Early Silent Graft Failure in Off-pump Coronary Artery Bypass Grafting: A Computed Tomography Analysis

Aortocoronary bypass surgery is one of the most common operations in the western world. The goal of the surgeon is to perform a complete revascularization of the coronary arteries with the best, available bypass material.

Aortocoronary bypass surgery can be performed with (on-pump) or without (off-pump) the heart lung machine. If the operation is performed without the heart lung machine, the heart is continuously beating while the surgeon sews the bypass to the diseased coronary artery. In randomized trials, the benefits of the off-pump technique in the hands of experienced surgeons in terms of shorter operating times, less transfusions and less pulmonary and renal complications were proven. A criticism of the off-pump technique is the reduced number of distal anastomoses, which means that fewer coronary arteries may be connected with bypass grafts because of the technically sophisticated situation. A worse quality of the connection (anastomosis) between coronary artery and bypass is often discussed, leading to a bypass occlusion already in the early stage after surgery resulting in more re-interventions on the coronary vessels. So-called silent bypass failure without clinical correlation has been examined in three relevant studies including both, the on- and the off-pump technique, with inhomogenous results. In addition to the technique, other parameters such as the degree of narrowing (stenosis) of the diseased coronary artery and collateralization of a closed coronary artery may play a role in early occlusion.

All bypass patients after off-pump surgery receive routinely a computed tomographic examination of the heart. With this method, silent bypass occlusions without clinical correlation, i.e. cardiac infarction, elevated cardiac laboratory parameters or ECG changes, can be detected easily. In case of an occlusion of a relevant bypass, an intervention before discharge can be planned and performed.

We would like to investigate the occlusion rate of this retrospective patient cohort after off-pump surgery and the potential risk factors, that may influence on early graft failure. We hypothesize, that early graft failure depends not only on the choice of the graft material, but also on the local grade of coronary stenosis, the collateralisation of occluded coronary vessels and the intraoperative flow results, as well as on the region of the target vessel.