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CLINICAL RESEARCH: ARRHYTHMIAS

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

Wanchun Tang, MD^*,*, Max Harry Weil, MD, PhD^*, Shijie Sun, MD^*, Dawn Jorgenson, PhD, Carl Morgan, MSEE, Kada Klouche, MD^* and David Snyder, MSEE

^* Institute of Critical Care Medicine, Palm Springs, California, USA
Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
Philips Medical Systems, Seattle, Washington, USA

Manuscript received August 7, 2003; revised manuscript received October 14, 2003, accepted October 20, 2003.

^* Reprint requests and correspondence: Dr. Wanchun Tang, The Institute of Critical Care Medicine, 1695 North Sunrise Way, Building #3, Palm Springs, California 92262-5309, USA.
drsheart{at}aol.com

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.

Abbreviations and Acronyms   BTEH = high-energy biphasic truncated exponential   BTEL = low-energy biphasic truncated exponential   CO = cardiac output   CPR = cardiopulmonary resuscitation   EF = ejection fraction   FAC = fractional area change   LV = left ventricle/ventricular   SV = stroke volume   VF = ventricular fibrillation

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