WO2025019369A1

WO2025019369A1 - Devices, systems, and methods for treating volume overload

Info

Publication number: WO2025019369A1
Application number: PCT/US2024/037918
Authority: WO
Inventors: Ankit Garg; Kevin BUI; Stacie ARECHAVALA; Jesus Magana; John Morriss; Bernard Andreas
Original assignee: Leland Stanford Junior University
Current assignee: Leland Stanford Junior University
Priority date: 2023-07-14
Filing date: 2024-07-12
Publication date: 2025-01-23
Anticipated expiration: 2026-01-14

Abstract

Devices, systems, and methods for treating volume overload are disclosed herein. According to some examples, the present technology includes a method comprising delivering a distal portion of an elongate shaft to a treatment site within a vein of an upper chest of a patient, where the treatment site is between a superior vena cava and a left axillary vein. The method can include expanding an occlusive member at the treatment site proximal of an opening to a thoracic duct, thereby blocking blood flow proximal of the occlusive member. The method can further include injecting a contrast agent at the treatment site distal of the occlusive member such that the contrast agent flows retrograde into the thoracic duct.

Description

DEVICES, SYSTEMS, AND METHODS FOR TREATING VOLUME OVERLOAD

CROSS-REFERENCE TO RELATED APPLICATION(S)

[000.1] The present application claims the benefit of priority to U.S. Provisional Application No. 63/513,748, titled SYSTEMS AND METHODS FOR IMPROVING LYMPHATIC DRAINAGE CAPACITY TO TREAT VOLUME OVERLOAD, filed July 14, 2023, and U.S. Provisional Application No. 63/582,842, filed September 14, 2023, both of which are incorporated by reference herein in their entireties.

TECHNICAL FIELD

[0002] The present technology relates to devices, systems, and methods for treating volume overload. In particular, the present technology is directed to treating volume overload by improving lymphatic system drainage.

BACKGROUND

[0003] Chronic and acute congestive heart failure (CHF) generally occurs when the heart is incapable of circulating an adequate blood supply to the body. This is typically due to inadequate cardiac output, which has many causes. In CHF decompensation fluids back up in a retrograde direction through the lungs and venous/lymphatic systems throughout the body, causing discomfort and organ dysfunction. Many diseases can impair the pumping efficiency of the heart to cause CHF, such as coronary artery disease, high blood pressure, and heart valve disorders.

[0004] In addition to fatigue, one of the prominent features of CHF is the retention of fluids within the body. Commonly, gravity causes the retained fluid to accumulate to the lower body, including the abdominal cavity, liver, and other organs, resulting in numerous related complications. Fluid restriction and a decrease in salt intake can be helpful to manage the fluid retention, but diuretic medications are the principal therapeutic option, including furosemide, bumetanide, and hydrochlorothiazide. Additionally, vasodilators and inotropes may also be used for treatment.

[0005] While diuretics can be helpful, they are also frequently toxic to the kidneys and if not used carefully can result in acute and/or chronic renal failure. This mandates careful medical management while in a hospital, consuming large amounts of time and resources. Hence, the ability to treat fluid retention from CHF without the need for toxic doses of diuretics would likely result in better patient outcomes at substantially less cost.

[0006] Fluid retention is not limited only to CHF. Conditions such as organ failure, cirrhosis, hepatitis, cancer, and infections can cause fluid buildup near the lungs, referred to as pleural effusion. The space is lined by two thin membranes (the visceral and parietal pleura) that line the surface of the lungs and the inside of the chest wall. Normally, only a few teaspoons of fluid are located in this space so as to help the lungs to move smoothly in a patient's chest cavity, but underlying diseases can increase this amount. Patients with pleural effusion may need frequent draining directly via a guided needle and catheter introduced directly to the pleura. These procedures are expensive, traumatic, and require hospitalization. [0007] Accordingly, there is a need for improved treatments for fluid buildup in the body.

SUMMARY

[0008] The subj ect technology is illustrated, for example, according to various aspects described below, including with reference to FIGS. 1A-13. Various examples of aspects of the subject technology are described as numbered clauses (1, 2, 3, etc.) for convenience. These are provided as examples and do not limit the subject technology.

1. A method for treating volume overload, the method comprising: delivering a distal portion of an elongate shaft to a treatment site within a vein of an upper chest of a patient, wherein the treatment site is between a superior vena cava and a left axillary vein; expanding an occlusive member at the treatment site proximal of an opening to a thoracic duct, thereby blocking blood flow proximal of the occlusive member; and injecting a contrast agent at the treatment site distal of the occlusive member such that the contrast agent flows retrograde into the thoracic duct.

2. The method of Clause 1 , further comprising visualizing the thoracic duct under an imaging modality after injecting the contrast agent at the treatment site.

3. The method of Clause 2, wherein the imaging modality is fluoroscopy.

4. The method of Clause 2, further comprising advancing an elongate member into the thoracic duct after visualizing the thoracic duct. 5. The method of any one of the previous Clauses, further comprising expanding an implant within at least a portion of the thoracic duct.

6. The method of any one of the previous Clauses, further comprising dilating the thoracic duct after visualizing the thoracic duct.

7. The method of any one of the previous Clauses, further comprising dilating the thoracic duct.

8. The method of any one of the previous Clauses, wherein the method further comprises monitoring the pressure within the thoracic duct to guide dilation of the thoracic duct.

9. The method of any one of the previous Clauses, wherein the treatment site is a first treatment site, and wherein the method further comprises: collapsing the occlusive member, advancing the elongate shaft distally to a second treatment site, wherein the first treatment site is along a left brachiocephalic vein and the second treatment site is along a left subclavian vein, expanding the occlusive member at second treatment site, and injecting a contrast agent at the second treatment site distal of the occlusive member such that the contrast agent flows retrograde into the thoracic duct.

10. The method of any one of the previous Clauses, wherein the occlusive member is a first occlusive member expanded in the left brachiocephalic vein, and wherein the method further comprises expanding a second occlusive member in a left subclavian vein.

11. The method of Clause 10, wherein the second occlusive member is carried by the distal portion of the elongate shaft.

12. The method of Clause 10, wherein the elongate shaft is a first elongate shaft, and wherein the second occlusive member is carried by the second elongate shaft.

13. The method of Clause 10, further comprising expanding a third occlusive member in the internal jugular vein.

14. The method of any one of the previous Clauses, wherein the treatment site is a first treatment site, and wherein the method further comprises: collapsing the occlusive member, advancing the elongate shaft distally to a second treatment site, wherein the first treatment site is along a left brachiocephalic vein and the second treatment site is along a left internal jugular vein, expanding the occlusive member at a second treatment site, and injecting a contrast agent at the second treatment site distal of the occlusive member such that the contrast agent flows retrograde into the thoracic duct.

15. The method of any one of the previous Clauses, wherein the occlusive member is a first occlusive member expanded in the left brachiocephalic vein, and wherein the method further comprises expanding a second occlusive member in a left internal jugular vein.

16. The method of Clause 15, wherein the second occlusive member is carried by the distal portion of the elongate shaft.

17. The method of Clause 15, wherein the elongate shaft is a first elongate shaft, and wherein the second occlusive member is carried by the second elongate shaft.

18. The method of Clause 1, wherein the occlusive member is shaped such that injection of the contrast agent is localized to a lymphovenous junction.

19. The method of any one of the previous Clauses, wherein the occlusive member comprises multiple lobes.

20. The method of any one of the previous Clauses, wherein the occlusive member is shaped such that, when expanded at the treatment site, the occlusive member has a first portion positioned in a left brachiocephalic vein and a second portion positioned in a left internal jugular vein.

21. The method of Clause 1, wherein the occlusive member is shaped such that, when expanded at the treatment site, the occlusive member has a first portion positioned in a left brachiocephalic vein and a second portion positioned in a left subclavian vein.

22. The method of any one of the previous Clauses, wherein the occlusive member is shaped such that, when expanded at the treatment site, the occlusive member has a first portion positioned in a left brachiocephalic vein, a second portion positioned in a left internal jugular vein, and a third portion positioned in a left subclavian vein.

23. A method for treating volume overload, the method comprising: delivering a distal end portion of an elongate shaft to a treatment site within a vein of an upper chest of a patient, where the treatment site is between a superior vena cava and a left axillary vein; creating a localized pressure gradient at the treatment site proximal of an opening to a thoracic duct, thereby blocking blood flow proximal of the occlusive member; and injecting a contrast agent at the treatment site distal of the occlusive member such that the contrast agent flows retrograde into the thoracic duct.

24. A method comprising: positioning a first pressure sensor within the thoracic duct of a patient; positioning a second pressure sensor within a vein of a patient at a location proximate the lymphovenous junction (LVJ); measuring a pressure within the thoracic duct via the first pressure sensor; while measuring the pressure in the thoracic duct, measuring a pressure within the vein via the second pressure sensor; determining a difference between the thoracic duct pressure and the venous pressure; and based on the difference, determining whether the patient is a candidate for receiving a thoracic duct implant and/or dilation of the thoracic duct.

25. The method of Clause 24, wherein the vein is one of a brachiocephalic vein, a subclavian vein, an external jugular vein, or an internal jugular vein.

26. The method of Clause 24 or Clause 25, wherein the pressures within the thoracic duct and the vein are measured over a time period inclusive of at least one respiratory cycle.

27. The method of any one of Clauses 24 to 26, wherein determining a difference between the thoracic duct pressure and the venous pressure includes determining a difference between the thoracic duct pressure and the venous pressure during an inspiration phase of the respiratory cycle.

28. The method of any one of Clauses 24 to 27, wherein positioning the first pressure sensor within the thoracic duct comprises advancing the first pressure sensor retrograde through the venous system and crossing the ostium at the LVJ into the thoracic duct.

29. The method of Clause 28, wherein the first pressure sensor is carried by an elongate member, and wherein the method further comprises advancing an access shaft retrograde through the venous system and into the thoracic duct, and wherein the elongate member is advanced through the access shaft into the thoracic duct.

