Abstract
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 ≤ 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 ≤ 0.05). MVO2 (measured directly in eight studies with a coronary sinus catheter) correlated well with k2 (y = 78.8x-0.4 with r = 0.80, P < 0.05). This regression equation was used to estimate MVO2 in all studies. Myocardial efficiency was calculated using a standard equation where the percentage efficiency is equal to (stroke work multiplied by heart rate) divided by (MVO2 multiplied by a conversion constant). Dobutamine increased MVO2 (P < 0.05) while nitroprusside tended to decrease MVO2. Both agents significantly increased efficiency (P ≤ 0.05). It was concluded that 11C acetate PET can be used to determine MVO2 and myocardial efficiency. In these studies, dobutamine and nitroprusside had differing effects on MVO2, yet both agents increased myocardial efficiency. This improvement may be due to beneficial effects of both agents on reducing vascular resistance. 11C acetate PET provides objective means for evaluating effects of therapy on the metabolic and hemodynamic performance of the heart.
Original language | English |
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Pages (from-to) | 293-300 |
Number of pages | 8 |
Journal | Canadian Journal of Cardiology |
Volume | 11 |
Issue number | 4 |
State | Published - 1995 |
Externally published | Yes |
Keywords
- C acetate
- Heart failure
- Myocardial efficiency
- Myocardial oxygen consumption
- Oxidative metabolism
- Positron emission tomography