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<.01) and a positive association with myocardial perfusion reserve (r = .62, P<.01) in the patient group. These 2 parameters along with resting left ventricular work explained 57 % of the variability in peak exercise capacity.
Impaired perfusion reserve and an exaggerated imbalance in right to left ventricular oxidative metabolism appear to significantly contribute to the impaired exercise capacity in these DCM patients.