Myocardial metabolism of¹²³I-BMIPP in patients with hypertrophic cardiomyopathy: Assessment by radial long-axis SPET

To elucidate the metabolism of free fatty acid in the myocardium of hypertrophic cardiomyopathy (HCM), SPET was performed with¹²³I-15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP), an analogue of free fatty acid, and with²⁰¹TI in nine patients with HCM and eight healthy volunteers who acted as controls. For quantitative analysis of the apical area, a radial long-axis tomogram was reconstructed every 6° after short-axis tomography. The relative regional uptake (RRU, %) in each segment was obtained by normalizing to the maximal value among all segments. The 3-h washout rate was calculated both for BMIPP and for²⁰¹TI. The ratio of the RRU of BMIPP to that of²⁰¹TI was significantly lower in the apical and antero-septal regions compared with other walls (P<0.01) in the patients with HCM, whereas uptake of both BMIPP and²⁰¹TI in the controls was homogeneous and there was a significant correlation between them. The coefficient of variation (CV) in all segments in the HCM patients was significantly higher (P<0.01) than that of the controls for both BMIPP and²⁰¹TI, indicating inhomogeneous uptake of BMIPP in the HCM patients. The washout rate of BMIPP over 3 h was significantly higher in the patients with HCM (mean ± S.D. 26.3 ± 7.3%) than the controls (18.3 ± 7.5%, P<0.05). The ratio of segmental washout rate of BMIPP to that of²⁰¹TI in the HCM patients was increased, especially in the septum and apex. These results indicate that the discordance between blood flow and metabolism in the myocardium, and the abnormal myocardial fatty acid metabolism in HCM patients, involve not only hypertrophic myocardium but also the areas of myocardium adjusting to the hypertrophic regions.