Effects of coronary artery bypass surgery on the stunned and hibernating myocardium in the cases with depressed left ventricular function

Chronic left ventricular (LV) dysfunction may result from irreversible damage (cell death), stunned myocardium (ST), or hibernating myocardium (HB). However, both of ST and HB are expected to be reversible. In this report, the effects of coronary artery bypass grafting on the regions of ST and HB were evaluated in 37 patients with less than 40% of LV ejection fraction. The patients were divided into two groups. Group I consisted of the patients whose postoperative LV ejection fraction rose by more than 10% compared to the preoperative value. Group II included the remaining patients with no significant improvement. After successful revascularization, 61% of HB changed to ST and 52% of ST to normal in group I. These changes were significant in comparison with group II because 48% of HB and 83% of ST in group II remained unchanged. Immediate or rapid recovery of HB hardly occurred in both of the groups. To recover normal function, HB may pass through a stage of ST on reperfusion. On the other hand, it is difficult to determine whether HB and ST with no significant changes after reperfusion are irreversibly damaged or reversible and take time to return to normal.