WO1998049963A1

WO1998049963A1 - Method and apparatus for performing transmyocardial revascularization

Info

Publication number: WO1998049963A1
Application number: PCT/IL1998/000214
Authority: WO
Inventors: Michael Slatkine; Gerald Talpalariu; Ricardo Schleifer; Ytzhak Rozenberg
Original assignee: Laser Industries Ltd.
Priority date: 1997-05-08
Filing date: 1998-05-07
Publication date: 1998-11-12
Also published as: AU7231198A; IL120811A0

Abstract

The present invention relates to a method for cutting tissue of the heart (20) to create a channel or a plurality of channels (38), such as for revascularizing a desired portion of a patient's myocardium, each of the channels extending at least partially through the heart. The method includes the steps of providing a scanner (24) in communication with a laser source (L) for producing a beam (24a) of laser energy, suitable for cutting heart tissue when the laser source is activated, activating the laser source (L) and scanning the beam (24a) of laser energy over an area of the heart to deliver energy for cutting the tissue of the heart to create the channels (38).

Description

METHOD AND APPARATUS FOR PERFORMING TRANSMYOCARDIAL

REVASCULARIZATION

FIELD OF THE INVENTION

The present invention relates generally to laser devices and biomedical

applications thereof. More specifically, the invention relates to laser-based

scanning methods and apparatus for performing transmyocardial

revascularization (TMR).

BACKGROUND OF THE INVENTION

Proper functioning of the heart as a pump requires that the heart

muscles receive a steady uninterrupted supply of fresh (oxygenated) blood

through the coronary arteries. In particular, the blood from the coronary arteries

provides nutrients to the heart muscle through the myocardium by capillaries that

extend from the coronary arteries. These coronary arteries may become blocked

(occluded) or stenosed with fatty plaques, stenoses or the like, from various

diseases. Drugs, such as vasodilators, and angioplasty, where a balloon catheter

is inserted into these coronary arteries and the balloon is expanded at the

stenosis, are common treatments for opening these blockages. When balloon

angioplasty is not expected to solve this problem, a coronary bypass procedure is

often performed, where a portion or portions of the coronary arteries are replaced

by vein grafts, taken from other parts of the body.

However, some patients do not respond to drug therapy and are not

candidates for angioplasty and/or bypass surgery. These patients typically include those with insufficient strength to withstand the surgery, frail health,

severe reactions to anesthesia and chronic conditions, such as diabetes, poor

ventricular function, and those who have had poor results from previous surgery.

One solution to assist such patients as well as others is by procedures

commonly known as myocardial revasculahzation (MR). These procedures

revascularize the myocardium by creating channels through the ventricular walls,

either from inside the heart, known as Percutaneous Myocardial

Revasculahzation (PMR) or from outside the heart, known as Transmyocardial

Revasculahzation (TMR). These channels serve to direct oxygenated blood

from the ventricles to the myocardium. As reported in Mirhoseini, et al., "Clinical

Report: Laser Myocardial Revasculahzation", in Lasers in Surgery and Medicine,

6:459-461 (1986), early attempts including needle punctures in the left ventricle

were unsuccessful in the long term, as the channels created by these needles

closed due to fibrosis, scarring, and the like.

In order to achieve longer-term success, carbon dioxide lasers were

employed to create channels in the myocardium. However, this procedure

exhibited several drawbacks, as it required high powered lasers of at least

300-350 Watts, when working with beating hearts. See, Mirhoseini et al. (above).

When the heart was cooled and arrested, this procedure could be performed with

carbon dioxide lasers of lower power (80-100 Watts). However, this requires

aorto-coronary vein bypass procedures and placing the patient on a heart-lung

machine, unsuitable for people such as diabetics, and those with similar chronic

conditions. An alternate TMR approach using laser technology is disclosed in U.S.

Patent No. 5,554,152 (Aita, et al.). The apparatus disclosed is a laser connected

to an optical fiber, in turn connected to a lens for outputting the laser. The

apparatus is inserted into the chest cavity into contact with the heart. The heart is

then irradiated with sufficient laser energy for a sufficient time, to cause a channel

to be formed from the epicardium through the myocardium and the endocardium.

Another alternate TMR approach is disclosed in U.S. Patent 5,125,926

(Rudko, et al.). Here, there is disclosed a pulsed laser system for a carbon

dioxide laser. The laser beam is delivered by an articulated optical arm or a fiber

optic element, in pulses of 50 Joules.

