61. The system of any one of claims 50-60, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

62. The system of any one of claims 50-59, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

63. The system of any one of claims 50-62, wherein the inlet valve is arranged in the conduit between the inlet and the volume displacement member.

64. The system of any one of claims 50-63, wherein the intermediate region is tubular.

65. The system of any one of claims 46-64, wherein the inlet valve is configured to convey the received blood to a volume in the conduit outside of the volume displacement member.

66. The system of any one of claims 46-65, wherein the inlet valve is a one-way valve.

67. The system of any one of claims 46-66, wherein the volume displacement member comprises a balloon.

68. The system of any one of claims 46-67, wherein the conduit has a conduit length extending along the flow axis and the volume displacement member has a total member volume in the expansion phase, and wherein a distal portion of the member volume ranging between about 5% and about 50% of the total member volume is located along a distalmost third of the conduit length.

69. The system of any one of claims 46-68, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a member length extending along the flow axis, and wherein a distal portion of the member length ranging between about the distalmost 5% of the member length and about the distalmost 15% of the member length is located along a distalmost third of the conduit length.

70. The system of any one of claims 46-69, further comprising: an inflation member in fluidic communication with the volume displacement member; and a pump configured to operate the balloon in the expansion phase and the contraction phase via the inflation member.

71. The system of claim 70, wherein the pump is configured to transition the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

72. The system of any one of claims 46-71, wherein the pump body is configured to convey received blood through the outlet at least partially via momentum of the blood during both the expansion phase and the contraction phase.

73. The system of any one of claims 46-72, wherein the pump body is configured to convey blood through the outlet with a flow rate of at least about 5 L/min.

74. A method comprising: positioning a pump device in the circulatory system of a patient, the pump device comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit and operable in an expansion phase and a contraction phase; and an inlet valve configured to receive fluid into the conduit, wherein the portion of the conduit between the volume displacement member and the outlet is valveless; cyclically operating the volume displacement member in the expansion phase and the contraction phase; and allowing received fluid to exit the conduit through the outlet during at least a portion of the expansion phase and at least a portion of the contraction phase.

75. The method of claim 74, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during the entire expansion phase and the entire contraction phase.

76. The method of claim 74 or 75, wherein positioning the pump device comprises positioning at least a portion of the pump body in a left ventricle of the patient.

77. The method of any one of claims 74-76, wherein positioning the pump device comprises positioning a distal portion of the pump body in the left ventricle and a proximal portion of the pump body in an aorta of the patient.

78. The method of any one of claims 74-76, wherein positioning the pump device comprises positioning a majority of the pump body in the left ventricle of the patient.

79. The method of any one of claims 74-76, wherein positioning the pump device comprises positioning a proximal portion of the pump body in the right ventricle and a distal portion of the pump body in a pulmonary artery of the patient.

80. The method of claim 74 or 75, wherein positioning the pump device comprises positioning the entire pump body in a blood vessel.

81. The method of any one of claims 74-80, wherein the volume displacement member comprises a balloon.

82. The method of claim 81, wherein cyclically operating the balloon in the expansion phase and the contraction phase comprises controlling fluid flow in a catheter fluidically coupled to the balloon.

83. The method of any one of claims 74-82, wherein cyclically operating the volume displacement member comprises transitioning the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

84. The method of any one of claims 74-83, wherein the method comprises allowing received fluid to exit the conduit through the outlet at least partially via momentum during both the expansion phase and the contraction phase.

85. The method of any one of claims 74-84, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter larger than a diameter of an intermediate region extending between the inflow region and the outflow region.

86. The method of claim 85, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

87. The method of any one of claims 74-84, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

88. A blood pump system comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit having a first member volume Vc in a contracted state and a second member volume Ve in an expanded state, wherein the volume displacement member is operable between the contracted and expanded states at a pump frequency /; and an inlet valve configured to receive blood into the conduit, wherein the pump body is configured to convey the received blood through the outlet at a volumetric flow rate that is greater than (Ve - Vc) */when /is greater than about 5 Hz.

89. The system of claim 88, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during an entire expansion phase and an entire contraction phase of the volume displacement member.

90. The system of claim 88 or 89 wherein the conduit comprises a membrane.

91. The system of any one of claims 88-90, wherein the conduit further comprises an expandable support, wherein the membrane is adjacent to a surface of the expandable support.

92. The system of any one of claims 88-91, wherein the conduit comprises a distal inflow region comprising the inlet, a proximal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

93. The system of any one of claims 88-91, wherein the conduit comprises a proximal inflow region comprising the inlet, a distal outflow region comprising the outlet, and an intermediate region extending between the inflow region and the outflow region.

94. The system of claim 92 or 93, wherein the conduit comprises a membrane covering at least a portion of the intermediate region.

