Obesity paradox in coronary artery bypass grafting: Myth or reality?

Objective: A high body mass index has been suggested to be protective in patients with coronary artery disease and in those undergoing coronary artery bypass grafting (CABG). However, these conflicting results might be related to the different risk profiles among the various body mass index categories. We sought to clarify the effect of varying degrees of excessive body weight on hard clinical outcomes in patients undergoing CABG. Methods: A retrospective analysis of prospectively collected data was conducted to investigate the effect of a high body mass index on early and late mortality after first-time isolated CABG. Propensity score matching was used to adjust for confounding factors. Results: The study sample consisted of 3269 normal weight, 6662 overweight, 3821 obese, and 211 morbidly obese patients. After matching, early mortality was not affected by overweight (mean difference, 0.7%; 95% confidence interval [CI], -0.2% to 1.5%), obesity (mean difference, 0.5%; 95% CI, -0.7% to 1.7%), and morbid obesity (mean difference, 1.6%; 95% CI, -1.0% to 1.0%), regardless of the patients' risk profile according to the European system for cardiac operative risk evaluation. Overweight status was not protective for late death (hazard ratio, 1.05; 95% CI, 0.9-1.08; P = .4). Compared with normal weight patients, both obese and morbidly obese patients had a higher risk of late death (hazard ratio, 1.22; 95% CI, 1.07-2.66; P = .006 for obese patients; hazard ratio, 1.36; 95% CI, 0.74-2.49; P = .3 for morbidly obese patients). Conclusions: Obesity did not increase operative mortality, but it was associated with reduced late survival in patients undergoing primary isolated CABG. Our results raise concerns in supporting any protective effect of obesity in cardiovascular disease, specifically in patients undergoing surgical myocardial revascularization.