Effects of body size on operative, intermediate, and long-term outcomes after coronary artery bypass operation

Background. To investigate the role of body size, if any, on operative and longer term outcomes following coronary artery surgery. Methods. A total of 3,560 consecutive patients undergoing coronary artery bypass grafting from 1991 to 1997, including 2,401 (67%) males and a mean +/- SD age of 63 +/- 10 years were ranked based on their body mass index (BMI). The association in these patients of preoperative, long-term, and economic data with variations in BMI were studied using regression analyses. Long-term survival was studied using 5-year Kaplan-Meier survival analysis. Results. Operative mortality, myocardial infarction, cerebrovascular accidents, blood transfusions, and length of hospital stay were all increased in the smallest patients (BMI less than or equal to 24 kg/m(2)). Obesity did not increase adverse operative outcomes except for a greater rate of sternal wound infections occurring with increasing severity of obesity. Direct variable costs were lowest in patients clustered around normal BMI, with cost increasing similarly at low and high extremes. This effect was correlated with similar BMI effects on ventilatory and intensive care requirements. Excluding operative mortality, 5-year survival trends were similarly worse for the smallest (BMI less than or equal to 24) and most severely obese (BMI > 34) patients. Mild obesity (BMI greater than or equal to 30 to BMI < 34) did not affect long-term survival. Conclusions. Among study patients, immediate operative outcomes were adversely affected by small body size, which reflected older age (66 +/- 10 years) and an exaggerated adverse impact of cardiopulmonary bypass. Younger age and smaller effects of cardiopulmonary bypass lead to better operative outcomes in the obese. Long-term outcomes were, however, suboptimal in severely obese patients although that group was the youngest (60 +/- 10 years). In addition to their large body habitus, other factors, including substantial prevalence of diabetes, insulin dependence and hypertension, probably played a significant role in the poor long-term outcome in the severely obese. (C) 2001 by The Society of Thoracic Surgeons.