LABORATORY INVESTIGATION LASER PHOTOABLATION Transcatheter ablation: comparison between laser photoablation and electrode shock ablation in the dog

To characterize and compare the effects of transcatheter laser and electrical energy on endocardium, 35 laser pulses were delivered to the endocardial surfaces of isolated canine hearts, and 33 endocardial lesions were produced by the transarterial delivery of either transcatheter laser irradiation or electrical shock in closed-chest anesthetized dogs. Laser-induced lesion dimensions in vitro and in vivo increased with increased total dose of energy; however, the lesions produced in vivo were different in morphology and were significantly larger than lesions produced by equivalent doses of energy delivered in vitro (p < .05). Endocardial lesions produced in vivo by laser at 40 and 80 J (7.9 x 5.4 x 6.6 and 7.9 X 5.1 x 7.5 mm) were comparable in gross morphology and size to those produced by electrical shock at 100 and 200 J (8.5 x 6.6 x 6.6 and 10.0 x 8.5 x 8.2 mm, respectively; p = NS), but transcatheter electrode shock produced significantly more ventricular tachycardia (p < .003), premature ventricular beats in the 7 min after energy discharge (p < .05), and wall motion abnormality (p < .005). Transcatheter laser photoablation can create controlled endocardial lesions with less energy and fewer deleterious effects than transcatheter electrode shock. Circulation 71, No. 3, 579-586, 1985. RECURRENT sustained ventricular tachycardia continues to be a difficult problem in patients with ischemic heart disease, and it has been estimated that only 41% of such patients referred for electrophysiologic testing respond to standard medical antiarrhythmic drug regimens.' Despite disappointing results with conventional drug treatment, important advances have been made in the development of alternative treatment modalities, including encircling ventriculotomy,2 endocardial resection,3 and, most recently, transcatheter shock ablation.4 The therapeutic goals of these procedures are the surgical isolation or interruption of reentrant circuits and the excision or ablation of endocardial arrhythmogenic foci either surgically or via catheter-mediated destruction of tissue. From the Cardiology Section, Veterans Administration Medical Center and Georgetown University School of Medicine, Washington, D.C., and the Pathology Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda. Supported in part by a grant from the Veterans Administration, and a grant-in-aid from the Nation's Capital Affiliate of the American Heart Association. Address for correspondence: Benjamin I. Lee, M.D., Cardiology Section, Veterans Administration Medical Center, 50 Irving Street, N.W., Washington, D.C. 20422. Presented in part at the 33rd Annual Scientific Session of the American College of Cardiology, Dallas, Texas, March 25-29, 1984. Received June 25, 1984; revision accepted Nov. 29, 1984. Vol. 71, No. 3, March 1985 Laser radiation is monochromatic, coherent, and can be delivered by flexible optical fibers; thus, it has potential utility in the selective ablation of ventricular endocardial sites. Although the interaction of laser and various isolated tissues has been studied,5'7 little is known about the interactions of laser energy with the beating heart in vivo. The purpose of this study was to characterize the short-term functional, electrocardiographic, and morphologic sequelae of laser discharge on ventricular endocardium in vitro and in vivo, and to compare these effects to those of electrical discharge. Methods Twenty-six mongrel dogs weighing approximately 15 to 20 kg each were studied. Laser energy was supplied by a Nd:YAG (neodymium, yttrium, aluminum, garnet) laser (Molectron Medical Model 8000) coupled to a 0.9 mm diameter quartz core fiber (Molectron Medical Model 8200). For transcatheter laser photoablation studies, the quartz fiber was housed within the lumen of a No. 8F flexible catheter, with the tip of the fiber protruding 1 mm from the end of the catheter. In transcatheter electric shock studies, unipolar direct-current shock was delivered from the distal pole of a No. 7F bipolar electrode catheter (United States Catheter and Instruments Co.), positioned against the left ventricular endocardium, to an external left chest paddle. The proximal pole was used only for recording endocardial electrograms. Electrical energy was supplied by a standard 579 by gest on A ril 3, 2017 http://ciajournals.org/ D ow nladed from