Catheter ablation: relationship of defibrillator waveform to the production of postshock ventricular tachyarrhythmias and myocardial damage.

The myocardial damage and arrhythmogenicity of percutaneous transcatheter shocks utilizing two different defibrillator waveforms (truncated exponential and damped sinusoidal) were compared. Ten dogs (33.7 +/- 3.6 kg) were studied. Five received left ventricular damped sinusoidal R-synchronous shocks during sinus rhythm and the other five received truncated exponential waveform shocks. Each dog received four energies (60, 120, 180, and 240 joules) randomly assigned to four left ventricular sites. The immediate postshock rhythms were recorded. Ventricular tachycardia occurred after 90% of the damped sinusoidal shocks compared to only 25% of the truncated exponential shocks (p less than 0.005). The animals were sacrificed 14 days later. Infarct size as determined by planimetry was not significantly different for the two waveforms. Thus intracavitary shocks utilizing a truncated exponential waveform are less arrhythmogenic than damped sinusoidal waveform shocks but produce similar morphologic changes and therefore may offer a significant safety advantage for catheter ablation procedures.