ABSENCE OF EFFECTS OF SHORT-TERM ESTROGEN REPLACEMENT THERAPY ON RESTING AND EXERTIONAL QT AND QT(C) DISPERSION IN POSTMENOPAUSAL WOMEN WITH CORONARY-ARTERY DISEASE

Women, on average, have a longer QT interval on the electrocardiogram and are at higher risk of developing torsade de pointes from antiarrhy thmic therapy than men. Although endogenous estrogen may play a role i n these sex differences, the effect of estrogen replacement therapy ha s not been examined. Ten women, 65 +/- 7 years of age, with stable ang ina pectoris, positive exercise test, and angiographically proven coro nary artery disease (at least one greater than or equal to 70%) stenos is were studied. All women had been postmenopausal for at least 1 year , and none had ever received hormone replacement therapy (HRT). The pa tients received standard dose HRT (0.625 mg/day oral conjugated estrog en) or matching placebo for 4 weeks in random order, with crossover af ter a 4-week washout period. Exercise testing using the standard Bruce protocol was performed at the end of the first and third months of th e study. Antianginal medications remained unchanged throughout the stu dy period. Compared to placebo, HRT caused a significant increase in p lasma estradiol levels from 5.55 +/- 1.66 to 31.11 +/- 14.95 pg/mL (P = 0.001). QT and QTc, as well as QT and QTc dispersion, did not differ at rest and at peak exercise between the two exercise tests. Likewise , other test results, including angina score, exercise time, ST-T chan ges, blood pressure, heart rate, and double product were unchanged. Sh ort-term HRT did not alter cardiac repolarization at rest and during e xercise in postmenopausal women with known coronary disease.