Detection of viable myocardium with p-iodophenyl-9-(R,S)-methylpentadecanoic acid in ischemic rat myocardium

Background. The methyl-branched free fatty acid analog 15-(p-iodophenyl)-9-(R,S)-methylpentadecanoic acid (9MPA) is metabolized more rapidly than 15-(p-iodophenyl)-3(β)-(R,S)-methylpentadecanoic acid. This study investigates whether myocardial ischemic injury to β-oxidation and viable myocardium can be detected with the use of 9MPA in a rat myocardial ischemia model. Methods and Results. In the acute study the left coronary arteries were occluded for 15 or 45 minutes and then reperfused; the rats were killed after 2 hours. Iodine 125 and iodine 123 9MPA was injected 60 minutes (delayed images) and 3 minutes (early images), respectively, before the rats were killed. In the subacute study the left coronary arteries were either occluded for 45 minutes and then reperfused or occluded and not reperfused. One week later, I-125 and I-123 9MPA was injected 60 minutes and 3 minutes, respectively, before the rats were killed. The distribution of 9MPA was examined with the use of dual-tracer autoradiography. In the acute study the delayed images showed a higher uptake in viable regions at risk than in normal areas and nonviable regions. In the subacute study a difference in uptake between viable regions at risk and normal areas was visible on the early images, but this difference disappeared on the delayed images. Conclusions. 9MPA is a useful tracer for detecting viable regions of ischemic myocardium during acute and subacute disease stages.