Sex hormones and arrhythmia in myocardial ischemia.

The mechanisms by which gender affects cardiac electrophysiological parameters and alters the predisposition to certain arrhythmias are not well understood, although differences in the expression and function of ion channels and in the activation of the autonomic nervous system may contribute. In their study Philp and coworkers address the issue of the effect of 17beta-estradiol on ventricular vulnerability in a rat model of ischemia. Their data show that there is a dose-dependent antiarrhythmic activity of 17beta-estradiol administration with suppression ventricular premature beats, ventricular tachycardia and ventricular fibrillation during ischemia. Furthermore they show a dose-dependent blockage of I(CaL) by 17beta-estradiol which is again stronger in female than in male mice. They postulate that the shown gender-selective, concentration-dependent inhibition of I(CaL) is sufficient to account for the reduction in ischaemia-induced arrhythmia. With this data they have added important information on the influence of sex hormones on cardiac electrophysiology under pathophysiological conditions.