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WO1998031281A9 - Systeme laser pour revascularisation transmyocardique - Google Patents

Systeme laser pour revascularisation transmyocardique

Info

Publication number
WO1998031281A9
WO1998031281A9 PCT/US1998/000220 US9800220W WO9831281A9 WO 1998031281 A9 WO1998031281 A9 WO 1998031281A9 US 9800220 W US9800220 W US 9800220W WO 9831281 A9 WO9831281 A9 WO 9831281A9
Authority
WO
WIPO (PCT)
Prior art keywords
heart
laser
milliseconds
wall
beating heart
Prior art date
Application number
PCT/US1998/000220
Other languages
English (en)
Other versions
WO1998031281A1 (fr
Filing date
Publication date
Application filed filed Critical
Publication of WO1998031281A1 publication Critical patent/WO1998031281A1/fr
Publication of WO1998031281A9 publication Critical patent/WO1998031281A9/fr

Links

Definitions

  • the present invention is a medical laser system for treating ischemia with transmyocardial revascularization.
  • the heart has four chambers for receiving and pumping blood to various parts of the body.
  • oxygen-poor blood returning from the body enters the right atrium.
  • the right atrium fills with blood and eventually contracts to expel the blood through the tricuspid valve to the right ventricle.
  • Contraction of the right ventricle ejects the blood in a pulse-like manner into the pulmonary artery nd each lung.
  • the oxygenated blood leaves the lungs through the pulmonary ve ns and fills the left atrium.
  • the left atrium fills with blood and eventually contracts to expel the blood through the mitral valve to the left ventricle.
  • the heart muscle receives its bl ⁇ pd supply from the coronary arteries, which feed out and around onto the outsid ⁇ of the heart muscle.
  • the laser has developed into a very useful tool in modern surgery because of its pinpoint accuracy.
  • the carbon dioxide laser has been used for excision and vaporization of tissue in neurosurgery and plastic surgery as well as gastroenterology, urology, oto laryngology, gynecology and, most recently, in cardiac applications.
  • Transmyocardial revascularization is a method for treating ischemic heart disease.
  • Heart disease is the leading cause of disability and death in all industrialized nations, accounting for nearly twice as many deaths as those resulting from cancer. The majority of these deaths are due to coronary artery disease, a condition which results in the heart muscle (or myocardium) not receiving an adequate nutritive blood supply.
  • Transmyocardial revascularization is a technique used to supplement the blood supply delivered to the heart by providing the ischemic myocardium direct access to blood within the ventricular chamber.
  • the myocardium does not have direct access to the ventricular chamber and receives its nutritive blood supply entirely from the coronary arteries branching through the heart wall.
  • the additional blood flow provided by the transmyocardial revascularization makes up for the reduced blood flow from the coronary arteries and relieves the ischemia.
  • TMR transmyocardial revascularization
  • CW continuous wave
  • CO 2 carbon dioxide
  • a 800 watt laser is turned on for a time period of about 40 to 50 milliseconds, which provides about 30 to 40 joules.
  • the motion of the heart wall In order to drill a straight, uniform hole through the heart wall while the heart is beating, the motion of the heart wall must be essentially zero for the duration of the pulse. For a laser pulse 50 milliseconds long, there is only one period during the heart cycle when the heart wall is at rest for a time of that extent, this is between the end of diastole and the beginning of systole. At this short period, the motion is minimal when the fully expanded ventricles are waiting for the depolarization of the cells which initiates the contraction process. The length of this resting period varies with the pulse rate of the individual and can be significantly less than 50 milliseconds for some patients, resulting in less laser energy available and the possibility of incomplete penetration of the laser beam.
  • Holmium:YAG or excimer lasers do not produce sufficient energy to fully penetrate the myocardium in one heart cycle. Due to the long time required to create the channel, and in the case of the Holmium:YAG laser a relatively low absorption in the tissue, the thermal damage to adjacent tissue is quite high. The subsequent healing process then tends to close the channels as described above.
  • Optimized channels means channels or holes through the heart wall during the creation of which there is much less thermal damage to the surrounding tissue. Minimizing thermal damage to the surrounding tissue results in a more benign healing process in which there is minimal closure of the channels due to scar formation. The more benign healing process preserves the structural integrity of the adjacent tissue and provides a less thrombogenic surface. Channels which stay open more consistently and more uniformly will provide a much greater auxiliary blood flow to the treated regions of the myocardium.
  • a second possible source of additional blood flow is by means of the growth of new blood vessels in the vicinity of the channel during the healing, a process known as angiogenesis.
  • the ability of these new blood vessels to relieve ischemia depends upon their forming interconnections to the collateral artery system of the heart. If the channel is surrounded by a large, heavily fibrotic scar tissue layer, these vessels tend to terminate in the scar. Therefore, creating the channels with minimal thermal damage, and subsequent minimal scar formation, will enhance the contribution of angiogenesis to the new blood flow resulting from the TMR procedure.
  • a laser pulse on the order of about 1 millisecond in accordance with the present invention produces very little heating of, and consequent damage to, adjacent tissue because the laser energy is applied in a time which is shorter than the thermal diffusion time in the tissue. During the applied laser pulse, the heat generated by the laser does not have enough time to flow out of the tissue being vaporized into the adjacent tissue thus minimizing or eliminating thermal damage to the adjacent tissue. Also if the wavelength of the laser is such that the absorption of the laser energy is at the surface, then there is no direct heating of the adjacent tissue by the incident laser radiation.
  • the present system utilizes a high-energy, short-pulsed laser operating at a wavelength which is highly absorbed at the surface of, and in the myocardial tissue.
  • channels formed which provide the following: 1) preservation of the integrity of the surrounding tissue, 2) a more benign healing process resulting in minimal fibrosis and scarring, and 3) a less thrombogenic surface. All of these contribute to a process which provides for greater additional blood flow to the ischemic myocardium.
