Evaluation of a percutaneous catheter technique for ablation of ventricular tachycardia in a canine model.

Catheter ablation of arrhythmias is a promising new technique. The consequence of high-energy discharges in the right ventricle were investigated in a canine model of inducible ventricular tachycardia. Seventeen dogs were studied. Four served as controls while 13 underwent thoracotomy with right coronary artery ligation. Three animals died suddenly postoperatively. Programmed stimulation was performed 4 days later using a pervenous right ventricular electrode catheter. No control dog had inducible ventricular tachycardia. Eight of the experimental animals had inducible ventricular tachycardia and underwent catheter mapping. The earliest endocardial site during tachycardia was located in four dogs with monomorphic ventricular tachycardia. These sites received one or more 300 J transcatheter stored charges from a defibrillator, and at least temporary ablation was accomplished in each case. Five animals had inducible polymorphic ventricular tachycardia which could not be mapped. The endocardial electrogram amplitude decreased 55 +/- 7% (p less than 0.001) and the pacing threshold increased from 0.7 +/- 0.1 mA to 7.9 +/- 1.7 mA (p less than 0.001) after the shocks. Five of the discharges caused ventricular tachycardia or fibrillation. Autopsy revealed discrete transmural wedge-shaped necrosis without perforation. Thus when monomorphic tachycardia was induced, mapping and ablation were feasible. Transcatheter 300 J discharges produced only localized damage but had a propensity to initiate ventricular arrhythmias.