Myocardial fat fraction in Becker muscular dystrophy and women carrying pathogenic DMD gene variants assessed by Dixon cardiac MRI.

Background/ObjectivePathogenic variants in the dystrophin gene (DMD) cause dystrophinopathies. These variants can cause skeletal and cardiac involvement. Disease progression in skeletal muscle is characterized by fatty replacement, but whether similar processes occur in the myocardium remain unclear. Dixon cardiovascular magnetic resonance (CMR) can quantify myocardial fat fraction (FF). This study used Dixon CMR to quantify myocardial FF in patients with BMD and women carrying DMD gene variants, and to explore associations with cardiac function, assessed by left ventricular ejection fraction (LVEF), age, and skeletal muscle FF.MethodsThis cross-sectional study included 20 patients with BMD, 27 women carrying DMD gene variants, and 40 healthy controls who underwent three-point Dixon CMR to quantify myocardial FF. Muscle MRI was performed to assess lower-limb muscle FF.ResultsMyocardial FF did not differ significantly among the three groups (p = 0.11); mean values were 10.0% in patients with BMD, 11.2% in women carrying DMD gene variants, and 10.4% in healthy controls. Subgroup analyses showed no significant differences between patients with BMD and healthy men or between women carrying DMD gene variants and healthy women. Myocardial FF was not associated with LVEF, age, or skeletal muscle FF.ConclusionsDixon CMR revealed no increase in myocardial FF in patients with BMD or women carrying DMD gene variants compared with healthy controls. Unlike skeletal muscle, myocardial remodeling in dystrophinopathies does not appear to be adipogenic and is likely predominantly fibrotic. Dixon CMR is useful for skeletal muscle imaging but has limited clinical use for myocardial assessment.