It's part of a puzzling gender gap: Women tend to have different heart attack symptoms than men. They're more likely to die in the year after a first heart attack.

In fact, more than 40 percent of women still don't realize that heart disease is the No. 1 female killer. One in 30 women's deaths in 2007 was from breast cancer, compared to about 1 in 3 from cardiovascular disease, according to the American Heart Association.

A new report says there's been too little progress in tackling the sex differences in heart disease. It outlines the top questions scientists must answer to find the best ways to treat women's hearts - and protect them in the first place.

Make no mistake: Heart disease is the leading killer of men, too. The illness is more prevalent in men, and tends to hit them about a decade earlier than is usual for women.

But while overall deaths have been dropping in recent years, that improvement has been slower for women who face some unique issues, says the report from the nonprofit Society for Women's Health Research and WomenHeart: The National Coalition for Women with Heart Disease.

Sure, being a couch potato and eating a lot of junk food is bad for a woman's heart just like a man's. High cholesterol will clog arteries. High blood pressure can cause a stroke.

But here's one problem: Even if a test of major heart arteries finds no blockages, at-risk women still can have a serious problem - something called coronary microvascular disease that's less common in men. Small blood vessels that feed the heart become damaged so that they spasm or squeeze shut.