Increase in skeletal muscle extracellular volume as an under-recognised change detected at cardiac MRI in hypertrophic cardiomyopathy.

AIM: To explore skeletal muscle change and its correlation with the myocardium in hypertrophic cardiomyopathy (HCM) using cardiac magnetic resonance imaging (cMRI) with T1 mapping and late gadolinium enhancement (LGE).

MATERIALS AND METHODS: This retrospective study enrolled 50 HCM patients and 35 healthy controls. The extracellular volume (ECV) of the skeletal muscle and myocardium, the presence and absence of LGE of the myocardium, and cardiac troponin T (cTnT), were assessed. In the HCM group, the elevated ECVskeletal group was defined as ECVskeletal >2 standard deviations (SD) above the mean value of the controls. Statistical analyses included Student's t-test, the Mann-Whitney U-test, and linear regression.

RESULTS: ECVskeletal in the HCM group was higher than in the control group (mean 13.0 versus 10.9%; p<0.001), with 20 (40%) HCM patients having elevated ECVskeletal (ECVskeletal ≥13.7%). In the HCM group, ECVskeletal had a positive linear correlation with global myocardial ECV (r=0.37, p=0.009). In addition, the elevated ECVskeletal group had a higher cTnT than the non-elevated group (log cTnT, mean 1.55 versus 1.16, p=0.045). Furthermore, segmental myocardial ECV in the elevated ECVskeletal group was higher than in the non-elevated group, despite the presence or absence of myocardial LGE (median 30.1 versus 27.2%; 26.5 versus 24.6%, both p<0.001) or hypertrophy (median 29.0 versus 26.0%; 26.8 versus 24.8%, both p<0.001).

CONCLUSION: In the HCM patients, ECVskeletal was higher than in the healthy controls. Furthermore, some ECVskeletal changes had corresponding changes in the cTnT and myocardium.