MYOCARDIAL METABOLIC ABNORMALITIES IN HYPERTROPHIC CARDIOMYOPATHY ASSESSED BY IODINE-123-LABELED BETA-METHYL-BRANCHED FATTY-ACID MYOCARDIALSCINTIGRAPHY AND ITS RELATION TO EXERCISE-INDUCED ISCHEMIA

Reversible thallium-201 (Tl-201) abnormalities during exercise stress have been used as markers of myocardial ischemia in hypertrophic cardi omyopathy (HCM) and are most likely to identify relatively underperfus ed myocardium. Although metabolic abnormalities in HCM were reported, the relationship between impaired energy metabolism and exercise-induc ed ischemia has not been fully elucidated as yet. To assess the relati onship between myocardial perfusion abnormalities and fatty acid metab olic abnormalities, 28 patients with HCM underwent exercise Tl-201 and rest I-123-15-(p-iodophenyl)-3-methyl pentadecanoic acid (BMIPP) scin tigraphy. Perfusion abnormalities were observed by exercise Tl-201 in 19/28 patients with HCM. I-123-BMIPP uptake was decreased compared wit h delayed Tl-201 in 106/364 (29%) of the total myocardial segments (p< 0.01, McNemar symmetry test). Such disparity between I-123-BMIPP and T l-201 was observed more often in the 49/75 (65%) segments with reversi ble exercise Tl-201 defects (p<0.001). Our results indicate that exerc ise-induced myocardial ischemia exists in HCM, resulting iii metabolic abnormalities, The combination of 123I BMIPP and Tl-201 suggests that myocardial ischemia may play an important role in metabolic abnormali ties in HCM.