Changes in myocardial oxygen consumption and efficiency with heart failure therapy measured by 11C acetate PET

The application of 11C acetate kinetics determined by positron emission tomography (PET) imaging has been proposed as a noninvasive means to measure myocardial oxygen consumption in order to determine myocardial efficiency. Such an approach considers the balance of the effect of ventricular performance and myocardial oxygen consumption (MVO2), which may be important in the assessment of heart failure but is not usually evaluated by current methods. In this paper, the authors review their previously published series of studies, in which the aim was to: first, apply the 11C acetate PET approach in patients with dilated cardiomyopathy in order to determine myocardial oxidative metabolism and estimate myocardial efficiency; second, verify a correlation between 11C acetate kinetics and directly measured MVO2; and third, evaluate the effects of dobutamine and nitroprusside on MVO2 and efficiency in dilated cardiomyopathy. In these previous studies, 13 patients with severe dilated cardiomyopathy were studied, via echocardiography, hemodynamic and PET studies, at baseline and during drug infusion. Seven patients were given dobutamine and six were given nitroprusside. A two-compartment kinetic model approach was applied to 11C time activity curves obtained from dynamic 11C acetate PET imaging to determine the clearance rate constant, k2. Myocardial efficiency was estimated from a work metabolic index, defined as (stroke work index multiplied by heart rate) divided by k2. The k2 significantly increased with dobutamine (P < or = 0.05), consistent with increased MVO2, and tended to decrease with nitroprusside. The work metabolic index derived from hemodynamic parameters increased significantly with both drug regimens (P < or = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)