The cause of the hidden disease is a diffuse buildup of fatty deposits inside the walls of the coronary arteries and in the very small arteries in the heart.

The condition, which may affect 3 million American women, greatly increases the risk of a heart attack. Its main symptom is chest pain or discomfort.

In many women, the pain occurs but nothing shows up on an angiogram, a test in which dye is injected into the coronary arteries and they are X-rayed in a search for blockages, so doctors conclude that no treatment is needed.

But patients may then go on to have heart attacks or develop heart failure, a weakening of the heart muscle that can be debilitating and ultimately fatal.

Previous Studies Done Mostly in Men

"When there are no blockages, everybody slacks off, including the patient, and we don't want to do that," said Dr. George Sopko of the National Heart, Lung and Blood Institute. Such patients almost certainly need treatment, he said.

The findings are among those in a series of articles to be published Wednesday in two medical journals -- Circulation and the Journal of the American College of Cardiology -- exploring the differences in heart disease between men and women.

The subject has drawn increasing interest in recent decades, as scientists began to realize that the results of previous studies, done mostly in men, did not always apply to women.

Should Be Treated Aggressively

The cause of the hidden disease being described Wednesday is a diffuse buildup of fatty deposits inside the walls of the coronary arteries and in the very small arteries in the heart.

The deposits, or plaques, do not show up as blockages on X-rays, but they still interfere with blood flow and can damage the heart muscle, causing ischemic heart disease. ("Ischemia" means "inadequate blood flow.")

But often the condition is not recognized, and the women are told they have nothing to worry about.

Instead, Sopko said, they should be treated aggressively for other problems that lead to artery disease like high cholesterol, high blood pressure and diabetes.

If necessary, he added, they should also be advised to quit smoking, lose weight and exercise more.