The use of iodinated free fatty acids for assessing fatty acid metabolism

Free fatty acid is a major substrate fuel for normal myocardium. Cardiovascular disease is frequently associated with impairment of fatty acid oxidation. Therefore assessment of fatty acid metabolism may be an important tool for the early detection of myocardial abnormalities and may provide insight into pathologic heart conditions. Although carbon 11-labeled palmitate is a well-established tracer for probing myocardial fatty acid metabolism, a variety of iodinated fatty acid compounds have been introduced for assessing fatty acid metabolism, including straight-chain and branched-chain fatty acid compounds. Straight-chain fatty acid has advantages for measuring fatty acid oxidation on the basis of tracer clearance from the myocardium. Branched-chain fatty acid can be trapped in the myocardium without further washout and uptake in the myocardium may reflect fatty acid retention and some aspect of fatty acid metabolism. A long tracer retention period makes feasible the acquisition of single-photon emission computed tomographic images. This review examines the characteristics of both types of tracers and our recent clinical experience with beta-methyliodophenyl pentadecanoic acid, which has potential for detecting and characterizing both ischemic heart disease and cardiomyopathy.