Unrecognized Heart Attacks in Women with Known Coronary Artery Disease

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The summary below is from the full report titled "The Incidence of Unrecognized Myocardial Infarction in Women with Coronary Heart Disease." It is in the 5 June 2001 issue of Annals of Internal Medicine (volume 134, pages 1043-1047). The authors are MG Shlipak, DA Elmouchi, DM Herrington, F Lin, D Grady, and MA Hlatky, for the Heart and Estrogen/progestin Replacement Study Research Group.

What is the problem and what is known about it so far?

Heart attacks occur when blood flow through the arteries to the heart (coronary arteries) is blocked for a time long enough to damage or kill a portion of heart muscle. Most, but not all, heart attacks cause symptoms, such as severe crushing chest pain, nausea, shortness of breath, or a feeling of impending doom. Some people with heart attacks die immediately, before they are able to receive medical attention. Others are admitted to hospitals and treated for their symptoms. Still others may live without ever recognizing that they had a heart attack. Past studies suggested that unrecognized heart attacks are generally common, representing as many as a third of all heart attacks, and are more common in women than men. It is not clear, however, exactly how frequently heart attacks go unrecognized in women with known heart disease.

Why did the researchers do this particular study?

To find out how frequently unrecognized heart attacks occur in women with known coronary heart disease.

Who was studied?

The study included 2763 postmenopausal women with known coronary heart disease. The participants had previously had a heart attack or had undergone a heart procedure for coronary heart disease. All of the women were younger than 80 years of age.

How was the study done?

Researchers used information from a study that was originally designed to assess benefits of hormone treatment for postmenopausal women. The women were asked about symptoms and hospitalizations every 4 months for 4 years. They had electronic heart tracings (electrocardiograms) each year. The researchers used the tracings to diagnose heart attacks. The researchers also reviewed the women's medical records and hospitalizations to see which women had had symptoms or recognized heart attacks.

What did the researchers find?

The researchers diagnosed 256 nonfatal heart attacks among the women. Of these, only 11 (4%) had been unrecognized. Compared with women who had recognized heart attacks, women with unrecognized heart attacks were less likely to have diabetes mellitus or previous chest pain and were more likely to have previously had heart surgery for coronary heart disease.

What were the limitations of the study?

This study was originally designed to assess benefits of hormone therapy in postmenopausal women. Participants in the study knew that they had coronary heart disease and were followed closely. Because women in the general population may be less aware of their heart disease, unrecognized heart attacks may be more frequent among them than in these study participants.

What are the implications of the study?

Unrecognized heart attacks sometimes occur in postmenopausal women with known coronary heart disease, but they appear to be less frequent than has been thought previously.