The effect of weight loss on the outcome after coronary artery bypass grafting in obese patients

The role of body mass index (BMI) in the setting of coronary artery bypass graft (CABG) surgery has been a focus of past studies. However, the effects of postoperative weight loss in patients after CABG is yet to be known. We performed a retrospective study of 899 patients who underwent CABG at our institution. Perioperative patient information was collected from an onsite electronic record system. Patients were grouped into four BMI categories: normal controls, overweight, obese and morbidly obese. Based on the postoperative BMI changes, patients were then grouped into three categories: gainers, no change and losers. Statistical analyses were performed using analysis of variance and linear regression to establish an association among the data. Hazard ratios (HR) and cumulative survival were obtained by the Cox-Mantel and Kaplan-Meier analyses, respectively. The normal controls exhibited a markedly higher mortality postoperatively, at 27.9%, especially when compared with the obese individuals (16.1%). Patients who lost weight faced a significantly increased risk of mortality than those who experienced no changes or gained weight after surgery. This trend was especially salient among the obese patients, who more than tripled their mortality risk (HR = 3.24) versus individuals who gained weight, and more than doubled their risk (HR = 2.87) versus those who had no changes. We conclude that obesity confers a survival advantage in the setting of the CABG surgery. Weight loss among all BMI categories of patients studied results in an adverse effect on postoperative survival.