Significance of myocardial uptake of iodine 123-labeled beta-methyl iodophenyl pentadecanoic acid: comparison with kinetics of carbon 11-labeled palmitate in positron emission tomography

Abstract

Background: A radioactively labeled beta-methyl branched fatty acid analog, 123I-15-(p-iodophenyl)-3-methyl pentadecanoic acid (BMIPP), has been developed to probe regional myocardial fatty acid metabolism. However, the significance of BMIPP uptake in the myocardium remains unclear.

Methods and results: To evaluate the significance of BMIPP uptake, single-photon emission computed tomography was performed 30 minutes after injection of BMIPP, and 201Tl-labeled single-photon emission computed tomography was taken on a separate day in 10 patients. Findings of BMIPP and 201Tl-labeled imaging were compared with the data obtained from positron emission tomography with 11C-labeled palmitate. The BMIPP uptake (percent of maximum) was significantly correlated with the early uptake (percent) and delayed uptake (percent) of 11C-labeled palmitate (r = 0.659 and r = 0.687, respectively) (p < 0.01 each), whereas it was not significantly correlated with the residual fraction (r = 0.205) or the clearance half-time of the early component (r = 0.138) of 11C-labeled palmitate as a marker of beta-oxidation of the fatty acid.

Conclusions: These data indicate that, although the myocardial uptake of BMIPP may not directly reflect beta-oxidation of fatty acids, its uptake may reflect both regional myocardial blood flow and fatty acid extraction.