A 25-year-old man suffers a sudden cardiac arrest. He is resuscitated. On examination his vital signs are normal. Echocardiography shows that the left ventricle is normal but there is marked thinning with dilation of the right ventricle. MR imaging of his chest shows extensive fibrofatty replacement of the myocardium, but no inflammation. Which of the following is the most likely cause for his findings?

Arrhythmogenic right ventricular cardiomyopathy (arrhythmogenic right ventricular dysplasia) is most likely an autosomal dominant inherited condition with abnormal desmosomal adhesion proteins in myocytes. Infections of the heart are accompanied by inflammation, though a late finding in Chagas disease is ventricular fibrosis with ventricular wall thinning. Hypertension leads to ventricular hypertrophy. There is no characteristic gross or microscopic finding with long QT syndrome caused by myocyte channelopathies. Prior radiation therapy results in fibrosis, but it is not likely to be localized to the right ventricle; improving techniques that focus the beam and synchronize it with breathing motion reduce cardiac damage when treating chest cancers.