Body weight is a predictor of biphasic shock success for low energy transthoracic defibrillation.
BACKGROUND
Transthoracic impedance and current flow are determinants of defibrillation success with monophasic shocks. Whether transthoracic impedance, either independently or via its association with body weight, is a determinant of biphasic waveform shock success has not been determined.


RESULTS
We studied 22 swine, weighing 18-41 kg. After 15 s of ventricular fibrillation, each pig received transthoracic truncated exponential biphasic shocks (5/5 ms), 70-360 J. Shock success was strongly associated individually with body weight, leading-edge transthoracic impedance and current at low energy levels (70 and 100 J, all P<0.001). Multiple logistic regression analysis showed a significant association of body weight with shock success after adjusting for the effect of leading-edge impedance (odds ratio of success for 1 kg decrease in weight at 70 J was 1.29, 95% CI: 1.05-1.59, P=0.02; and at 100 J was 1.30, 95% CI: 1.14-1.49, P<0.0001). The same result was observed after adjusting for the effect of leading-edge current. At 150 J or higher energy levels, no significant association was observed.


CONCLUSIONS
Body weight is a determinant of shock success with biphasic waveforms at low energy levels in this swine model.
Department of Internal Medicine, Division of Cardiovascular Diseases, The Cardiovascular Center, The University of Iowa and Clinics, 200 Hawkins Drive, 52242, Iowa City, IA, USA.
Yi
Y
Zhang
Craig B
CB
Clark
L Ray
LR
Davies
Gudjon
G
Karlsson
M Bridget
MB
Zimmerman
Richard
R
Kerber
D000818:Animals; D001835:Body Weight; D004554:Electric Countershock / Q000379:methods; D013552:Swine