30. The method of Clause 29, wherein the access shaft has a tapered distal tip.

31. The method of Clause 28 or Clause 29, wherein the access shaft is advanced through a support shaft having a distal end disposed in the vein, proximate the LVJ. 32. The method of any one of Clauses 24 to 31, wherein positioning the second pressure sensor within the thoracic duct comprises advancing the second pressure sensor retrograde through the venous system to a location proximate the LVJ.

33. The method of any one of Clauses 24 to 32, wherein the first and second pressure sensors are disposed on the same device.

34. The method of any one of Clauses 24 to 32, wherein the first and second pressure sensors are disposed on different devices.

35. The method of Clause 34, wherein the first pressure sensor is carried by a pressure wire, and wherein the second pressure sensor is carried by an access shaft.

36. The method of Clause 34, wherein the first pressure sensor is carried by a pressure wire, and wherein the second pressure sensor is carried by a support shaft.

37. The method of any one of Clauses 24 to 36, wherein determining a difference between the thoracic duct pressure and the venous pressure comprises determining whether a difference between the thoracic duct pressure and the venous pressure is greater than zero, and based on the difference being greater than zero, determining that the patient is a candidate for receiving a thoracic duct implant and/or a procedure for dilating the thoracic duct.

38. A method for treating volume overload, comprising: positioning a distal portion of a delivery system within the thoracic duct, wherein the delivery system includes an implant in a compressed state; expanding a proximal portion of the implant into apposition with an inner surface of the thoracic duct ostium, thereby dilating the ostium and anchoring the implant; after expanding the proximal portion of the implant, expanding a distal portion of the implant into apposition with an inner surface of the thoracic duct; withdrawing the delivery system, thereby leaving the implant implanted within the thoracic duct.

39. The method of Clause 38, wherein the delivery system is advanced through the venous system to the thoracic duct.

40. The method of Clause 38 or Clause 39, wherein the delivery system is advanced retrograde through the venous system to the thoracic duct.

41. The method of any one of Clauses 38 to 40, wherein the delivery system is advanced through the venous system to the thoracic duct over a guidewire. 42. The method of any one of Clauses 38 to 41, wherein the implant is a an open-form scaffold.

43. A method for treating volume overload, comprising: advancing an occlusion device to the lymphovenous junction (LVJ) and occluding a portion of a vein proximate the LVJ while infusing contrast to visualize the thoracic duct; performing a lymphatic flow reserve assessment; implanting an implant within the ostium of the thoracic duct, wherein the implant is advanced through the venous system and into the thoracic duct.

44. The method of Clause 43, wherein performing a lymphatic flow reserve assessment includes advancing a pressure sensing device retrograde through the venous system into the thoracic duct.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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.

[0010] FIGS. 1A-1D illustrate common anatomical variations in the location of the lymphovenous junction in accordance with the present technology.

[0011] FIG. 1.5 shows a method in accordance with several examples of the present technology.

[0012] FIG. 2A shows a perspective view of a support assembly configured in accordance with several examples of the present technology.

[0013] FIG. 2B is an axial cross-sectional view of the support assembly shown in FIG. 2 A, taken along line 2B-2B.

[0014] FIG. 3A is a side view of an implant configured in accordance with several examples of the present technology.

[0015] FIG. 3B is an enlarged view of a portion of the implant shown in FIG. 3 A.

[0016] FIG. 3 C is an enlarged view of a distal portion of an implant configured in accordance with several examples of the present technology.

[0017] FIG. 3D is an enlarged view of a distal portion of an implant configured in accordance with several examples of the present technology. [0018] FIG. 4 is a delivery assembly configured in accordance with several examples of the present technology.

[0019] FIGS. 5A-5C depict a method for visualizing a lymphovenous junction in accordance with several examples of the present technology.

[0020] FIG. 6 illustrates a support system with an occlusive member expanded near a lymphovenous junction and configured in accordance with several examples of the present technology.

[0021] FIG. 7 illustrates a support system with an occlusive member expanded near a lymphovenous junction and configured in accordance with several examples of the present technology.

[0022] FIG. 8 illustrates a support system comprising multiple occlusive members, shown positioned near a lymphovenous junction and configured in accordance with several examples of the present technology.

[0023] FIG. 8.5 illustrates a method for performing a lymphatic flow reserve assessment according to several examples of the present technology.

16024] FIGS. 9A-9C depict a method for dilating the thoracic duct in accordance with several examples of the present technology.

[0025] FIG. 10 shows a steerable elongate shaft configured in accordance with several examples of the present technology.

[0026] FIG. 11 shows a distal portion of a treatment system comprising independently steerable elongate shafts configured in accordance with several examples of the present technology.

[0027] FIG. 12 shows an implant configured to extend from the thoracic duct into the venous circulation in accordance with several examples of the present technology.

[0028] FIG. 13 shows a clip configured in accordance with several examples of the present technology, shown positioned at the lymphovenous junction.

DETAILED DESCRIPTION

[0029] A multitude of cardiovascular conditions result in insufficient cardiac output, limiting the ability of the heart to circulate blood throughout the vascular system. With limited circulation, fluid builds up in the venous system and increases venous blood pressure. This increase in pressure inhibits drainage from the lymphatic system to the venous system and causes the lymphatic system to drain at a lower rate than it absorbs fluid, resulting in edema. Excess fluid typically accumulates within the abdomen and causes discomfort and organ damage in patients.

[0030] Historically, patients suffering from edema as a result of heart failure have managed the condition with dietary changes such as reduced sodium intake and diuretic medications. However, these methods alone are insufficient to treat edema and diuretics can become toxic to the kidneys when used in high doses. Recent efforts have focused on accessing the lymphatic system and manually removing fluid using a catheter. However, these methods have significant drawbacks. Acute internal drainage is a time-consuming process and must be done in-hospital, and only offers a temporary solution that does not address recurring congestion. Acute or chronic external drainage is also a complex process, requiring multiple pieces of specialized equipment. Furthermore, removing lymph from the body could result in the removal of important lymph components, causing detrimental health effects.

[0031] Accordingly, there is a need for a safe, long-term, and effective method for balancing fluid exchange between the venous and lymphatic systems in patients suffering from edema. Lymphatic vessels drain fluid called lymph from tissues throughout the body and return the fluid to the venous system through two collecting ducts, the thoracic duct (terminating almost always the left side of the body) and the right lymphatic duct (terminating on the right side of the body). An ideal location for accessing the lymphatic system is the lymphovenous junction (LVJ), which is where the thoracic duct drains into the venous system near the left subclavian and jugular veins.

[0032] While the thoracic duct is one of the largest lymphatic vessels, with roughly 75% of all lymph in the body passing through it, the thoracic duct is still relatively small (about 2.5 mm in diameter in healthy individuals, and about 4-7 mm in diseased patients) and notoriously difficult to cannulate. Challenges accessing the thoracic duct at the LVJ include complications associated with excessive venous pressure (at least for patients with CHF), the rigid anatomy /limited extensibility of the thoracic duct at the LVJ, that the thoracic duct typically narrows at the LVJ (not depicted in the drawings). In addition, some but not all TDs include a valve at the LVJ, presumably to regulate the flow of lymph into the venous circulation and prevent blood from entering the lymphatic system. The mechanism by which the valve does this is not well understood, and its role is made less clear by the fact that the valve is frequently absent, and when it is present it has a highly variable morphology.

[0033] In addition to the foregoing challenges, the precise location of the LVJ is not well understood, in part location of the LVJ can vary considerably between patients. As pictured in FIG. 1 A, in most patients the TD joins the venous system at the venous angle (e.g., where the internal jugular vein and subclavian vein unite to form the brachiocephalic vein). It is also common for the LVJ to be located on the internal jugular vein (see FIG. IB). In rare cases, the LVJ is located on the external jugular vein (see FIG. 1C), or along the subclavian vein, proximal to the external jugular vein (along the direction of blood flow) (see FIG. ID). In a vast majority of cases, the TD terminates on the left side of the body, but may rarely terminate on the right side of the body, or bilaterally. The TD usually terminates as a single vessel, but in some cases ends in bilateral vessels or as several terminal branches. In some instances, the TD may travel within the wall of the vein before joining with the venous lumen. [0034] The devices, systems, and methods of the present technology are configured to identify and access the lymphovenous junction, in a location between the superior vena cava and a left axillary vein (e.g., the left brachiocephalic vein, the subclavian vein, the internal jugular vein, the external jugular vein, etc.), as well as increase flow from the TD into the draining vein by implanting a stent in the thoracic duct, at the LVJ. An example method 1.50 in accordance with the present technology is shown at FIG. 1.5. The method can include advancing a support assembly retrograde through the venous system to a position within the venous system proximate the LVJ (1.52). The support assembly can be utilized to visualize the thoracic duct (1.54). To cannulate the thoracic duct, an access assembly can be advanced through the support assembly and across the LVJ, into the thoracic duct (1.56). Next, a lymphatic flow reserve assessment can be performed (1.58) to determine whether the patient is a candidate for stent placement. Depending on the results, a treatment assembly can be advanced to the LVJ to restructure and improve flow across the LVJ (1.60). Additional details regarding the foregoing methods and associated systems are provided below.

[0035] FIG. 2 A shows an example support assembly 100 in accordance with several examples of the present technology. As shown in FIG. 2A, the support assembly 100 can have a proximal portion 100a configured to be positioned external to the patient and a distal portion 100b configured to be intravascularly positioned within a vessel at or proximate an LVJ. As used herein, “vessel” refers to a blood vessel (such as a vein), the thoracic duct, and/or any other tissue connecting the terminal portion of the TD with the corresponding vein at the LVJ. The support assembly 100 can include a handle 104 at the proximal portion 100a, an elongate support shaft 106 extending from a proximal portion 106a of the support shaft 106 at the handle 104 to a distal portion 106b of the support shaft 106, and an occlusive member 102 at the distal portion 106b of the support shaft 106. [0036] As shown in the axial cross-sectional view of the support shaft 106 in FIG. 2B, the support shaft 106 can comprise a generally tubular sidewall defining a lumen 108 therethrough. The lumen 108 can be sized to receive one or more interventional devices, such as a guidewire, a visualization device, a catheter (such as a balloon catheter, an implant- loaded catheter, etc.), an implant and associated delivery system, and others. The lumen 108 may also be configured to be coupled to a fluid source to deliver fluid (such as contrast) to the access site.

