Assessing the need for pacemaker in adults with myotonic dystrophy type 1 - An evaluation of standard electrocardiogram and holter monitoring in cardiac screening

Background Patients with Myotonic Dystrophy type 1 (DM1) have an increased risk of sudden cardiac death due to conduction disorders and arrhythmias. Cardiac follow-up is recommended to identify patients in need of cardiac pacing. However, since DM1 is a rare disease the knowledge about the optimal screening modality is scarce. Purpose To evaluate the usefulness of Holter monitoring and 12-lead electrocardiogram (ECG) in identifying indications for cardiac pacing in patients with DM1. Methods We conducted a retrospective observational study including all adult patients with genetically confirmed DM1 who had follow-up at a tertiary centre specialized in neuromuscular diseases and who received a pacemaker between January 2000 - March 2023. All patients had undergone cardiac screening as part of the routine follow up, including biennial Holter monitoring and annual ECG. Data were collected from electronic health records. Results We included 112 patients (mean age 50 years, 44% women) with DM1 who were referred for pacemaker implantation. Three patients (2.7%) also received an implantable cardioverter-defibrillator (ICD) and two patients (1.8%) received a cardiac resynchronization therapy with a defibrillator (CRT-D). 52 patients (46%) received a pacemaker due to findings from the Holter monitoring and 51 patients (46%) due to findings from the annual screening ECG. Nine patients (8%) received a pacemaker due to conduction disorders diagnosed in acute circumstances. Most common findings from Holter monitoring leading to pacemaker implantation were second-degree atrioventricular block and sinus node dysfunction, while findings from ECG leading to pacemaker implantation predominantly showed left bundle branch block and bifascicular block. Conclusion In real-world clinical practice, we found that an equal proportion of patients received a pacemaker due to findings from ECG and Holter monitoring. Screening with both ECG and Holter monitoring seems to have an additive effect since they reveal different conduction disorders. Thus, our results support the combined use of Holter monitoring and ECG in routine follow-up of patients with DM1.