Emergency Conversion to Cardiopulmonary Bypass During Attempted Off-Pump Revascularization Results in Increased Morbidity and Mortality

Objective: We sought to evaluate outcomes and predictors of emergency conversion to cardiopulmonary bypass during attempted off-pump coronary bypass surgery.

Methods: From January 1999 through July 2002, 1678 consecutive isolated coronary artery bypass operations were performed at Lenox Hill Hospital, with the intention to treat all patients with off-pump coronary bypass surgery. Fifty (2.97%) patients required urgent conversion to cardiopulmonary bypass. All the preoperative, intraoperative, and postoperative variables were collected and analyzed in accordance with the New York State Cardiac Surgery Reporting System. Multivariate regression analysis was performed to determine predictors for conversion.

Results: In-hospital mortality and major morbidity were significantly lower in the nonconverted group compared with the converted patients (mortality: 1.47% [n = 24] vs 12% [n = 6], P= .001; stroke: 1.1% [n = 18] vs 6% [n = 3], P= .02; renal failure: 1.23% [n = 20] vs 6% [n = 3], P= .02; deep sternal wound infection: 1.54% [n = 25] vs 8% [n = 4], P= .009; respiratory failure: 3.75% [n = 61] vs 28% [n = 14], P< .0001; nonconverted vs converted patients, respectively). The annual incidence of conversion decreased during the study period. There was a significant reduction in the incidence of conversion after routine use of a cardiac positioning device to performing lateral and inferior wall grafts (4.2% [n = 27] vs 2.3% [n = 23], P= .04). None of the preoperative variables were independent predictors of conversion on multivariate regression analysis.

Conclusions: Because emergency conversion to cardiopulmonary bypass during attempted off-pump coronary bypass surgery results in significantly higher morbidity and mortality, studies comparing off-pump coronary bypass surgery with conventional coronary artery surgery should include converted patients in the off-pump group. In our experience, emergency conversion is an unpredictable event. The incidence of conversion decreases with increasing experience of surgeons in performing off-pump coronary surgery and use of a cardiac positioning device.