[0037] The occlusive member 102 may comprise a low-profile state for delivery to the treatment site (as shown in FIG. 2A) and an expanded state in which the occlusive member 102 is configured to engage at least a portion of the vessel wall to arrest the flow of fluids (such as blood or contrast) at the location of the occlusive member 102 and/or anchor the support shaft 106 with respect to a surrounding vessel. In some examples, the occlusive member 102 comprises a balloon. For example, the occlusive member 102 can comprise a thin film adhered at its longitudinal ends to an outer surface of the support shaft 106, and the support assembly 100 can include an inflation lumen 110 extending through the sidewall of the support shaft 106 and terminating at an opening in the sidewall coincident with an interior region of the occlusive member 102, as shown in FIG. 2B. The support assembly 100 can further include a fluid source 112 (e.g., a syringe, a pump, etc.) configured to be fluidly coupled to a proximal end of the inflation lumen 110 to deliver fluid to and remove fluid from an interior region of the occlusive member 102 (e.g., to infl ate/defl ate the occlusive member 102). Introduction of a fluid (e.g., gas or liquid) to a space between the film and the surface of the support shaft 106 causes the film to stretch and expand radially away from the support shaft 106, thus inflating the balloon. Likewise, removal of fluid (e.g., via the application of negative pressure) causes the film to radially collapse down onto the support shaft 106, thus deflating the balloon. According to certain examples, the support assembly 100 includes two or more occlusive members 102 disposed on the support shaft 106 (see, for example, FIG. 6). [0038] The support assembly 100 can further include a fluid source 114 (e.g., a syringe, a pump, etc.) configured to be fluidly coupled to the proximal portion 106a of the support shaft 106 to supply fluid (e.g., saline, contrast agents, therapeutic agents, etc.) to the potential access site (for example, to facilitate visualization of the TD). The fluid may be delivered either through the lumen 108 of the support shaft 106 or through a different lumen (not shown) within the support shaft 106. In the latter examples, the fluid delivery lumen can terminate distally at an opening on the distal face of the support shaft 106, or may terminate at one or more ports disposed along the sidewall of the support shaft 106. In some examples, the support assembly 100 includes a second, separate elongate shaft (not shown) for delivery of the fluid to the treatment site. The second elongate shaft can be configured to be coupled to the fluid source 114, and can be configured to be slidably received through a lumen of the support shaft 106 (including lumen 108) for positioning at the potential access site.

[0039] Methods of utilizing the support assembly 100 to visualize the LVJ are discussed below, for example with reference to FIGS. 5A-8.

[0040] The present technology can further include a treatment assembly comprising an expandable implant 300 (FIGS. 3A and 3B) configured to be implanted partially or completely within the TD at the LVJ and an associated delivery system 400 (FIG. 4) for positioning and deploying the implant 300. The implant 300 is shown in FIG. 3A in an unconstrained state, which is a state the implant 300 assumes in the absence of external sources of constraint, such as a sheath during delivery of the implant 300 or a wall of the thoracic duct after deployment of the implant 300. As shown in FIG. 3A, the implant 300 comprises a proximal end portion 300a, a distal end portion 300b, and a longitudinal axis extending therebetween. The proximal end portion 300a of the implant 300 can be configured for placement at the LVJ and/or in a vein proximate the LVJ, and the distal end portion 300b can be configured for placement in the thoracic duct. As such, the proximal end portion 300a of the implant can be configured to be stiffer and/or provide greater radial outward than the distal end portion 300b, both to anchor the implant 300 at the ostium and prevent migration, but also to dilate the ostium and relieve pressure at the LVJ. The distal end portion 300b, and in some cases any portion of the implant 300 distal of the proximal end portion 300b, may be more flexible to accommodate the more delicate thoracic duct tissue, and the curvature of the thoracic duct, and may have a greater porosity /less surface area to allow lymphatic flow into lymph vessels branching off of the thoracic duct along the implant.

[0041] In some examples, the implant 300 comprises an open-form stent comprising a filament 302 (e.g., a wire, a strand, a strut, etc.) wrapped around a longitudinal axis of the implant such that no portion of the filament 302 crosses over itself. The filament 302 can be a wire having a round or rectangular cross-section, or can be the remaining portion of a tube that has been laser cut to leave behind the winding strut design. The flexibility and conformability provided by the open-form configuration can be beneficial for placement within the smaller and more delicate anatomy of the lymphatic vessels (as compared to the more robust blood vessels). [0042] The turns of the filament 302 form the generally tubular sidewall of the implant 300, and along the length of the sidewall, the filament 302 wraps around the longitudinal axis to form a plurality of sinusoidal bands 306 connected by individual bridges 308. At least when the implant 300 is in the unconstrained state, longitudinally adjacent bands 306 are spaced apart from one another by gaps 310 measured by a distance d. Depending on the number of bands 306, the distance d can be, for example, about 5 mm to about 200 mm, about 50 mm to about 150 mm, about 50 mm to about 100 mm, or no more than 200 mm. The spacing of the bands 306 can also vary along the length of the implant 300, thereby imparting different zones of flexibility, as the greater number of bands per unit length, the stiffer that section of the implant 300.

[0043] Within a given band 306, the filament 302 may undulate and/or extend along a sinusoidal path around the circumference of the band 306 such that the band 306 comprises a plurality of alternating peaks 312 and valleys 314. The peaks 312 are closer to the distal end portion 300b of the implant 300 and the valleys 314 are closer to the proximal end portion 300a. The openings defined by the undulating filaments 302 within the bands 306 and the openings between adjacent bands 306 allow flow through the sidewall of the implant 300, which can be beneficial for maintaining flow into collateral lymphatic vessels once the implant 300 is implanted within the thoracic duct.

[0044] As previously mentioned, the bands 306 are connected to one another only by way of the single, continuous wire and/or strut. Advantageously, all of the peaks 312 and valleys 314 are free peaks and valleys, meaning that none of the peaks 312 and valleys 314 are connected to a peak, valley, or other portion of a longitudinally adjacent band 306. This lack of interconnectedness amongst axially adjacent structures provides the implant 300 with enhanced axial flexibility and stretchability as compared to conventional stents that include one or more bridges or other linkages between longitudinally adjacent struts and/or apices. This flexible configuration enables the implant 300 to stretch and bend with the thoracic duct in response to different loads (e.g., bending, torsion, tensile) while still maintaining a threshold radial force, especially at the proximal end portion 300a. Moreover, the elimination of longitudinal linkages and/or closed cells along the length of the implant 300 may help maintain collateral flow to lymphatic vessels branching off of the thoracic duct, as closed cells may impede flow. In some examples, the bands 306 are configured to allow for greater flexibility while providing enough radial force to keep open any lymphatic valves (disposed along the length of the thoracic duct) without blocking collateral lymphatic flow. [0045] Other open-form configurations of the implant 300 are possible. For example, in some examples the implant 300 can comprise a coil formed of a wire wound helically about a longitudinal axis or a helical strut that has been laser cut from a tube. The coil can have a pitch that remains constant or varies along the length of the implant 300. In some cases, the pitch of the coil can be adjusted during delivery.

[0046] In some examples, all or a portion of the implant comprises a closed-form design. For example, at least the proximal end portion 300a of the implant 300 may comprise a plurality of interconnected struts and closed cells between the struts, while the remainder of the implant may have an open form design (including any of the configurations detailed herein). The stiffer, closed-form proximal end portion 300a can thus be configured to exert a higher radial outward force against the LVJ to both anchor the implant 300 and dilate the ostium, while intermediate and distal portions of the implant 300 positioned within the thoracic duct remain open-form and thus sufficiently flexible to accommodate the curvature of the thoracic duct and also to allow collateral flow.

[0047] In some examples, the implant comprises an expandable ring configured to be positioned at the ostium. The ring, for example, can comprise an expandable stent structure having a length just long enough to span the ostium.

[0048] According to some aspects of the technology, all or a portion of the implant comprises a weave and/or a braid formed of a plurality of interwoven filaments, or a single filament interwoven with itself, or a laser-cut stent comprising a plurality of interconnected struts and cells between the struts.

[0049] The implant 300 may have a substantially constant diameter along its length of about 2 mm to about 30 mm, about 2 mm to about 20 mm, or no more than about 20 mm. In some examples, the implant 300 may have a diameter that varies along the length of the implant 300. For example, the implant 300 can have a diameter that may be tapered along the body in a distal direction (e.g., away from the LVJ, further into the thoracic duct). This taper can have the benefit facilitating forward flow (toward the vein) by maintaining a slight pressure gradient. In these and other examples, a diameter at the proximal end portion 300b of the implant 300 may be larger than the remainder of the implant 300 (which may have the same or a continuously tapering diameter) to help anchor the implant and/or dilate the ostium. In some examples, the implant 300 has a resting (unconstrained) diameter the same as or slightly greater than that of the native thoracic duct lumen such that the implant expands into apposition with the inner walls of the thoracic duct. According to several examples, the diameter of the implant may be at least 1.5 or 2 times larger than the diameter of the native thoracic duct, for example in order to promote greater flow capacity.

[0050] The implant 300 can have a length of about 5 mm to about 250 mm, about 10 mm to about 100 mm, or no more than about 200 mm.

