Simultaneous evaluation of fatty acid metabolism and myocardial flow in an explanted heart.

Abstract

The biodistribution of the fatty acid analog [131I]PHIPA 3-10, was compared to the flow tracer 99mTc-sestamibi by quantitative analysis in a dual-isotope study performed during a heart transplantation. Iodine-131-PHIPA 3-10 and 99mTc-sestamibi were injected simultaneously approximately 20 min prior to the start of surgical procedure. Scintigraphic images of the sliced explanted heart were compared to the preoperative in vivo scans using [123I]PHIPA 3-10, 201TI and 99mTc-sestamibi. In 14 tissue samples of the explanted heart, the radioactive contents from [131I]PHIPA 3-10 and 99mTc-sestamibi were calculated as %ID/g-values and correlated with the corresponding histology. In the preoperative scans, a mismatch of fatty acid uptake and perfusion ([123I]PHIPA 3-10 > flow) was observed which indicated residual viable myocardium, while a matched defect was associated with scar. In viable myocardium, there was a significantly higher accumulation of [131I]PHIPA 3-10 compared to 99mTc-sestamibi (mean 5.9 x 10(-3) versus 2.7 x 10(-3)%ID/g),whereas in scars the uptake of both tracers was comparable (1.2 x 10(-3) versus 1.4 x 10(-3)%ID/g). Myocardial viability can be defined more accurately with radioiodinated PHIPA 3-10 than with 99mTc-sestamibi. The differences of biodistribution in viable myocardium and scars indicate that not only perfusion but also the metabolic state of the myocardium can be evaluated with radioiodinated PHIPA 3-10.