The probability of defibrillation success and the incidence of postshock arrhythmia as a function of shock strength.
The effects of high voltage defibrillation shocks given to six swine were studied to determine if there is a limit to the advantage gained from increasing the shock strength. An endocardial electrode was placed in the right ventricle, and a 114-cm2 cutaneous patch was placed on the left lateral thorax. Monophasic (10 msec) and single capacitor biphasic (5/5 msec) shocks with leading edge voltages of 200, 400, 600, 800, and 990 volts (approximately 2.3-59 J) were tested. For monophasic shocks, the probability of successful defibrillation ranged from 0% at 200 V to 90% at 990 V. The incidence of postshock arrhythmia increased from 0% for successful shocks at 600 V to 67% for successful shocks at 990 V. For biphasic shocks, the probability of success peaked at 97% for the 600-, 800-, and 990-V shocks. The incidence of postshock arrhythmia increased from 8% at 400 V to 55% at 990 V. Although more postshock arrhythmias occurred at lower strengths for biphasic than for monophasic shocks, an efficacy criterion, quantifying the probability of defibrillation success and the probability that a postshock arrhythmia will not occur, was always higher for biphasic shocks. The probability of success never reached 100% for either waveform while the incidence of postshock arrhythmia increased as the shock strength increased. In conclusion, for the catheter-patch electrode configuration, increasing the shock strength does not always improve the probability of success and may increase the incidence of postshock arrhythmia.
Cates
A W
AW
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
Wolf
P D
PD
Hillsley
R E
RE
Souza
J J
JJ
Smith
W M
WM
Ideker
R E
RE
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology*; D001794:Blood Pressure; D001919:Bradycardia / Q000209:etiology; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D004560:Electricity; D004562:Electrocardiography; D004566:Electrodes; D015994:Incidence; D011336:Probability; D013552:Swine; D013610:Tachycardia / Q000209:etiology; D016896:Treatment Outcome