BackgroundPositron emission tomography (PET) metabolic studies have investigated the pathways involved in fatty acid, glucose, and oxidative metabolism in cardiomyopathy and the impairments that occur in the damaged myocardium, but none have provided absolute quantitative variables. Recently, quantitative measurements of the metabolic rate of oxygen (MMRO2) and oxygen extraction fraction (OEF) using O2-15–labeled oxygen gas have been validated in animals and healthy volunteers. The purposes of the current study were to measure MMRO2and OEF in cardiomyopathy with left ventricular (LV) dysfunction.MethodsThe authors selected 25 study participants: 16 patients (10 with ischemic and 6 with dilated) cardiomyopathy with LV dysfunction, and 9 healthy volunteers. As evaluated by echocardiography, LV ejection fraction (LVEF) was decreased in patients (35% ± 9% vs. 65% ± 5%,P< 0.01). The PET protocol consisted of transmission, C O2-15 static, H2O-15 dynamic, and O2-15 gas inhalation steady state scans. An entire myocardial region of interest was drawn to encompass the entire LV myocardium on three midventricular slices in each participant.ResultsData showed in patients with dilated cardiomyopathy significant reductions of MMRO2(0.051 ± 0.02 ml · min−1· g−1vs. 0.108 ± 0.02 ml · min−1· g−1,P= 0.01) and OEF (0.55 ± 0.15 vs. 0.71 ± 0.08,P= 0.01) when compared with healthy volunteers. Furthermore, OEF decreased significantly in lateral and inferior walls. Significant correlations were observed among OEF and the rate-pressure product (RPP) (P= 0.02), LVEF (P< 0.001), MMRO2 and RPP (P= 0.04), and LVEF (P= 0.05). In patients with ischemic cardiomyopathy, MMRO2was significantly reduced (0.039 ± 0.02 ml · min−1· g−1vs. 0.108 ± 0.02 ml · min−1· g−1;P= 0.005) but not OEF (0.63 ± 0.2 vs 0.71 ± 0.08;P= NS), when compared with healthy volunteers. Significant correlations were observed among OEF and RPP (P= 0.03), LVEF (P= 0.002), MMRO2and RPP (P< 0.01), and LVEF (P= 0.03).ConclusionsThese data show that O2-15 gas inhalation and PET allow myocardial MMRO2and OEF to be measured in patients with cardiomyopathy.