Ischemia and reperfusion induced ventricular arrhythmias in the dog: effects of estrogen. McHugh, N. A., S. M. Cook, J. L. Schairer, M. M. Bidgoli, and G. F. Merrill. Department of Biological Sciences, and Graduate Program in Physiology and Neurobiology, Rutgers, The State University, Piscataway, New Jersey 08855-1059
APStracts 2:0086H, 1995.
The purpose of this investigation was to determine if exogenous estrogen could attenuate the ventricular arrhythmias caused by myocardial ischemia and reperfusion. Conjugated equine estrogen, administered as an i.v. bolus injection (100 [mu]g) to anesthetized, instrumented beagles of both genders, significantly attenuated the incidence of ventricular arrhythmias during a 20 min period of ischemia (2+/-1 vs. 19+/-16 percent ectopy) and in the first five minutes of reperfusion (15+/-9 vs. 69+/-20 percent ectopy). By 15-20 min of ischemia ventricular salvos and non-sustained ventricular tachycardia were frequently observed in nontreated dogs. One dog in this group fibrillated during ischemia. In contrast, estrogen-treated dogs exhibited only an occasional ventricular premature beat during the same period of ischemia. When compared to baseline values, percent ectopy during ischemia in estrogen-treated dogs was insignificant. During reperfusion, nontreated dogs displayed severe, life-threatening arrhythmias such as sustained ventricular tachycardia. In two of these dogs ventricular tachycardia deteriorated to ventricular fibrillation. In comparison, estrogen -treated dogs displayed only innocuous ventricular arrhythmias during reperfusion, i.e. ventricular premature beats, ventricular salvos and ventricular bigeminy. In addition to the effect of estrogen on arrhythmias, there was a gradual increase in coronary blood flow upon reperfusion in estrogen treated dogs. This effect of estrogen was preceded by a significantly higher coronary perfusion pressure during ischemia (31+/-2mmHg vs. 18+/-4mmHg, P<0.05). In conclusion, our findings suggest that antiarrhythmic effects of estrogen treatment might stabilize ventricular rhythmicity during ischemia and reperfusion. 

Received 12 December 1994; accepted in final form 10 March 1995.
APS Manuscript Number H1089-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.