the number one cause of death in the United States -- men and women are not created equal. The decided advantage goes to women.

"Women have much lower coronary heart disease mortality rates than men at all ages," Dr. Henry McGill, professor of pathology at University of Texas at San Antonio, said at the 58th annual American Heart Association meeting, held here last week. For every woman who develops heart disease, almost two men are afflicted.

Yet the study of heart disease in women is increasing as more and more women work outside the home in high-powered, stressful jobs (one of the behavioral risk factors linked to heart disease in men) and the number of post-menopausal women, also at higher risk for heart disease, increases.

Among the questions being pursued by medical investigators:

*What effect do birth control pills have on heart disease risk?

*After menopause, can estrogen replacement therapy prevent heart disease?

*Is there a gender difference in the safety and effectiveness of heart disease treatment, particularly coronary artery by-pass surgery?

*Will the increased number of women working in high-powered, stressful jobs increase the likelihood that they will develop heart disease at rates approaching those for men?

The notion that heart disease is increasing for women because of their entry into the working world is a myth, says Suzanne Haynes, Chief of the Medical Statistics Branch at the federal government's National Center for Health Statistics.

Heart disease mortality rates have been declining in the United States for the past several years, Haynes said. "In women, there's been a greater percentage of decline in all ages as compared with men."

Studies show, she said, that women with Type A personality are about "twice as likely to develop coronary artery disease regardless of occupation."

Work may contribute to some increase in heart disease among women in clerical positions -- those with "high job demands, but very little job control."

As for the effect of birth control pills on a woman's cardiovascular health, study results are mixed. Oral contraceptives contain the hormones estrogen and progesterone, substances that have "many metabolic and physiologic effects," including altering levels of blood cholesterol and triglycerides, said Dr. Robert Wallace of Iowa University.

While specific changes vary according to the dose and type of oral contraceptive, Wallace said in general "there tends to be a modest increase total blood cholesterol."

There is enough evidence, Wallace said, to warrant further investigation of the role oral contraceptives may play in the development of heart disease.

"We're left with some simple but unanswered questions," Wallace said. "Should doctors prescribing oral contraceptives screen before and after for blood lipid levels of cholesterol and triglycerides?" Probably not, he said. But doctors should ask women who have symptoms of coronary heart disease about their use of birth control pills, and perhaps suggest alternative methods of contraception for a while.

Also unclear is whether older women, past the age of menopause, should take estrogen to protect against heart disease. Prior to menopause, women produce levels of estrogen that seem to decrease the chances of developing heart disease.

Again study results are conflicting, University of Texas' McGill said, but worth pursuing. About two thirds of some 15 studies conducted on this question "found that taking postmenopausal estrogens reduces cardiovascular disease risk," he said.

The most recent studies showed a 30 percent decrease in heart disease among women taking these hormones. Yet "the potential cardiovascular benefits of estrogens are balanced by some of their other effects," McGill said, including an increased likelihood of developing endometrial cancer. Estimates are, McGill said, that estrogen replacement therapy increases the risk of cancer from two to 30 times.

"These conflicting results should not be discouraging," he said. Rather, they "should encourage us to get on with the job of finding out which women benefit from estrogens and which ones do not."

For those who develop cardiovascular diseases, there seem to be important gender differences in the safety and effectiveness of treatment. The number of women undergoing coronary artery bypass surgery is increasing, said Dr. Delos Cosgrove, a surgeon at the Cleveland Clinic. But women have a higher risk of complications and death from bypass surgery and are less likely to derive as many benefits from the operation, Cosgrove said.

Women had "twice the risk of developing a stroke" with surgery when compared with men, according to a Cleveland Clinic study. They required blood transfusions more often (60 percent of women compared with 23 percent of men), and when transfused, women needed more pints of blood than men. On the average men needed half a pint of blood, while women required almost two pints.

Death rates also are higher for women undergoing bypass surgery. Approximately 0.5 percent of men die from the surgery compared to 1.5 percent of women.

Following surgery, he said, "women achieve less relief from angina heart pain than men do."

Two major factors probably contribute to the higher risk for women, Cosgrove said. One is that women are usually older than men when they undergo surgery and often have more complicating conditions, including diabetes. Certain widely used surgical techniques are also more difficult to perform on women, Cosgrove said, because generally women are smaller than men. It may be, he said, that "size, not gender, is the risk factor."