On-pump versus off-pump coronary artery bypass surgery: a comparison of two consecutive series

On-pump and off-pump techniques are both widely used approaches to coronary artery bypass surgery. Yet, statistically valid comparisons of the results between the two groups have been limited, in part, by patient selection bias.

Two hundred sixty-nine consecutive patients undergoing off-pump coronary artery bypass and 379 consecutive patients undergoing on-pump bypass were compared in a retrospective chart review. The two groups were compared for preoperative characteristics as well as operative outcomes. To avoid selection bias, no on-pump coronary artery bypass surgery was performed during the off-pump coronary artery bypass series, and no patients were done off-pump during the coronary artery bypass series.

There was no statistical difference in the groups pre-operatively except that there were slightly more patients with three-vessel disease in the on-pump group and more patients with single vessel disease in the off-pump group. Significant benefits were found in the off-pump group in that they required fewer re-operations for bleeding (0.8% vs. 5.7%, p-value < 0.002), and they left the hospital with higher hematocrits (32.1% vs. 30.8%, p-value < 0.001). Patients who had off-pump coronary artery bypass also had fewer sternal dehiscences (0% vs. 1.8%, p-value < 0.027). More patients receiving off-pump bypass demonstrated the need for prolonged mechanical ventilation (8.2% vs. 2.5%, p-value < 0.027), and they also had significantly fewer grafts (3 vs. 3.2, p-value < 0.005). There was no statistically significant difference among the other outcomes investigated.

While there were no significant differences in some of the outcomes studied, others showed significant advantages in favor of off-pump surgery. Substantial advantages in off-pump coronary artery bypass were seen in bleeding reduction, improved sternal healing, and higher discharge hematocrits despite fewer transfusions. These advantages and others reported in specific high-risk patient groups, combined with documented cost reductions, warrant continued use of off-pump techniques. Off-pump coronary artery bypass is a safe, proven method with significant advantages over on-pump methods and, when appropriate, should be offered to patients undergoing coronary bypass surgery.