Method for transvenous ablation of cardiac electrically conductive tissue by laser photocoagulation

The invention provides an apparatus and method for the ablation of cardiac electrically conductive tissue by laser photocoagulation. Reference points of cardiac tissue to be ablated are transvenously mapped. A laser balloon catheter having electrodes positioned on each lateral aspect of the balloon is transvenously positioned in the coronary sinus a the predetermined reference points. The electrodes are used to localize the laser balloon by detecting electrical activity of the tissue adjacent to the laser balloon at the area to be ablated. The tissue area adjacent the balloon is then irradiated to thermally damage the cardiac tissue outside of the vein and adjacent the balloon to render the cardiac tissue electrically inert.

TECHNICAL FIELD 
The present invention relates to a method of percutaneous ablation of 
conductive pathways of tissue, such as cardiac tissue. More specifically, 
the present invention can be utilized for the percutaneous ablation of 
left sided accessory pathways in patients with symptomatic arrhythmias by 
means of thermocoagulation with a Nd:YAG laser balloon catheter positioned 
in the coronary sinus. 
BACKGROUND OF THE INVENTION 
Catheter ablation of posteroseptal accessory pathways through the coronary 
sinus by means of direct current electrical shock is an accepted technique 
for the treatment of drugresistant patients of the Wolff-Parkinson-White 
syndrome. Morady F., Scheinman MM, Winston SA, et al; efficacy and Safety 
of Transcatheter Ablation of Posteroseptal Accessory Pathways--Circulation 
72:170, 1985. The Wolff-Parkinson-White syndrome is frequently associated 
with rapid supraventricular arrhythmias that are related to the presence 
of accessory atrioventricular connections, which are usually in close 
contiguity to the coronary sinus. These rhythm disturbances are usually 
symptomatic and may be life threatening in a subset of patients. Klein GJ, 
Bashore TM, Sellers TD, et al: Ventricular Fibrillation in the 
Wolff-Parkinson-White Syndrome. N. Engl. J. Med. 01:1080, 1979. Drug 
therapy has been effective for suppressing or controlling many of these 
arrhythmias. With many patients, surgery is becoming the treatment of 
choice. Prystowsky EN, Pressley JC, Gallagher JJ, et al: The Quality of 
Life and Arrhythmia Status After Surgery for Wolff-Parkinson-White 
Syndrome: an 18 years perspective. JACC 9:100A, 1987. The possibility of 
avoiding surgery by achieving destruction of accessory pathways with 
ablative techniques represents a major breakthrough in the treatment of 
the disease. Presently, available ablation techniques involving the 
coronary sinus are limited to accessory pathways located in the 
posteroseptal area. The ability to safely and effectively ablate left free 
wall accessory atrioventricular connections (the most prevalent variety) 
using laser energy delivered percutaneously via a catheter would represent 
a significant advance in the management of this disease. 
The term "ablative techniques" refers to the use of physical agents capable 
of modifying conduction in a restricted area of the myocardium for 
treating or preventing cardiac arrhythmias without losing the structural 
integrity of the tissue. Fontaine G, Scheinman MM: Ablation in Cardiac 
Arrhythmias. Futura Publishing Company, Inc., Mount Kisco, N.Y., 1987. 
There have been several reports of a therapeutic application of 
intraoperative ablative techniques to sever the normal atrioventricular 
conduction system. Gianelli S, Ayers SM, Gomprecht RF, et al: Therapeutic 
Surgical Division of the Human Conduction System. JAMA 199:155, 1968. 
Slama R., Blondeau P, Aigueperse J, et al: Creation Chirurgicale d'un Bloc 
Auriculoventriculaire et implantation d'un Stimulateur daus deux cas de 
Troubles du Rythme Irreductibles. Arch. Med Geur Vaisseaux 60:406, 1967. 
Other reports have observed the effect of ablation on other conductive 
systems. Cobb FR, Blumenschein DF, Sealy WC, et al: Successful Surgical 
Interruption of the Bundle of Kent in a Patient with Wolff-Parkinson-White 
Syndrome. Circulation 38:1018, 1968. Vedel J, Frank R, Fontaine G, et al: 
bloc Avriculoventriculaire Intrahisien Definitif Induit au Cours D'une 
Exploration Endoventriculaire Droit. Arch Med Coeur Vaisseaux 72:107, 
1979. Scheinman MM, Morady F, Hess D, et al: Catheter-induced Ablation of 
the Atrioventricular Junction to Control Refractory Supraventricular 
Arrhythmias. JAMA 248:851,1982. Gallagher JJ, Svenson RH, Kasell JU, et 
al: Catheter Technique for Closed-Chest Ablation of the Atrioventricular 
Conduction System. A Therapeutic Alternative for the Treatment of 
Refractory Supraventricular Tachycardia. N Eng J Med 306:194, 1982. 