SUMMARY OF THE INVENTION

The present invention improves on the prior art transmyocardial

revasculahzation (TMR) methods by providing TMR methods that employ laser

beam scanning for cutting channels in heart tissue. Scanning is preferably with a

flash scanner, that in conjunction with a laser source, allows for the use of a low

power (approximately 60-200 Watt) laser for producing a controlled beam, for

movement in accordance with a controlled scanning pattern, cutting channel(s) in

the heart that allow for its revasculahzation. These TMR methods of the present

invention may be performed either by open chest surgery or endoscopically.

There is disclosed a method where the heart is accessed, by

procedures including conventional surgical open chest access, such that the laser

beam will be in communication with the heart, preferably at an area proximate a

ventricle. Laser firing and ultimately scanning are synchronized by a

synchronization system, that activates and subsequently deactivates the requisite

laser pulse for scanning in accordance with the heartbeat cycle from the

electrocardiogram (ECG) of the instant patient. When the laser source is

activated, a laser beam of a sufficient energy for heart tissue ablation, may be

scanned by the flash scanner, preferably in a controlled spiral pattern, for a time

period sufficient to cut the requisite channel in the heart. Additional channels may

be cut into the heart by repeating this procedure.

A second embodiment of the present invention discloses a TMR

method, similar to the first embodiment, except that the heart is accessed

endoscopicly. The apparatus disclosed for this second embodiment is similar to that disclosed in the first embodiment, and where necessary, is adapted for

endoscopic use.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the

accompanying drawings, wherein like reference numerals identify like or

corresponding components.

In the drawings:

FIG. 1 is a schematic diagram of a first embodiment of the present

invention;

FIG. 2 is diagram of an ECG (ECG signal);

FIG. 3 is a diagram of a spiral scanning pattern generated by the flash

scanner of the present invention;

FIG. 4 is a cross sectional view of a heart with a channel cut therein by

the present invention;

FIG. 5 is a schematic diagram of a second embodiment of the present

invention; FIG. 6 is a cross-sectional of view of the working channel of the

endoscope used in the method shown in Fig. 5; and

FIG. 7 is a photograph of a dog heart treated in accordance with the

present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGs. 1-4 show a first embodiment of the method of the present

invention. This first embodiment involves accessing the heart 20 by opening the

chest of a patient. A surgeon 22 places a flash scanner 24, that emits a focused

beam 24a of laser energy, from a handpiece 25, proximate the heart 20 and in

particular, proximate the epicardium 26. The flash scanner 24 is computer

controlled to scan a target area 28 on the heart 20, preferably in a spiral pattern

30. The flash scanner 24 is connected to a laser source (L) 32, that is coupled to

a synchronization system (SS) 34, that synchronizes laser activation and

deactivation, preferably in the form of pulses of laser energy, based on the

patient's heartbeat cycle, as established by an electrocardiogram (ECG) 36 (the

patient being connected to an ECG machine), the ECG is shown in detail in FIG.

2 and described below. Activation of the laser source 32, begins scanning, that

results in channels 38 in the heart 20 for its revascualrization.

With specific reference to FIG. 1 , the heart (beating) is shown having

been accessed by conventional medical (surgical) procedures well known to

those of skill in the art. The patient is placed on the requisite life support

machinery. The flash scanner 24 is positioned proximate the heart 20, preferably

proximate a ventricle 20a.

The flash scanner 24, handpiece 25, and computer control, employed

with the present invention, are disclosed in commonly assigned U.S. Patent

Application Serial No. 08/346,878, filed November 30, 1994, entitled: METHOD

AND APPARATUS FOR HAIR TRANSPLANTATION USING A SCANNING CONTINUOUS-WORKING C0₂ LASER, now allowed, this patent application

being incorporated by reference herein. This flash scanner 24 focuses the laser

energy beam 24a from the laser of the laser source 32 into a spot 40 (FIG. 3).

Alternately, a flash scanner that scans a Lissajou pattern as described in U.S.

Patent No. 5,411 ,502 (Zair) (the '502 patent), this patent being incorporated by

reference herein, may also be employed as the flash scanner 24.

These flash scanners 24 employ mirrors, whose movements can be

continuous or in steps. Continuous mirror movement involves scanning in a

predetermined pattern at a constant speed. Step mirror movement involves

scanning in patterns, that are variable from site to site, creating a scanned pattern

from a multiple of adjacent sites at multiple locations. The above discussed

scanners are designed to employ a suitable handpiece 25 fitted thereto, these

handpieces being disclosed in U.S. Patent Application Serial No. 08/346,878

(above). Both of the flash scanners 24, and all components thereof, employed

with the present invention are electronically controlled and preferably computer

controlled, by conventional computer control hardware (not shown) and software

(not shown).

