A small study of 184 women conducted by Dr. Eva Swahn of the department of cardiology at University Hospital in Linkoping, Sweden, found that women who had major heart operations such as a coronary bypass were more likely to die within a year than men.
The study was part of a larger study funded by pharmaceutical companies Sanofi-Aventis and GlaxoSmithKline.
Though experts said no definitive conclusions can be drawn from Swahn's study, they agreed the idea that women might need different treatment compared to men should be studied further.
"We have had hints in the past that women don't respond to treatment in exactly the same way as men," said Dr. Christopher Cannon, an associate professor of medicine at Harvard University and spokesman for the American College of Cardiology . He was not connected to Swahn's research.
Last month, the college revised its treatment guidelines to recommend that doctors should think twice before subjecting women at low risk of heart disease to invasive procedures.
For example, when doctors see women who could have a clogged coronary artery, instead of performing an immediate angioplasty a procedure in which a tiny balloon inflates the clogged vessel they should wait and see if further symptoms develop.
In Europe, the guidelines for treating heart disease are not generally different for men and women.
Women typically have a better chance of surviving a heart attack than men. But in Swahn's study, as in two previous Scandinavian trials that looked at hundreds of women, experts found women had a higher death rate than men when invasive heart procedures were performed.
In Swahn's study, the women were divided into two equal groups: one that had an invasive procedure like a coronary bypass surgery or an angioplasty, and another that waited until further symptoms developed.
Of the women who had an invasive procedure, eight died after one year. That compares to just one death in the other group.
"There is a big question mark over why this is happening," Swahn said. "We want there to be equality between the genders, but that doesn't mean that women and men should get the same treatment."
Doctors are not sure what accounts for the discrepancy. But women tend to have smaller hearts and vessels, which could complicate any surgical procedure. For example, when catheters need to be inserted into the artery to take photos of what is happening inside the body, having smaller arteries does not help.
"Catheters only come in certain sizes," Cannon said. "If the doctor misses, there could be some bleeding."
Women also tend to have more side-effects from medicines. Hormonal factors could also play a role, though doctors are not exactly sure how female-specific hormones affect the cardiovascular system.
Compounding the problem is the fact that women are usually about a decade older than men by the time they develop heart problems, so other health problems associated with old age could also worsen their chances of surviving heart surgery.