Patients undergoing off-pump coronary artery bypass grafting (CABG) may need emergent institution of cardiopulmonary bypass (CPB) for circulatory collapse during the operation. Our aim was to evaluate outcome in such patients and identify preoperative and intraoperative risk factors.

This is an observational study in a University Hospital setting. In the period June 2001–July 2003, data from 988 consecutive patients undergoing CABG in our institution were prospectively collected. No interventions were made. Prolonged hospital stay (>7 days), hospital mortality, temporal trends and risk factors for conversion from off-pump to on-pump surgery were studied.

Fifty-four patients with emergency operations and six with associated carotid artery surgery were excluded. Of the remaining 928 patients, 450 (48.5%) were planned for off-pump surgery. Thirty-seven (8.2%) of them required conversion to CPB on an emergency basis. These patients had higher mortality (5.4%) than the off-pump group (1.5%) and the CPB group (0.4%), P = 0.02. The incidence of prolonged hospital stay was also higher (conversion group = 27%, off-pump group = 12.3%, CPB group = 17.6%; P = 0.02). We did not identify any perioperative characteristics significantly associated with the risk of requiring conversion. The conversion rate was uniformly distributed over the study period.

Patients who are emergently converted to CPB during attempted off-pump procedures are at higher risk of death and prolonged hospital stay; this population should be included in comparative studies as ‘intention to treat’ in the off-pump group.