[0051] In any of the implant examples disclosed herein, the implant can be formed of a superelastic material or other resilient material that the implant is self-expanding and resiliently assumes a preset expanded configuration in the absence of a countervailing force. Additionally or alternatively, the implant may be configured for expansion by a balloon or other expandable structure. Materials comprising the expandable implant could include but are not limited to shape-memory metals, soft platinum metal, stainless steel, titanium, titanium alloy, cobalt-chromium alloy, nitinol, platinum, other biocompatible metal alloys, alumina, bioglass, hydroxyapatite, medical-grade silicone, polyvinylchloride, polyethylene, polypropylene, polytetrafluoroethylene, polymethylmethacrylate, trimethylcarbonate, TMC NAD-lactide, or zirconia.

[0052] The implant or any portion of the system may optionally include a nonbiodegradable or biodegradable polymer coating to facilitate drug adhesion, drug release, biocompatibility, or modulate thrombogenicity within blood or lymphatic fluid. These polymers may include but are not limited to polylactic acid, polyglycolic acid, polylactic-co- glycolic acid, caproic acid, polyanydride ester, salicylic acid, or sebacic acid. The system may also have a drug coating that may include but is not limited to sirolimus, tacrolimus, everolimus, leflunomide, M-prednisolone, dexamethasone, interferon r-lb, mycophenolic acid, mizoribine, cyclosporine, tranilast, paclitaxel (e.g., to prevent restenosis), actinomycin, methotrexate, angiopeptin, vincristine, mitomycin, statins, C-myc antisfense, ABT-578, resten ASE, batimastat, prolyl hydroxylase inhibitors, halofuginone, C-proteinase inhibitors, probucol, BCP671, VEGF, estradiols, NO donor compounds, EPC antibodies, biorest, nintedanib, pirfenidone, and phenformin.

[0053] In some examples, the implant 300 has a proximal element 360 (shown schematically in FIG. 3A) disposed at the proximal end portion 300a and configured to facilitate placement the LVJ. The proximal element 360, for example, may be configured to support the vein and/or thoracic duct ostium at the LVJ to maintain patency of the lymphovenous valve. In some examples, the proximal element 360 comprises a curved portion of the LVJ. This has the advantage of directing flow in the direction of venous flow to avoid the risk of venous reflux. The angled element can range from 1 to 150 degrees and the length of the angled part can be up to 5cm. This can be achieved by adding connector elements of a certain length to one side of a strut. In some examples, the proximal element 360 comprise two connected rings.

[0054] According to some aspects of the technology, the implant has a distal element 350 (shown schematically in FIG. 3A) disposed at the distal end portion 300b of the implant 300. In some examples, the implant is shaped to have a curved distal element. In some examples, the implant is intentionally constructed off-axis to make the deployment around the cervical thoracic duct arch or lymphovenous junction easier. The curved distal element helps to conform to the natural shape of the thoracic duct. The angled part can range from 30 to 150 degrees and the length of the angled part can be up to 20cm. This can be achieved by adding connectors of a certain length just to one side of a strut. In some examples, this section is covered, open, or has a valve element.

[0055] FIG. 3C shows one example of a distal element 350 including a plurality of distal projections 380, each comprising a rounded and/or atraumatic distal tip 382. Some or all of the projections 380 and/or distal tips 382 can include a radiopaque marker or comprise a radiopaque material.

[0056] FIG. 3D shows another example of a distal element 350/370 comprising a plurality of peaks 314 having different heights. Such a configuration may be beneficial for distributing the radially outward force along more than just a single circumferential plane.

[0057] In some examples, one or more portions of the implant 300 may optionally include a cover 320. The benefit of this design is that it may promote forward flow based on the contractility of the thoracic duct, which is regulated by respiratory and cardiac cycles.

[0058] In some examples, the implant optionally comprises one or more tines or anchors. In some examples, the tines or anchors are disposed along the perimeter of proximal end portion 300a or proximal element 360. In some examples, these tines or anchors are deployed using balloon inflation to push them against or into the vessel wall. In some examples, multiple balloons are utilized for simultaneous or serial post-implant placement dilatation of the junction and implant anchoring. This has the benefit of preventing implant migration.

[0059] In some examples, the final strut of the spring is used to anchor the coil in place. This has the benefit of preventing coil migration.

[0060] In some examples, one or more marker elements are placed on the implant to make it visible during the procedure. These marker elements may be placed on the distal and proximal end of the implant and are visible under fluoroscopy. The marker elements can be made of radiopaque material including but not limited to barium sulfate, bismuth compounds, gold, tantalum, and tungsten. In some examples, the marker elements may be placed at varying intervals in both the vertical and horizontal position. This has the benefit of creating a unique constellation of markers on a two-dimensional view regardless of the angle.

[0061] In some examples, a method may be applied using the marker elements to calculate 3D position from two different fluoroscopic views. This method applies stereovision and inverse kinematic principles to determine the orientation of the implant in relation to anatomy. This has the advantage of being able to inform better positioning and understanding target vessel anatomy.

[0062] As shown in FIG. 4, the delivery system 400 can have a proximal portion 400a configured to be positioned external to the patient and a distal portion 400b configured to be intravascularly positioned within a vessel at a treatment site at or proximate an LVJ. The delivery system 400 can include a handle 406 at the proximal portion 400a and an elongate shaft 402 (or “delivery shaft 402”) extending distally from the handle 406 to the distal portion 400b of the system 400. The delivery shaft 402 can define a lumen configured to slidably receive a guidewire 404 therethrough. As shown schematically in FIG. 4, the lumen may also be configured to contain the implant 300 in a low-profile or collapsed configuration. The delivery system 400 can optionally include an expansion member 408 slidably disposed within the delivery shaft 402, radially inwardly of the implant 300, and configured to be expanded at the treatment site to facilitate expansion of the implant 300 into apposition with an inner surface of the TD. Additionally or alternatively, the delivery system 400 can optionally include a dilation member (not shown for ease of viewing other features) disposed at an outer surface of the distal portion of the delivery shaft 402 and configured to be expanded at a treatment site within the TD to directly dilate the TD. In some examples, a distal tip of the delivery shaft 402 can be softer than the rest of the length of the delivery shaft 402 to reduce vessel trauma. Additionally or alternatively, a distal portion of the delivery shaft 402 may be tapered to facilitate entry into the TD.

[0063] The delivery shaft 402 can be configured to be slidably received within a lumen of the support shaft 106 (including lumen 108) for delivery to a treatment site within or near the TD. In some cases, the delivery shaft 402 and/or treatment assembly 30 is configured to be delivered to the LVJ and/or thoracic duct separate from the support assembly 10, such as over a guidewire already positioned in the thoracic duct. Methods of utilizing the treatment assembly to dilate the LVJ are discussed below, for example with reference to FIGS. 9A-9C. In some cases, the delivery system 400 can be configured for reverse deployment of the implant 300, as discussed herein.

[0064] FIGS. 5A-5C illustrate a method of visualizing the LVJ using the support assembly 100 described with respect to FIGS. 2A and 2B. While FIGS. 5A-5C show the most common location of the LVJ (detailed in FIG. 1A), the methods disclosed herein are not limited to a particular variant. Access to the venous system can be obtained percutaneously by inserting a guidewire 130 into a peripheral vein (e.g., femoral, basilic, cephalic, axillary, subclavian, internal jugular, or iliac veins) and advancing the guidewire 130 retrograde (e.g., against the flow of blood B) until a distal portion of the guidewire 130 is proximate the LVJ, such as within the brachiocephalic vein or subclavian vein (as shown in FIG. 5A). As previously mentioned, in the vast majority of cases the LVJ is on the left side of the patient’s body, so most likely the procedure will begin with placement of the guidewire 130 in the left brachiocephalic vein or left subclavian vein.

[0065] As depicted in FIG. 5B, the support shaft 106 may then be advanced over the guidewire 130 with the occlusive member 102 in its low-profile configuration. Positioning of the guidewire and/or support shaft 106 may be aided by imaging guidance, such as fluoroscopy, computed tomography, magnetic resonance imaging, ultrasound, intravascular ultrasound, or optical coherence tomography.

[0066] Once the support shaft 106 is positioned within the vein proximate and downstream of the expected location of the LVJ, the occlusive member 102 may then be expanded into opposition with the venous wall (as shown in FIG. 5C). As the LVJ is most commonly at either the juncture of the subclavian and internal jugular veins or along the internal jugular vein, in many cases the support shaft 106 can be positioned such that the occlusive member 102 is expanded within the brachiocephalic vein, at least initially. The occlusive member 102 can additionally or alternatively be expanded within the subclavian vein between the internal jugular vein and the external jugular vein (as shown in FIG. 6), or within the subclavian vein across or distal to the external jugular vein. In any case, expansion of the occlusive member 102 blocks the flow of blood downstream of the occlusive member 102. In some examples, the occlusive member 102, the support shaft 106, or both can have one or more radiopaque markers to help guide positioning and/or deployment of the occlusive member 102. [0067] Referring still to FIG. 5C, a contrast agent C can be delivered to the treatment site while the occlusive member 102 remains expanded and occluding flow. The guidewire 130 remains in place or may be withdrawn while the contrast agent C is injected. The localized pressure gradient created by the expanded occlusive member 102 causes a temporary backflow of blood into surrounding vessels (including the TD) such that the contrast agent C enters the TD. In FIG. 5C, the contrast agent C is shown being delivered through a lumen (such as lumen 108, or another lumen) of the support shaft 106 that terminates at the distal end of the support shaft 106. In other examples, the contrast agent C may be delivered through one or more side ports of the support shaft 106. In such examples, the contrast agent C may be delivered simultaneously at different angles through multiple side ports to increase the probability of directing the contrast agent C into the TD. In some examples, the contrast agent C may be delivered through a separate support shaft 106 that is delivered through or separately of the elongated shaft 106. In some examples, a separate elongate shaft (not shown) is advanced to the treatment site from a different access location than the support shaft 106 with the occlusive member 102. For example, a separate elongate shaft for contrast delivery could be advanced to the treatment site via the axillary and/or subclavian veins, internal jugular vein, and/or external jugular vein. In some cases, the occlusive member 102 can be inflated/deflated multiple times to avoid prolonged occlusion of the vein.

