Dystrophic myotonia is a widespread hereditary disease. Pathological process touches development and functioning of various organs and tissues: smooth and skeletal muscular tissue, the heart, organ of vision, brain. Pathology of the heart serves as one of frequent manyfestations of dystrophic myotonia. Degenerative changes and fatty infiltration of myocardium not infrequently leads to dilated cardiomyopathy. Involvement of the heart in such patients is represented mainly by disturbance of cardiac rhythm and conduction. Course of the disease is progressive.