Aug. 29, 2005 -- A new study may help shed light on why women are twice as likely as men to die following heart bypass surgery.
Death rates after coronary artery bypass graft (CABG or "cabbage") have been considerably higher in women than in men, writes researcher Ron Blankstein, a cardiologist at the University of Chicago Hospitals.
"Our study shows that a significant degree of their higher mortality rate may be due to the fact that women generally have smaller bodies," write the researchers in a news release.
Yet they also write that the higher death rates seen in women may in part be due to the fact that many women are referred for treatment at a more advanced stage than men.
The study appears in Circulation.
During CABG, a segment of a healthy blood vessel from another part of the body is used to create a detour around the blocked portion of the artery, thereby allowing oxygen-rich blood to flow freely into the heart.
What accounts for the fact that women have a higher risk of dying following CABG?
Smaller Bodies, Higher Risk
In general, people with smaller bodies may have smaller coronary arteries that are more difficult to operate on, Blankstein explains.
As part of their study, the researchers sought to determine how much of a role additional factors might play in women's increased death rates. They included:
- Increased age
- Advanced disease
- The presence of other diseases or health conditions
They established a database of 15,440 patients who underwent CABG at 31 Midwestern hospitals from 1990-2000. The women averaged 66 years of age; men on average were 63.
The death rates took into account various risk factors.
Overall, 4.2% of the women and 2.2% of the men died during or immediately after surgery; that's a 90% higher death rate for women than men.
"Nearly half of the excess mortality may be because women were often older and sicker at the time of the surgery than men were," Blankstein notes.
When other risks were factored in, the gender gap in death rates decreased significantly, from 90% to 49%.
The gap narrowed even further when the researchers took into account patients' body surface area, or BSA. BSA is a way of measuring body size based on height and weight.
When women's lower average BSA was factored in, a large part of women's higher death rate was explained.
In fact, the death-risk gap between the two sexes went from 49% to 22%.
"Our study shows that body surface area, or body size, is a very important independent predictor for mortality on top of all the other risk factors," says Blankstein.
The risk isn't confined to women exclusively. The researchers determined that for men as well as women, the smaller the body surface area, the higher the risk of dying.
Worth the Risk
According to Blankstein, women should not allow the risks to discourage them from having the surgery. "For many patients," he says, "CABG still represents the optimal therapy for their coronary heart disease."
Overall, he says, additional research is needed. "After accounting for lower BSA and other risk factors, why are women still 22% more likely to die after CABG than men are? That is a critical question for future research," he says.
Researchers need to explore potential factors such as differences in body fat composition, which may make tissues and blood vessels harder to heal, and the role of hormones, especially in postmenopausal women, he says.