Women have a 22% greater risk of dying during or immediately after coronary artery bypass graft (CABG) procedures, an excess risk that can't be explained by body size differences between the sexes.

The reason that women are at greater risk of dying after heart bypass surgery than men is because, well, they're women, according to University of Chicago Hospitals investigators here. Why that should be, however, is anybody's guess, said the researchers.

Although several studies have suggested that women are at greater risk for death following CABG because of their generally smaller body size, being female alone is enough to increase one's risk for dying following a bypass procedure, Ron Blankstein, M.D., and colleagues reported in Circulation, Journal of the american heart association.