The Journal of Thoracic and Cardiovascular Surgery, Vol 73, 269-277, Copyright © 1977 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Effects of coronary bypass surgery on the electrical activity of revascularized myocardium. Immediate and early postoperativeobservations
RJ Sung, AL Bassett, RJ Thurer, A Vargas, W Williams, GA Kaiser, H Gelband and RJ Myerburg
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.
