SIMULTANEOUS EVALUATION OF FATTY-ACID METABOLISM AND MYOCARDIAL FLOW IN AN EXPLANTED HEART

The biodistribution of the fatty acid analog [I-131]PHIPA 3-10, was co mpared to the flow tracer Tc-99m-sestamibi by quantitative analysis in a dual-isotope study performed during a heart transplantation. Method s: lodine-131-PHIPA 3-10 and Tc-99m-sestamibi were injected simultaneo usly approximately 20 min prior to the start of surgical procedure, Sc intigraphic images of the sliced explanted heart were compared to the preoperative in vivo scans using [I-123]PHIPA 3-10,(TI)-T-201 and Tc-9 9m-sestamibi. In 14 tissue samples of the explanted heart, the radioac tive contents from [I-131]PHIPA 3-10 and Tc-99m-sestamibi were calcula ted as %ID/g-values and correlated with the corresponding histology, R esults: In the preoperative scans, a mismatch of fatty acid uptake and perfusion ([I-123]PHIPA 3-10 > flow) was observed which indicated res idual viable myocardium, while a matched defect was associated with sc ar, In viable myocardium, there was a significantly higher accumulatio n of [I-131]PHIPA 3-10 compared to Tc-99m-sestamibi (mean 5.9 x 10(-3) versus 2.7 x 10(-3) %ID/g), whereas in scars the uptake of both trace rs was comparable (1.2 x 10(-3) versus 1.4 x 10(-3) %ID/g). Conclusion : Myocardial viability can be defined more accurately with radioiodina ted PHIPA 3-10 than with Tc-99m-sestamibi. The differences of biodistr ibution in viable myocardium and scars indicate that not only perfusio n but also the metabolic state of the myocardium can be evaluated with radioiodinated PHIPA 3-10.