The laser source (L) 32 preferably includes a laser, such as a CW

(continuous working) mode C0₂ (carbon dioxide) laser or a pulsed mode C0₂

laser, in accordance with that disclosed in U.S. Patent Application Serial No.

08/346,878 (above), preferably of low power (approximately 60-200 Watts).

Alternate lasers may include pulsed excimer and pulsed Erbium-YAG lasers. The laser source 32 is also under the control of the above discussed computer control

hardware and software.

The ECG (ECG signal) 36, detailed in FIG. 2, shows the patent's

heartbeat cycle as four different waveforms (waves), Q, R, S, T. The

synchronization system (SS) 34 is connected with the ECG machine (for example,

a type HP78352A from Hewlett Packard Company, Palo Alto, California), and

coordinates laser pulsing (firing), ultimately resulting in scanning, with the

heartbeat cycle based on the patient's ECG. The preferred synchronization

system is that disclosed in U.S. Patent 5,125,926 (Rudko, et al.) (the '926 patent),

this patent being incorporated by reference herein. Pulsing (activation and

deactivation) of the laser of the laser source 32 is in accordance with that

disclosed for the laser in the '926 patent (above), and such pulsing effectuates

scanning for the time period (scanning duration) listed in Table 1 below. It is

highly preferred that pulsing occur in the time interval between the R and T waves

of the ECG (ECG signal) 36, for at this time, the heart is most still and its electrical

sensitivity is minimal (this time period is also known as systole or the systolic

phase). With the laser of the pulsed laser source 32, scanning occurs in

accordance with that disclosed in U.S. Patent Application Serial No. 08/346,878

(above), and scanning parameters are described in TABLE 1 below.

Turning also to FIG. 3, the preferred scanning occurs as the spot 40 is

scanned in a spiral pattern 30, preferably at a constant velocity, to cover the target

area 28, preferably with the C0₂ laser at a power level of approximately 150

watts, to avoid any possible charring of the heart tissue. Lack of char assures minimal thermal necrosis on the walls of the channel 38 (FIG. 4) of the heart

tissue. The spot 40 is preferably focused at a focal length of approximately 50

mm to 150 mm, to generate a spot size of a diameter of approximately 0.2 mm.

By utilizing this spiral scanning, target areas 28 of diameters D of approximately

0.8 mm to 1.5 mm can be scanned for creating (cutting) the requisite channel(s) in

the heart 20. Specifically, single or multiple channels 38 may be cut into the heart

20, by this scanning. Preferably, scanning is adjacent to an area, such as a

ventricle 20a, in need of increased blood circulation. However, portions of the

heart other than the ventricles 20a can also be revascularized by this method. A

typical scan to create a single channel 38 takes approximately 10 milliseconds to

approximately 100 milliseconds, is started preferably between the R and T waves

(in the time interval therebetween), and stops preferably approximately 0.2 to 0.4

seconds after the R wave crest, to avoid fibrilations. Parameters for scanning a

channel 38 are listed in the following TABLE 1.

TABLE 1 - PREFERRED FLASH SCANNER SPECIFICATIONS

Focal length 80 mm

Scanning diameters 0.8 - 1.5 mm

Scanning duration 0.1 sec

Spot size 0.2 mm

Scan Velocity (for continuous mirror movements) 200 mm/sec

Instantaneous Dwelling Time (for a step scan with non-continuous scanner mirror movements) 1 millisecond Scanning pattern a. Continuous mirror movements -

Spiral (constant velocity - Fig. 3 above) b. Non-continuous mirror movements (step scan) - Spiral (as above) or Circular

The scanning is such that once the channel 38 is formed, the portion of

the channel opening through the epicardium 26 is temporarily covered while a

portion of the channel 38 extending through the epicardium 26 seals itself.

Turning now to FIG. 4, there is shown the heart 20 with the resultant

channel 38 cut therein by scanning. While only a single channel 38 is shown in

this drawing figure, multiple channels are also permissible. It is preferred that the

channel 38 extend from the epicardium 26, through the myocardium 44 and

perforating the endocardium 46. These channels 38 should preferably be

scanned to dimensions of approximately 0.8 mm to 1.5 mm in diameter and

approximately 1 cm to 3 cm in depth.