[0068] During or immediately after injection of the contrast agent C, the LVJ and/or TD can be visualized via an imaging modality, such as fluoroscopy, computed tomography, magnetic resonance imaging, ultrasound, intravascular ultrasound, or optical coherence tomography, etc., to identify the LVJ. If the LVJ and/or TD is not sufficiently visualized after injecting the contrast agent C, the occlusive member 102 can be collapsed (e.g., deflated), repositioned, and re-expanded as many times as needed to target a different LVJ location and ensure sufficient backflow into the TD. For instance, to target an LVJ at the external jugular vein EJV (as shown in FIG. 1C) or along the subclavian vein SV (as shown in FIG. ID), the occlusive member 102 may be expanded within the subclavian vein SV at a location upstream of the internal jugular vein IJV. In some cases, the occlusive member 102 is expanded within the subclavian vein SV between the internal jugular vein IJV and external jugular vein EJV, as shown in FIG. 6.

[0069] The occlusive member 102 can be sized and shaped to better localize the generated pressure gradient at the LVJ. For example, in some examples the occlusive member 102 comprises multiple lobes. As shown in FIG. 7, the multiple lobes can be configured to complement the anatomy at the LVJ, for example at the venous angle. The occlusive member 102 can comprise a first lobe 102a configured to expand within the subclavian vein between the internal jugular vein and external jugular vein, a second lobe 102b configured to expand within the internal jugular vein, and a third lobe 102c configured to expand within the brachiocephalic vein. Other shapes and configurations are possible. For example, in some examples the occlusive member 102 can have only two lobes or may have four or more lobes.

[0070] In some cases, it may be beneficial to utilize more than one occlusive member 102 to help localize the pressure gradient. For example, each of the occlusive members can be positioned so as to block nearby blood vessels, advantageously allowing more direct flow of contrast agent C into the TD. As shown in FIG. 8, in some examples the support assembly 100 may include a first occlusive member 102 and a second occlusive member 122 disposed on the support shaft 106, longitudinally spaced apart from the first occlusive member 102. The first occlusive member 102 can be configured to be expanded into contact with the brachiocephalic vein while the second occlusive member 122 can be configured for expansion within the subclavian vein, upstream of the venous angle (as shown in FIG. 8). Positioning the multiple occlusive members proximal and distal of the potential LVJ site can enhance localization of the backflow, thereby improving visualization.

[007.1] In some examples in which the support assembly 100 includes multiple occlusive members, the support shaft 106 may include one or more ports disposed between the occlusive members. FIG. 8, for example, shows a side port 124 disposed along the support shaft 106 between the first and second occlusive members 102, 122.

[0072] In certain examples, multiple occlusive members 102 can be positioned at the treatment site on separate elongate shafts 106. For example, the support shaft 106 with the occlusive member 102 can be positioned in the brachiocephalic vein while another elongate shaft carrying another occlusive member can be positioned in the internal jugular vein. In some cases, the support shaft 106 with the occlusive member 102 can be positioned in the brachiocephalic vein while another elongate shaft carrying another occlusive member can be positioned in the subclavian vein. Additional variations are possible, including the use of three or more elongate shaft/occlusive members.

[0073] Following identification of the LVJ as described herein, a lymphatic flow reserve assessment (LFRA) may be performed to identify patients who are likely to benefit from dilatation of the LVJ. This assessment can measure the degree to which the LVJ is resisting flow, which can be indicative of a patient’s risk of having a future major heart or lymphatic issues. In general, methods for performing an LFRA include measuring certain parameters indicative of resistance, such as flow rate and pressure, proximal and distal of the LVJ and using the difference to characterize the resistance attributable to a narrowing of the thoracic duct at or near the LVJ.

[0074] FIG. 8.5 shows an example method 8.50 for identifying a patient for stent placement by performing an LFRA, which can be done utilizing any of the thoracic duct sensors and access methods detailed above. As shown in FIG. 8.5, the method can comprise positioning a first pressure sensor within the thoracic duct (8.52) and a second pressure sensor within a vein proximate the lymphovenous junction (e.g., the left brachiocephalic vein, the left subclavian vein, the left external jugular vein, or the left internal jugular vein) (8.54). A pressure within the thoracic duct can be measured with the first sensor (8.56) while a pressure within the vein can be measured with the second pressure sensor (8.58). The method 8.50 continues with determining a difference between the thoracic duct and venous pressures (8.60) and, based on that difference, identifying a patient for treatment via placement of an implant at the LVJ. For example, a measured pressure differential greater than a threshold value may indicate the patient is a candidate for treatment. Without being bound by theory, the inventors believe that in many cases of edema and/or volume overload, a stenosis at the LVJ and/or thoracic duct ostium causes the thoracic duct pressure to be greater than the venous pressure, which, according to the present technology, can be helped by placing an implant at the LVJ and/or ostium and/or performing a dilatation procedure. Thus, according to the present technology, placement of an implant may be indicated for a positive pressure gradient between the thoracic duct and vein (e.g., Piymphatic - Pvein > 0). In contrast, some existing temporary drainage therapies believe it is venous pressure elevation alone that blocks flow from the LVJ, and thus only institute a temporary, external drainage therapy if the thoracic duct pressure is lower than the venous pressure (e.g., Piymphatic - Pvein < 0).

[0075] In some cases in which a pressure gradient may be lower than the predetermined threshold, further assessment of resistance at the LVJ may be performed by adjusting the measured pressure gradient for flow at the junction, as pressure-gradients may be under-estimated in cases of low lymphatic flow. This may identify patients who remain candidates for dilatation or placement of an implant at the LVJ due to low-flow low-gradient lymphovenous obstruction or stenosis. [0076] The first sensor (for measuring thoracic duct pressure) can be, for example, a pressure sensor, a flow sensor, a temperature sensor, and/or any other sensor configured to measure a parameter that can be utilized to determine a pressure differential across the LVJ. The first sensor can be disposed on a delivery device (e.g., an elongate shaft, a solid rod, a wire, etc.) that is delivered independently to the thoracic duct or within a separate access shaft that cannulates the thoracic duct prior to delivery of the delivery device. In both scenarios, the support shaft 106 can be used to guide the transition from the vein into the thoracic duct. For instance, while the support shaft 106 remains positioned in a vein proximate the LVJ following a visualization procedure, an access shaft can be advanced through the lumen 108 of the support shaft 106 (or any other lumen of the support shaft 106) and pushed distally beyond the distal tip of the support shaft 106, through the ostium at the LVJ and into the thoracic duct. In some examples, the support shaft 106 can have a steerable and/or curved distal region (see, for example, FIGS. 10 and 11 below) to help guide the access shaft into the thoracic duct. Likewise, in some cases the access shaft can have a curved and/or steerable region to aid navigation into the thoracic duct. Additionally or alternatively, the access shaft can have a tapered distal region to facilitate insertion through the LVJ.

[0077] In some cases, no access shaft is used, and instead the delivery device carrying the first sensor is advanced alone through the support shaft 106 and into the thoracic duct. However, when the delivery device comprises a flexible wire, such as a pressure wire typically used in coronary procedures (e.g., OMNIWIRE (Philips), PRESSUREWIRE X (Abbott), etc.), it may be beneficial to use an access shaft to gain access to the thoracic duct, as such flexible wires may not have sufficient rigidity and/or column strength to overcome the structural obstacles presented by additional tissue layers surrounding the ostium (due to the intramural relationship between the thoracic duct and the vein) and the (potential) presence of a valve. While a more rigid version of a standard pressure wire may overcome aforesaid challenges, if the wire is too rigid it may poke or otherwise cause trauma to nearby tissue before, during, or after introduction to the thoracic duct. An access shaft can thus advantageously provide the increased rigidity for crossing the ostium while presenting a broader, more atraumatic surface to the exposed tissues. In some examples, the first sensor is carried by a distal region of the access shaft and no separate sensory delivery device is used. [0078] The second sensor (for measuring venous pressure) can be, for example, a pressure sensor, a flow sensor, and/or any other sensor configured to measure a parameter that can be utilized to determine a pressure differential across the LVJ. In some examples, the second sensor is disposed on the same delivery device (e.g., an elongate shaft, a solid rod, a wire, etc.) as the first sensor, but proximal of the first sensor so that the first and second sensors can be simultaneously positioned in the thoracic duct and vein, respectively. In such examples, the access shaft and/or support shaft 106 may need to be withdrawn proximally to a location proximal of the second sensor such that the second sensor is exposed to the physiological environment.

[0079] In some examples, the second sensor is disposed on a device separate from that of the first sensor. For instance, the first sensor may be disposed on a sensor delivery device while the second sensor is disposed on an access shaft or support shaft 106. As another example, the first sensor may be disposed on an access shaft while the second sensor is disposed on the support shaft 106. In these and other examples, the second sensor can be disposed on a device advanced from a different access site. For example, the first sensor can be disposed on a device introduced through a first access site at a brachial, jugular, or femoral location, while the second sensor can be disposed on a device introduced through a second access site at a different one of a brachial, jugular, or femoral location (e.g., first access site may be brachial while second access site is jugular, first access site is jugular while second access site is femoral, etc.).

[0080] Thoracic duct and venous pressure measurements may be taken continuously over the course of a measurement period long enough to cover at least one respiratory cycle (e.g., at least 3 seconds). In some cases, only the pressure data corresponding to the inspiration phase of the respiratory cycle is used, rather than an average of the pressure measurements over the inspiratory and expiratory phases. This is because the ostium at the LVJ is typically closed during expiration, and thus lymphatic flow only occurs during inspiration. In scenarios when flow occurs in other phases of the respiratory cycle, such as expiration, the LFRA will identify when during the respiratory cycle flow is occurring and use that information to determine the resistance to flow.

