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(Circulation. 2000;102:1569.)
© 2000 American Heart Association, Inc.

Basic Science Reports

Mechanisms of Ventricular Fibrillation Induction by 60-Hz Alternating Current in Isolated Swine Right Ventricle

Olga Voroshilovsky, MS; Zhilin Qu, PhD; Moon-Hyoung Lee, MD; Toshihiko Ohara, MD; Gregory A. Fishbein, BA; Hsun-Lun A. Huang, BS; Charles D. Swerdlow, MD; Shien-Fong Lin, PhD; Alan Garfinkel, PhD; James N. Weiss, MD; Hrayr S. Karagueuzian, PhD; Peng-Sheng Chen, MD

From the Division of Cardiology (O.V., M.-H.L., T.O., G.A.F., H.-L.A.H., C.D.S., H.S.K., P.-S.C.), Department of Medicine, Cedars-Sinai Medical Center, and the Departments of Medicine (Cardiology), Physiology, and Physiological Science (Z.Q., A.G., J.N.W.), UCLA School of Medicine, Los Angeles, Calif, and the Department of Physics and Astronomy (S.-F.L.), Vanderbilt University, Nashville, Tenn.

Correspondence to Peng-Sheng Chen, MD, Room 5342, CSMC, 8700 Beverly Blvd, Los Angeles, CA 90048. E-mail CHENP{at}CSMC.EDU

Background—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 µA). AC captured the right ventricles at 100±65 µA, 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 µA, 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.

Key Words: electrical stimulation • electrophysiology • mapping • action potentials

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