Background

Despite the fact that obesity is a known risk factor for cardiovascular disease, many studies have failed to demonstrate that obesity is independently associated with an increased risk of cardiovascular morbidity and mortality in nondiabetic patients undergoing coronary artery bypass graft surgery. The authors investigated the influence of obesity on adverse postoperative outcomes in diabetic and nondiabetic patients after primary coronary artery bypass surgery.

Methods

A retrospective cohort study of patients undergoing primary coronary artery bypass surgery (n= 9,862) between January 1995 and December 2004 at the Texas Heart Institute was performed. Diabetic (n= 3,374) and nondiabetic patients (n= 6,488) were classified into five groups, according to their body mass index: normal weight (n= 2,148), overweight (n= 4,257), mild obesity (n= 2,298), moderate obesity (n= 785), or morbid obesity (n= 338). Multivariate, stepwise logistic regression was performed controlling for patient demographics, medical history, and preoperative medications to determine whether obesity was independently associated with an increased risk of adverse postoperative outcomes.

Results

Obesity in nondiabetic patients was not independently associated with an increased risk of adverse postoperative outcomes. In contrast, obesity in diabetic patients was independently associated with a significantly increased risk of postoperative respiratory failure (odds ratio [OR], 2.26; 95% confidence interval [CI], 1.41-3.61; P< 0.001), ventricular tachycardia (OR, 2.27; 95% CI, 1.18-4.35; P< 0.02), atrial fibrillation (OR, 1.56; 95% CI, 1.03-2.38; P< 0.04), atrial flutter (OR, 2.38; 95% CI, 1.29-4.40; P< 0.01), renal insufficiency (OR, 1.66; 95% CI, 1.10-3.41; P< 0.03), and leg wound infection (OR, 5.34; 95% CI, 2.27-12.54; P< 0.001). Obesity in diabetic patients was not independently associated with an increased risk of mortality, stroke, myocardial infarction, sepsis, or sternal wound infection.

Conclusion

Obesity in diabetic patients is an independent predictor of worsened postoperative outcomes after primary coronary artery bypass graft surgery.