Muscular dystrophies and the heart: The emerging role of cardiovascular magnetic resonance imaging

Muscular dystrophies (MD) constitute a group of inherited disorders, characterized by progressive skeletal muscle weakness and heart involvement. Cardiac disease is common and not necessarily related to the degree of skeletal myopathy; it may be the predominant manifestation with or without any other evidence of muscular disease. Death is usually due to ventricular dysfunction, heart block or malignant arrhythmias. In addition to MD patients, female carriers may present with cardiac involvement. Clinical evaluation, electrocardiography, echocardiography and cardiovascular magnetic resonance imaging (CMR) are the diagnostic tools used for the assessment of these patients. Heart failure in MD may be delayed due to relative physical inactivity. The most common electrocardiographic findings include conduction defects, arrhythmias, hypertrophy and, potentially, evidence of myocardial necrosis, depending on the type of MD. Echocardiography is a routine technique used to assess left ventricular dysfunction, independent of age of onset or mutation. In some cases, it can also identify early, silent cardiac dysfunction. CMR is the best technique for accurate and reproducible quantification of ventricular volumes, mass and ejection fraction. CMR has documented a pattern of epicardial fibrosis in both dystrophinopathy patients and mutation carriers that can be observed even if overt muscular disease is absent. Recently, CMR techniques, such as postcontrast myocardial T1 mapping, have been used in Duchenne muscular dystrophy to detect diffuse myocardial fibrosis. A combined approach using clinical assessment and CMR evaluation may motivate early cardioprotective treatment in both patients and asymptomatic carriers, and prevent the development of serious cardiac complications.