Introduction: Myotonic dystrophy type 1 (DM1 or Steinert disease) is the most common adult-onset muscular dystrophy, with an estimated prevalence of 1 per 8,000 individuals. It is caused by CTG trinucleotide repeat expansion in the 3′ untranslated region of the DMPK gene on chromosome 19q13.3. Cardiac involvement is frequent in DM1 and represents the second leading cause of death in this population. It remains unclear whether significant sex-based differences exist in cardiac involvement among DM1 patients. This study aimed to compare clinical characteristics and the need for implantable cardiac devices – pacemakers (PM) and implantable cardioverter-defibrillators (ICD) – between male and female DM1 patients.
Methods: We conducted a multicentre retrospective analysis across 16 hereditary cardiac disease units in Spain. Clinical records, ECGs, Holter monitoring, electrophysiological studies, and device implantation data were collected. Patients were stratified by sex for comparative analysis.
Results: Data from 549 DM1 patients (285 male, 264 female) across 18 Spanish hospitals were analysed. Both groups showed comparable age at diagnosis, diagnostic indications, and CTG repeat length. During follow-up, 130 individuals (23.6%) underwent device implantation (PM or ICD): 78 men (27.4%) and 52 women (19.7%). This difference was statistically significant (hazard ratio 1.04–2.16, p=0.031). When analysed separately, ICD implantation occurred in 6.0% of men vs. 1.9% of women (p=0.015), whereas pacemaker implantation rates did not significantly differ.
Conclusion: In this Spanish multicentre cohort, male DM1 patients required ICD implantation significantly more often than female patients, despite similar baseline clinical profiles. These findings suggest a sex-specific predisposition to life-threatening arrhythmias in males with DM1, highlighting the need for sex-tailored cardiac monitoring and prophylactic strategies.