AU8506398A - Apparatus and method for transmyocardial revascularization by laser ablation - Google Patents

Description

WO99/04708 PCT/US98/15139 APPARATUS AND METHOD FOR TRANSMYOCARDIAL REVASCULARIZATION BY LASER ABLATION 5 BACKGROUND Technical Field The present disclosure relates to improved 10 apparatus and methods for transmyocardial revascularization (TMR) by laser ablation with a lasing device. 2. Background of the Related Art TMR is a procedure for treating heart disease, 15 wherein multiple channels of small diameter are created in the heart wall, extending into the ventricle. Such channels facilitate delivery of blood directly from the ventricle to oxygen starved areas of the heart. TMR is typically used on patients with ischemic heart disease, particularly those who 20 are not candidates for coronary artery bypass or percutaneous transluminal angioplasty. During a typical TMR procedure, dozens of channels are created from the epicardium, through the myocardium and endocardium and into the ventricle, with each channel being 25 of sufficiently small diameter such that the end portions of the channels at the epicardium can be closed by blood clotting. The channels can be created by employing either a mechanical coring apparatus or a lasing device. With either technique, an objective is to produce channels that remain 30 internally patent in the long term and which do not close up due to fibrosis and/or scarring. In early laser myocardial revascularization, a CO 2 laser was used to produce holes in the heart wall by transmitting laser energy from the laser to the heart wall. 35 Typical CO 2 lasers used for TMR are externally located and have an articulated support arm for aiming and directing laser energy through a series of mirrors that reflect the energy onto the heart wall. Thus, some surgical opening of WO99/04708 PCT/US98/15139 the chest wall is required to access the heart muscle. The entrance wound in the heart can be closed by relatively brief external pressure while the endocardial and myocardial layers remain open to permit blood flow from the ventricle 5 to the heart muscle. Less traumatic approaches to laser myocardial revascularization have been disclosed. These methods include the use of optical fibers introduced either through a patient's vasculature or alternatively, directly into the 10 patient's chest cavity. The intravascular method involves the direction of laser energy from inside the heart to form a bore in the heart wall while the other method involves introduction of the lasing apparatus through a relatively small iincision in the patient's chest to access the outer 15 wall of the heart. U.S. Patent No. 4,658,817 to Hardy discloses a method and apparatus for TMR using a laser wherein a hollow needle having a sharp distal tip is inserted into the epicardium and a laser beam is focussed through the needle 20 to create channels. It is stated in the Hardy patent that this technique eliminates surface bleeding and the need for suture. However, there is no laser ablation member (e.g., optical fiber) that advances through the needle and into the myocardium contemporaneously with laser energy being 25 generated. With current TMR procedures wherein channels are formed from the outer heart wall, the technique for stopping the bleeding from each channel at the epicardium after channel formation typically entails applying pressure to the 30 opening of the just-formed channel. Pressure is typically applied by the finger of the surgeon or assistant during open heart surgery, or with a laparoscopic instrument when the procedure is performed laparoscopically. In either case, because pressure is applied to each channel opening 35 for at least several seconds, and it is impractical to begin forming another channel until the bleeding is stopped from -2- WO99/04708 PCTIUS98/15139 the previous channel, the overall TMR procedure can be undesirably prolonged by the time expended on applying pressure to each channel. Accordingly, a need exists for a TMR procedure 5 wherein the time spent to stop the blood flow from each of the individual transmyocardial channels is reduced or eliminated, thereby increasing the likelihood of success of each operation. 