[0081 ] In some examples, simultaneous continuous thoracic duct and venous pressure measurements taken over one or more respiratory cycles may be further segmented into distinct phases of flow, such as lymphatic systolic flow (thoracic duct contraction phase), lymphatic diastolic flow (thoracic duct relaxation phase), venous systole or diastole (atrial contraction vs relaxation phases). Segmentation of flows on this beat-to-beat basis (based on lymphatic pulsatile rate, or heart rate), may allow for assessment of specific flow patterns in cases in which the lymphatic flow across the lymphovenous junction is not solely dependent on the respiratory cycle. In some cases, only the pressure data corresponding to a specific distinct phase within the lymphatic or venous cycle may therefore be used.

[0082] The systems of the present technology may measure thoracic duct pressure at a single location or multiple locations along the thoracic duct. Thoracic duct pressure can be measured, for example, at the lymphovenous junction, along the cervical arch of the thoracic duct, and/or more proximally (along the direction of lymph flow) in the abdominal portion of the thoracic duct, including as far as the cisterna chyli. Obtaining measurements at multiple locations within the thoracic duct distal to the LVJ can indicate a length of the thoracic duct that may benefit for dilation (e.g., via placement of an implant).

[0083] In some cases, the measured pressure differential may be negative, indicating reflux into the thoracic duct. In those examples, an implant including one or more valves may be selected in order to maintain a forward pressure and prevent reflux.

[0084] In some examples, a vasodilator or other drug may be administered to induce higher lymphatic or blood flows to aid with the LFRA. For example, some methods of the present technology include injecting intraductal adenosine to cause vasodilation of the thoracic duct. This may be advantageous given that the patient is supine and under sedation during the procedure, which could lead to false negative determination of flow resistance.

[0085] In some cases, the LFRA may be done one or more times during a procedure. The first LFRA may be done prior to deploying the implant, and a subsequent one may be done after device deployment to assess the efficacy of the treatment before the procedure terminates. This approach has the advantage of providing a real-time indication that the treatment was successful.

[0086] Imaging modalities such as computed tomography, angiography, or magnetic resonance imaging maybe be used to measure the thoracic duct diameter at various points. This could be done after a contrast agent has been introduced to visualize the thoracic duct, with the assistance of imaging software that can measure the vessel diameter. For example, identifying a smaller diameter at the LVJ and comparing it to the size of the abdominal or cervical part of the thoracic duct may provide additional inputs to calculate resistance to flow at the LVJ. This information may also aid in selecting the size of the implant.

[0087] The methods of the present technology further include dilating the TD to passively drain accumulated fluid into the venous system. FIGS. 9A-9C illustrate a method of dilating the thoracic duct using a support assembly 100 as described above. In some examples, the support shaft 106 may remain in place near the lymphovenous junction and serve as a sheath for through which additional equipment for lymphovenous access and intervention can be passed, such as guide wires for crossing the LVJ, a microcatheter for cannulating the LVJ, balloon catheters for dilating and stenting the LVJ, etc. As shown in FIG. 9A, the guidewire 404 of the implant delivery system 400 can be advanced through the support shaft 106 and distally across the LVJ (including across any valve(s) that may be present) and positioned within the TD such that a distal terminus of the guidewire 404 is positioned at or downstream of the descending portion of the TD. As shown in FIG. 9B, the delivery shaft 402 of the implant delivery system 400 can be advanced over the guidewire 130 (through the support shaft 106) and through the orifice at the LVJ and positioned within the TD. The delivery shaft 402 can then be withdrawn, leaving behind the implant 300, as shown in FIG. 9C. The implant 300 may self-expand upon removal of the constraints of the delivery shaft 402 and/or, as previously mentioned, the delivery system 400 can include an expansion member 408 that can be expanded and/or inflated (if a balloon) to facilitate expansion of the implant 300 into apposition with the wall of the TD. In some examples, prior to or while expanding the implant, an elongate member including an expansion element (such as a balloon or other device) can be positioned at the LVJ (for example, through the support shaft 106) and expanded to dilate the orifice at the LVJ. In some examples, a third elongate shaft is used to access the TD, and the delivery shaft 402 is advanced over the guidewire and through the third elongate shaft.

[0088] In some examples, the occlusive member(s) 102 is collapsed (e.g., deflated) during placement of the implant and associated delivery systems. In some examples, the occlusive member may remain expanded (e.g., inflated) to help anchor the support shaft 106 and/or guide the implant delivery systems into the TD. The components of the implant delivery system may have a tendency to enter a larger branch of the vein such as the internal jugular vein, subclavian vein, external jugular vein. In some examples, the catheter or wire with balloon tip is inflated temporarily to block a side branch or multiple side branches, such that when an additional catheter or guidewire or microcatheter is inserted, it is blocked from entering the branches, and instead, is redirected to the LVJ of interest.

[0089] According to some aspects of the present technology, the implant can be deployed from a proximal to distal direction to leverage the anchoring properties of the proximal end portion of the implant. For example, a method can include positioning a distal portion of a delivery system within the thoracic duct, where the delivery system includes an implant in a compressed state, and expanding a proximal portion of the implant into apposition with an inner surface of the thoracic duct ostium, thereby dilating the ostium and anchoring the implant. The method further includes, after expanding the proximal portion of the implant, expanding a distal portion of the implant into apposition with an inner surface of the thoracic duct. The method further includes withdrawing the delivery system, thereby leaving the implant implanted within the thoracic duct.

[0090] In some examples, the distal end of the support shaft 106 may have a steerable distal portion that facilitates delivery of equipment into the LVJ once visualized. For example, the support shaft 106 may include a plurality of pull-wires to control deflection of its sidewall, be configured for coupling to a robotic steering system, and/or having selectively deflectable portions activated by heating different portions of the sidewall. In some examples, the distal tip of the support shaft 106 (distal to the occlusion member 102) can selectively bent, flexed, and/or deflected to create a desired curvature that optimally orients the support shaft 106 (and any component passing therethrough) for cannulating the TD. FIG. 10, for example, shows the support shaft 106 having a first, non-deflectable portion 1202 and a second deflectable portion 1204. The first portion 1202 can extend from a location proximal of the occlusive member 102 to a location along the support shaft 106 that is aligned with or distal of a distal edge of the occlusive member 102. Accordingly, the entire second portion 1204 can be disposed distal of the occlusive member 102 such that deflection of the second portion 1204 does not cause the first portion 1202 of the support shaft 106 and occlusive member 102 to deflect. The second portion 1204 can have a bend radius, for example, of about 0.1 cm to about 3 cm.

[0091 ] The delivery shaft 402 can also have a steerable distal portion. According to some aspects of the technology, the support shaft 106 and the delivery shaft 402 may each be steerable, independent of one another, for example as shown in FIG. 11. This arrangement beneficially decouples steering and the ability to make a variety of advanced curves (e.g., such as S-shaped curves, reverse-shaped curves, etc.), thereby providing adequate catheter support for the cannulation of the TD and delivery of equipment across the junction. In some examples, the independent steerability can be controlled via a single handle with two actuators (e.g., knobs, dials, etc.).

[0092] In any of the examples disclosed herein, the support shaft 106 can have an outer diameter of at least 6 Fr, at least 8 Fr, at least 10 Fr, at least 12 Fr, at least 15 Fr, or at least 20 Fr. [0093] In some examples, the catheter may be pre-shaped to cannulate the thoracic duct. This may be pre-shaped based on imaging before or during the procedure.

[0094] In some examples, the support shaft 106 (or other component of the treatment system) may include a pressure-sensing port in a region such that a measure of venous pressure can be obtained during inflation near the LVJ of interest. In some examples, once the venous pressure as a result of balloon inflation (e.g., expansion of the occlusive member 102) has increased to either 5mmHg, lOmmHg, 15mmHg, 20mmHg, 25mmHg, 30mmHg, 35mmHg, 40mmHg or higher, dye contrast is injected into the venous system. In some examples, the dye can be injected through a side port of the catheter (such as support shaft 106, or others), with an end-hole proximal to the balloon tip, such that the contrast flows into the venous region of interest. In some examples, a separate injection catheter or system can be used with the end-hole of the catheter placed near the region of interest. In some examples, after balloon inflation, the venous pressure increases near the LVJ, and as a result of venous pressure increasing above a level of that in the thoracic duct, contrast flows retrograde into the duct, opacifying the duct. In some examples, this may allow opacification of the terminal thoracic duct LVJ under fluoroscopy. In some examples, the catheter may contain a port that is placed proximal to the balloon, that allows passage of microcatheters or guidewires other systems into the LVJ with the use of a single access.

[0095] In some examples, a conduit (with or without a valve) is placed at the LVJ. As shown in FIG. 12, a first portion 802 of a conduit 800 can be positioned within the TD and a second portion 804 can be positioned within the vein V. The second portion 804 can have one or more protrusions (e.g., anchors) configured to engage an inner surface of the vein wall to stabilize the second portion 804 in place against the wall. The second portion 804 can be more compliant than the first portion 802. All, some, or none of the conduit 800 may be covered. The conduit can comprise any of the implant 300 designs and materials disclosed herein. In some examples, the conduit 800 may comprise shape-memory metals, soft platinum metal, stainless steel, titanium, titanium alloy, cob alt- chromium alloy, other biocompatible metal alloys, alumina, bioglass, hydroxyapatite, medical-grade silicone, polyvinylchloride, polyethylene, polypropylene, polytetrafluoroethylene, polymethylmethacrylate, trimethylcarbonate, TMC NAD-lactide, or zirconia.

[0(196] In some examples, a portion or all of the system may be compliant and compress as blood is passing (FIG. 12). This provides the advantage of passively pushing lymphatic fluid out of the conduit. [0097] In some examples, the support assembly 100 optionally includes a sensor for measuring a pressure across the LVJ. The sensor can be disposed, for example, at the distal portion of the support shaft 106 and/or delivery shaft 402. The sensor can be configured to measure the pressures across the lymphov enous junction simultaneously across a distance of up to 1cm, 2cm, 3cm, 4cm, 5cm, 6cm, 7 cm, 8cm, 9cm or 10cm. The pressure sensing element may be placed such that it would simultaneously measure pressures distal and proximal to the valve, such as between the thoracic duct and the internal jugular or subclavian vein. The benefit of this would be to allow for precise location of pressure gradient measurements.

