Ablation of Ventricular Tachycardia Using Multiple Sequential Transcatheter Application of Radiofrequency Energy

Multiple sequential radiofrequency energy was applied in the left and right ventricles of 24 dogs to produce large ablated areas limited to endocardial and subendocardial regions. Endocardial ablation was performed in nine dogs with normal ventricles and 15 that had survived remote myocardial infarcts, three with inducible sustained monomorphic ventricular tachycardia. A quadripolar catheter was positioned either at the site of earliest ventricular activation during induced monomorphic ventricular tachycardia or at circumscribed areas of the left ventricle. Radiofrequency energy was delivered between two adjacent poles of the catheter, successively applying radiofrequency energy to the distal, middle, and proximal electrode pairs; this was repeated 9 to 11 times with the catheter in a slightly different position. A cumulative energy of 9,688 +/- 4,191 joules resulted in an ablated endocardial/subendocardial surface area of 4.7 +/- 2.2 cm2 (range 2.4-10 cm2, maximum depth 4 mm). Sustained tachycardia was not inducible by aggressive programmed ventricular stimulation in the dogs with previously inducible tachycardia, indicating successful ablation of the tachycardia foci. Only seven normal dogs were available for electrophysiological studies; three were used in acute and four in chronic studies. Ventricular tachycardia was not induced in the remaining dogs either before or after radiofrequency ablation, indicating the lack of an arrhythmogenic effect of this method. Histologic examination was performed in all nine normal dogs (five were sacrificed for acute pathological examination) as well as in the 15 with myocardial infarction. The late pathological examination of the radiofrequency lesion in these 19 animals showed homogeneous areas of coagulation necrosis and endocardial proliferation. Thus, this modified technique of radiofrequency ablation produced large homogeneous endocardial/subendocardial scars suitable for treating ventricular tachycardia and showed no evidence of an arrhythmogenic influence.