The effects of biphasic waveform design on post-resuscitation myocardial function

Abstract

Objectives This study examined the effects of biphasic truncated exponential waveform design on survival and post-resuscitation myocardial function after prolonged ventricular fibrillation (VF). Background Biphasic waveforms are more effective than monophasic waveforms for successful defibrillation, but optimization of energy and current levels to minimize post-resuscitation myocardial dysfunction has been largely unexplored. We examined a low-capacitance waveform typical of low-energy application (low-energy biphasic truncated exponential [BTEL]; 100 μF, ≤200 J) and a high-capacitance waveform typical of high-energy application (high-energy biphasic truncated exponential [BTEH]; 200 μF, ≥200 J). Methods Four groups of anesthetized 40- to 45-kg pigs were investigated. After 7 min of electrically induced VF, a 15-min resuscitation attempt was made using sequences of up to three defibrillation shocks followed by 1 min of cardiopulmonary resuscitation. Animals were randomized to BTEL at 150 J or 200 J or to BTEH at 200 J or 360 J. Results Resuscitation was unsuccessful in three of the five animals treated with BTEH at 200 J. All other attempts were successful. Significant therapy effects were observed for survival (p = 0.035), left ventricular ejection fraction (p < 0.001), stroke volume (p < 0.001), fractional area change (p < 0.001), cardiac output (p = 0.044), and mean aortic pressure (p < 0.001). Hemodynamic outcomes were negatively associated with energy and average current but positively associated with peak current. Peak current was the only significant predictor of survival (p < 0.001). Conclusions Maximum survival and minimum myocardial dysfunction were observed with the low-capacitance 150-J waveform, which delivered higher peak current while minimizing energy and average current. © 2004 by the American College of Cardiology Foundation.