The effect of estrogen replacement therapy on ventricular repolarization dynamics in healthy postmenopausal women.

Even though gender-specific differences in ventricular repolarization have gained wide recognition, the underlying mechanisms remain unknown. Because estrogen hormones may represent a causative factor for the changes in ventricular repolarization in women, this study evaluates a potential impact of estrogen replacement therapy on ventricular repolarization dynamics. Beat-to-beat QT and RR interval variability and QT/RR relationship during 5 minute resting high-resolution electrocardiogram recordings were measured in 30 healthy postmenopausal women (mean age 54.5 years) before and after 10 weeks of estrogen replacement therapy (ERT) with estradiol 2 mg/day. The 2 control groups included 12 healthy postmenopausal women of the similar age, who did not receive ERT, and 11 comparably healthy age-matched men. To evaluate ventricular repolarization dynamics, QT/RR linear regression slopes were calculated. After the 10-week period, the QT/RR regression slope increased by 93% in the ERT group (P <.001), but no alterations were noted in either the male or female controls. The overall variability of RR and QT intervals did not change in any of the groups studied. Our results suggest that ERT causes alterations in ventricular repolarization dynamics without significantly affecting the autonomic nervous tone.