A comparison between terminally radioiodinated hexadecenoic acid (125I-HA) and heptadecanoic acid (131I-H0A) in the dog heart.

The regional myocardial distribution of 125I-16-iodo-9-hexadecenoic acid (125I-HA) and 131I-17-iodo-heptadecanoic acid (131I-H0A) was determined in one normal dog and in five dogs within 5 min after coronary artery occlusion. The total myocardial uptake of 125I-H A was about 40% lower than that of 131I-H0A. The ratio 125I:131I in the normally perfused parts of the myocardium was 0.38-0.81, but the ischemic tissue showed a higher 125I:131I ratio (0.87-1.03), due to lower accumulation of 131I-H0A in ischemic myocardium. We conclude that both radioiodinated fatty acids are reliable indicators of myocardial perfusion and that iodo-heptadecanoic acid, when labeled with 123I, may be preferred to iodo-hexadecenoic acid as the labeled fatty acid for cardiac imaging agent in clinical practice.