Method for non-synchronous laser-assisted myocardial revascularization

Abstract

A method of selecting laser parameters for performing laser-assisted myocardial revascularization to avoid inducing undesired cardiac arrhythmia without synchronization of delivery of laser energy and the patient's cardiac cycle, the method comprising the steps of minimizing the power level of laser energy used, thereby decreasing the overall trauma to the heart, selecting a pulse frequency as great as possible while avoiding adverse summation effects, selecting a pulse width as wide as possible to prevent excessively high peak powers per pulse and not so wide as to cause undesired thermal damage, selecting an energy flux rate, shaping the front end of each pulse of laser energy to provide efficient, non-explosive TMR channeling, and correcting the selected power level, pulse width, pulse frequency and energy flux rate for mechanical events, including method of access to the heart, position of selected portions of myocardium in the heart, temporal duration of the procedure, natural movement of the heart, specific heart geometry, pre-existing heart arrhythmia and other factors causing a predisposition to heart arrhythmia. A method for performing laser-assisted transmyocardial revascularization (TMR) and percutaneous transluminal myocardial revascularization (PTMR) using such laser energy with parameters selected to avoid inducing undesired cardiac arrhythmia, the method comprising the steps of generating laser energy having a predetermined non-square wave shape, a predetermined wavelength, a predetermined energy flux and a predetermined power level, and delivering the laser energy in a plurality of pulses, the plurality of pulses having a predetermined pulse frequency and a predetermined pulse width, to selected portions of myocardium to form TMR and PTMR channels without synchronizing delivery of the laser beam with the cardiac cycle.

We claim:  
     
         1 . A method for performing transmyocardial revascularization (TMR) with laser energy having parameters selected to avoid cardiac arrhythmia, the method comprising the following steps, in combination: 
 determining a wavelength of the laser energy from a laser selected to perform transmyocardial revascularization;    using the wavelength determination to select parameters for the laser energy to produce a non-square wave shape;    generating the laser energy at the determined wavelength with the selected parameters to produce the non-square wave shape; and    delivering the generated laser energy in one or more pulses to selected portions of heart tissue to perform transmyocardial revascularization in myocardium without inducing cardiac arrhythmia and without synchronizing delivery of the laser energy to a cardiac cycle.    
     
     
         2 . The method of  claim 1  wherein the selected parameters are power level, energy flux, pulse width, and pulse frequency.  
     
     
         3 . The method of  claim 2  wherein the laser energy has a wavelength of between about 1.8 and about 2.2 microns, an energy flux of about 1.78 J/square millimeter and a power level of at least about 6 watts, the laser energy being delivered with a pulse frequency of at least about 5 Hertz and a pulse width of between about 150 and about 350 millisecond, the laser energy as delivered causing about 5 millimeters or less lateral necrosis surrounding a transmyocardial treatment site.  
     
     
         4 . The method of  claim 3  wherein the laser energy is generated by a Holmium:YAG laser.  
     
     
         5 . The method of  claim 2  wherein the laser energy has a wavelength of about 0.308 microns, a power level of about 2 watts and an energy flux of between about 2 and about 8 J/square millimeter, and is delivered with a pulse frequency of between about 5 and about 25 Hertz and a pulse width of about between about 10 and about 200 microseconds, and causes about 5 microns lateral necrosis surrounding the TMR channel produced thereby.  
     
     
         6 . The method of  claim 5  wherein the laser energy is generated by a Xe:CI excimer laser.  
     
     
         7 . The method of  claim 2  wherein the laser energy has a wavelength of about 10.6 microns, an energy flux of about 51 J/square millimeter and a power level at least about 800 watts, is delivered in a single pulse about of 0.03 seconds and can be gated, and causes between about 0.05 to about 0.2 millimeters lateral necrosis surrounding a TMR channel produced thereby.  
     
     
         8 . The method of  claim 7  wherein the laser energy is generated by a CO 2  laser.  
     
     
         9 . The method of  claim 2  wherein the laser energy has a wavelength of between about 0.488 and about 0.514 microns, an energy flux of between about 1.3 and about 12.74 J/square millimeter and a power level at least between about 1 and about 10 watts, is delivered in a single pulse, and causes approximately 4 millimeters lateral necrosis surrounding a TMR channel produced thereby.  
     
     
         10 . The method of  claim 9  wherein the laser energy is generated by an Argon laser.  
     
     
         11 . The method of  claim 2  wherein the laser energy has a wavelength of about 1.06 microns, an energy flux of between about 9.5 and about 13 J/square centimeter and a power level at least between about 2 and about 100 watts, is delivered with a pulse frequency of between about 1 and about Hertz and a pulse width of about 10 nanoseconds, and causes at least about 15 millimeters lateral necrosis surrounding a TMR channel produced thereby.  
     