[0098] In some examples, the pressure sensing element may contain pressure sensing elements along the length of the catheter. In some examples, a system that allows for modulation of the local venous pressure at the thoracic duct outlet may be used if no gradient is initially observed while using the pressure sensing system. The benefit of this is to evaluate the true resistance to flow across the thoracic duct orifice and to identify a gradient that may be masked or missed due to elevations in downstream venous pressures which may occur in disease states such as heart failure or cirrhosis. In some examples, the system may comprise one or more pressure sensing elements and one or more occluding elements to modulate the venous outflow pressure. The pressure sensing element could be placed on a catheter, microcatheter, guidewire, balloon, stent, or valve. The occluding element can be placed on the pressure sensing element or be a separate component on a catheter, microcatheter, guidewire, balloon, stent, or valve. The occluding element may be but is not limited to a balloon or valves. The occluding element(s) may be deployed in the vein proximally, distally, or both to the thoracic duct outlet, such as in the subclavian vein, in the internal jugular vein, between the innominate vein and the thoracic duct outlet, or in between the thoracic duct outlet and the cephalic vein. The occluding element temporarily reduces the local venous outflow pressure. This has the benefit of removing the confounder of elevated venous pressures and enabling the true gradient to be measured across the lymphovenous junction. The pressure sensing element(s) may continuously measure pressure across the lymphovenous junction.

[0099] The orifice of the thoracic duct at the LVJ can be narrow relative to the diameter of the thoracic duct distal of the junction. Moreover, the tissue surrounding the orifice is generally inelastic. The treatment systems of the present technology can be configured to increase distensibility of the thoracic duct venous junction or junction orifice diameter to reduce resistance to flow and increase lymphatic flows across the thoracic duct venous junction. For example, in some examples, the treatment systems of the present technology may be configured to modify (e.g., disrupt, damage, inhibit, release and/or otherwise change the status quo of) smooth muscle in the wall of the junction and/or vein to reduce smooth muscle tension or constriction and thereby increase distensibility. The increased distensibility may advantageously lead to increased flow across the function, especially in cases of excess interstitial volumes or edema, such as heart failure or cirrhosis. [0100] In some examples, a catheter can be passed transvenously from peripheral (leg/arm) or central (cervical neck vein, subclavian vein, cephalic vein) access and the LVJ in the cervical region is then cannulated. In some examples, upon cannulation, a guidewire is passed across the LVJ retrograde from the venous side into the duct. In some examples, a disruption element is passed over the guidewire and placed at the treatment site adjacent targeted smooth muscle at or near the orifice. In some examples, the sub-intimal layer of smooth muscle is targeted. In some examples, the treatment site is a specific region in which there is a band of smooth muscle that resembles a sphincter. In some examples, the element to damage smooth muscle can be placed at the LVJ or 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm distal or proximal to the junction.

[0101] In some examples, the disruption element is passed over the guidewire and placed at the treatment site. In some examples, the disruption element may comprise a balloon. In some examples, the balloon is placed at the treatment site and is inflated at pressures to damage the smooth muscle. These can include pressures of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40 or higher atm.

[0102] In some examples, the disruption element may comprise a balloon with sharpened protrusions configured to score the smooth muscle. In some examples, the balloon and sharpened protrusions may be sized to obtain a cutting depth of less than the depth between the intimal to adventitial layer that may aid in disrupting smooth muscle without causing perforation of the adventitial layer. In some examples, a balloon may comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more sharpened protrusions that are along the circumference of the balloon. In some examples, the cutting blades may be adjustable in size in order to adapt to the specific wall thickness of the layers of the LVJ. In some examples, the cutting balloon length may be adjusted after intravascular imaging to measure the layers of the wall of interest including the smooth muscle. [0103] According to some methods, the treatment system is configured to perform a circumferential dissection of the intimal wall extending into the smooth muscle to modify the smooth muscle layer. In some examples, this may be performed with a rotational system with a diameter specifically set to disrupt the vessel wall diameter of interest. In some examples, the rotational system includes a knife or sharp edge that cuts the region of interest upon proximal/distal displacement of the system across the region of interest.

[0104] In some examples, the disruption element is a cutting element directly disposed on a catheter that may be passed over a guidewire to be delivered to the treatment site. The cutting element can be electrically or mechanically actuated to perform a cutting maneuver of the LVJ. In some examples, the cutting element is activated by radiofrequency, or ultrasonic energy. In some examples, the cutting element is placed on a catheter at one or more locations circumferentially along the outer surface of the catheter. In some examples, the catheter can be rotated to rotate the cutting element and perform a cutting maneuver along all or a portion of the surrounding vessel wall. In these and other examples, there may be cutting elements disposed on the catheter circumferentially including but not limited to the 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and/or 12 o’clock position.

[01 5] In some examples, the depth of the cutting element extruding from the catheter or balloon is adjusted to adapt to the desired depth of cut required to modify smooth muscle at the treatment site. In some examples, the depth of the cutting element may be based on the intravascular imaging of the LVJ. In some examples, intravascular imaging of the junction including imaging of the lymphatic vessel segments can performed with ultrasound, optical coherence tomography or intravascular echocardiography catheter, or intracardiac echocardiography (ICE) catheter.

[0106] In some examples, the disruption element can be disposed on a wire or catheter and may have an adjustable angle, so as to restrict the depth of cut of smooth muscle. This may have the added benefit of reducing perforation while still ensuring an adequate disruption of smooth muscle. In some examples, the cutting element depth or length disposed on a catheter may be adjusted from knobs or dials placed on the handle of a catheter externally of the patient.

[0107] In some examples, imaging of the LVJ with an ICE catheter, optical coherence tomography (OCT) catheter, or intravascular ultrasound (IVUS) catheter is performed simultaneously during use of the cutting element used to disrupt smooth muscle at the junction. Such imaging advantageously enables direct visualization of the cutting element for safety to reduce the risk of perforation. In some examples, imaging of the LVJ and movement of the guidewire, catheter, or cutting element may be co-registered in order to provide feedback on location and/or depth of the guidewire/catheter or cutting element.

[0108] In some examples, the smooth muscle at the LVJ is modulated by either stimulation or inhibition to cause either constriction or dilatation of the smooth muscle at the junction.

[0109] In some examples, the LVJ can be dilated to a diameter larger than its original state. As shown in FIG. 13, in some examples, a clip system 900 is used to pull open the TD. The system 900 can include a plurality of clips 902, 904 placed between (a) one or more sides of the wall of the thoracic duct aspect of the junction and (b) one or more sides of the vein wall, with tension placed to open up the junction. In some examples, the system comprises a single clip. In some examples, the clip has grasping claws 904a, 904b and 910a, 910b with a link 906, 912, respectively, extending therebetween. The claws enable anchorage of the clip(s) on the venous and lymphatic aspects of the vessels. In some examples, the clip can extend from the thoracic duct to the IJV, or from the thoracic duct to the EJV, or from the thoracic duct to the SV, or the thoracic duct to the innominate vein, or some combination thereof.

[0110] In some examples, catheterization of the terminal thoracic duct or other lymphovenous junctions may also be performed via percutaneous access of the cistema chyli or the long thoracic duct in the mediastinum. The benefit of this would be to facilitate an alternative access if the thoracic duct cannot be accessed via a peripheral vein (anterograde). [0111] In some examples, the catheter or other ancillary devices used for catheterization may have special markers for identification of positioning. This may be to facilitate positioning and visualization under imaging guidance, such as hyperechoic and hypoechoic markers for detection under ultrasound or radiolucent and radiopaque markers for detection under fluoroscopy.

[0112] In some examples, resistance to flow at the junction of the thoracic duct into the venous system may be measured after cannulation of the thoracic duct. The pressure gradient across the thoracic duct-draining vein junction (may be internal jugular or subclavian vein or innominate vein) may be measured by passing a pressure measuring element located at the end of an ancillary device, such as a guidewire or catheter, through to the distal (terminal) thoracic duct, at a distance of up to 1cm, 2cm, 3cm, 4cm, or 5cm or more from the venous portion. While collecting pressure measurements, the pressure measuring element can be pulled back up to 1cm, 2cm, 3cm, 4cm, 5cm, 6cm, 7 cm, 8cm, 9cm, or 10cm or more toward to the draining vein and across the lymphovenous junction. The pull-back speed of the pressure measuring element may be done at a rate to detect a pressure gradient with expiration and inspiration. The patient may also be asked to hold their breath after expiration or inspiration.

[0113] In some examples, the system is configured to dilate the lymphovenous junction if a resistance to flow at the lymphovenous junction is identified or if a larger lymphovenous junction is desired.

[0114] In some examples, if access to the lymphovenous junction has not been obtained, access is obtained percutaneously by inserting a needle and guidewire into a peripheral vein, such as the femoral, basilic, cephalic, axillary, subclavian, internal jugular, or iliac veins. The guidewire is passed through the vein and then a sheath is advanced over the guidewire. A catheter is directed to the region of the lymphovenous junction. This procedure may involve fluoroscopy, computed tomography, magnetic resonance imaging, ultrasound, intravascular ultrasound, or optical coherence tomography to provide the benefit of imaging guidance to facilitate navigation of the wire and catheters. Once the catheter is advanced to the desired position in or near the thoracic duct outlet, the guidewire may be removed. A microcatheter can then be passed through the main catheter, with an intraluminal diameter smaller than the main catheter of no more than 1mm, 2mm, 3mm, or up to the width of the main catheter. The microcatheter may also be advanced over a guidewire that is passed first through the orifice to facilitate microcatheter access. If the anterograde approach is challenging, a guidewire can be advanced retrograde through the cisterni chylli, with a receiving snare catheter on the venous side of the thoracic duct. Further imaging may be done at the lymphovenous junction to identify stenosis, the intramural course, and luminal diameter. Once the guidewire is across the junction, a balloon catheter can be placed at the junction in which there is resistance to flow and inflated to a pressure that causes the diameter of the junction to increase. The benefit of this is to reduce resistance to flow at the junction. The pressure gradient can be measured before and after inflating the balloon catheter to measure the effect of the treatment.

