Functional recovery after coronary revascularization for chronic coronary artery disease is dependent on maintenance of oxidative metabolism

Abstract

Objectives. This study was performed to define the importance of maintenance of oxidative metabolism as a descriptor and determinant of functional recovery after revascularization in patients with left ventricular dysfunction attributable to chronic coronary artery disease. Background. Although myocardial accumulation of ¹⁸F-fluorodeoxyglucose indicates the presence of tissue that is metabolically active, it may not identify those metabolic processes required for restoration of myocardial contractility. Experimental studies suggest that, under conditions of ischemia and reperfusion, maintenance of myocardial oxidative metabolism is an important metabolic determinant of the capacity for functional recovery. Methods. In 16 patients positron emission tomography was performed to characterize myocardial perfusion (with H₂¹⁵O), oxidative metabolism (with ¹¹C-acetate) and utilization of glucose (with ¹⁸F-fluorodeoxyglucose). Dysfunctional but viable myocardium was differentiated from nonviable myocardium on the basis of assessments of regional function before and after coronary revascularization. To define the importance of coronary revascularization on myocardial perfusion and metabolism, tomography was repeated in 11 patients after revascularization. Results. Before revascularization, perfusion in 24 dysfunctional but viable myocardial segments and 29 nonviable segments averaged 79% and 74%, respectively, of that in 42 normal myocardial segments (both p < 0.01). Dysfunctional bat viable myocardium exhibited oxidative metabolism comparable to that in normal myocardium. In contrast, in nonviable myocardium, oxidative metabolism was only 66% of that in normal (p < 0.01) and 69% of that in reversibly dysfunctional myocardium (p < 0.003). Regional utilization of glucose normalized to regional perfusion in dysfunctional but viable myocardium was greater than that in normal myocardium (p < 0.01). However, in both reversibly and persistently dysfunctional myocardium, utilization of glucose normalized to relative perfusion was markedly variable. Conclusions. The results indicate that preservation of oxidative metabolism is a necessary condition for recovery of function after coronary recanalization in patients with chronic coronary artery disease. Consequently, approaches that measure myocardial oxygen consumption, such as dynamic positron emission tomography with ¹¹C-acetate, should facilitate the identification of those patients most likely to benefit from coronary revascularization.