[Myotonic dystrophy type 1 - a rare cause of bradycardia in the young].

Myotonic dystrophy type 1 (Steinert's disease) is a rare but important cause of bradycardia in the young. Syncope is primarily considered to be caused by high-degree atrioventricular block II-III but may also be caused by sinus node dysfunction. Life-threatening ventricular arrhythmias do occur, and in cases with impaired systolic left ventricular function, indication for a primary preventive implantable cardiac defibrillator should be evaluated. All patients with myotonic dystrophy type 1 should undergo clinical assessment, 12-lead ECG, 24-hour Holter, and echocardiography annually. We here describe the case of a 24-year-old woman who received a pacemaker due to sinus arrests with syncope caused by myotonic dystrophy type 1.