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

OBJECTIVES: To investigate the effects of body mass index (BMI) on early outcomes after revascularization using either on-pump or offpump surgery. METHODS: 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 ≥35 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. RESULTS: 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. CONCLUSIONS: 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.