STRUCTURAL AND METABOLIC CORRELATES OF THE REVERSIBILITY OF CHRONIC LEFT-VENTRICULAR ISCHEMIC DYSFUNCTION IN HUMANS

Assessment of regional myocardial perfusion and glucose uptake with po sitron emission tomography (PET) identifies dysfunctional myocardium t hat shows improvement in function after revascularization. Yet little is known about the ultrastructural patterns of ischemic injury in myoc ardium with and without postoperative functional improvement in relati on to residual perfusion and metabolism. Therefore dynamic PET with [N -13]ammonia and F-18-labeled deoxyglucose was performed in 24 patients with coronary artery disease and anterior wall dysfunction undergoing bypass surgery. Transmural biopsies were obtained from the dysfunctio nal area during surgery and analyzed by optical and electron microscop y to quantify the presence of fibrosis and cardiomyocytes. As judged f rom the postoperative changes in contraction, left ventricular functio n improved in 16 patients. In myocardium that showed improved function after revascularization, preoperative flow and glucose uptake were hi gher by PET than in persistently dysfunctional myocardium. In tissue s amples from myocardium that improved postoperatively, there were more cardiomyocytes, including a larger proportion of cells with excess gly cogen stores (35 vs. 21%), and there was less fibrosis (24 vs. 49%) th an in tissue samples from myocardium that did not improve functionally . Preoperative perfusion and postoperative wall motion were inversely correlated with the amount of tissue fibrosis, whereas preoperative F- 18-labeled deoxyglucose uptake correlated positively with the amount o f cardiomyocytes showing excess glycogen stores.