Up to six times more women die of heart disease than of breast cancer; in fact, heart disease is the number-one killer of women, and the number-three killer of women under 45. Surprised? Given a lack of awareness about gender-specific risks, even women who think they practice good heart health may be relying on outdated or mistargeted information. Here, experts answer common questions about women’s cardiovascular health.

Q. My cholesterol, blood pressure, and stress test results are normal. Am I still at risk?                                                                          A. You might be. A 2010 study found traditional risk factors like high cholesterol and blood pressure failed to identify two-thirds of women with the highest risk: those whose heart X rays showed “substantial” narrowing of the arteries. In the 6,800-person Multi-Ethnic Study of Atherosclerosis (MESA), researchers found a third of the “low risk” female subjects in fact had heart disease. Cholesterol numbers can be deceiving partly because when it comes to LDL (bad) cholesterol, size matters, says Patrick Fratellone, MD, an integrative cardiologist in New York. Small, dense LDL particles block arteries; large, fluffy ones float. “A woman could have normal cholesterol but the wrong particle size, and she could have a heart attack,” he says. Ask your doctor for a cholesterol fractionation test, also called a VAP or NMR test.

Stress tests also aren’t reliable. To fail a stress test you need at least a 70 percent blockage in at least one artery. But the vast majority of heart attacks (86 percent) occur in blood vessels with less than 70 percent blockage, says William Blanchet, MD, a prevention-focused physician in Boulder, Colorado. This phenomenon is slightly more common in women because they have less obstructive disease (when cholesterol blocks the whole artery) and more plaque lining vessel walls (where it can break off to form a blood clot and lead to heart attack). And because most women don’t become hypertensive until after menopause, blood-pressure readings tend not to raise red flags, either.