10 SUMMARY The present disclosure is directed to methods for performing transmyocardial revascularization employing a laser device having a laser ablation member, e.g., one or more optical fibers. One preferred method includes the 15 steps of: advancing the laser ablation member a predetermined distance within the patient's heart tissue to mechanically pierce the epicardium; then outputting laser energy from the laser ablation member to ablate heart tissue and create a patent channel extending into the patient's 20 ventricle; and, withdrawing the laser ablation member from the heart tissue, whereby epicardial tissue pushed aside during the initial advancing step substantially returns to a position coinciding with the channel and acts as a channel cap to reduce bleeding from the channel. In an alternative 25 method, the distal end of the laser fiber is advanced to or maintained at a position such that it extends distally from a laser handpiece held by the surgeon; the fiber is caused to press against the epicardium prior to laser firing, thereby causing the exterior tissue to "tent". The fiber is 30 then advanced at a desired rate as the laser fires to form the channel. In each of the above methods, it is preferable to advance the laser ablation member at a rate coordinated with the magnitude of laser energy generated in order to precisely form each channel. 35 In another alternative method, the laser fiber can be placed against the epicardium and initially advanced at a -3- WO99/04708 PCT/US98/15139 rate faster than the tissue ablation rate of the laser. In this method, the fiber during this stage, will mechanically pass through the heart tissue. After the fiber travels though at least a portion of the epicardium, the fiber 5 advancement rate can be decreased to such a rate that the laser energy alone ablates the tissue to form the channel. In yet another alternate method, the fiber can be advanced at a constant rate while the pulse rate of the 10 laser is varied to allow mechanical passage of the fiber through at least a portion of the epicardium. More specifically, the amount of energy delivered by the laser fiber can be low, e.g., fewer pulses per second, while passing through a portion of the epicardium, and increased 15 thereafter to complete the channel. Advantageously, with the present methods, the fiber creates a flap or "channel cap" in the epicardial surface. The interface between the channel cap and the adjacent epicardial/myocardial tissue defines a very narrow 20 opening such that blood clotting can occur rapidly at the interface. Thus, the time expended for applying pressure to the channel opening at the epicardium following each channel's formation is substantially reduced as compared to prior art methods. The present method may even allow the 25 pressure-applying step to be eliminated entirely. In addition, the pressure of the channel cap may permit larger channels to be formed, as compared to channels without the cap, due to the channel cap's ability to moderate or prevent the flow of blood from the channel. 30 BRIEF DESCRIPTION OF THE DRAWINGS Various preferred embodiments are described herein with reference to the drawings, wherein: FIG. 1 illustrates a laser ablation device used to 35 create TMR channels; -4- WO99/04708 PCT/US98/15139 FIG. 2 is a perspective view of the laser ablation device; FIG. 3 is a perspective view of the hand piece of the laser ablation device; 5 FIG. 4 is an exploded view showing the various components of the hand piece; FIG. 5 is a side view of the hand piece having a fiber extended in proximity to the epicardium; FIG. 6 is a side view showing piercing of the 10 epicardium; FIG. 7 is a side view showing the fiber being advanced through the myocardium and endocardium; FIG. 8 is a side view showing withdrawal of the fiber from the heart tissue to reveal the channel created 15 therein; FIG. 9A is a cross-sectional view of a completed transmyocardial channel; FIG. 9B is an end view of the epicardium having a channel capped by a flap; 20 FIGS. 10-13 illustrate an alternate method for performing TMR disclosed herein, where: FIG. 10 is a side view of the hand piece in proximity to the epicardium; FIG. 11 is a side view showing piercing of the 25 epicardium; FIG. 12 is a side view showing the fiber being advanced through the myocardium and endocardium; FIG. 13 is a side view showing withdrawal of the fiber from the heart tissue to reveal the channel created 30 therein; FIGS. 14-16 illustrate an alternative method for performing TMR disclosed herein; where: FIG. 14 is a side view showing piercing of the epicardium; 35 FIG. 15 is a side view showing the fiber being advanced through the myocardium and endocardium; -5- WO99/04708 PCT/US98/15139 FIG. 16 is a side view showing withdrawal of the fiber from the heart tissue to reveal the channel created therein; FIGS. 17-19 illustrate an alternative method for 5 performing TMR disclosed herein, where: FIG. 17 is a side view showing piercing of the epicardium; FIG. 18 is a side view showing the fiber being advanced through the myocardium and endocardium; and 10 FIG. 19 is a side view showing withdrawal of the fiber from the heart tissue to reveal the channel created therein. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 15 Preferred embodiments of TMR methods will now be described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements. Referring to FIGS. 1 and 2, a laser ablation 20 device, designated generally as 10, is employed to practice a TMR procedure in accordance with the present disclosure. Device 10 is capable of advancing a laser ablation member 18 through heart tissue while concomitantly outputting laser energy, where the advancement rate is coordinated with the 25 magnitude of laser energy generated and with the pulsing frequency of the laser source. This coordination enables highly patent and precise TMR channels to be created. Lasing device 10 is similar to lasing devices disclosed in copending, commonly assigned U.S. Patent Application Serial 30 No. 08/648,638 to Pacala et al., filed May 13, 1996, the subject matter of which is incorporated herein by reference. Laser ablation device 10 includes a hand piece 11, an optical fiber advancing mechanism 12, a laser generator 14, a foot operated actuator 16, and a control module 17. 35 The optical fiber advancing mechanism 12 is of the type capable of precisely transmitting longitudinal motion to -6- WO99/04708 PCT/US98/15139 laser ablation member 18, e.g., an optical fiber, optical fiber bundle or other laser energy transmission mechanism. The controlled longitudinal motion can be provided by one or more motors and preferably by one or more commercially 5 available stepper motors. The laser generator 14 may be either a continuous wave laser or a pulsed, high energy laser, such as, for example, an excimer, CO 2 , Yag or an alexandrite laser. The optical fiber advancing mechanism 12 and the 10 laser generator 14 are operably connected to foot actuator 16. By depressing foot actuator 16, laser energy is transmitted through the optical fiber 18 by laser generator 14 while fiber advancing mechanism 12 contemporaneously advances optical fiber 18 relative to hand piece 11. 15 Alternately, foot actuator 16 can cause at least partial advancement of the fiber without transmission of laser energy, as will be described in greater detail. An electrical signal from foot actuator 16 actuates control module 17 which communicates with fiber advancing mechanism 20 12. Control module 17 is programmable and controls the motors or other suitable advancing structure in advancing mechanism 12 upon actuation of foot actuator 16. Control module 17 is shown with a receptacle 19 adapted to engage a terminal of a programmable computer to interface control 25 module 17 with the computer. As such, instructions required to operate advancing mechanism 12 can then be stored in memory within control module 17. A toggle switch 15 may be provided on the control module 17 to switch from an operation mode to a test mode. In a particular test mode, 30 when the foot actuator 16 is acted upon, the flexible optical fiber is moved sequentially from a retracted position, to a predetermined extended position, and back to the retracted position. Fiber advancing mechanism 12 can be equipped with 35 two internal limit switches (not shown). The first limit switch is activated when the optical fiber 18 is at a -7- WO99/04708 PCT/US98/15139 desired retracted position (i.e., a "home" position), wherein the mechanism that is retracting the fiber is caused to stop. Optical fiber 18 is in the retracted position unless foot actuator 16 is depressed or the test mode is 5 activated. The exact retracted position is selectable by means of selector 23, e.g., a rotatable knob. One way of implementing a TMR procedure in accordance with the present disclosure using laser ablation device 10 is to select the retracted position as a position in which the distal end of 10 optical fiber 18 protrudes from the distal end of hand piece 11, the purpose of which is discussed in greater detail, below. The second limit switch within unit 12 limits/controls the maximum distance that the optical fiber 15 can extend from hand piece 11. This limit switch is an indexer which includes external selector 21. Selector 21 is provided so that the operator can select the desired maximum extension of the distal end of the optical fiber from the handpiece. For example, selector 21 can be in the form of a 20 rotatable knob that can be set at selectable positions, wherein each position corresponds to a predetermined maximum longitudinal position of the optical fiber. When the fiber reaches the selected maximum position, a limit switch automatically terminates the fiber's advancement. By way of 25 example, the operator can select maximum fiber extension positions so that the distal end of the fiber extends from the distal end of hand piece 11 from between about 0.5 cm and about 5.0 cm, with the ability to select in increments of about 0.25 cm to about 0.5 cm. The maximum extension 30 position is preferably chosen to be slightly longer than the heart wall thickness for the particular patient such that fiber 18 will penetrate into the patient's ventricle. Once the maximum extended position is reached, output of laser energy is automatically suspended. 