Chest pain or discomfort is one of the hallmarks of having a heart attack, but a new U.S. study suggests women aren't as likely as men to have that symptom when they enter hospital and may also be at higher risk of dying.

Dr. John Canto of the Watson Clinic and Lakeland Regional Medical Center in Florida and colleagues analyzed data from the industry-sponsored National Registry of Myocardial Infarction from 1994-2006 for the study, considered one of the largest of its kind. Of the 1,143,513 patients assessed, 42.1 per cent were women.

The study, published in Wednesday's Journal of the American Medical Association (JAMA), emphasizes the importance of medical professionals recognizing someone is having a heart attack and getting them acute medical care quickly, even if they don't have chest pain or discomfort.

The study concluded that patients with no chest pain symptoms tend to be treated "less aggressively, and have almost twice the short-term mortality compared with [patients] with more typical symptoms of MI."

The researchers found the average age of women who entered hospital with heart attacks (myocardial infarction, or MI) was 74, compared with 67 for men. They then examined MI patients who didn't suffer chest pain or discomfort in these age groups:

• Younger than 45 years old.
• 45 to 54 years.
• 55 to 64 years.
• 65 to 74 years.
• 75 years or older.

The overall proportion of patients who entered hospital without chest pain was 35.4 per cent but was much higher for women (42 per cent) than men (31 per cent). While chest pain or discomfort was the most common symptom of MI in both women (58 per cent) and men (69 per cent), women, especially those under age 45, were less likely to report feeling such problems.

As well, the rate of MI patients dying in hospital was 14.6 per cent for women and 10.3 per cent for men. But the most telling finding is that younger women who didn't enter hospital with chest pain died at a much higher rate than men who also didn't have that symptom. Only after age 75 did men without chest pain die at a higher rate.

Early treatment important

The importance of recognizing that heart attack doesn't discriminate based on gender has been highlighted in recent years, with more researchers including women in studies on cardiovascular disease.

Heart disease is the No. 1 killer of both men and women in the U.S. and Canada.

In Canada, according to Statistics Canada's latest figures, cardiovascular disease accounted for 29 per cent of all deaths in Canada — 28 per cent of all male deaths and 29.7 per cent of female deaths. As well, 54 per cent of cardiovascular deaths were due to ischemic heart disease and 23 per cent from heart attack.

In the U.S., 1.5 million heart attacks occur each year, with 500,000 deaths, and more than 233,000 women die annually from cardiovascular disease.

Heart attack doesn't discriminate

“Although men and women can experience chest pressure that feels like an elephant sitting across the chest, women can experience a heart attack without chest pressure, ” says Dr. Nieca Goldberg, an American Heart Association volunteer and medical director for the Joan H. Tisch Center for Women's Health at the NYU Langone Medical Center.

“Instead they may experience shortness of breath, pressure or pain in the lower chest or upper abdomen, dizziness, lightheadedness or fainting, upper back pressure or extreme fatigue.”

Women suffering a heart attack often believe the symptoms are due to less life-threatening conditions such as acid reflux, the flu or normal aging, adds Goldberg. “They do this because they are scared and because they put their families first. There are still many women who are shocked that they could be having a heart attack.”

Researchers in Wednesday's JAMA study have received funding from various sources, including the National Institutes of Health, and various pharmaceutical companies.