[Conduction disturbances and cardiac arrhythmias in myotonic dystrophy--diagnosis and clinical significance in adult populations].

Myotonic dystrophy (DM) is the most frequent adult form of muscular dystrophy. The clinical presentation consists of both muscular and systemic involvement. One of the main causes of high mortality is sudden cardiac death due to tachyarrhythmias and conduction disturbances. The knowledge of cardiovascular complications is very important because of diagnostic and therapeutic possibilities. The main cardiological complications of DM are arrhythmias associated with the destruction of the conduction system. The main electrocardiographic changes (prolongation of the P-R interval, left anterior hemiblock, increased QRS duration) reflect destruction of the His-Purkinje system and may progress very rapidly, leading to death due to Stokes-Adams attacks. The most frequent tachyarrhythmias are atrial and ventricular extrasystoles, atrial flutter and fibrillation, as well as ventricular tachycardia, that can be a cause of sudden death. The mechanisms underlying ventricular arrhythmias are conduction disturbances, prolongation of the QT interval, impaired coronary reserve and autonomic function. A common type of tachycardia seen in patients with DM is that originating from the branches of the bundle of His (bundle-branch re-entry). Risk stratification (in respect of cardiological complications) is possible on the basis of electrophysiological studies, clinical symptoms and a family history. Invasive electrophysiological investigation and implantation of a pacemaker may be indicated in patients with electrocardiographic features of a significant disease of the conduction system. Multicentre clinical trials assessing the efficacy of this therapeutic strategy are underway.