35 FIG. 3 illustrates a perspective view of the hand piece 11 of laser ablation device 10. Briefly, hand piece -8- WO99/04708 PCT/US98/15139 11 includes housing 20 formed from molded housing half sections 20a and 20b. Housing 20 has an elongated body 22 with a conically tapered section 24. Optional locator ring 26 is provided at the distal end of conically tapered 5 section 24. The front surface 27 is positioned in abutting relation with the epicardium of a patient directly following the piercing of the epicardium with the tip of fiber 18 during a TMR procedure. Locator ring 26 facilitates proper orientation of the hand piece with respect to the heart 10 tissue. However, locator ring may be eliminated if it is desired to improve visibility of the epicardium with some trade-off of stability. Locator ring 26 can be formed integrally with housing half-sections 20a and 20b or can be removably fastened to tapered section 24. A ridged surface 15 28 is formed on an outer wall of housing half-sections 20a and 20b to facilitate grasping of the device 10. FIG. 4 illustrates hand piece 11 with housing half-sections 20a and 20b and the internal components separated. Housing half-sections 20a and 20b define a 20 central bore 30, a proximal recess 32, and a distal recess 34. The proximal recess 32 is configured to receive a swivel connector 36 which is fastened to the optical fiber casing 38. The swivel connector 36 has an annular flange 40 dimensioned to be received within an increased diameter 25 section 42 of proximal recess 32 to permit rotation of housing 20 with respect to optical fiber casing 38. As shown, the locator ring 26 has a cylindrical body portion 44 having an annular flange 46 formed at its proximal end. The cylindrical body portion 44 includes a 30 central bore 50 and is configured to be received within the distal recess 34 defined by housing half-sections 20a and 20b. Central bore 50 of cylindrical body portion 44 is aligned with a central opening 48 formed in the distal end of the housing 20 and the central bore 30 of housing 20. 35 Locator ring 26 can either swivel, to allow independent rotation of the hand piece relative thereto, or be fixed in -9- WO99/04708 PCTIUS98/15139 place. The optical fiber 18 is slidably positioned within central bores 30 and 50 such that it can be advanced through opening 48 in housing 20. Pins or screws 49 can be used to fasten the housing half-sections 20a and 20b together to 5 secure the locator ring 26 and the swivel connector 36 to the housing 20. If locator ring 26 is eliminated, front surface 31 of tapered portion 29 can act as the stop which contacts the patient's outer epicardial surface to prevent initial penetration of fiber 18 beyond distance Di. This 10 surface 31 can be buttressed slightly whereby it would form a small diameter collar that is seated against the epicardium during the channel formation procedure. As seen in FIG. 3, the distal end of hand piece 11 corresponds to the front surface 27 of locator ring 26. 15 Allowing optical fiber 18 to protrude enables the surgeon to pierce the epicardium with the tip of fiber 18 without initially firing the laser, such that fiber 18 penetrates a predetermined distance into the outer heart wall. This initial penetration of the fiber is stopped at the 20 predetermined distance by means of the surface 27 contacting the epicardial wall. The operator then depresses foot actuator 16 to cause laser energy to be generated and form the channel. By virtue of the initial penetration without laser energy output, the transmyocardial channel that is 25 formed will be "capped" at the epicardium by the outer heart tissue which is not ablated. This will become more apparent below. As an alternative to selecting a protruding retraction position and utilizing the first surface 27 to 30 prevent excess initial penetration of fiber 18, the advancing mechanism 12 (FIG. 1) can be designed in conjunction with the control unit 17 to activate fiber 18 to automatically advance longitudinally by the desired predetermined initial distance without laser energy output. 35 (This initial distance will be designated hereafter as distance Di). This automatic initial advancement can be -10- WO99/04708 PCTIUS98/15139 implemented either by activating an additional switch (not shown) on unit 12 or 17, or it can advance automatically whenever actuator 16 is initially depressed. In either of these cases, the above-noted retracted position would 5 preferably not be adjustable but rather, would be preset to approximately coincide with the distal surface 27. The operator would then place the surface 27 directly on the epicardium and then depress foot actuator 16 (or activate the additional switch), whereupon the fiber 18 would first 10 automatically advance the distance Di without laser energy being generated. Following the initial advance, laser energy would automatically commence and the fiber correspondingly