Advanced Conduction Disease After Incident Heart Failure in Myotonic Dystrophy Type 1.

BACKGROUND

Myotonic dystrophy type 1 (DM1) is associated with progressive cardiac conduction disease, heart failure (HF) and increased mortality. However, the association of incident HF with conduction disease and survival in DM1 is not well defined.

OBJECTIVE

To determine whether adults with pre-existing DM1 who develop incident HF experience higher rates of advanced conduction disease, permanent pacemaker or ICD/CRT-D implantation, and mortality compared with matched HF controls without DM1.

METHODS

We performed a retrospective cohort study using the TriNetX database to identify adults with incident HF and pre-existing DM1 from 2013-2023. Patients with DM1 were propensity matched 1:1 to HF controls without DM1. The primary outcome was incident advanced conduction disease. Secondary outcomes included permanent pacemaker implantation, ICD or CRT-D implantation, bundle branch block or intraventricular conduction delay, ventricular tachycardia or fibrillation, cardiac arrest, and all-cause mortality. Outcomes were assessed over three years using risk ratios and time-to-event analyses.

RESULTS

The cohort included 815 DM1 patients matched to 815 HF patients without DM1. Compared with matched HF controls, patients with DM1 had higher risks of advanced conduction disease (RR 2.45, 95% CI 1.61-3.74) and ICD/CRT-D implantation (RR 2.56, 95% CI 1.24-5.30), as well as higher all-cause mortality (HR 1.82, 95% CI 1.45-2.29). Permanent pacemaker implantation did not differ significantly between groups (RR 1.22, 95% CI 0.53-2.80). Bundle branch block or intraventricular conduction delay was more frequent in DM1, while ventricular tachyarrhythmias and cardiac arrest did not differ significantly between groups.

CONCLUSION

Among patients with incident HF, those with DM1 represent a distinctly high-risk subgroup with substantially elevated rates of advanced conduction disease, ICD/CRT-D implantation, and mortality compared with matched HF controls. These findings identify the intersection of DM1 and HF as a clinical state warranting closer rhythm surveillance and earlier electrophysiology assessment.