It has been suggested that the anatomic relationship of the close proximity 
of the atrioventricular accessory pathways through subepicardial fat of 
the atrioventricular groove in close proximity to the coronary sinus may 
be used to create localized lesions from the coronary sinus using 
different energy sources, such as direct current electrical shock or radio 
frequency in an effort to ablate the anomulous atrioventricular 
connections. Morady F, Scheinman MM: Transvenous Catheter Ablation of A 
Posteroseptal Accessory Pathway in a Patient with the 
Wolff-Parkinson-White Syndrome. N. Eng J Med 310:705, 1984. Morady first 
described the use of this transvenous technique using high energy direct 
electrical shock. In patients with posteroseptal accessory pathways, this 
technique has gained increasing popularity as an appealing alternative to 
surgery due to its high success rate and low incidence of complications. 
Morady, F., Scheinman, M.M.: Catheter Ablation of Accessory Pathways, 
Scheiman, M.M. (Ed.): Catheter Ablation of Cardiac Arrhythmias, Martinez 
Pub. Nighoff Publishing, Boston, pp.163-164. However, a much lower success 
rate has been achieved for left free wall accessory pathways where the 
rate of complications of high energy electrical shocks is very high. 
Fisher JD, Brodman R, Kim SG, Matos JA, Brodman E, Wallerson D, Waspe LE: 
Attempted Non-Surgical Electrical Ablation of Accessory Pathways via the 
Coronary Sinus in the Wolff-Parkinson-White Syndrome. JACC 4:685, 1984. 
This difference is due to the anatomic variations in susceptibility to 
barotrauma secondary to high energy electrical current shocks. Attempts to 
reduce the electrical energy to prevent complications have proved to be 
ineffective for ablations of left sided pathways. Fisher et al, supra. 
Radiofrequency current has been proposed as an alternative energy source 
for catheter ablations. Huang SK, Graham AR, Bharati S, Lee MA, Gorman G, 
Lev M: Short and Long Term Effects of Transcatheter Ablation of the 
Coronary Sinus by Radiofrequency Energy. Circulation 78:416,1988. In this 
technique, current is delivered at a low power during longer periods of 
time to achieve tissue desiccations. This technique is relatively free of 
complications, but appears to have a lower success rate than direct 
current electrical shocks in the few clinical studies that have been 
published. Borggrefe M, Budde T, Martinez-Rubio A, Hindricks G, Haverkamp 
W, Gulker H, Breithardt G: Radiofrequency Catheter Ablation for 
Drug-Refractory Supraventricular Tachycardia. Circulation 78, II:305, 
1988. 
Studies have shown that the use of the ND:YAG laser provides the best 
available laser wavelength to achieve subsurface penetration and 
thermocoagulation of tissue. McCord RC, Weinberg W, Gorisch W, et al: 
Thermal Effects of Laser Irradiated Biology Tissue. In: Proceedings, 
Symposium In Laser in Medicine and Biology. GSF-Berichte, BPT 5, 
Neuherberg, 1977. Further, unlike other laser delivery systems, the ND:YAG 
laser balloon catheter distributes energy to a significant area of the 
coronary sinus thereby resolving the problem of targeting an otherwise 
narrow laser beam. The ND:YAG laser balloon catheter has been developed 
for percutaneous transluminal coronary angioplasty restenosis prevention. 
Spears JR: Percutaneous Transluminal Coronary Angioplasty Restenosis: 
Potential Prevention WIth Laser Balloon Angioplasty. Am J Cardiol 60:61B, 
1987. 
The present invention provides means for ablating electrically conductive 
tissue by laser photocoagulation. It further provides means for pacing and 
recording thereby allowing the localization of the accessory pathways to 
be ablated. This features, in combination with a novel mapping method and 
apparatus, provide an improved means for ablation of cardiac electrically 
conductive tissue by laser photocoagulation. More specifically, the 
present invention provides the means for more precise and effective 
catheter ablation of all left sided accessory pathways thereby providing a 
treatment for drug resistant patients having the Wolff-Parkinson-White 
syndrome. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a method of 
ablating cardiac electrically conductive tissue by laser photocoagulation, 
the method including the steps of transvenously mapping reference points 
of cardiac area to be ablated and transvenously positioning a laser 
balloon catheter at the predetermined reference points. The area adjacent 
the balloon is irradiated by the laser, thermally damaging the cardiac 
tissue and rendering the tissue electrophysiologically inert.