advanced to create the TMR channel. In this embodiment, selector switch 23 would be designed in 15 conjunction with advancing mechanism 12 to allow selection of the initial penetration distance Di, not to select the retracted position. With either of the above approaches, i.e., retracted position protruding by distance Di or automatic 20 advancement to distance Di without laser energy, the operator/surgeon preferably selects the initial penetration distance Di. (Optionally, this distance could be preset and not alterable by the operator). Typically, a healthy heart has a wall thickness of 10-15mm. A diseased heart may be as 25 thick as 40mm (measured from the outer surface of the epicardium to the inner surface of the endocardium). As such, the initial penetration distance Di is typically selected in the range of about 1 to about 2-5mm and preferably from about 2 to about 5mm so that the fiber 18 30 penetrates slightly into the myocardium. This will ensure that an adequate channel cap will be subsequently formed. The diameter of the fiber (or fiber optic bundle) 18 is typically in the range of about 0.5 to about 2.5mm, and preferably about 1.4mm. The TMR channel to be formed has 35 about the same size diameter as the fiber or fiber bundle 18. -11- WO99/04708 PCTIUS98/15139 In either of the above methods, the heart tissue may "tent" in response to the partially advanced fiber pressing against the epicardium. If this occurs, upon commencement of laser firing, the heart tissue will swiftly 5 move towards the handpiece (the "tent" will collapse). This movement of the tissue will cause the outer layers of the heart tissue to receive less laser energy, resulting in at least a partial channel cap to aid in closing the channel. Referring now to FIGS. 5-8, a method for producing 10 a TMR channel utilizing the laser ablation device 10 is illustrated. As shown in FIG. 5, hand piece 11 is brought in proximity to the epicardium 52 of a heart patient. Prior to entry into the epicardium, the tip of optic fiber 18 protrudes slightly from the locator ring 26 by distance Di, 15 where Di is measured from the distal surface 18a of fiber 18 to the front surface 27 of locator ring 26. It is noted that the surface 18a may be flat as shown; however, it could alternatively be beveled to facilitate piercing of the epicardium and preliminary advancement into the 20 epicardial/myocardial tissue. In any case, the distance Di is selectable by means of select switch 23 (FIG. 1) discussed earlier. With the tip of fiber 18 protruding in this manner (retracted position), and without depressing the foot actuator 16 to output laser energy, the fiber tip 25 surface 18a is brought into contact with epicardium 52 so as to mechanically pierce or "tent" the epicardial outer surface. The fiber tip initially advances through at least a portion of the epicardium 52 and myocardium 50 either without laser energy being generated or immediately after 30 lasing begins. As the tip of fiber 18 penetrates, epicardial tissue (and as shown, myocardial tissue, if desired) adjacent to the fiber tip is pushed aside. This pushed aside tissue will not be ablated by the laser energy. Tissue 53 will substantially return to its natural position 35 following channel formation and act as a cap to reduce bleeding from the channel as will become apparent below. -12- WO99/04708 PCT/US98/15139 In a preferred method, initial penetration of the fiber occurs until the front surface 27 contacts the epicardium 52 (FIG. 6). At this point, fiber 18 has penetrated approximately the distance Di into the heart 5 tissue. Locator ring 26 enhances the surgeon's ability to position and stabilize the laser device 10 with respect to the heart, which can be beating during the procedure. However, as explained above, some embodiments may not utilize locator ring 26. 10 As depicted in FIG. 7, the TMR channel is formed by transmitting laser energy from the tip of fiber 18 to ablate heart tissue while correspondingly advancing optical fiber 18. The fiber tip is advanced through the myocardium 50 and endocardium 54 until it reaches its maximum extended 15 position corresponding to the distance D2 between fiber tip surface 18a and the surface 27 of locator ring 26. In methods disclosed herein, while forming the channel below the channel cap, fiber 18 is preferably advanced at a rate that is coordinated with the power level 20 and the frequency of pulsing of the laser generator. For example, optical fiber 18 can be advanced at a rate of between about 0.125mm/sec (0.005 in/sec) to about 12.7mm/sec (0.5 in/sec) with a laser power level of about 10 mJ/mm 2 to about 60 mJ/mm 2 and a pulsing frequency of about 5 Hz to 25 about 400 Hz. Preferably, the optical fiber is advanced at a rate of about 0.75mm/sec to about 2.0mm/sec with a laser power level of between about 30 mJ/mm 2 to about 40 mJ/mm 2 and a pulse