Myocardial emission computed tomography with iodine-123-labeled beta-methyl-branched fatty acid in patients with hypertrophic cardiomyopathy.

We studied whether emission computed tomography (ECT) with 123I-labeled 15-(p-iodophenyl)-3R,S-methylpentadecanoic acid (BMIPP) shows myocardial distribution different from 201Tl in hypertrophic cardiomyopathy. In 10 patients with asymmetric septal hypertrophy (ASH), 5 with diffuse hypertrophy and 2 with apical hypertrophy, ECT was acquired 30 min (early) and 4 hr (late) after injection of 123I-BMIPP at rest and was compared with ECT with 201Tl. In 10 patients with ASH, the relative regional uptake (RRU) of the septum was lower in the early 123I-BMIPP study than in the 201Tl study, although that of the posterior wall was similar. In the early and late 123I-BMIPP studies, the RRU of the septum was lower in 10 patients with ASH than in 7 without ASH, although that of the posterior wall was similar. In the 201Tl study, however, the RRU of both the septum and posterior wall was similar in those with and without ASH. Moreover, in 16 patients, the apparent left ventricular size was larger in the early 123I-BMIPP study than in the 201Tl study, which suggested reduced 123I-BMIPP uptake in the subendocardium. In patients with hypertrophic cardiomyopathy, thus, 123I-BMIPP imaging may reveal impaired regional fatty acid utilization, which is independent of regional perfusion.