Myocardial perfusion reserve and oxidative metabolism contribute to exercise capacity in patients with dilated cardiomyopathy

Exercise intolerance is a hallmark symptom in patients with heart failure; however, myocardial factors contributing to the limited exercise capacity are not fully characterized. Twenty patients with stable heart failure resulting from idiopathic dilated cardiomyopathy (DCM) and 13 controls were studied. Myocardial perfusion, biventricular oxidative metabolism, and insulin-stimulated glucose uptake were measured using positron emission tomography and [15O]H2O, [11C]acetate, and [18F]FDG. Hyperemic perfusion and perfusion reserve were significantly lower in the DCM patients compared with the healthy subjects. There was no difference in left ventricular oxidative metabolism between the 2 groups; however, the patients had a 19% higher right ventricular oxidative metabolism (P=.005). Consequently, the ratio of right to left ventricular oxidative metabolism was also higher (31%) in the patients. There was a strong inverse association between decreased exercise capacity and the ratio of right to left ventricular oxidative metabolism (r=–.68, P