frequency of about 20 to about 50 Hz. In a most preferred embodiment, the rate of advancement of the optical 30 fiber is no greater than the rate of ablation of tissue in order to minimize mechanical tearing by the fiber. Alternatively, if some degree of mechanical tearing is desired in addition to laser ablation, the advancing mechanism can be set to advance the fiber at a rate greater 35 than the ablation rate. Studies have shown that a xenon chloride excimer laser operating at a power level of about -13- WO99/04708 PCT/US98/15139 35mJ/mm 2 can ablate about 30-35 microns of animal heart tissue per pulse. As discussed above, the maximum extended position corresponding to the distance D2 is selectable by the 5 surgeon by means of select switch 21. Once the maximum extended position is reached, wherein fiber 18 typically penetrates slightly into ventricle 56, output of laser energy is automatically suspended. At this point, the operator releases depression of foot actuator 16, causing 10 fiber 18 to retract to the retracted position, as depicted in FIG. 8. The hand piece 11 is then drawn away from the heart wall whereby transmyocardial channel 60 is completed. The completed transmyocardial channel 60 is shown in cross-section in FIG. 9A, while FIG. 9B shows the end 15 view of the epicardium 52. The epicardium/myocardial tissue 53 that was pushed aside without being ablated during the preliminary penetration of fiber 18, returns to its original location coinciding with channel 60 upon the fiber's withdrawal. This tissue 53 forms a flap that acts as a cap 20 for the channel 60 to reduce bleeding from the channel at the epicardium 52. The interface 59 between the flap of tissue 53 and the adjacent tissue is generally an annular ring less than 360_ in extent. As shown, the cap 53 can consist of both epicardial and myocardial tissue, but could 25 alternatively be just epicardial tissue. Once channel 60 is completed, fiber 18 can be moved to another location on the epicardium to begin forming another channel, without the necessity of applying extended pressure to the portion of the epicardium coinciding with 30 just-formed channel 60. The overall procedure wherein dozens of channels 60 are typically formed can thus be performed much faster as compared to other methods. Three alternate methods of forming a TMR channel having a channel cap will now be discussed with reference to 35 Figs. 10-19. In a first alternative method, the distal end 18a of the laser fiber 18 is initially flush with the distal -14- WO99/04708 PCT/US98/15139 end of laser handpiece 11 (FIG. 10). The fiber 18 is then caused to puncture the epicardium 52 prior to or upon commencement of laser firing (FIG. 11) by advancing the fiber a distance Di prior to firing. The fiber is then 5 advanced at a specifically desired rate as the laser fires to form the channel 60 (FIG. 12); and is withdrawn upon completion of the channel 60 (FIG.13). In a second alternative method, the laser fiber 18 can be placed against the epicardium 52 and initially 10 advanced at a rate faster than the tissue ablation rate of the laser (FIG. 14). In this method, the fiber 18 will mechanically pass through the heart tissue. After the fiber 18 travels through at least a portion of the epicardium 52, the fiber advancement rate can be decreased to such a rate 15 that the laser energy ablates the tissue to form the channel 60 (FIG. 15). The fiber 18 is then withdrawn from the heart tissue (FIG. 16). In a third alternative method shown by FIGS. 17 19, the fiber 18 pierces the heart tissue (FIG. 17) and is 20 advanced at a constant rate while the firing rate of the laser energy is varied to allow mechanical passage of the fiber 18 through at least a portion of the epicardium 52 (FIG. 18). More specifically, the amount of energy delivered by the laser fiber 18 can be low, e.g., fewer 25 pulses per second, while passing through a portion of the epicardium 52, and increased thereafter to complete the channel 60. The fiber 18 is then withdrawn from the heart tissue (FIG. 19). It is also contemplated to produce multiple 30 channel caps in the epicardium sequentially in the same channel by repetitively and consecutively advancing the fiber and firing the laser. Multiple channel caps will provide better assurance that the channel has been successfully capped. 35 It will be understood that various modifications can be made to the embodiments disclosed herein. For -15- WO99/04708 PCT/US98/15139 example, other types of devices for delivering laser energy could alternatively be used to produce TMR channels utilizing the method of the present disclosure. For instance, the method can be performed endoscopically, 5 wherein the fiber is entroduced through a small tube to access the heart wall. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope 10 and spirit of the claims appended hereto. -16-

