Cardiac Manifestations in Myotonic Dystrophy Type 1 Patients Followed Using a Standard Protocol in a Specialized Unit

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Myotonic dystrophy type 1 is characterized by muscle damage and systemic manifestations, including cardiac involvement. Our aim was to document the frequency and severity of cardiac involvement (left ventricular dysfunction and arrhythmia or conduction disorders), the need for a pacemaker, implantable cardioverter-defibrillator, or electrophysiological study, and the development of sudden death during follow-up. Retrospective observational study of myotonic dystrophy type 1 patients referred to a specialized cardiac unit. Patients received clinical, electrocardiographic (Holter monitoring), and echocardiographic follow-up. We included 81 patients (51.9% men; mean age, 29.9 [14.8] years). The mean follow-up was 5.7 (3.9) years (range: 1-20 years). During this period sinus bradycardia was documented in 48.8%, PR interval≥220 ms in 31.3%, long corrected QT interval in 5%, and QRS interval≥120 ms in 7.5%. A total of 13.8% of patients developed sinus node dysfunction, 10% of patients had supraventricular arrhythmias, 5% had ventricular tachycardia, and 8.8% developed second- or third- degree atrioventricular block. Only 1 patient had severe ventricular dysfunction. During the follow-up, 15 pacemakers and 2 implantable cardioverter-defibrillators were implanted and 5 electrophysiological studies were performed (mainly due to ventricular tachycardia). There was only 1 sudden death. Arrhythmia or conduction disorders are frequent during the course of myotonic dystrophy type 1 patients. A significant percentage of patients require electrophysiological study and the use of a device (pacemaker or implantable cardioverter-defibrillator). In our experience, systolic dysfunction and sudden death are rare.