Comparison of outcomes for off-pump versus on-pump coronary artery bypass grafting in low-volume and high-volume centers and by low-volume and high-volume surgeons

In terms of in-hospital outcomes, controversy still remains whether off-pump coronary artery bypass grafting is superior to on-pump coronary artery bypass surgery. We investigated whether the volume of off-pump coronary artery bypass procedures by hospital and individual surgeon influences patient outcomes when compared with on-pump coronary artery bypass surgery. Discharge records from the Nationwide Inpatient Sample were retrospectively reviewed for in-hospital admissions from 2003 to 2011, including 999 hospitals in 44 states. A total of 2,094,094 patients undergoing on- and off-pump coronary artery bypass surgery were included. In patients requiring 2 or more grafts, off-pump coronary artery bypass compared with on-pump coronary artery bypass was associated with increased risk-adjusted mortality when performed in low-volume centers (<29 cases per year) (odds ratio [OR] 1.32, 95% confidence interval [CI] 1.06 to 1.57) or by low-volume surgeons (<19 cases per year) (OR 1.26, 95% CI 1.02 to 1.56). In high-volume off-pump coronary artery bypass centers (≥164 cases per year) and surgeons (≥48 cases per year), off-pump coronary artery bypass reduced mortality compared with on-pump coronary artery bypass in cases requiring a single graft (OR 0.66, 95% CI 0.49 to 0.89 and OR 0.33, 95% CI 0.22 to 0.47, respectively) or 2 or more grafts (OR 0.82, 95% CI 0.66 to 0.99 and OR 0.63, 95% CI 0.49 to 0.81, respectively). In conclusion, the outcome of off-pump coronary artery bypass grafting procedures is dependent on volume at both the institution and the individual surgeon level. Off-pump coronary artery bypass should not be performed at low-volume centers and by low-volume surgeons.