Estrogen Therapy Increases Risk of Arrythmia

Women who take estrogen replacement therapy to relieve menopausal symptoms are nearly twice as likely to develop risk factors for arrythmia and heart attacks than women not using hormone therapy, according to a study in the August 2003 issue of the Annals of Epidemiology.

Researchers who conducted a nine-year study of 3,100 postmenopausal women found that estrogen replacement therapy prolongs a segment of the electrocardiogram called the QT interval, a part of the repeating electrical pattern of the heart that is measured in fractions of a second. Prolongation of the QT interval is associated with an increased risk for arrhythmia, coronary heart disease, and sudden cardiac death. The researchers not only found that the risk for QT prolongation in women taking estrogen was almost twice that of women not taking hormones but also twice that of women taking progestin plus estrogen.

Mercedes Carnethon, an assistant professor of preventive medicine at the School of Medicine at Northwestern University (Evanston, IL, USA) who led the study, noted that women are known to have longer QT intervals than men and that the interval varies over the course of a woman's life. It is believed that QT length may be controlled, at least in part, by sex hormones, particularly estrogen.




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