External detection of regional myocardial metabolism with radioiodinated hexadecenoic acid in the dog heart.

In a previous study we have demonstrated that terminally iodinated hexadecenoic acid (131I-HA) and Thallium-201 (201T1) are comparable in myocardial uptake and distribution in the ischemic dog heart (Westera et al. 1980). In the present study the potential value of 131I-HA was proved in determining regional myocardial metabolism in 19 dog experiments. In ten dogs, 131I-HA was administered 5 min after occlusion of a coronary artery (group II), in six dogs after a 90 min occlusion period (group III). Three dogs served as controls (group I). The turnover rates (t 1/2) of 131I-HA were calculated from mono-exponential time-activity curves, obtained by external detection over ischemic and normally perfused areas during a 30 min period after IV injection of 0.7-1.5 mCi 131I-HA. The t 1/2 values in ischemic regions were found to be significantly longer (group II, 25.1 +/- 2.6 min; group III, 22.6 +/- 1.8 min) than in non-ischemic areas (group II, 12.5 +/- 1.8 min; group III, 14.2 +/- 1.4 min). The t 1/2 values in the control dogs (group I, 13.4 +/- 1.4 min) were not significantly different from the turnover rates in the non-ischemic areas of the occluded hearts. We conclude that the study of turnover rates of radioiodinated free fatty acids allows the determination of regional myocardial metabolism and offers a means to distinguish normally perfused from ischemic myocardial tissue.