Mechanisms of ventricular fibrillation induction by 60-Hz alternating current in isolated swine right ventricle
Authors
Voroshilovsky, Olga ; Qu, Zhilin ; Lee, Moon-Hyoung ; Ohara, Toshihiko ; Fishbein, Gregory A. ; Huang, Hsun-Lun A. ; Swerdlow, Charles D. ; Lin, Shien-Fong ; Garfinkel, Alan ; Weiss, James N. ; Karagueuzian, Hrayr S. ; Chen, Peng-Sheng
The mechanisms by which 60-Hz alternating current (AC) can induce ventricular fibrillation (VF) are unknown.
METHODS AND RESULTS:
We studied 7 isolated perfused swine right ventricles in vitro. The action potential duration restitution curve was determined. Optical mapping techniques were used to determine the patterns of activation on the epicardium during 5-second 60-Hz AC stimulation (10 to 999 microA). AC captured the right ventricles at 100+/-65 microA, which is significantly lower than the direct current pacing threshold (0.77+/-0.45 mA, P:<0.05). AC induced ventricular tachycardia or VF at 477+/-266 microA, when the stimulated responses to AC had (1) short activation CLs (128+/-14 ms), (2) short diastolic intervals (16+/-9 ms), and (3) short diastolic intervals associated with a steep action potential duration restitution curve. Optical mapping studies showed that during rapid ventricular stimulation by AC, a wave front might encounter the refractory tail of an earlier wave front, resulting in the formation of a wave break and VF. Computer simulations reproduced these results.
CONCLUSIONS:
AC at strengths less than the regular pacing threshold can capture the ventricle at fast rates. Accidental AC leak to the ventricles could precipitate VF and sudden death if AC results in a fast ventricular rate coupled with a steep restitution curve and a nonuniform recovery of excitability of the myocardium.