Y. Murakawa et al., ELECTROPHYSIOLOGICAL BACKGROUND OF INDIVIDUAL VARIABILITY IN ELECTRICAL DEFIBRILLATION EFFICACY, American journal of physiology. Heart and circulatory physiology, 40(3), 1996, pp. 1094-1098
This study was performed to test whether heart-to-heart variability of
defibrillation efficacy is attributable to differences in postshock r
efractory state of nondepolarized myocardium. In 30 anesthetized dogs,
a localized potential gradient was created using 1-16 V of stimulus a
cross a pair of platinum plate electrodes on the right ventricle (5-mm
interelectrode distance). The postshock recovery interval (PSRI) of t
he relatively refractory myocardium directly adjacent to the excited a
rea was estimated by measuring the recovery interval after an appropri
ately timed field stimulus. The transcardiac defibrillation threshold
(DFT) was also determined. The results showed that DFT normalized by t
he weight of the heart was inversely correlated with the PSRI measured
with a field stimulus of 6 V (local shock intensity similar to 5 V/cm
) or more (6 V: r = -0.502, P < 0.005; 16 V: r = -0.635, P < 0.0005).
This observation suggests that variability of defibrillation efficacy
in intact hearts is largely due to differences in the postshock refrac
tory state of the nondepolarized myocardium.