With a first channel 38 formed, additional channels may be formed by

computer controlled repositioning of the mirrors for the flash scanner 24, as

described in U.S. Patent Application Serial No. 08/346,878 (above), to scan

another target area (on the heart 20), similar to the previously discussed target

area 28 (above). This computer-controlled retargeting does not require manual

repositioning of the flash scanner 24. This allows for the efficient scanning of

other areas of the heart 20 for cutting these additional channels.

FIG. 5 shows a second embodiment of the present invention, where

channels 38 are cut into the heart 20 by scanning, similar to the first embodiment,

except that certain instrumentation is adapted for endoscopic use. This method initially involves making an incision in the chest cavity, preferably subxyphoid, to

access the heart. The heart 20 is accessed, preferably at an area proximate the

ventricle 20a, by conventional instrumentation, including a standard rigid

endoscope 50 (through the incision), that is preferably advanced to a point

approximately 1 mm from the heart 20.

The endoscope 50 is a conventional multiple channel endoscope, and

includes at least two channels, a viewing channel 51 (FIG. 5) and an operating

channel 52 (FIG. 6). This endoscope could also be a conventional thorasoscope

or the like. The viewing channel 51 is fitted with standard optics (not shown) and

conventional image conveying apparatus (not shown) for direct vision on a video

monitor 53 or the like. The operating channel 52 receives the flash scanner (SC)

24', that emits a focused beam 24a' of laser energy. This flash scanner 24' is

similar to the flash scanner 24 described above, except that it has been modified

slightly for endoscopic use. The flash scanner 24' is connected to the laser

source (L) 32 (described above), that is in turn connected to a synchronization

system (SS) 34 (described above), the synchronization system 34 that utilizes the

ECG 36 (described above) of the individual patient, all connections in accordance

with those described above. The endoscope 50 also includes a conventional

control mechanism 54 for steering it, upon its advancement toward the heart 20,

in accordance with conventional surgical techniques.

Turning also to FIG. 6, the focused beam 24a' of laser energy extends

into and through the operating channel 52 of the endoscope 50, during scanning

in accordance with the above detailed laser-beam scanning procedure, in the above described scanning patterns 28, for cutting a channel(s) 38 in the heart 20.

Once the requisite channel(s) 38 have been cut, all instrumentation (e.g.,

endoscope 50 and other instrumentation associated therewith) is removed in

accordance with conventional surgical procedures.

EXAMPLE 1

In accordance with the first embodiment of the present invention,

detailed above, a live dog (mongril, approximately 30 kilograms) was anesthetized

by conventional surgical techniques, the heart was accessed by conventional

chest opening techniques, and an ECG was taken. Channels 1 , 2, 3, as shown in

FIG. 7, were scanned with the flash scanner (described above) and cut in the

heart by activating a CW C0₂ laser (as described above) in the time interval

between the R and T waves of the ECG (FIG. 2), for approximately 0.2 seconds,

at an output of 150 watts, the activation ending approximately 0.2 seconds after

the crest of the R wave. Scanning was performed in the spiral shaped pattern in

accordance with FIG. 3. In doing so, the flash scanner was set to a scanning

diameter of 1.0 mm. The channels 1 , 2, 3 extended completely through the heart

(from the endocardium to the epicardium, a depth of approximately 7 mm) and

had a diameter of approximately 1 mm.

While embodiments of the present invention have been described so as

to enable one skilled in the art to practice the present invention, the preceding

description is intended to be exemplary. It should not be used to limit the scope of

the invention, which should be determined by reference to the following claims.

Claims

1. A method for cutting tissue of the heart to create a channel extending at

least partially throughout the walls of said heart comprising:

providing at least a scanner and a laser source for producing

a beam of laser energy, the scanner in communication with said laser

source;

accessing the heart, to place said scanner into a position

proximate said heart where said beam of laser energy is suitable for

cutting heart tissue when said laser source is activated;

activating said laser source; and

scanning said beam of laser energy over an area of said heart

to deliver energy to said tissue of the heart for cutting said tissue, to

create a channel extending at least partially through the heart.

2. The method of claim 1 , wherein said laser source is a CW mode C0₂

laser.

3. The method of claim 1 , wherein said scanning step additionally

comprises moving said beam of laser energy in a spiral pattern.

4. The method of claim 1 , wherein said laser source is a pulsed mode C0₂

laser.

5. The method of claim 1 , wherein said scanning step additionally

comprises moving said beam of laser energy in a circular pattern.

. The method of claim 1 , wherein the step of accessing the heart includes

placing said scanner proximate a ventricle of said heart, whereby said

beam of laser energy beam will cut tissue of the heart proximate a

ventricle of said heart.

