Myocardial impairment detected by late gadolinium enhancement in hypertrophic cardiomyopathy: Comparison with 99mTc-MIBI/tetrofosmin and 123i-BMIPP SPECT

Purpose: Myocardial fibrosis is considered to be an important factor in myocardial dysfunction and sudden cardiac death in hypertrophic cardiomyopathy (HCM). The purpose of this study was to compare myocardial fibrosis detected by late gadolinium enhancement (LGE) on cardiac MRI with myocardial perfusion and fatty acid metabolism assessed by single photon emission computed tomography in HCM. Materials and Methods: We retrospectively evaluated 20 consecutive HCM patients (female, 7; mean age, 53.4 years) who underwent LGE, technetium-99m methoxyisobutylisonitrile/tetrofosmin (^99mTc-MIBI/tetrofosmin), and iodine-123 beta-methyl-iodophenylpentadecanoic acid (¹²³I-BMIPP) imaging. We calculated the myocardium-to-lumen signal ratio (M/L) for LGE in 17 segments based on the American Heart Association statement. Scoring of ^99mTc-MIBI/tetrofosmin (PI) and ¹²³I-BMIPP (BM) was performed for each segment using a 5-point scale (0, normal; 4, highly decreased). Results: Nineteen of 20 patients (95%) and 153 of 340 segments (45%) showed LGE. M/Ls were 0.42±0.16, 0.55±0.17, and 0.65±0.24 in PI0/BM0, PI0/BM1-4 and PI1-4/BM1-4, respectively. All M/Ls were significantly higher than that of a normal control (0.34±0.14) (p<0.001). Conclusions: Myocardial fibrosis in HCM can occur despite normal perfusion and fatty acid metabolism, and is more strongly associated with disorders of fatty acid metabolism than with perfusion abnormalities. M/L may be a useful indicator of disease severity.