Postmenopausal women without cardiovascular symptoms who have minor or major electrocardiographic abnormalities are at increased risk for future cardiovascular events and death, according to an article in the March 7 issue of the Journal of the American Medical Association.

Resting 12-lead electrocardiogram (ECG) abnormalities are independently associated with incident coronary heart disease (CHD) and cardiovascular disease (CVD) events. Many prior studies included only men or compared men and women, but women were not selected for age or presence or absence of underlying heart disease, according to background information in the article.

Data are sparse regarding the prevalence, incidence, and independent prognostic value of minor or major electrocardiographic abnormalities in asymptomatic postmenopausal women. There is no information on the effect, if any, of hormonal treatment on the prognostic value of the test.

Pablo Denes, MD, of the Feinberg School of Medicine, Northwestern University, Chicago, and colleagues conducted a study to examine the association of baseline and new ECG findings with cardiovascular outcomes in the placebo and hormonal treatment groups of the Women's Health Initiative estrogen plus progestin trial. This portion of the trial, which was stopped in July 2002, examined whether in healthy postmenopausal women the hormone combination would reduce coronary heart disease and cardiovascular disease events. The trial found that there was a significant increase in coronary heart disease rates among women taking hormone therapy compared with the placebo group.

The sample analyzed included 14,749 postmenopausal asymptomatic women with an intact uterus who received 1 daily tablet containing 0.625 mg of oral conjugated equine estrogen and 2.5 mg of medroxyprogesterone acetate or a matching placebo. Participants were enrolled from 1993 to 1998.

The researchers found that among women with absent (9,744), minor (4,095), and major (910) electrocardiographic abnormalities, there were 118, 91, and 37 incident coronary heart disease events, respectively. The incident annual coronary heart disease event rates per 10,000 women with absent, minor, or major abnormalities were 21, 40, and 75, respectively.

After three years of follow-up, 5 percent of women who had a normal test at baseline developed new abnormalities with an annual coronary heart disease event rate of 85 per 10,000 women. There were no significant interactions between hormone treatment assignment and abnormalities for risk prediction of cardiovascular end points.

"In a large cohort of postmenopausal, asymptomatic women who were without a history of prior cardiovascular disease and participating in the estrogen plus progestin group of the WHI trial, we found that minor and major baseline electrocardiographic abnormalities were associated with significantly increased risks for coronary heart disease and cardiovascular disease events, independent of established risk factors and hormone treatment," the authors wrote.