Claims (24)

1. A method of performing transmyocardial revascularization, comprising the steps of: 5 providing a lasing device having a laser ablation member; advancing the laser ablation member at a predetermined distance within the patient's heart tissue to mechanically pierce the epicardium; 10 outputting laser energy from said laser ablation member to ablate heart tissue and create a channel extending into the patient's ventricle; and withdrawing the laser ablation member from the heart tissue, whereby epicardial tissue pushed aside during 15 said advancing step substantially returns to a position coinciding with the channel and acts as a channel cap to reduce bleeding from the channel.

2. The method according to claim 1, wherein said 20 laser ablation member comprises an optical fiber.

3. The method according to claim 1, wherein said step of outputting laser energy further includes automatically advancing said laser ablation member within 25 said heart tissue to create said channel.

4. The method according to claim 3, wherein said laser ablation member is advanced within said heart tissue to create said channel at a rate coordinated with magnitude 30 of laser energy generated.

5. The method according to claim 4, wherein said rate is further coordinated with a pulsing frequency of said lasing device. 35 -17- WO99/04708 PCTIUS98/15139

6. The method according to claim 1, wherein said predetermined distance corresponds to a distance extending into the patient's myocardium, whereby a portion of the myocardium coinciding with the channel is mechanically 5 penetrated and forms part of said channel cap subsequent to formation of said channel.

7. The method according to claim 1, wherein said predetermined distance is in the range of about 1mm to about 10 5mm.

8. The method according to claim 1, further comprising the step of forming a second transmyocardial channel without applying pressure to the portion of the 15 epicardium that caps the channel previously created.

9. The method according to claim 1, wherein said laser ablation member is housed within a handle piece of said laser ablation device, said laser ablation device 20 further including means for providing a retracted position for said laser ablation member in which said laser ablation member protrudes a given distance from a front surface of said hand piece, said given distance being substantially equal to said predetermined distance, said method further 25 comprising the step of setting said laser ablation member in the retracted position prior to advancing it against the epicardium to pierce and penetrate the epicardium, said front surface acting as a stop to prevent excess penetration of said laser ablation member. 30

10. The method according to claim 9, wherein said laser ablation device further includes a selector to enable an operator to select said retracted position, and further including the step of selecting the retracted position prior 35 to advancing said laser ablation member against the epicardium. -18- WO99/04708 PCT/US98/15139

11. The method according to claim 10, wherein said laser ablation device further includes an additional selector to enable an operator to select a maximum extension position for said laser ablation member, said method further 5 comprising the step of selecting said maximum extended position prior to outputting laser energy, said step of outputting laser energy being performed until said maximum extended position is reached wherein laser energy is no longer generated. 10

12. The method according to claim 1, wherein said channel cap is in the form of a flap of heart tissue defining an annular interface with proximal heart tissue, said annular interface being less than 360 degrees in 15 angular extent.

13. A method for performing transmyocardial revascularization, comprising the steps of: providing a lasing device having at least one 20 optical fiber for outputting laser energy, said lasing device including an indexer for providing a retracted position for said fiber protruding from a front surface of a hand piece retaining said fiber; placing said fiber in the retracted position and 25 advancing the fiber against the epicardium of a patient without outputting laser energy therefrom to mechanically pierce the epicardium; outputting laser energy from said fiber while correspondingly advancing the fiber to thereby create a 30 channel extending into the patient's ventricle; and withdrawing the fiber from the heart tissue, whereby epicardial tissue pushed aside by said fiber during said placing step returns to a position coinciding with the channel and acts as a channel cap to reduce bleeding from 35 the channel. -19- WO99/04708 PCTIUS98/15139

14. The method according to claim 13, wherein said step of outputting laser energy from said fiber is performed while advancing said fiber contemporaneously at a rate coordinated with magnitude of said laser energy 5 generated and with a pulsing frequency of said lasing device.