[0115] In some examples, the dilating element may be in the form of a implant. It may be placed at the lymphovenous junction to maintain patency and durability of the expanded lymphovenous junction. The implant may extend into the thoracic duct, the draining vein, or both. Its properties may include being able to withstand transmural pressures of up to 5mmHg, lOmmHg, 15mmHg, 20mmHg, 25mmHg, 3OmmHg, 35mmHg, 40mmHg, or 50mmHg; having a coating to prevent obstruction; having a coating designed to prevent clot formation; or having a drug eluting element to prevent restenosis or clot formation. The implant may have a diameter of up to 2mm, 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm, or 30mm.

[0116] In some examples, the dilating element may be in the form of a balloon inflated across the lymphovenous junction for up to 30 seconds, 45 seconds, 60 seconds, 90 seconds, 120 seconds, 150 seconds, 180 seconds, 240 seconds, 300 seconds, or 360 seconds. The balloon may have a length of up to 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, or 50mm. In some examples, the dilating element(s) may be coated with and/or elute or release over time a substance to prevent restenosis or repeat narrowing of the lymphovenous junction. This coating may be a third-party pharmacological or non- pharmacological substance.

[0117] In some examples, the dilating element may be coated with different substances for the venous and lymphatic sides of the element in order to reduce restenosis or clotting based on the difference in tissue property of the different vessels.

[0118] In some examples, the dilating element(s) may be in the form of a bridge or separator to maintain vessel patency. In some examples, the dilating element may have a proximal diameter that is narrower than the distal diameter, or vice versa. It may also have one or more artificial valves. The valve may be a mechanical, tissue bioprosthetic, monocuspid, multi-cuspid, or ball and cage design. It may be designed to open based on the transmural pressure difference across the valve or based on a phase of the respiratory cycle, such as inspiration or expiration.

[0119] In some examples, the orifice lymphovenous valve is removed to increase the flow across the thoracic duct and draining vein. This beneficially enables passive and continuous draining, overcoming the closing of the valve during respiration or elevated venous pressures. The elements of this system may include a valve removal element and a collection element. The lymphovenous valve is removed by passing a guidewire across the valve, then deploying a valve removal element. The valve rupturing element may consist of a balloon, cutting balloon, radiofrequency ablation, cryoablation, or laser energy. A collection element is used to collect the ruptured valve and remove it from the body.

[0120] In some examples, in a case in which the thoracic duct has an intramural junction with the vein, in which the terminal duct sits within the end of the vein, a dilating element may be placed inside the junction in order to prevent transmural junction occlusion at times of elevated venous pressures such as in disease states like heart failure.

[0121] In some examples, the local venous outflow pressure at the thoracic duct outlet can be modulated by inserting one or more occluding elements such as a balloon catheter from independent access sites such as the jugular veins or other peripheral veins and guided to the thoracic duct outlet. The occluding elements can then be activated to cause a reduction in the local venous outflow pressure, and pressure measurements across the lymphovenous junction can be simultaneously measured during the period of occlusion in order to identify a gradient.

[0122] In some examples, the implant contains one or more valve elements in series. The benefit of the valve element is that it prevents venous reflux, ensures more flow while preserving the inherent flow pattern, and mitigates the risk of damaging or crushing the terminal lymphovenous valve. The valve may be made of a polymer or animal venous valve. A potential side effect of removing thoracic duct valves and/or enlarging the diameter of the thoracic duct is reversal of flow into the thoracic duct, which may be exacerbated when the patient is lying down or has a higher cardiac flow rate during exercise or a higher venous pressure. Valves in the lymphatic system may have other beneficial effects. Thus, having one or more valves to replace these functions would allow the implant to more physiologically mirror the native thoracic duct. In some examples, the valve may open when a certain pressure gradient is achieved and close when the gradient is resolved. In some examples, the valve may open and close with the respiratory cycle. In some examples, the valve is closed only when the pressure on the venous side is higher than the pressure on the thoracic duct side and is open in every other condition.

[0123] In some examples, the valve element could be configured as, but not limited to, leaflet valves, windsock valves, ball-and-cage valves, incomplete valves, duckbill, or valves that open to a larger diameter based on increased driving pressure. In some examples, the valve elements should be compressible to allow for delivery via a catheter.

[0124] In some examples, the valve element is placed at the terminal lymphovenous junction where the thoracic duct terminates in the venous system. In other examples, the valve element may be placed further into the thoracic duct or into the vein. This would have the advantage of driving flow and reducing the risk of venous reflux. Conclusion

[0125] Although many of the examples are described above with respect to systems, devices, and methods for treating heart failure by reducing volume overload, the present technology is applicable to other applications and/or other approaches, including treatment of edema and/or volume overload resulting from conditions other than CHF, such as weakened venous valves, kidney disease, lung disease, liver disease, thyroid disease, side effects of certain medications, pregnancy, immune system complications, and traumatic injuries. Moreover, the treatment devices, systems, and methods of the present technology can be used for visualizing and/or treating portions of the lymphatic system other than the TD, such as the right lymphatic duct. Moreover, other examples in addition to those described herein are within the scope of the technology. Additionally, several other examples 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 examples with additional elements, or the technology can have other examples without several of the features shown and described above with reference to FIGS. 1A-13.

[0126] The descriptions of examples 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 examples 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 examples may perform steps in a different order. The various examples described herein may also be combined to provide further examples.

[0127] 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.

[0128] 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 examples 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 examples of the technology have been described in the context of those examples, other examples may also exhibit such advantages, and not all examples need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other examples not expressly shown or described herein.

Claims

CLAIMS I/We claim:

1. A method comprising: positioning a first pressure sensor within the thoracic duct of a patient; positioning a second pressure sensor within a vein of a patient at a location proximate the lymphovenous junction (LVJ); measuring a pressure within the thoracic duct via the first pressure sensor; while measuring the pressure in the thoracic duct, measuring a pressure within the vein via the second pressure sensor; determining a difference between the thoracic duct pressure and the venous pressure; and based on the difference, determining whether the patient is a candidate for receiving a thoracic duct implant and/or dilation of the thoracic duct.

2. The method of Claim 1, wherein the vein is one of a brachiocephalic vein, a subclavian vein, an external jugular vein, or an internal jugular vein.

3. The method of Claim 1, wherein the pressures within the thoracic duct and the vein are measured over a time period inclusive of at least one respiratory cycle.

4. The method of Claim 1, wherein determining a difference between the thoracic duct pressure and the venous pressure includes determining a difference between the thoracic duct pressure and the venous pressure during an inspiration phase of the respiratory cycle.

5. The method of Claim 1, wherein positioning the first pressure sensor within the thoracic duct comprises advancing the first pressure sensor retrograde through the venous system and crossing the ostium at the LVJ into the thoracic duct.

6. The method of Claim 5, wherein the first pressure sensor is carried by an elongate member, and wherein the method further comprises advancing an access shaft retrograde through the venous system and into the thoracic duct, and wherein the elongate member is advanced through the access shaft into the thoracic duct.

7. The method of Claim 6, wherein the access shaft has a tapered distal tip.

8. The method of Claim 5, wherein the access shaft is advanced through a support shaft having a distal end disposed in the vein, proximate the LVJ.

9. The method of Claim 1, wherein positioning the second pressure sensor within the thoracic duct comprises advancing the second pressure sensor retrograde through the venous system to a location proximate the LVJ.

10. The method of Claim 1, wherein the first and second pressure sensors are disposed on the same device.

11. The method of Claim 1, wherein the first and second pressure sensors are disposed on different devices.

12. The method of Claim 11, wherein the first pressure sensor is carried by a pressure wire, and wherein the second pressure sensor is carried by an access shaft.

13. The method of Claim 11, wherein the first pressure sensor is carried by a pressure wire, and wherein the second pressure sensor is carried by a support shaft.

14. The method of Claim 1, wherein determining a difference between the thoracic duct pressure and the venous pressure comprises determining whether a difference between the thoracic duct pressure and the venous pressure is greater than zero, and based on the difference being greater than zero, determining that the patient is a candidate for receiving a thoracic duct implant and/or a procedure for dilating the thoracic duct.

15. A method for treating volume overload, comprising: positioning a distal portion of a delivery system within the thoracic duct, wherein the delivery system includes an implant in a compressed state; expanding a proximal portion of the implant into apposition with an inner surface of the thoracic duct ostium, thereby dilating the ostium and anchoring the implant; after expanding the proximal portion of the implant, expanding a distal portion of the implant into apposition with an inner surface of the thoracic duct; and withdrawing the delivery system, thereby leaving the implant implanted within the thoracic duct.

16. The method of Claim 15, wherein the delivery system is advanced through the venous system to the thoracic duct.

17. The method of Claim 15, wherein the delivery system is advanced retrograde through the venous system to the thoracic duct.

18. The method of Claim 15, wherein the delivery system is advanced through the venous system to the thoracic duct over a guidewire.

19. The method of Claim 15, wherein the implant is a an open-form scaffold.

20. A method for treating volume overload, comprising: advancing an occlusion device to the lymphovenous junction (LVJ) and occluding a portion of a vein proximate the LVJ while infusing contrast to visualize the thoracic duct; performing a lymphatic flow reserve assessment; and implanting an implant within the ostium of the thoracic duct, wherein the implant is advanced through the venous system and into the thoracic duct.

21. The method of Claim 20, wherein performing a lymphatic flow reserve assessment includes advancing a pressure sensing device retrograde through the venous system into the thoracic duct.