     
         12 . The method of  claim 11  wherein the laser energy is generated by an Nd:YAG laser.  
     
     
         13 . The method of  claim 2  wherein the laser energy has a wavelength of about 2.94 microns, an energy flux of between about 50 and about 500 J/square millimeter, is delivered with a pulse frequency of between about 1 and about 15 Hertz and a pulse width of between about 1 and about 250 microseconds, and causes about 0.1 millimeters lateral necrosis surrounding a TMR channel produced thereby.  
     
     
         14 . The method of  claim 13  wherein the laser energy is generated by an Er:YAG laser.  
     
     
         15 . The method of  claim 1  wherein the laser energy is delivered to the selected portions of heart tissue using a catheter apparatus with laser delivery means, the method further comprising the following steps: 
 introducing the catheter apparatus with laser delivery means percutaneously into the vasculature of the patient; and  
 positioning the laser delivery means at the endocardial surface of the selected portions of heart tissue.  
 
     
     
         16 . The method of  claim 1  wherein the laser energy is delivered to the selected portions of heart tissue in a surgical procedure using laser delivery means, the method further comprising the following steps: 
 surgically accessing the selected portions of heart tissue; and  
 positioning the laser delivery means at an epicardial surface of the heart tissue.  
 
     
     
         17 . The method of  claim 1  wherein assess to the selected portions of heart tissue is achieved from inside a coronary artery.  
     
     
         18 . The method of  claim 15  further including the following step: 
 mechanically piercing the endocardial surface adjacent the selected portions of heart tissue prior to delivering the laser energy into the myocardium.  
 
     
     
         19 . The method of  claim 16  further including the following step: 
 mechanically piercing the epicardial surface adjacent the selected portions of heart tissue prior to delivering the laser energy into the myocardium.  
 
     
     
         20 . A method of percutaneous transluminal myocardial revascularization of a patient's myocardium for relieving angina and avoiding cardiac arrhythmia, comprising the steps of: 
 inserting a guidable elongated flexible lasing apparatus encompassing an optical fiber into a patient's vasculature;    guiding a distal end of the lasing apparatus to an area within the patient's heart;    directing the distal end of the lasing apparatus to an area within the heart to be revascularized;    providing a Holmium:YAG laser source operating at around 5 Hz with a laser pulse width between 100-250 milliseconds, and approximately 0.7-0.9 Joules/mm 2  emitted from the distal end of the lasing apparatus; and    irradiating an inner wall of the heart with the no more than five laser pulses to form at least one channel by the method whereby the channel extends into myocardial tissue without epicardial penetration.    
     
     
         21 . The method of  claim 20  wherein the step of irradiating the inner wall of the heart uses the optical fiber that is between 600-1100 microns in diameter and pulsation number is between 2-5 pulses with an average laser power of 3.5 watts.  
     
     
         22 . The method of  claim 20  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises placement of the optical fiber end at the endocardial wall prior to the step of laser irradiation.  
     
     
         23 . The method of  claim 21  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises placement of the optical fiber end at the endocardial wall prior to the step of laser irradiation.  
     
     
         24 . The method of  claim 20  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises the step of piercing the optical fiber end partially through the endocardial wall prior to the step of laser irradiation.  
     
     
         25 . The method of  claim 21  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises the step of piercing the optical fiber end partially through the endocardial wall prior to the step of laser irradiation.  
     
     
         26 . The method of  claim 20  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises having the optical fiber end pierce totally through the endocardial layer prior to the step of laser irradiation.  
     
     
         27 . The method of  claim 21  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises having the optical fiber end pierce totally through the endocardial wall prior to the step of laser irradiation.  
     
     
         28 . The method of  claim 20  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises having the optical fiber end pierce totally through the endocardial layer and part way into the myocardial tissue and the average power level setting is reduced prior to the step of laser irradiation.  
     
     
         29 . The method of  claim 21  wherein the step of directing the distal end of the lasing apparatus to an area within the patient's heart comprises having the optical fiber end pierce totally through the endocardial layer and part way into the myocardial tissue and the average power level setting is reduced prior to the step of laser irradiation.  
     
     
         30 . The method of  claim 22  wherein the method further includes a step of progressively advancing the optical fiber end between successive laser pulses.  
     
     
         31 . The method of  claim 24  wherein the method further includes a step of progressively advancing the optical fiber end between successive laser pulses.  
     
