Conversion From Off-Pump Coronary Artery Bypass Grafting to On-Pump Coronary Artery Bypass Grafting

Off-pump coronary artery bypass grafting (OPCAB) has been shown to be an effective strategy for surgical revascularization. The purpose of this study was to define the incidence of intraoperative conversion from OPCAB to on-pump coronary artery bypass grafting (ONCAB) and report outcomes based on the reason for conversion.

Starting in July 2007, the Society of Thoracic Surgeons database captured patients that were planned OPCAB but then were converted to ONCAB. A total of 196,576 patients undergoing planned OPCAB within the Society of Thoracic Surgeons National Database from July 2007 to June 2014 were evaluated. Patients were grouped according to their intraoperative conversion to cardiopulmonary bypass: (1) planned conversion, (2) unplanned conversion for visualization, (3) unplanned conversion for hemodynamic instability, and (4) no conversion (OPCAB). Multiple logistic regression analysis was used to determine risk factors for conversion.

The overall rate of conversion from OPCAB to ONCAB was 5.5%, with 49.6% of the conversions being planned. When compared with those not undergoing conversion (OPCAB, 30-day mortality observed to expected ratio [O/E], 0.8), those undergoing conversion to ONCAB experienced greater 30-day mortality regardless of etiology of conversion (planned conversion O/E, 1.4; unplanned conversion for visualization O/E, 1.6; and unplanned conversion for hemodynamic instability O/E, 2.7). Similar O/E ratios were observed for renal failure and prolonged ventilation following conversion. Logistic regression analysis showed advanced age, ejection fraction less than 35%, preoperative intraaortic balloon pump placement, increasing number of diseased coronary arteries, preoperative heart failure within 2 weeks, and urgent procedural status were all independent predictors for conversion to ONCAB (p ≤ 0.01).

Intraoperative conversion from OPCAB to ONCAB remains a morbid event with a risk of mortality much higher than expected. Surgeons should consider elective ONCAB in those with a high risk for conversion during OPCAB.