Effects of Obesity and Small Body Size on Operative and Long-Term Outcomes of Coronary Artery Bypass Surgery: A Propensity-Matched Analysis

Background The effects of body habitus on coronary artery bypass graft surgery (CABG) operative and long-term outcomes are not well defined. We aimed to elucidate the independent effects of small body size and obesity on CABG outcomes. Methods Primary isolated CABG patients were grouped based on body surface area (BSA, m2) and body mass index (BMI, kg/m2) as follows: 611 very small (BSA ≤1.70); 933 slightly small (1.70 < BSA ≤1.85); 945 moderately obese (32 < BMI <36); 594 very obese (BMI ≥36); and 3,018 normal (BSA >1.85; BMI = 22 to 32). Subcohorts of very small (371 pairs, 61%), slightly small (717, 77%), moderately obese (874, 92%), and very obese (516, 87%) patients were propensity-matched to normal. Results Compared with normal, very small had more transfusions (46% versus 32%; p< 0.001), reoperation for bleeding (3.2% versus 0.3%; p = 0.002), and pulmonary edema (2.4% versus 0.5%; p = 0.033). For slightly small, transfusion (41% versus 29%; p< 0.001) and bleeding (2.5% versus 1.0%; p = 0.04) were increased. For moderately obese, sternal wound infections (1.9% versus 0.8%; p = 0.04) were greater. Complications were most frequent in very obese: reoperation (5.2% versus 1.6%; p< 0.001), sternal wound infections (3.5% versus 0.2%; p< 0.001), pulmonary edema (2.9% versus 1.2%; p = 0.047), renal failure (6.0% versus 2.3%; p = 0.003), atrial fibrillation (20% versus 12%; p = 0.001), gastrointestinal problems (3.7% versus 1.6%; p = 0.032), and postoperative stay (8.0 versus 6.4 days; p = 0.003). When slightly small and very small are considered together, operative mortality was significantly greater (3.22% versus 1.65%; p = 0.026). Both very small (risk ratio [RR] = 1.39; p = 0.044) and very obese (RR = 1.44; p = 0.020) were independent predictors of worse 0- to 12-year mortality. Conclusions Large deviations from normal body size in either direction—particularly extreme obesity—are associated with increased postoperative morbidity and worse long-term survival.