Electrophysiological Study Superior to ECG for Prophylactic Pacing Selection in Myotonic Dystrophy Type 1: JAMA
France: The findings of a new study published in JAMA Cardiology suggest that an electrophysiological study (EPS) provides greater accuracy than an electrocardiogram (ECG) in identifying patients with myotonic dystrophy type 1 (DM1) who may benefit from prophylactic permanent pacing.
The multicenter cohort analysis, led by Dr. Nicolas Clementy of the Department of Cardiology at Université de Tours, CHU de Tours, Paris, France, evaluated 706 adults with genetically confirmed DM1 drawn from the DM1 Heart Registry. The study aimed to determine whether ECG or EPS criteria better predict major bradyarrhythmic events (MBAEs), which include sudden cardiac death, resuscitated cardiac arrest, or advanced atrioventricular block.
The study revealed the following findings:
- Participants had a median follow-up of nearly six years.
- At baseline, 38% of patients had a His-ventricular (HV) interval ≥70 milliseconds.
- At baseline, 32% of patients met ECG-based criteria (PR interval ≥240 milliseconds or QRS duration ≥120 milliseconds).
- During follow-up, 14% of patients experienced a major bradyarrhythmic event (MBAE).
- Multivariable analysis showed that the HV interval was the only variable significantly associated with MBAE incidence.
- An HV interval ≥70 milliseconds was a stronger predictor of MBAEs than ECG criteria, with hazard ratios of 2.89 versus 1.95.
- EPS correctly identified 68.35% of patients at risk, compared with 34.76% for ECG-based assessment.
- Lowering the HV threshold to 65 milliseconds increased sensitivity to over 90% and improved net patient reclassification by 33.7%.
According to the researchers, these results suggest that EPS allows for more precise risk stratification in DM1 patients, potentially guiding timely prophylactic pacemaker implantation and preventing sudden cardiac death. In contrast, reliance on ECG criteria alone may underestimate risk in a substantial proportion of patients, potentially leaving high-risk individuals unprotected.
Professional practice guidelines currently recommend prophylactic pacemaker implantation in asymptomatic DM1 patients who meet ECG or EPS thresholds as class IIa indications. This study provides strong evidence that EPS, particularly HV interval assessment, may be the more reliable method for selecting patients who would benefit most from pacing.
The authors note that adopting a slightly lower HV threshold could further optimize patient care by identifying more at-risk individuals without significantly increasing unnecessary interventions. While the study is retrospective and observational, it is strengthened by a large, multicenter cohort and long-term follow-up.
"The study highlights the clinical value of electrophysiological evaluation over ECG in DM1. Using EPS to guide prophylactic pacemaker implantation could significantly improve outcomes by accurately identifying patients at the highest risk for major bradyarrhythmic events, ultimately enhancing both survival and quality of care in this vulnerable population," the authors concluded.
Reference:
Clementy N, Labombarda F, Grolleau F, et al. Electrocardiogram vs Electrophysiological Study and Major Conduction Delays in Myotonic Dystrophy Type 1. JAMA Cardiol. Published online September 24, 2025. doi:10.1001/jamacardio.2025.3055
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