95. The system of claim 94, wherein the membrane covers a portion of the inflow region.

96. The system of claim 95, wherein the covered portion of the inflow region is flared radially outward.

97. The system of claim 95 wherein the covered portion of the inflow region is tapered radially inward.

98. The system of any one of claims 95-97, wherein the inlet valve is arranged inside the covered portion of the inflow region.

99. The system of any one of claims 94-98, wherein the membrane covers a portion of the outflow region.

100. The system of claim 99, wherein the covered portion of the outflow region is flared radially outward.

101. The system of claim 99, wherein the covered portion of the outflow region is tapered radially inward.

102. The system of any one of claims 92-101, wherein at least one of the inflow region or the outflow region has a maximum diameter larger than a diameter of the intermediate region.

103. The system of any one of claims 92-102, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

104. The system of any one of claims 92-101, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.

105. The system of any one of claims 92-104, wherein the inlet valve is arranged in the conduit between the inlet and the volume displacement member.

106. The system of any one of claims 88-105, wherein the intermediate region is tubular.

107. The system of any one of claims 88-106, wherein the inlet valve is configured to convey the received blood to a volume in the conduit outside of the volume displacement member.

108. The system of any one of claims 88-107, wherein the inlet valve is a one-way valve.

109. The system of any one of claims 88-108, wherein the volume displacement member comprises a balloon.

110. The system of any one of claims 88-109, wherein the conduit has a conduit length extending along the flow axis and the volume displacement member has a total member volume in the expansion phase, and wherein a distal portion of the member volume ranging between about 5% and about 50% of the total member volume is located along a distalmost third of the conduit length.

111. The system of any one of claims 88-110, wherein the conduit has a conduit length extending along the flow axis, and the volume displacement member has a member length extending along the flow axis, and wherein a distal portion of the member length ranging between about the distalmost 5% of the member length and about the distalmost 15% of the member length is located along a distalmost third of the conduit length.

112. The system of any one of claims 88-111, further comprising: an inflation member in fluidic communication with the volume displacement member; and a pump configured to operate the balloon in the expansion phase and the contraction phase via the inflation member.

113. The system of claim 112, wherein the pump is configured to transition the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

114. The system of any one of claims 88-113, wherein the pump body is configured to convey blood through the outlet with a flow rate of at least about 5 L/min.

115. A method comprising: positioning a pump device in the circulatory system of a patient, the pump device comprising: a pump body comprising: a conduit having an outlet; a volume displacement member arranged in the conduit having a first member volume Vc in a contracted state and a second member volume Ve in an expanded state; and an inlet valve configured to receive blood into the conduit; cyclically operating the volume displacement member between the contracted state and the expanded state at a pump frequency/; and conveying the received fluid to exit the conduit through the outlet at a volumetric flow rate that is greater than (Ve - Vc) * f.

116. The method of claim 115, wherein is at least about 5 Hz.

117. The method of claim 115 or 116, wherein the portion of the conduit between the volume displacement member and the outlet is open to fluid flow through the outlet during an entire expansion phase and an entire contraction phase of the volume displacement member.

118. The method of any one of claims 115-117, wherein positioning the pump device comprises positioning at least a portion of the pump body in a left ventricle of the patient.

119. The method of any one of claims 115-118, wherein positioning the pump device comprises positioning a distal portion of the pump body in the left ventricle and a proximal portion of the pump body in an aorta of the patient.

120. The method of any one of claims 115-119, wherein positioning the pump device comprises positioning a majority of the pump body in the left ventricle of the patient.

121. The method of any one of claims 115-118, wherein positioning the pump device comprises positioning a proximal portion of the pump body in the right ventricle and a distal portion of the pump body in a pulmonary artery of the patient.

122. The method of any one of claims 115-117, wherein positioning the pump device comprises positioning the entire pump body in a blood vessel.

123. The method of any one of claims 115-122, wherein the volume displacement member comprises a balloon.

124. The method of claim 123, wherein cyclically operating the balloon in the expansion phase and the contraction phase comprises controlling fluid flow in a catheter fluidically coupled to the balloon.

125. The method of any one of claims 115-124, wherein cyclically operating the volume displacement member comprises transitioning the volume displacement member between the expansion phase and the contraction phase at a frequency of between about 300 beats per minute and about 5000 beats per minute.

126. The method of any one of claims 115-125, wherein the method comprises allowing received fluid to exit the conduit through the outlet at least partially via momentum during both the expansion phase and the contraction phase.

127. The method of any one of claims 115-126, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter larger than a diameter of an intermediate region extending between the inflow region and the outflow region.

128. The method of claim 127, wherein the inflow region, the outflow region, or both the inflow region and the outflow region have a bulbous shape.

129. The method of any one of claims 115-128, wherein the pump body has at least one of an inflow region or an outflow region having a maximum diameter equal to or smaller than a diameter of an intermediate region extending between the inflow region and the outflow region.