DETAILED DESCRIPTION OF THE DRAWINGS 
A laser balloon catheter constructed in accordance with the present 
invention is generally shown at 10 in FIG. 1. The catheter 10 includes a 
fiberoptic support shaft generally shown at 12 having a distal termination 
portion 14. The shaft 12 is of the type for conducting laser energy from a 
source to a diffusing tip 16. The diffusing tip 16 is a helical diffusing 
tip wound about the distal termination portion 14. An inflatable balloon 
18 is mounted on the distal termination 14 over the tip 16. Such a device 
has been disclosed in detail in several articles cited above. e.g. Spears, 
supra. The device further includes localizing means mounted on the distal 
termination 14 for detecting electrically conductive activity of tissue 
adjacent the balloon 18. 
More specifically, the localizing means includes a pair of unipolar 
electrodes 20,22 mounted on the distal termination 14 adjacent each end of 
the balloon 18. The electrodes 20,22 are capable of recording electrical 
activity of conductive tissue adjacent the balloon 18 and thereby adjacent 
the diffusing tip 16 for detecting electrical activity of the tissue 
adjacent the catheter. If the catheter is positioned within a cardiac 
vessel, the electrodes 20,22 can record electrical activity of the 
adjacent cardiac tissue extension to the vessel. 
An example of a laser balloon catheter used with the present invention is 
an instrument comprising an 8Fr double-lumen balloon catheter with an 
optical fiber terminating in the cylindrical diffusing tip 16 in the 
central portion of a two centimeter long, 3 millimeter diameter balloon 
such as that disclosed in the Spears article, supra. In animal models, an 
ND:YAG CW laser (1.060 nm) radiation is delivered via the optical fiber in 
the catheter so as to achieve a total energy of 450 J (35W.times.5 sec 
25W.times.5 sec, 15W.times.10 sec) (during a 20 second exposure). An 
estimated plateau temperature of approximately 125.degree. C. 0.5 to 1 mm 
from the balloon surface and approximately 80.degree. C. to 90.degree. C. 
3 mm from the balloon surface can be achieved with this dose. Jenkins RD, 
Sinclair IN, Anand RK, James LM, Spears JR: Laser Balloon Angioplasty: 
Effect of Exposure Duration on Shear Strength of Welded Layers of 
Postmortem Human Aorta. Lasers in Surgery and Medicine 8:392, 1988. 
The balloon 18, when inflated, displaces blood from the tip 16 within the 
vessel and the tissue to be irradiated, thereby removing the highly 
absorbant blood interface between the balloon and the vessel wall. This 
results in improved efficiency of the thermocoagulation. Secondly, the 
balloon 18 dilates the vein which is then in essence fixed by the 
thermocoagulation process. Since the thermocoagulation process reduces the 
elastic recoil of the tissue, the vein will remain in the expanded 
condition once the balloon 18 is deflated. 
The electrodes 20,22, either unipolar or bipolar, provide for improved 
localization of the laser balloon which is necessary to insure that the 
area which is to be ablated is in actuality the area which is ablated. The 
electrodes 20,22 allow for a mapping of this structure within 1-2 cm 
thereby insuring that the 1-1.5 cm irradiation extent of the laser 16 
irradiates the predetermined area which is to be ablated. As discussed 
below, this device can be useful for ablation of otherwise hard to discern 
cardiac pathways, such as the left sided accessory pathways which must be 
ablated for the effective treatment of Wolff-Parkinson-White Syndrome. 
Utilization of the present invention provides a novel method of ablation of 
cardiac electrically conductive tissue by laser photocoagulation. The 
method generally includes the steps of transvenously mapping reference 
points of the cardiac area to be ablated, tranvenously positioning the 
laser balloon catheter at the predetermined reference points, localizing 
the laser balloon by detecting electrical activity of the cardiac tissue 
adjacent the laser balloon at the area to be ablated, and irradiating the 
cardiac tissue area adjacent the balloon and thermally damaging the 
cardiac tissue and rendering the cardiac tissue electrophysiologically 
inert. The irradiated cardiac tissue is made electrically silent while the 
tissue maintains structural integrity. 
The present invention also provides a novel means of initially mapping 
reference points of cardiac area to be ablated. This mapping procedure can 
be used as a preablation procedure at the operators discretion. The 
mapping procedure utilizes a multi-polar electrode catheter specially 
devised to facilitate accurate electrophysiologic localization or 
"mapping" of the accessory pathway prior to introduction of the laser 
balloon. 
The mapping catheter is generally indicated at 24 in FIG. 2. The catheter 
24 includes a hollow soft support shaft generally shown at 26 having a 
distal end portion 28. A plurality of ring electrodes 30 are mounted on 
and spaced at regular intervals over the distal end portion 28. The 
catheter 26 is hollow so as to be able to slide over an internal guide 
wire 32. The electrode wires 34 would be connected to a recording device, 
not shown. 
