January 11 1994
Media Contact:Joann Rodgers
Phone: (410) 955-8659
Johns Hopkins cardiologists report preliminary evidence that
affects coronary blood flow in postmenopausal women. Their results
strengthening the links
between estrogen replacement therapy and decreased risk of heart disease in
older women appear in the January issue of the journal, Circulation.
We knew that postmenopausal women taking supplemental estrogen were likely to have as much as a 50 percent reduction in morbidity and mortality from coronary artery disease," says Steven E. Reis, M.D., lead author of the article. 'However, the mechanism of estrogens favorable effect on the heart is unclear."
Using coronary angiography, the researchers studied the coronary blood flow of 33 postmenopausal women before and 15 minutes after a high dose of intravenous estrogen was administered. Coronary flow increased by an average 23 percent in 22 of the women. Placebo given to the other 11 elicited no change.
Further evidence of estrogen's effect on blood flow was found in a second part of the study. This time, the researchers studied 15 postmenopausal women and gave all acetylcholine, a drug that increases blood flow in normal coronary arteries and decreases blood flow in abnormal arteries in much the same way as do exercise and stress. Seven women had abnormal responses to the acetylcholine and as a result their blood flow decreased by an average 33 percent. But after researchers administered estrogen, the blood flow response to acetylcholine tended to return to normal.
"It appears that the estrogen lessened the abnormal response to acetylcholine," says Reis. "In doing so, estrogen may raise the threshold for developing ymptoms of coronary heart disease during stress and exercise."
Because researchers used single, high doses of estrogen for their
studies, the effects of smaller long-term doses must still be evaluated for
similar effects. Meanwhile, the Hopkins doctors warn women
not to increase the amount of estrogen they now take,
"Long-term dosage studies are just beginning says Howard Zacur, M.D.,
Ph.D., director of Hopkins' estrogen consultation service and co-author on the
report, and need to be completed before any further
associations are drawn.
"More than anything," says Zacur, "this study validates the information we have been giving menopausal women and women with heart disease. We can now add biological data to the epidemiologic studies which have tried to explain some of estrogen's cardioprotective properties."
According to the American Heart Association, 500,000 deaths due to coronary artery disease occur in the United States each year, half in women who have reached or concluded menopause and no longer naturally produce estrogen in their ovaries. Other authors on the study include Sean T. Gloth, M.D.; Roger S. BlumenthaL M.D.; Jon R. Resar, M.D.; Gary Gerstenblith, M.D.; and Jeffrey A. Brinker, M.D.