Risk factors for conversion to cardiopulmonary bypass during off-pump coronary artery bypass surgery

Background: Off-pump coronary artery bypass graft (OPCAB) may be associated with improved hospital outcomes compared with on-pump coronary artery bypass graft. However, intraoperative conversion to on-pump coronary artery bypass graft has been associated with adverse outcomes. The purpose of this study was to identify preoperative risk factors for intraoperative conversion in nonemergent patients undergoing isolated OPCAB. Methods: From 2002 to 2010, 8,077 consecutive OPCAB cases were performed at a single US academic center. Of these, 200 (2.5%) required intraoperative conversion. Standard variables from The Society of Thoracic Surgeons database were analyzed. A multivariable logistic model with adjusted odds ratios (OR) and 95% confidence intervals was used to identify independent risk factors for conversion. Adjusted in-hospital and long-term survival between converted and nonconverted patients were determined using multiple logistic regression and Cox proportional hazards regression, respectively. Results: Converted patients had a higher Society of Thoracic Surgeons predicted risk of mortality (2.8% versus 2.1%; p < 0.001). Surgeon identity was the most significant multivariable predictor of conversion. After adjustment for surgeon identity, the following independent risk factors were associated with intraoperative conversion: previous coronary artery bypass graft (OR, 3.43; p = 0.018), congestive heart failure (OR, 1.51), myocardial infarction (OR, 1.86), number of grafts (OR, 1.45), left main disease (OR 1.41), and urgent status (OR, 1.77; all p < 0.05). Conversion to on-pump coronary artery bypass graft was associated with increased in-hospital (OR, 4.8; p < 0.001) and long-term mortality (hazard ratio, 1.65; p < 0.001). Conclusions: Conversion to cardiopulmonary bypass during OPCAB is associated with increased in-hospital and long-term mortality and may be related to surgeon experience. Recognition of the preoperative risk factors associated with an increased risk of conversion may allow for better patient selection and reduce the incidence of intraoperative conversion during OPCAB.