Initially, a soft tipped guide wire 22 is introduced into the coronary 
sinus by a specially designed guiding catheter. The location of the 
guiding catheter and guide wire 32 will be confirmed by a fluoroscopy. 
This allows access of the mapping catheter 24 to lateral positions of the 
coronary sinus which currently may be difficult to reach with conventional 
stiff electrode catheters. Unlike the stiff electrode catheters, the 
mapping catheter includes a soft support shaft 26. Once positioned, the 
mapping catheter 24 detects electrical activity and records the electrical 
activity along the atrioventricular groove. By being soft, the mapping 
catheter 24 can be guided over the guide wire 32. The ability to navigate 
this flexible catheter 24 laterally along the atrioventricular groove 
enhances the likelihood that the accessory pathway location can be truly 
bracketed or electrically mapped between several electrodes during 
electrophysiologic mapping. 
Once the conduction times are documented for the region corresponding to 
the presumed accessory pathway location, these parameters can be recorded 
for later reproduction using electrodes 20,22 surrounding the balloon 18 
of the laser balloon ablation catheter 10. 
Once mapping is completed, the mapping catheter 24 is removed from the 
guide wire 32. The laser balloon catheter 10 is then entrained over the 
guide wire 32, as shown in FIG. 1. The laser balloon catheter 10 is 
positioned accordingly with the previously determined reference points 
mapped by the mapping catheter 24. Confirmation of the precise location of 
the helical diffusing tip 16 is achieved by unipolar or bipolar recordings 
obtained via the electrodes 20,22 of the laser balloon catheter 10. In 
other words, localization of the heat producing helical diffusing tip is 
achieved by the electrodes 20,22 reproducing the reference points 
initially mapped by a conventional electrode catheter or by the mapping 
electrode 24 and pacing and recording the electrical activity of the 
adjacent area with the electrodes 20,22 positioned on either longitudinal 
end the lasing port of the laser balloon catheter 10 adjacent to the 
tissue to be ablated. 
Upon precise localizing of the helical diffusing tip, the area adjacent the 
balloon 18 is irradiated to electrically silence the cardiac tissue 
adjacent the balloon 18 while the tissue maintains structural integrity. 
This is achieved by the application of the laser energy through the 
balloon, the laser energy penetrating and thermocoagulating the adjacent 
tissue so as to render the tissue electrophysiologically inert. 
The functional disappearance of the accessory pathway can be confirmed by 
the reference electrodes of the laser balloon catheter. 
Of course, the present invention can be used for other ablations where 
mapping of the area to be ablated is critical and positioning of the 
helical diffusing tip is critical. Thusly, the present invention provides 
a novel apparatus and process for first mapping the area to be ablated and 
then for localizing the laser irradiating portion of the ablation 
catheter. 
EXPERIMENTS 
Three canine studies have been performed utilizing the Spears TM laser 
balloon angioplasty catheter in coronary sinus. The first study was a 
feasibility study using 35 watts of Nd:YAG laser energy delivered over 20 
seconds (total energy, 700 J) to the distal coronary sinus, resulting in 
localized coagulation necrosis of the region of the atrioventricular 
groove. There were no adverse hemodynamic or electrocardiographic 
sequelae. Coronary angiography revealed no evidence of circumflex coronary 
artery stricture or thrombosis and no coronary sinus thrombosis or 
perforation. There was no evidence of mitral regurgitation during 
post-ablation ventriculography. 
Different doses of laser energy also delivered to coronary sinus were used 
respectively, in two additional dogs: i) 35 W.times.10 sec followed by 25 
W.times.5 sec followed by 15 W.times.5 sec (total 550 J), applied three 
consecutive times (grand total 1650 J); and ii) 35 W "ramped" downward to 
15 W over a 20 sec period (total 600 J), again applied three consecutive 
times (grand total 1800 J). Even at these higher energies there was no 
evidence of hemodynamic, electrographic or arteriographic damage; 
moreover, mitral valve competence was maintained. Yet, in both these cases 
coagulation necrosis extended beyond the atrioventricular groove into the 
atrial wall-- indicating damage to the very region through which accessory 
pathway fibers are known to course in humans. 
The present invention provides an effective means for ablation of cardiac 
electrically conductive tissue by laser photocoagulation. Evidence of the 
feasibility of this process at the coronary sinus makes it a prime 
candidate for the treatment of Wolff-Parkinson-White syndrome. To achieve 
this, the invention would be specifically used for the ablation of the 
abnormal conduction pathways associated with Wolff-Parkinson-White 
syndrome. 
The invention has been described in an illustrative manner, and it is to be 
understood that the terminology which has been used is intended to be in 
the nature of words of description rather than of limitation. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is, therefore, to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described.