Operative Strategies to Reduce Cerebral Embolic Events During Coronary Artery Bypass Surgery

One of the most devastating complications of coronary artery bypass surgery (CABG) is postoperative stroke. While the etiology of stroke after CABG is multifactorial, atheroemboli generated during aortic manipulation is believed to account for most cerebral embolic events. Manipulation of the aorta during CABG occurs during aortic cannulation, institution and maintenance of cardiopulmonary bypass, and during aortic clamping and unclamping with either a cross-clamp, partial-occluding clamp, or both. One operative strategy to minimize aortic manipulation is to avoid cardiopulmonary bypass altogether by using off-pump techniques (OPCAB). Another method is to avoid the use of aortic clamps and to construct proximal aortocoronary anastomoses with facilitating devices that do not require aortic clamping. The effect of these strategies on reducing cerebral embolic events and the underlying mechanism for this reduction are not well-defined.

This study will test the hypothesis that an off-pump (OPCAB) approach and facilitating devices to perform clampless proximal anastomoses will result in the least amount of aortic manipulation and therefore the lowest incidence and frequency of cerebral embolic events. The approach associated with the lowest incidence of TCD-detected cerebral embolic events will also result in the lowest incidence and severity of postoperative neurocognitive decline. Transcranial Doppler ultrasonography is an established method to detect cerebral embolic signals during cardiac surgery and will be utilized to detect cerebral embolic events during the operation. After an on- or off-pump strategy is selected, patients will be subsequently randomized to one of two clamping strategies. There will be 4 groups of patients: 1) OPCAB patients randomized to no clamping (facilitating device); 2) OPCAB patients randomized to partial clamping; 3) on-pump patients randomized to double clamping; and 4) on-pump patients randomized to a single clamp strategy.