Morbidity and mortality following acute conversion from off-pump to on-pump coronary surgery

Many studies have described reduced morbidity in hospital and equivalent midterm outcomes with off-pump coronary artery bypass (OPCAB) surgery compared to conventional CABG (CABG-CPB). However, OPCAB is sometimes converted acutely to CABG-CPB. We describe the risk of acute conversion and compare patients' outcomes for acutely converted OPCAB with unconverted OPCAB and CABG-CPB.

Consecutive acute conversions, i.e. OPCAB patients in whom CPB was instituted urgently for hemodynamic or electrical instability, cardiac arrest or uncontrolled bleeding, were compared with propensity-matched unconverted OPCAB and CABG-CPB patients. Relative risks of death and complications in hospital, and subsequent survival were estimated.

The risk of acute conversion between 1996 and 2004 was 1.1% (27/2492): 5.1% in the first 2 years, 2.2% in the third year and 0.8% subsequently. Odds ratios for death in hospital compared to unconverted OPCAB and CABG-CPB were 4.4 (95% confidence interval (CI) 0.67-29.1) and 4.7 (95% CI 1.03-21.1), respectively, and ranged from 0 to 4.5 for serious complications. Converted patients had an increased hazard of death for 3 years after surgery compared to unconverted OPCAB (hazard ratio 3.21, 95% CI 1.20-8.59) and CABG-CPB patients (hazard ratio 3.23, 95% CI 1.41-7.39).

Experienced OPCAB surgeons have a low risk of acute conversion. Acutely converted patients have a moderately increased risk of death and serious complications in hospital. These risks are difficult to quantify precisely because conversion is rare.