Effects of progestin-estrogen replacement therapy on QT-dispersion in postmenopausal women.

Female gender is considered to be a risk factor for ventricular arrhythmias. Furthermore, experimental studies have shown that estrogen has an impact on the electrophysiological properties of the heart. Thus, the effects of estrogen- (ERT) and progestin-estrogen- (PERT) replacement therapy on QT-interval length and dipersion as indicators of ventricular repolarisation have been examined in the present study. Twenty-two postmenopausal women without hormone replacement therapy and 16 postmenopausal women on ERT and 22 on PERT (age 48-71 years) were included. QT intervals were measured in five subsequent cycles of at least 10 leads of standard ECG. QT-dispersion was calculated as the difference between maximal and minimal QT-interval. QT-intervals and -dispersions were rate (QT(c)) and linear (QT(lc)) corrected. PERT significantly reduced ventricular QT-dispersion (QT-, QT(c)- and QT(lc)-dispersion) compared to the control group (QT(c)-dispersion (ms): 32+/-13 vs. 48+/-14; P<0.05), while ERT significantly prolonged QT-intervals (QT(c) mean (ms): 423+/-28 vs. 398+/-31; P<0.05) without affecting QT-dispersion. These findings support the hypothesis that sex hormones may directly modulate ventricular repolarisation in vivo. Above all, the progestin component of replacement therapy is suggested to homogenize spatial heterogeneity of ventricular repolarisation.