  • the high energy, short-pulsed laser system of the present invention can be synchronized to the heart's beating cycle to apply the laser pulse when the patient's ventricle is at or near full contraction such that the subsequent expansion phase of the heart's beating cycle keeps the lazed holes open mechanically at full diameter to prevent partial closing off of the holes and clotting. Because the heart wall is in motion throughout the contraction, the laser energy is delivered in about 1 millisecond so that the heart wall is effectively stationary relative to the pulse and uniform, straight holes are created through the heart wall.
  • a laser system for performing transmyocardial revascularization on a beating heart which comprises a laser having a beam operating at a wavelength with very high absorption in myocardial tissue with about a one millimeter diameter, means for directing the laser at a wall of the beating heart, and means for emitting the beam at the wall of the beating heart for about one millisecond to create a revascularizing channel completely through the wall in the about one millisecond.
  • a method for myocardial revascularization of a beating heart which comprises emitting laser energy with a beam having about a one millimeter diameter operating at a wavelength with very high absorption in myocardial tissue at a wall of the beating heart, and creating a revascularizing channel completely through the wall of the beating heart within five milliseconds or less with the beam.
  • a method for myocardial revascularization of a beating heart which comprises emitting a single, one millisecond laser pulse with a beam operating at a wavelength with very high absorption in myocardial tissue at a wall of the beating heart, and creating a revascularizing channel having about a one millimeter diameter completely through the wall of the beating heart with the single, one millisecond laser pulse.
  • FIG. 1 is a schematic block diagram of a heart-synchronized high- energy, short-pulsed laser system according to the present invention.
  • FIG. 2 illustrates the ECG signal and a firing pulse period in accordance with the present invention.
  • FIG. 1 a heart-synchronized, high energy, short- pulsed laser system 10 with electrocardiogram (ECG) unit 12 connected to a heart 14 which is to undergo the surgery.
  • ECG electrocardiogram
  • the ECG signal is delivered to trigger circuit 18, which provides a trigger pulse to laser unit 24 including a laser power supply and a high-energy, short-pulsed laser to produce a pulsed laser beam through articulating beam delivery optical arm or flexible waveguide 26 into optical handpiece 28 to make holes or channels in heart 14.
  • a number of channels can be formed from the outer wall (epicardium) extending through the myocardium and perforating the interior of the heart wall (endocardium).
  • the position of the trigger pulse in the heartbeat cycle is determined by trigger circuit 18.
  • the high energy, short-pulsed laser produces short pulses of energies in the range of about 5 to about 30 joules.
  • the delivered laser energy is between about 5 to about 30 joules according to the thickness of the myocardium as previously mapped by echocardiography.
  • the beam quality is sufficiently high to allow the output beam to be focused to a 1 millimeter diameter with a depth of field of at least about 20 millimeters.
  • the duration of the laser pulse is fixed (i.e. , every laser pulse has the same duration) at about 5 milliseconds or less, preferably fixed at about 2 milliseconds or less, most preferably fixed at about 1 millisecond or less.
  • a high energy, short-pulsed CO 2 laser operating over the range of 9.5 to 10.8 micrometers, preferably at 10.6 micrometers (such as available from Pulse Systems, Inc., Los Alamos, New Mexico) is used that creates complete holes through the myocardium with a single laser pulse, although depending on the resolution used to analyze the pulse, the pulse may appear as a series of micropulses within the single pulse.
  • the amount of energy delivered to the heart tissue is independent of pulse duration.
  • the laser energy is applied in a time which is shorter than the thermal diffusion time of the heart tissue so that the heat generated during the ablation of the heart tissue in the hole will not have time to flow out of the tissue being vaporized during the applied laser pulse to the surrounding tissue.
  • Trigger circuit 18 may be included as an additional board in a personal computer or a microprocessor controller, in which case the system can be controlled through the computer keyboard and suitable software or custom control panel.
  • the microprocessor controller and ECG unit 12 may have separate monitors, or they may have a single monitor which displays both the ECG and information about the laser system 10.
  • Trigger circuit 18 includes a gate which generally inhibits the delivery of a trigger pulse to laser unit 24. The inhibiting effect of this gate can be overcome when the surgeon steps on foot switch 16.
  • the heart cycle can be described in terms of the signals seen by an electrocardiograph (ECG) 21 as shown in Figure 2.
  • ECG electrocardiograph
  • the volume curve 22 of the left ventricle showing the expansion and contraction of the heart is also shown.
  • the impulse to begin a heart cycle starts at the sinus node and first triggers the activation of the atria, this is represented by the normal P wave of the electrocardiogram.
  • the impulse reaches the atrio ventricular (AV) node and subsequently the ventricular myocardium which then triggers the ventricular contraction.
  • the onset of ventricular depolarization is represented by the beginning of the normal Q wave.
  • the QRS complex that is, the combined Q, R and S waves, represents the sequence of ventricular depolarization, and is approximately 80 milliseconds in duration.
  • the ventricular contraction begins at the end of the S wave and continues for approximately 420 milliseconds to the end of the normal T wave.
  • the T wave represents the ventricular repolarization.
  • Diastole is the period from the end of the T wave to the beginning of the Q wave (i.e. , the period during which the ventricles expand to full volume and fill until the signal to begin the next contraction starts).
  • Systole is the period from the beginning of the QRS complex to the end of the T wave (i.e., when the ventricles undergo depolarization, contraction, ejection, and repolarization).
  • the laser pulse can be fired at anytime during the heart cycle and the relative wall motion during the pulse is negligible. Therefore, the present invention has the flexibility of firing at any time during the heartbeat cycle to achieve a high quality, optimized hole. It is preferred, however, that the holes are drilled sometime during the period 20 (FIG. 2) when the ventricle is in the region of maximum contraction. This typically corresponds to a period about 250 to about 400 milliseconds after the R wave. The subsequent expansion of the heart tends to further open the holes and at full diameter resulting in more significant blood flow through the holes.
  • the laser pulse With laser energy delivered in a laser pulse less than 5 milliseconds, preferably in less than 2 milliseconds, more preferably in 1 millisecond or less, the laser pulse has the ability to be placed at anytime during the heart cycle with ease, therefore it need not be synchronized with the heart cycle.

