Effects of coronary bypass surgery on the electrical activity of revascularized myocardium. Immediate and early postoperativeobservations.

The effect of myocardial revascularization on bipolar epicardial electrograms was recorded with fixed wire electrodes from revascularized left ventricular sites and from control sites on the right ventricle. Studies were performed during and after surgery in 19 patients undergoing aorta-coronary bypass grafting for occlusive coronary artery disease and in 6 additional patients having aortic valve replacement for isolated aortic valve disease. In the latter 6 patients, neither left nor right ventricular electrogram voltage changed immediately following aortic valve replacement; however, left ventricular electrogram voltage gradually decreased for 5 days postoperatively. In the 19 patients with coronary artery disease, electrogram voltage in the revascularized area increased immediately following coronary bypass grafting (+40 to +300 per cent) in 13 patients (68 per cent) and immediately decreased (-20 to -70 per cent) in 6 patients (32 per cent). In 5 of the patients showing immediate increases, temporary occlusion of the bypass grafts for 3 minutes during surgery resulted in a decrease of electrogram voltage in the distribution of the occluded bypass, followed by return to preocclusion levels after release. Postoperative monitoring of electrogram voltage for 5 days in all patients with coronary artery disease revealed that the electrogram voltage in the revascularized area decreased to or below control levels in 16 patients (84 per cent) and remained increased in 3 patients (16 per cent). These observed changes did not correlate with preoperative hemodynamics, number of grafts, graft flow rate, aortic cross-clamp time, cardiopulmonary bypass time, and the early postoperative course. These preliminary observations suggest that coronary bypass grafting does affect the electrophysiological state of the revascularized myocardium. However, the mechanism by which it occurs and its clinical implications remain to be determined.