The effects of biphasic waveform design on post-resuscitation myocardial function.
OBJECTIVE
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 microF, < or =200 J) and a high-capacitance waveform typical of high-energy application (high-energy biphasic truncated exponential [BTEH]; 200 microF, > or =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.
Tang
Wanchun
W
Insitute of Critical Care Medicine, Palm Springs, California 92262-5309, USA. drsheart@aol.com
Weil
Max Harry
MH
Sun
Shijie
S
Jorgenson
Dawn
D
Morgan
Carl
C
Klouche
Kada
K
Snyder
David
D
D000818:Animals; D016887:Cardiopulmonary Resuscitation; D004195:Disease Models, Animal; D004554:Electric Countershock; D019220:High-Energy Shock Waves / Q000627:therapeutic use*; D008297:Male; D008955:Models, Cardiovascular; D009206:Myocardium / Q000473:pathology*; D013552:Swine; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy