Electrocardiographic Features in Patients with Neuromuscular Diseases: A Retrospective Analysis

Background: Neuromuscular diseases (NMDs) are a group of progressive hereditary disorders frequently associated with significant cardiac involvement, which can represent a primary cause of mortality. This study aims to characterize the electrocardiographic findings in patients with Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD), and Myotonic Dystrophy Type 1 (DM1). Methods: We conducted a retrospective analysis of 131 ECGs from 74 patients (28 DMD, 24 BMD, 22 DM1) followed in the Department of Clinical and Experimental Medicine of the University of Messina, Italy. None of the enrolled patients had clinically manifest heart failure. Electrocardiographic and echocardiographic data were collected, and each ECG finding was considered present if documented in at least one ECG during follow-up. In the DM1 group, an exploratory analysis of the 12-lead P-wave voltage sum (ΣP) and of its ratio to the QRS voltage sum (ΣQRS) was performed and compared with DMD and BMD patients and healthy controls. Results: In DMD patients, the most common findings were deep Q waves (57.1%), negative T waves in the lateral leads (39.3%), and complete and incomplete right bundle branch block (RBBB) (25.0% each). In BMD, incomplete RBBB (27.3%), U waves (27.3%) and left atrial enlargement (23.8%) were prevalent, and 3 patients (12.5%) had a pacemaker. In DM1, atrial fibrillation (18.2%), PR interval prolongation (38.9% of patients in sinus rhythm) and early repolarization (42.9%) were frequent. Mean ΣP and ΣP/ΣQRS values were lower in DM1 patients than in DMD and BMD patients and healthy controls. Conclusions: This study confirms many previously described ECG abnormalities in NMDs and highlights disease-specific patterns. The finding of deep Q waves in DMD may reflect inferolateral fibrosis. Notably, the reduced P-wave voltage in DM1 patients is a novel, hypothesis-generating observation that may reflect atrial myopathy; its value as a predictor of atrial arrhythmias requires prospective validation. These findings underscore the critical role of routine ECG surveillance in the management of patients with NMDs.