15. The method according to claim 13, wherein said retracted position is selected such that said fiber 10 penetrates the patient's myocardium prior to said front surface contacting the epicardium, whereby a portion of the myocardium is pushed aside by the fiber during said placing step and, upon withdrawal of the fiber, returns to a position coinciding with the channel to form part of said 15 channel cap.

16. The method according to claim 13, wherein said retracted position corresponds to a distance from a distal surface of said fiber to said front surface of said 20 hand piece in the range of about 1mm to about 10mm.

17. The method according to claim 13, wherein said step of placing entails advancing the fiber within the patient's heart tissue until the front surface of said hand 25 piece contacts the epicardium.

18. A lasing device, comprising: a hand piece having proximal and distal ends and a front surface at said distal end; 30 a laser ablation member having first and second ends, the first end being extendible through said hand piece; an indexer for placing said laser ablation member in a stationary retracted position protruding a 35 predetermined distance from said front surface to enable said laser ablation member to mechanically penetrate the -20- WO99/04708 PCT/US98/15139 epicardium of a patient; a laser energy generator optically connected to the laser ablation member second end; and an advancing mechanism operably connected to the 5 laser ablation member for advancing the laser ablation member through the distal opening of the hand piece.

19. The lasing device according to claim 18, wherein said indexer includes a limit stop disposed within 10 said advancing mechanism.

20. The lasing device according to claim 19, wherein said indexer further includes a selector to allow an operator to adjust the retracted position. 15

21. The lasing device according to claim 18, wherein said advancing mechanism is operable to advance said laser ablation member at a rate coordinated with magnitude of laser energy output of said laser generator to ablate 20 heart tissue.

22. A method of performing transmyocardial revascularization, comprising the steps of: providing a lasing device having a laser 25 ablation member; advancing the laser ablation member against the epicardium of a patient to mechanically pierce the epicardium; advancing the laser ablation member at a 30 predetermined rate within the patient's heart tissue as the laser fires to form a channel; and withdrawing the laser ablation member from the heart tissue, whereby epicardial tissue pushed aside during piercing substantially returns to a position 35 coinciding with the channel and acts as a channel cap to reduce bleeding from the channel. -21- WO 99/04708 PCTIUS98/15139

23. A method of performing transmyocardial revascularization, comprising the steps of: providing a lasing device having a laser ablation member; 5 advancing the laser ablation member against the epicardium of a patient to mechanically pierce the epicardium; advancing the laser ablation member at a predetermined rate; 10 outputting laser energy from said laser ablation member to ablate heart tissue at a tissue ablation rate which is slower than said predetermined rate; decreasing the advancement rate of said laser ablation member from said predetermined rate to a rate 15 substantially identical to the tissue ablation rate of said laser ablation member after said laser ablation member travels through at least a portion of the epicardium to create a channel extending into the patient's ventricle; and withdrawing the laser ablation member from the 20 heart tissue, whereby epicardial tissue pushed aside during piercing substantially returns to a position coinciding with the channel and acts as a channel cap to reduce bleeding from the channel. 25

24. A method of performing transmyocardial revascularization, comprising the steps of: providing a lasing device having a laser ablation member; advancing the laser ablation member against the 30 epicardium of a patient to mechanically pierce the epicardium; advancing the laser ablation member at a predetermined rate; outputting laser energy from said laser ablation 35 member to ablate heart tissue at a tissue ablation which is slower than said predetermined rate; -22- WO99/04708 PCTIUS98/15139 increasing the tissue ablation rate to a rate substantially identical to the predetermined rate after said laser ablation member travels through at least a portion of the epicardium to create a channel into the patient's 5 ventricle; and withdrawing the laser ablation member from the heart tissue, whereby epicardial tissue pushed aside during piercing substantially returns to a position coinciding with the channel and acts as a channel cap to reduce bleeding 10 from the channel. -23-