QTc Interval: Gender Difference and effect of Menstrual Cycle

Context: Women are more predisposed to ventricular arrhythmias than men. The occurrence of Torsades-de-pointes is increased with the degree of QT interval prolongation, and female gender is a known risk factor for its occurrence. Drug induced QT prolongation are greater in women than in men. Sex hormones have potential role on the mechanisms involved in the cardiac repolarization

Aims: To note gender difference and menstrual cycle effect on cardiac electrophysiology

Settings and Design: Case-control study

Method and Material: Electrocardiogram (ECG) was recorded in randomly selected healthy 51 men and 51 women; aged between 17-20 yrs. ECG in women was taken during menstrual, proliferative and luteal phases of menstrual cycle. Basal body temperature throughout menstrual cycle was recorded in women to confirm that recordings were done in respective 3 phases of menstrual cycle. RR interval, QT interval and QTc interval were noted from Lead II recording of the subjects.

Statistical analysis used: Student's unpaired T test, Repeated measures ANOVA

Results: Study group was age matched. There was statistically highly significant gender difference during menstrual phase (p<0.001) and proliferative phase (p<0.001), and significant difference during secretory phase (p=0.008). Difference in mean QTc interval in women during different phases of menstrual cycle is statistically not significant (p=0.08).

Conclusions: There is gender difference in QTc interval of cardiac repolarization. There is no statistically significant difference in QTc interval in women during different phases of menstrual cycle. This difference is higher during menstrual phase in women