Electrophysiological Study With Prophylactic Pacing and Survival in Adults With Myotonic Dystrophy and Conduction System Disease

Study Questions:

Does prophylactic pacing when the His-ventricular interval (HV) is >70 ms improve survival in patients with type I myotonic dystrophy (MD)?


This was a retrospective analysis of 486 patients (mean age 42 years) in an MD registry who had a PR interval >200 ms or QRS duration >100 ms. Based on physician discretion, 341 patients were managed with an invasive strategy (electrophysiological study with pacemaker implantation if HV >70 ms) and 145 patients were managed noninvasively. Propensity score risk adjustment was used to adjust for selection bias. The median duration of follow-up was 7.4 years. The primary endpoint was survival.


A pacemaker was implanted in 164 patients in the invasive group who had an HV >70 ms. Overall 9-year survival was 74.4%. After adjustment for confounding variables, mortality was 40% lower in the invasive strategy group than in the noninvasive group. The 9-year incidence of sudden death was significantly lower in the invasive strategy group (4.5%) than in the noninvasive strategy group (18%).


The authors concluded that pacemaker implantation when the HV is >70 ms improves survival in patients with MD.


The most recent American College of Cardiology/American Heart Association/Heart Rhythm Society practice guidelines consider two- or three-degree atrioventricular block (AVB) at any level, even if asymptomatic, to be a Class I indication for a permanent pacemaker in patients with MD. One-degree AVB in patients with MD is considered a Class IIb indication for pacing. The present study makes a strong case for making one-degree AVB a Class I or IIa indication for pacing if the HV interval is >70 ms, which in this study was the case in almost 50% of patients who underwent electrophysiological testing.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias

Keywords: Atrioventricular Block, Confounding Factors (Epidemiology), Follow-Up Studies, Propensity Score, Myotonic Dystrophy, Pacemaker, Artificial, Death, Sudden, Cardiac, United States, Risk Adjustment

< Back to Listings