7. The method of claim 1 , additionally comprising:

monitoring the patient's ECG signal for determining the Q, R,

S and T waves of said signal.

8. The method of claim 7, wherein said step of activating said laser source;

and said step of scanning said beam of laser energy over an area of said

heart are performed in the time interval between said R and T waves.

9. The method of claim 1 , wherein said step of accessing the heart includes

positioning an endoscope proximate said heart, said endoscope being

adapted for accommodating said beam of laser energy and for

communicating with said scanner.

10. The method of claim 9, wherein said endoscope is positioned proximate

a ventricle of said heart, whereby said beam of laser energy beam will cut

tissue of the heart proximate a ventricle of said heart.

11. A method for creating a plurality of channels, each of said channels

extending at least partially through the heart, comprising the steps of:

providing a laser beam from a laser source;

accessing the heart; directing said beam to scan a first area of said heart in

accordance with a first predetermined pattern, so as to create a first

channel in said heart; and

moving said laser beam to scan at least a second additional

area of said heart in accordance with a second predetermined

pattern, so as to create at least a second channel in said heart.

12. The method of claim 11 , wherein said laser source is a C0₂ laser.

13. The method of claim 12, wherein said C0₂ laser is a CW mode laser.

14. The method of claim 12, wherein said C0₂ laser is a pulsed mode laser.

15. The method of claim 13, wherein said first predetermined pattern and

said second predetermined pattern are of the same shape.

16. The method of claim 15, wherein said shape is spiral.

17. The method of claim 14, wherein said first predetermined pattern and

said second predetermined pattern are of the same shape.

18. The method of claim 17, wherein said shape is selected from the group

consisting of spiral and circular pattern.

19. The method of claim 11 , additionally comprising:

monitoring the patient's ECG signal for determining the Q, R,

S and T waves of said signal.

20. The method of claim 19, wherein in the step of directing said beam to

scan a first area of said heart in accordance with a first predetermined pattern, and the step of moving said laser beam to scan at least a second

additional area of said heart in accordance with a second predetermined

pattern, said scanning of said first area with said laser beam and said

scanning of said second area with said laser beam are performed in the

time interval between said R and T waves.

21. The method of claim 11 , wherein said step of accessing the heart,

includes moving an endoscope to a position proximate said heart, said

endoscope being adapted for accommodating said laser beam.

22. A method of revascularizing a desired portion of a patient's myocardium,

comprising the steps of:

providing a source of laser energy in communication with a

flash scanner, said flash scanner including a proximal end and a

distal end;

guiding said distal end of the flash scanner within the patient's chest cavity to a

position at least proximate the patient's epicardium which is extensive

with the desired portion of the myocardium to be revascularized; and

transmitting laser energy from said source of laser energy through said distal

end of said scanner and directing said transmitted laser energy in a beam

onto the portion of the patient's epicardium in contact therewith, for a

sufficient length of time in accordance with a predetermined pattern,

whereby a revascularizing channel is formed through the epicardium, the

myocardium and the endocardium.

23. The method of claim 22, further comprising the step of:

monitoring the patient's ECG signal; and

said step of directing said transmitted laser energy in a beam onto the portion of

the patient's epicardium in contact therewith, for a sufficient length of time

is performed in the time interval between the R and T waves of said ECG

signal.

24. A method for creating at least one channel, said at least one channel

extending at least partially through the heart, comprising the steps of:

providing a laser beam from a laser source;

accessing the heart; and

directing said beam to scan an area of said heart in accordance

with a predetermined pattern, so as to create a channel in said heart.

25. The method of claim 24, wherein said laser source is a C0₂ laser.

26. The method of claim 25, wherein said C0₂ laser is a CW mode laser.

27. The method of claim 25, wherein said C0₂ laser is a pulsed mode laser.

28. The method of claim 26, wherein said predetermined pattern is spiral in

shape.

29. The method of claim 27, wherein said predetermined pattern has a shape

selected from the group consisting of spiral and circular pattern.

30. The method of claim 24, additionally comprising: monitoring the patient's ECG signal for determining the Q, R,

S and T waves of said signal.

31. The method of claim 30, wherein in the step of directing said beam to

scan an area of said heart in accordance with a predetermined pattern is

performed in the time interval between said R and T waves.

32. The method of claim 24, wherein said step of accessing the heart,

includes moving an endoscope to a position proximate said heart, said

endoscope being adapted for accommodating said laser beam.