Gender Differences in Electrophysiologic Effects of Mental Stress and Autonomic Tone Inhibition:

Abstract

Gender differences exist in electrophysiologic properties and the occurrence of certain arrhythmias. Mental stress may trigger serious arrhythmias, including ventricular tachycardias and ventricular fibrillation. This study investigates gender differences in the electrophysiologic effects on different levels of the cardiac conduction system elicited by mental stress and autonomic tone inhibition. Twenty-three healthy volunteers (11 male and 12 female) participated in the study. Electrophysiologic and hemodynamic variables were measured at baseline, during mental stress produced by Stroop's color word conflict test (CWT), and after autonomic tone inhibition (ATI) with propranolol (0.15 mg/kg) and atropine (0.02 mg/kg). During CWT, men showed shorter QT and JT durations, whereas women had shorter refractoriness in the atrial tissue and AV node. After ATI, no gender differences in sinus nodal properties were noted, whereas AV nodal refractoriness and conduction time became shorter in women, and QT and JT duration and the refractory period of the right ventricle were shorter in men. In women, mental stress produces a pronounced effect on the AV node and on the sinus node. Men react with a more pronounced effect on ventricular electrophysiologic properties. Certain gender differences in cardiac electrophysiologic properties seem to be intrinsic. After ATI, women have a higher heart rate and shorter AV nodal refractoriness but longer QT and JT intervals and longer effective refractory periods in the right ventricle. These differences may partly explain why certain arrhythmias occur more often in women than in men.