Resting and exercise electrocardiographic abnormalities associated with sex hormone use in women. The Lipid Research Clinics Program Prevalence Study.

Prevalence rates for resting and exercise electrocardiographic abnormalities were determined according to the use or nonuse of oral contraceptives and exogenous estrogens in 1,919 women participants from 10 defined North American study populations of the Lipid Research Clinics Program. Among women 30-49 years of age, no significant differences in the prevalence of resting electrocardiographic abnormalities between oral contraceptive users and nonusers were seen after adjustment for age, blood pressure, cigarette smoking, alcohol, and obesity. Abnormal graded exercise electrocardiograms, however, were more prevalent among the oral contraceptive users (odds ratio = 2.7, p less than 0.05). Among women 50 years and older, a significant deficit of abnormal Q waves on resting electrocardiogram and nonsignificant excess of abnormal S-T segment responses to exercise were noted in estrogen users compared with nonusers. Possible sources of bias and the pathophysiologic implications of these findings are discussed.