Arrhythmias in the muscular dystrophies.

The muscular dystrophies are a group of inherited diseases affecting skeletal muscle that also affect cardiac muscle. Cardiac involvement occurs as a degenerative process with fibrosis and fatty replacement of the myocardium. Electrophysiologists are asked to participate in the care of muscular dystrophy patients because of the risk of atrial arrhythmias, conduction disease, bradycardia, ventricular arrhythmias, and sudden death. Duchenne, Becker, and limb-girdle types 2C-2F and 2I are muscular dystrophies in which the development of a dilated cardiomyopathy is common. Arrhythmias and conduction disease occur after the development of the dilated cardiomyopathy. Patients are considered for pacemakers or implantable cardioverter-defibrillators on the basis of guidelines used for nonischemic cardiomyopathies. Myotonic types 1 and 2, Emery-Dreifuss, limb-girdle type 1B, and facioscapulohumeral muscular dystrophies present with conduction disease and associated arrhythmias and variably with a dilated cardiomyopathy. In myotonic type 1, Emery-Dreifuss, and limb-girdle type 1B muscular dystrophies, conduction abnormalities are frequent and often require pacing. Recent studies support the use of prophylactic implantable cardioverter-defibrillators rather than pacemakers. In all the muscular dystrophies, respiratory muscle involvement can impact quality and quantity of life and needs to be factored in when considering a prophylactic device.