     
         32 . The method of  claim 26  wherein the method further includes a step of progressively advancing the optical fiber end between successive laser pulses.  
     
     
         33 . The method of  claim 20  wherein the method further includes a step of providing an ultrasound device for determining a position of the fiber optical end with respect to a ventricle wall prior to each laser pulse emission.  
     
     
         34 . The method of  claim 20  wherein the step of directing the distal end of the lasing apparatus to an area within the heart to be revascularized comprises engaging the optical fiber end by piercing the endocardial wall surface with the optical fiber end.  
     
     
         35 . A method of percutaneous transluminal myocardial revascularization of a patient for relief from angina while avoiding cardiac arrhythmia during the procedure, comprising the steps of: 
 inserting a guidable elongated flexible lasing apparatus encompassing an optical fiber into the patient's vasculature;    guiding the distal end of the lasing apparatus to an area within the patient's heart;    directing the distal end of the lasing apparatus to an area within the heart to be revascularized; and    irradiating an inner wall of the patient's heart using a Holmium:YAG laser source with a single pulse of laser energy with a laser pulse width between 100-250 milliseconds and approximately 1.8 Joules/mm 2  emitted from the optical fiber's end of the lasing apparatus and the optical fiber that is between 600-1100 microns in diameter;    whereby a formed channel by the method extends no more than approximately 3 mm into myocardial tissue without epicardial penetration.    
     
     
         36 . The method of  claim 35  wherein the step of directing the distal end of the lasing apparatus to an area within the heart to be revascularized comprises engaging the optical fiber=s end by piercing the endocardial wall surface with the optical fiber's end.  
     
     
         37 . A method of percutaneous transluminal myocardial revascularization of a patient's heart for relieving angina and avoiding cardiac arrhythmia, comprising the steps of: 
 a) inserting a guidable elongated flexible lasing apparatus encompassing an optical fiber with a distal end into a patient's vasculature;    b) guiding the distal end of the lasing apparatus to an area within the patient's heart;    c) directing the distal end of the lasing apparatus to an area within the heart to be revascularized;    d) controlling a distance the lasing apparatus may be advanced into heart tissue;    e) providing a Holmium; YAG laser source operating at around 5 Hz with a laser pulse width between 100-250 milliseconds;    f) selecting a laser power level emitted from the distal end dependent upon a controlled distance of the distal end of the laser apparatus in step d);    g) selecting a number of laser pulses based upon the controlled distance in step d); and    h) irradiating an inner wall of the heart and forming a channel into myocardial tissue without epicardial wall penetration.    
     
     
         38 . The method of  claim 37  wherein the method further includes a step of providing an ultrasound device for determining a position of the distal end with respect to a ventricle wall prior to each laser pulse.  
     
     
         39 . A method of percutaneous transluminal myocardial revascularization of a patient's heart for relieving angina and avoiding cardiac arrhythmia, comprising the steps of: 
 a) inserting a guidable elongated flexible lasing apparatus encompassing an optical fiber with optical distal end into the patient's vasculature;    b) guiding the distal end of the lasing apparatus to an area within the patients heart;    c) directing the distal end of the lasing apparatus to an area within the heart to be revascularized;    d) controlling a distance the distal end may be advanced into heart tissue;    e) providing an excimer laser source operating at around 15 Hz with a laser pulse width where the distal end can emit radiation of at least about 50 mJ/mm 2 ,    f) selecting a laser power level emitted from the distal end of the lasing apparatus dependent upon a controlled distance of the laser apparatus in step d);    g) selecting a number of laser pulses based upon the controlled distance in step d); and    h) irradiating the heart's inner wall to form a channel into myocardial tissue without epicardial wall penetration.    
     
     
         40 . The method of  claim 38  wherein the number of pulses is less than ten and the optical fiber's distal end is approximately 1 mm in diameter.  
     
     
         41 . A method of selecting laser parameters for performing laser-assisted percutaneous transluminal revascularization (PTMR) to avoid cardiac arrhythmia and without synchronization of delivery of laser energy to a patient's cardiac cycle, the method comprising the following steps, in combination: 
 selecting a minimum power level of laser energy to be used, the minimum power level being sufficient to ablate heart tissue;    setting a pulse frequency as great as possible and selected to avoid summation effects;    setting a pulse width as long as possible and selected to prevent excessively high peak power without causing undesired levels of thermal damage during PTMR;    shaping a front end of each pulse of laser energy to provide non-linear pulses to avoid cardiac arrhythmia during PTMR; and    correcting the selected power level, pulse width, pulse frequency, and shaping for limiting the depth of a formed channel to no more than half the wall thickness of a patient's myocardium.