According to a new study when it comes to heart bypass surgery, women are nearly twice as likely as men to die from complications.
Researchers believe their typically smaller body size may be one of the reasons.
When the researchers reviewed the records for 15,440 patients who had undergone coronary artery bypass grafting (CABG), they found that 4.24 percent of women died during or immediately after surgery, compared to 2.23 percent of men, a statistically significant difference.
Dr. Ron Blankstein, the lead study author, says the main reasons for the gender gap were the higher rates of "traditional risk factors" among women.
The study found that in general women were older and more likely than men to have problems such as diabetes and advanced heart failure.
But another factor was body size, and because as a rule women have smaller bodies than men, and a relatively smaller "body surface area", they were at greater risk of dying from heart bypass surgery.
Blankstein, a cardiology fellow at the University of Chicago Hospitals, says that body surface area is an indication of the size of a person's coronary arteries, and smaller vessels can make the surgery technically more difficult.
He and his colleagues suggest that this may be why smaller body size was linked to poorer survival.
However, Blankstein says body size and traditional risk factors did not fully explain the higher death risk among female patients, and as it seemed that just being female is itself a risk factor.
During the CABG procedure, a surgeon takes blood vessels from a patient's leg or elsewhere in the body and uses them to reroute blood around a blockage in the arteries that normally supply the heart.
Though coronary artery disease can often be managed with drug therapy or angioplasty, which is a less invasive procedure that opens up clogged arteries, some patients require CABG.
While the new findings are "sobering," says Blankstein, women should not be discouraged from having the surgery if they need it, as it still might be the best option for their disease.
The study which involved patients who underwent CABG at one of 31 hospitals in the Midwestern U.S. in 1999 and 2000, found that overall, women were 90 percent more likely than men to die during or soon after surgery.
Even after the researchers accounted for a variety of potential risk factors, including age, co-existing diseases and body size, the gender gap narrowed substantially, but women still remained 22 percent more likely to die compared with men.
Blankstein says it is important to find out why this discrepancy persists even when standard risk factors are considered.
According to the researchers, questions such as whether body fat plays a role, since it affects healing in tissues and blood vessels, and whether hormonal differences between women and men could be at work, need to be addressed.
The research is published in the annual Cardiovascular Surgery Supplement of Circulation, a journal by the American Heart Association.