Abstract

L'invention concerne un système laser (10) à impulsions brèves et à haute énergie, ainsi qu'une méthode de revascularisation transmyocardique. Le système laser (10) applique une impulsion laser unique en une milliseconde, de façon à créer un canal de revascularisation traversant la totalité du myocarde.
PCT/US1998/000220 1997-01-21 1998-01-20 Systeme laser pour revascularisation transmyocardique WO1998031281A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US3613097P 1997-01-21 1997-01-21
US60/036,130 1997-01-21

Publications (2)

Publication Number Publication Date
WO1998031281A1 WO1998031281A1 (fr) 1998-07-23
WO1998031281A9 true WO1998031281A9 (fr) 1998-12-03

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Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5931834A (en) 1996-10-15 1999-08-03 Eclipse Surgical Technologies, Inc. Method for non-synchronous laser-assisted myocardial revascularization
US6468271B1 (en) 1999-02-24 2002-10-22 Scimed Life Systems, Inc. Device and method for percutaneous myocardial revascularization
US6217575B1 (en) 1999-02-24 2001-04-17 Scimed Life Systems, Inc. PMR catheter
ATE332104T1 (de) 1999-03-22 2006-07-15 Eschmann Holdings Ltd Chirurchische hochdruckflüssigkeitsschneidevorrichtung zur transmyokardialen revaskularisation
FR2797581B1 (fr) 1999-08-20 2001-12-07 Saphir Medical Products Gmbh Procede et appareil chirurgical a jet de liquide sous pression pour la revascularisation transmyocardiale
US6533779B2 (en) 2001-01-16 2003-03-18 Scimed Life Systems, Inc. PMR catheter and associated methods
US6544220B2 (en) 2001-02-14 2003-04-08 Scimed Life Systems, Inc. Fluid jet PMR

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5703985A (en) * 1996-04-29 1997-12-30 Eclipse Surgical Technologies, Inc. Optical fiber device and method for laser surgery procedures
US5672170A (en) * 1996-06-20 1997-09-30 Cynosure, Inc. Laser transmyocardial revascularization arrangement

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