Myocardium at risk is associated with adverse clinical events in women but not in men, after coronary artery bypass grafting

Background: Women undergoing coronary artery bypass grafting (CABG) are at increased risk for morbidity and mortality. Factors responsible for this observation include smaller coronary size and delayed presentation. To date, no studies have examined the effect of the degree of myocardium at risk (MAR) on the relationship between female sex and adverse postoperative events. Methods: Consecutive patients undergoing first-time isolated CABG at a single institution from 2002-2007 were identified. MAR was calculated using the weighted Duke Index and was categorized as low, moderate, or high. Multivariable logistic regression models were created to compare the impact of MAR on adverse clinical events. Results: We identified 3741 patients, 3325 (89%) of whom had complete angiographic data. Women (n= 755) were older (P= 0.0001) and presented more often with hypertension (P= 0.0001), diabetes (P= 0.0001), heart failure (P= 0.0001), and an urgent/emergent situation ( P= 0.002). After surgery, women experienced greater rates of adverse events (15.2% vs 9.3. %; P= 0.0001). In a fully adjusted logistic regression model, the nested interaction of sex in MAR showed that women had a significantly greater risk of major adverse cardiovascular events (MACE) when MAR was high (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.3-2.6; P= 0.0004). Greater severity of MAR emerged as an independent predictor of adverse events among women (high: OR, 2.9; 95% CI, 1.2-7.3; moderate: OR, 2.2; 95% CI, 0.8-5.7; low: OR, 1.0), but not among men. Conclusions: MAR was independently associated with higher rates of adverse events among women but not in men undergoing CABG. This finding may help explain differences in outcomes seen between women and men after revascularization.