Differences between men and women in hospital mortality associated with coronary artery bypass graft surgery. The Northern New England Cardiovascular Disease Study Group.

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Abstract
BACKGROUND A prospective study of patients undergoing coronary artery bypass graft surgery (CABG) was conducted to examine differences in hospital mortality by sex. Outcome data on 3055 CABG patients undergoing operation between 1987 and 1989 were examined for differences in patient, disease, and treatment factors. METHODS AND RESULTS Odds ratios (OR), risk differences, and 95% confidence intervals (CI95%) were calculated. Mortality rates for women (7.1%) and men (3.3%) differed, the OR (women versus men) being 2.23 (CI95%, 1.58 to 3.15). Women were older, more often diabetic, and had more urgent or emergent surgery; adjustment yielded an OR (women versus men) of 1.75 (CI95%, 1.17 to 2.63). Body surface area (BSA) was associated with risk of death in both sexes (P = .007) and positively associated with coronary artery luminal diameters. After adjustment for BSA, sex was no longer significantly associated with mortality (OR [women versus men] of 1.18; CI95%, 0.72 to 1.95). Internal mammary artery (IMA) grafting was performed less frequently among women than men (64.8% versus 78.4%, P < .001). Smaller BSA and absence of IMA grafting were each associated with increased risk of death (RD) from heart failure. Risk of death from heart failure (RD [women minus men] = 2.05; CI95%, 0.89 to 3.22) and hemorrhage (RD [women minus men] = 0.63; CI95%, 0.13 to 1.13) was greater among women; these accounted for 71.1% of the sex-specific difference in mortality rates. CONCLUSIONS Excess risk of hospital mortality among women having CABG was largely the consequence of death from heart failure and, to a lesser extent, from hemorrhage. Smaller BSA (probably because of its association with coronary artery luminal diameter) and the absence of IMA grafting were each associated with increased risk of death from heart failure.