Myocardial uptake of carbon-11-acetate as an indirect estimate of regional myocardial blood flow.

The rate of clearance of myocardial carbon-11 (11C) activity (after the administration of 11C-acetate) has been shown to correlate closely with myocardial oxygen consumption. In the present study, we hypothesized that regional net myocardial uptake of 11C-acetate, which reflects primarily delivery and extraction of tracer, would be markedly flow-dependent and potentially useful as an indirect index of regional myocardial blood flow. In 22 patients with stable coronary artery disease, the regional distribution of early net uptake of 11C-acetate was correlated with estimates of regional myocardial blood flow assessed with oxygen-15-water. The myocardial images of 11C-acetate uptake were of high quality. The correlation between the two approaches was close (r = 0.88) and not affected by the metabolic state of the tissue. Thus, in patients with stable coronary artery disease, under resting conditions, direct estimates of myocardial oxygen consumption in relation to the level of delivery of tracer to the tissue can now be obtained by PET with use of a single radiopharmaceutical, 11C-acetate. This approach may prove particularly useful in streamlining clinical protocols designed to assess myocardial oxygen consumption.