Clinical Experience with a New Cardioverter Defibrillator Capable of Biphasic Waveform Pulse and Enhanced Data Storage: Results of a Prospective Multicenter Study

Abstract

A recently introduced cardioverter defibrillator was implanted in 162 patients with refractory ventricular tachyarrhythmias and/or aborted sudden cardiac death. The new device is capable of delivering monophasic and biphasic defibrillation waveform pulses, arrhythmia detection, and therapy in two independently programmable zones, antibradycardia and postshock pacing. Additionally, the device enhanced data logs by storing intracardiac "far-field" electrograms of spontaneous arrhythmic episodes. One hundred sixty-two patients (mean age 55.5 years; mean left ventricular ejection fraction 36%) were enrolled in this multicenter investigation; coronary artery disease was the primary cardiac disease in 63.6% of the patients, idiopathic cardiomyopathy in 23.8%. Ventricular fibrillation was present in 49.7% of the patients; 29.3% of the patients experienced ventricular fibrillation and ventricular tachycardia; monomorphic ventricular tachycardia alone was present in 19.1% of the patients. In 26 patients the device was implanted with standard epicardial defibrillation leads (mean defibrillation threshold 11.5 +/- 3.7 J). One hundred thirty-nine patients underwent testing for implantation of a nonthoracotomy system and in 136 (98%), a nonthoracotomy system could be implanted. Defibrillation thresholds with a biphasic waveform (mean 10.2 +/- 4.3 J) were lower than with a monophasic waveform (mean 17.4 +/- 5.7 J). Two patients (1.2%) died perioperatively (< 30 days). During study time period follow-up, there were 338 device discharges in 49 patients. Analysis of stored electrograms classified 25% of discharges as inappropriate and due to supraventricular tachyarrhythmias. At a mean follow-up of 10.8 months, cumulative survival from sudden cardiac death was 98.8%, and survival from all-cause mortality was 96.3%. This study demonstrates the effectiveness of a new implantable cardioverter defibrillator in preventing arrhythmic death and the superior defibrillation efficacy of biphasic waveform pulses, which results in a higher implantation rate of nonthoracotomy systems, as well as the accurate arrhythmia classification made possible by the stored electrograms.