Heart patient Susan Goodreds says the signs of her condition were relatively subtle at first.
"I would just feel a fist-sized tightness in the middle of my chest, but it wasn't painful," she says in an interview with ABC News medical correspondent John McKenzie for "World News."
Still, her symptoms prompted her to consult with her physician. What doctors told her was that her heart was fine.
But when she insisted on a heart scan, doctors discovered that two of her coronary arteries were 95 percent blocked with plaque.
Goodreds' story is all too common.
Because women often have symptoms of heart disease different from those of men, they're often misdiagnosed.
However, that could change. New guidelines, released Monday by the American Heart Association, underscore the importance of preventing and treating heart disease in women.
The guidelines, published in the current issue of the journal Circulation, use information from the most recent scientific studies to highlight what works -- and what doesn't -- when it comes to protecting women from heart attacks and stroke.
The numbers are chilling.
In the United States, 42.1 million -- or just more than one-third of all women -- have heart disease.
Heart disease is also the largest single cause of death among women, accounting for nearly 40 percent of all female deaths.
All told, this means that about one out of every three women in this country will die of a heart attack or stroke -- more deaths than from all cancers combined.
"All women are at risk for heart disease and stroke, and we don't want women to wait until they have a risk factor or they have the disease before they begin to take action," New York Presbyterian Hospital's Dr. Lori Mosca tells McKenzie. Mosca is the chair of the expert panel that issued the new guidelines.
Mosca says in a statement that researchers have developed more definitive clinical trials since the last set of guidelines was developed.
Among other recommendations, the researchers say virtually all women are at risk of heart disease, and doctors should more strongly consider prescribing a daily aspirin for their female patients.
Additional prescription of aspirin isn't the only way that women can be protected from heart disease, according to the guidelines. Women should also try the following:
Reduce saturated fat from meat, cheese and butter. The new advice states that these food sources should only account for 7 percent of total calories a day.
Don't rely on supplements. Vitamin pills don't prevent heart disease, nor does folic acid, the new guidelines say.
Hormone replacement therapy and selective estrogen receptor modulators, such as the osteoporosis drug raloxifene, are not recommended to prevent heart disease in women.
Engage in more physical activity. The guidelines suggest at least 30 minutes a day of brisk walking. If a woman is overweight, the new guidelines say 60 to 90 minutes a day is needed.
For a comprehensive listing of Medicine on the Cutting Edge reports with John McKenzie, click here.