DEPENDENCE OF RECOVERY OF CONTRACTILE FUNCTION ON MAINTENANCE OF OXIDATIVE-METABOLISM AFTER MYOCARDIAL-INFARCTION

This study was performed to define the importance of maintenance of oxidative metabolism as a descriptor and determinant of the potential for functional recovery after revascularization in patients with recent myocardial infarction. In 11 patients (mean interval after infarction 6 days; 5 patients given thrombolytic therapy), positron emission tomography (PET) was performed to characterize myocardial perfusion (with oxygen-15-labeled water), glucose utilization (with fluorine-18-fluorodeoxyglucose) and oxidative metabolism (with carbon-11-acetate). Dysfunctional but viable myocardium was differentiated from nonviable myocardium by assessments of regional function before and after coronary revascularization. The impact of coronary revascularization on regional myocardial perfusion and metabolism was assessed in nine patients in whom tomography was repeated after revascularization. Before revascularization, dysfunctional but viable myocardium (19 segments) and nonviable myocardium (10 segments) exhibited relative perfusion equivalent to 74% and 63% of that of normal myocardium (33 segments), respectively (p < 0.02). Dysfunctional but viable myocardium exhibited oxidative metabolism equivalent to 74% of that of normal myocardium (p < 0.02). In contrast, in nonviable myocardium, oxidative metabolism was only 45% of that seen in normal (p < 0.02) and 60% of that in reversibly dysfunctional myocardium (p < 0.003). Regional glucose utilization (normalized to regional perfusion) in dysfunctional but viable myocardium was higher than that in normal myocardium (p < 0.02). Nonviable myocardium exhibited lower levels of glucose utilization than did normal tissue (p < 0.02). However, in both reversibly and persistently dysfunctional myocardium utilization of glucose normalized to relative perfusion was markedly variable. The results indicate that preservation of oxidative metabolism is a necessary condition for recovery of function consequent to coronary recanalization after myocardial infarction. Therefore, approaches that measure myocardial oxygen consumption, such as dynamic PET imaging with carbon-11-acetate, should facilitate the identification of dysfunctional but still viable myocardium in patients with recent myocardial infarction who are most likely to benefit from coronary revascularization.