Dr. Isadora Guarino

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

Dr. Isadora D. GuarinoResident Research Spotlight
Pacing and Clinical Electrophysiology, 2026View Publication →

Study Overview

Myotonic dystrophy type 1 (DM1) is the most common adult-onset muscular dystrophy and carries a well-recognized risk of progressive cardiac conduction disease. What has remained poorly understood is what happens to these patients once they develop heart failure (HF). HF is itself a driver of electrical remodeling, and the combined effects of HF-related structural changes and intrinsic DM1-associated conduction disease may accelerate arrhythmic risk beyond what either condition produces alone.

To investigate this, Dr. Isadora Guarino and colleagues used the TriNetX federated research network to identify adults with pre-existing DM1 who developed incident HF between 2013 and 2023. Using propensity score matching (1:1), they compared 815 DM1 patients with incident HF to 815 matched HF controls without DM1, balancing groups on demographics, comorbidities, and HF-related medications. Outcomes were tracked over three years.

Key Findings

  • DM1 patients had more than twice the risk of advanced conduction disease compared to matched HF controls (RR 2.45, 95% CI 1.61–3.74).
  • ICD or CRT-D implantation was also significantly more frequent in DM1 (RR 2.56, 95% CI 1.24–5.30), with a higher cumulative incidence over time (HR 2.65, 95% CI 1.28–5.53).
  • All-cause mortality was substantially elevated in the DM1 group (200/806, 24.8% vs 116/811, 14.3%; RR 1.74, 95% CI 1.41–2.13; HR 1.82, 95% CI 1.45–2.29).
  • Bundle branch block or intraventricular conduction delay occurred more frequently in DM1 (RR 1.49, 95% CI 1.08–2.06; HR 1.57, 95% CI 1.12–2.21).
  • Permanent pacemaker implantation, ventricular tachyarrhythmias, and cardiac arrest did not differ significantly between groups, suggesting that the dominant risk in this population is progressive conduction disease rather than ventricular arrhythmia.

Clinical Significance

These findings establish incident HF as a clinically meaningful inflection point in the cardiac trajectory of DM1. Current device implantation guidelines for DM1 are often based on neuromuscular-focused thresholds that may not fully account for the synergistic risk conferred by incident HF. This study provides real-world evidence that patients at the intersection of DM1 and HF represent a distinctly high-risk subgroup warranting closer rhythm surveillance and earlier electrophysiology referral.

Practically, internists and hospitalists caring for DM1 patients admitted with new HF should recognize that this transition may signal accelerating conduction system disease. Early cardiology and electrophysiology involvement, along with a low threshold for ambulatory rhythm monitoring, is supported by these data.