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Oestradiol-17β causes relaxation of isolated coronary arteries and increases blood flow in several vascular beds in human beings and animals. Oestrogen replacement therapy is associated with a lower incidence of cardiovascular disease, but the acute effects of Oestradiol-17β on myocardial ischaemia are unknown. We have studied the acute effect of sublingual oestradiol-17β on exercise-induced myocardial ischaemia in eleven women (mean age 58 [SD 8] years) with coronary artery disease. The women did two treadmill exercise tests on separate days; 40 min before the test they took sublingual oestradiol-17β (1 mg) or placebo, in random order. Plasma Oestradiol-17β concentrations were confirmed to be higher after sublingual oestradiol-17β than after placebo (2531 [1192] vs 155 [168] pmol/L, p<0·001). Oestradiol-17β increased both time to 1 mm ST depression (456 [214] vs 579 [191] s, p<0·004; difference of medians 92 [95% Cl 46-254]) and total exercise time (569 [249] vs 658 [193] s, p<0·01; difference 54 [10-212]). Acute administration of oestradiol-17β therefore has a beneficial effect on myocardial ischaemia in women with coronary artery disease. This effect may be due to a direct coronary-relaxing effect, to peripheral vasodilation, or to a combination of these mechanisms. Oestradiol-17β may prove to be a useful adjunct to the treatment of angina in postmenopausal women with coronary heart disease.

During their premenopausal years, women have a lower risk than men of getting cardiovascular disease. This protection continues after the menopause if women receive oestrogen replacement. Based on new experimental evidence we propose that some of the cardiovascular benefits of oestrogen replacement therapy may be due to a long-term calcium antagonist effect of oestrogen.

Summary Background Paroxysmal supraventricular tachycardia (SVT) in premenopausal women is often judged to be related to anxiety, and may be associated with the menstrual cycle. The aim of this study was to determine whether a cyclical variation of episodes of SVT exists and to correlate such variation with cyclical variation in plasma ovarian hormones. Methods 26 women (mean age 36 [SD 8]) years; with paroxysmal SVT were screened; those with regular menses who experienced at least three episodes of paroxysmal SVT in two consecutive 48-hour ambulatory ECG recordings were included. 13 patients (aged 32 [6] years) met these criteria. Patients underwent 48-hour ambulatory ECG monitoring and determination of plasma concentrations of oestradiol-17β and progesterone on day 7, 14, 21, and 28 of their menstrual cycle. Findings An increase in the number and duration of episodes of paroxysmal SVT was observed on day 28 as compared to day 7 of the menstrual cycle. A significant positive correlation was found between plasma progesterone and number of episodes and duration of SVT (5·6 [2·2] ng/mL; r=0·83, p=0·0004; and r=0·82, p=0·0005), while a significant inverse correlation was found between plasma oestradiol-17β and number of episodes and duration of SVT (155 [22] pg/mL; r=-0·89, p<0·0001; and r=-0·81, p=0·0007). Interpretation Women with paroxysmal SVT and normal menses exhibit a cyclical variation in the occurrence of the arrhythmia with their menstrual cycle. There is a close correlation between the episodes of paroxysmal SVT and the plasma concentrations of ovarian hormones. These data suggest that changes in plasma levels of ovarian hormones (and their interaction) may be of importance in determining episodes of arrhythmia in such patients. The mechanisms of these effects are unknown.