Evaluation of Fatty Acid .BETA.-Oxidation in Patients With Prior Myocardial Infarction in Relation to Myocardial Blood Flow, Total Oxidative Metabolism, and Left Ventricular Wall Motion

Abstract

Fatty acid metabolism in patients with myocardial infarction (MI) who undergo coronary reperfusion has not been fully elucidated and was investigated in the present study using positron emission tomography. The clearance rate constant of 11C-acetate (acetate-Kmono) and that of 11C-palmitate (palmitate-Kmono) from the myocardium were calculated using a monoexponential equation in 14 patients with MI. A total of 155 regions of interest were classified based on coefficient of determination (R2) values of monoexponential curves for 11C-palmitate clearance: well fitted regions (R2>or=0.5) and poorly fitted regions (R2<0.5). Regional relative myocardial blood flow calculated from the initial distribution of 11C-acetate and left ventricular (LV) wall motion were also evaluated. Peak 11C-palmitate uptake (14,434+/-3,052 vs 12,016+/-3,088 counts/s, p<0.001) and percent clearance during acquisition (38.2+/-10.1 vs 23.6+/-11.4%, p<0.001) were significantly greater in the well fitted regions (n=111) than in the poorly fitted regions (n=44). Acetate-Kmono was significantly higher in the former than in the latter (0.0641+/-0.0099 vs 0.0476+/-0.0103 min-1, p<0.001). LV wall motion and regional relative blood flow were also significantly greater in the former regions. Palmitate-Kmono in the well fitted regions was significantly higher in normal LV wall motion areas than in hypokinesis areas (0.0363+/-0.0062 vs 0.0274+/-0.0057 min-1, p<0.001) Maintenance of myocardial fatty acid beta-oxidation with better myocardial blood flow is substantial in the preservation of total myocardial oxidative metabolism and LV wall motion in patients with MI. The finding that the early-phase clearance of 11C-palmitate is fitted with a monoexponential curve may provide important information in the evaluation of myocardial fatty acid beta-oxidation.