A PROSPECTIVE RANDOMIZED COMPARISON OF DEFIBRILLATION EFFICACY OF TRUNCATED PULSES AND DAMPED SINE-WAVE PULSES IN HUMANS

Introduction: Damped sine wave pulses have been used for nearly 50 yea rs in transthoracic defibrillation systems. The purpose of this study was to determine whether damped sine wave pulses have a role in implan table defibrillators. Methods and Results: In 21 survivors of cardiac arrest, we prospectively compared defibrillation efficacy of a standar d truncated capacitor (RC) monophasic pulse with a damped sine wave in ductor-capacitor (LRC) pulse using a right ventricular-left ventricula r epicardial patch-patch electrode system. The RC pulse was a standard 65% tilt monophasic waveform generated from a 120 mu F capacitor. The LRC pulse was designed to simulate the waveform currently used in tra nsthoracic defibrillators and was generated by passing the charge stor ed on a 40 mu F capacitor through a 37-mH inductor. Capacitor voltage, peak delivered voltage, peak delivered current, discharge pathway res istance, delivered energy, and stored energy were compared for the two waveforms at the defibrillation threshold. There was no difference in defibrillation efficacy for the two waveforms. Peak delivered voltage was similar at the defibrillation threshold: 313 +/- 101 V for the RC pulse and 342 +/- 119 V for the LRC pulse (P = 0.16). Similarly, no d ifferences were found in defibrillation threshold peak delivered curre nt: 8.6 +/- 2.5 (RC) versus 9.3 +/- 2.7 (LRC) amperes (A) (P = 0.20); discharge pathway resistance: 37 +/- 11(RC) versus 38 +/- 13 (LRC) Ome ga (P = 0.71); delivered energy: 7.0 +/- 4.5 (RC) versus 7.0 +/- 4.0 ( LRC) joules (J) (P = 0.88); and stored energy: 8.7 +/- 5.7 (RC) versus 9.8 +/- 5.4 (LRC)J (P = 0.35). Although both waveforms performed the same, it was necessary to use substantially higher stored voltages wit h the damped sine wave delivery system than with the truncated wavefor m delivery system: 356 +/- 110 V for the RC pulse and 675 +/- 192 V fo r the LRC pulse (P < 0.0001). Conclusion: This study demonstrates that RC monophasic pulses provide equally effective epicardial defibrillat ion as LRC pulses with respect to delivered voltage and current and st ored and delivered energy. However, in order for LRC pulses to provide comparable delivered voltage, current, and energy to that of RC pulse s, nearly twice the voltage must be stored on the capacitor to accompl ish the same task. These findings suggest that despite the nearly 50-y ear experience with damped sine wave pulses with transthoracic defibri llators, there is no need to begin using damped sine wave pulses for i mplantable defibrillators. Moreover, these data raise a question regar ding the need for inductors in transthoracic defibrillators.