Does body mass index impact the early outcome of surgical revascularization? A comparison between off-pump and on-pump coronary artery bypass grafting

To investigate the effects of body mass index (BMI) on early outcomes after revascularization using either on-pump or off-pump surgery. Data for 3714 of 4314 patients who underwent surgical revascularization at our institution between 1999 and 2008 were analysed. Patients were divided into two groups [off-pump coronary artery bypass (OPCAB); n = 1958 and on-pump coronary artery bypass (ONCAB); n = 1756] and further assigned into five classes according to their BMI (underweight < 20 kg/m(2), normal 20-24.99 kg/m(2), overweight 25-29.99 kg/m(2), obese 30-34.99 kg/m(2) and morbidly obese a parts per thousand yen35 kg/m(2)). Thirty-day mortality, occurrence of major adverse cardiac events (MACEs), occurrence of major non-cardiac adverse events (MNCAEs) and length of in-hospital stay were analysed in relation to BMI only (whole cohort analysis), to BMI and chosen surgical method (ONCAB versus OPCAB) as well as confounding factors. In the whole cohort analysis (n = 3714), no significant differences between BMI classes could be identified with regard to 30-day mortality (P = 0.78), MACEs (P = 0.72), MNCAEs (P = 0.45) or length of in-hospital stay (P = 0.94). With increasing BMI values, 30-day mortality tended to steadily increase (1.8% in BMI class 'underweight' vs 2.6% in BMI class 'morbidly obese'; P = 0.78), whereas MNCAEs tended to decrease with an increasing BMI (17.5% in BMI class 'underweight' vs 12.2% in BMI class 'morbidly obese'; P = 0.45). Compared with ONCAB, in patients with higher BMI values, OPCAB appeared to reduce slightly the frequency of 30-day mortality, MACEs and MNCAEs, while slightly increasing the length of in-hospital stay. Adjustment for other risk factors by covariate analysis in multiple regression models did not change the inferences drawn. Our study did not detect significant differences between BMI classes with regard to mortality and morbidity. However, a slight trend towards a steadily increasing short-term mortality was detectable for patients with higher BMI values. When comparing ONCAB versus OPCAB, patients with higher BMI values appeared to have a weak tendency towards a reduced short-term morbidity and mortality in favour of OPCAB.