Surgical open-chest ventricular defibrillation: triphasic waveforms are superior to biphasic waveforms.
Triphasic shocks have been evaluated for endocardial defibrillation but not for open-chest epicardial defibrillation. The purpose of this study was to compare the efficacy and safety of biphasic versus triphasic shocks for epicardial defibrillation in a porcine model. Twenty-two adult swine (18-28 kg) were deeply anesthetized and intubated. After 30 seconds electrically induced VF, each pig received truncated exponential biphasic (7.2-ms positive pulse duration and 7.2-ms negative pulse duration, total waveform duration 14.4 ms) and triphasic (4.8/4.8/4.8 ms, total waveform duration 14.4 ms) epicardial shocks. Pigs in group 1 (n = 11) received epicardial biphasic and triphasic shocks from large hand held paddle electrodes (44.2 cm2); pigs in group 2 (n = 11) received shocks from small paddle electrodes (15.9 cm2). Shocks were given at five selected energy levels (3-30 J) in random sequence. Four shocks were delivered at each energy level to construct an energy versus percentage of success curve. In group 1 (large paddle electrodes), percentage of shock success was significantly higher for triphasic shocks at the energy levels of 3, 5, 10, and 20 J compared to biphasic shocks. In group 2 (small paddle electrodes), triphasic shocks yielded a significantly higher percentage of shock success than biphasic shocks at the energy levels of 5, 10, and 20 J). Shock induced ventricular tachycardia was similar for both waveforms; asystole was rare. For open-chest defibrillation, triphasic waveform shocks were superior to biphasic waveform shocks for VF termination at energy levels of 3-20 J and were as safe as biphasic shocks.
Zhang
Yi
Y
Cardiovascular Center, College of Medicine, University of Iowa, Iowa City, Iowa, USA.
Boddicker
Kimberly A
KA
Davies
Loyd R
LR
Jones
Janice L
JL
Kerber
Richard E
RE
D000818:Animals; D002302:Cardiac Output; D004554:Electric Countershock / Q000009:adverse effects / Q000379:methods*; D004562:Electrocardiography; D006439:Hemodynamics; D013552:Swine; D017180:Tachycardia, Ventricular / Q000209:etiology; D013908:Thoracotomy; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*