Ventricular stimulation in patients with myotonic dystrophy type 1 may not predict future ventricular arrhythmias.

Background: Myotonic dystrophy type 1 (DM1) is associated with progressive conduction disease. Furthermore, DM1 patients are at risk ventricular arrhythmias (VAs), although prediction remains difficult. The 2022 Heart Rhythm Expert Consensus Statement gives a IIb recommendation to the use of electrophysiology study (EPS) to risk-stratify patients for VAs. The utility of EPS in predicting the development of VAs, however, has not been explored in this patient population.

Objective: The study sought to examine the natural history of DM1 patients with positive and negative ventricular stimulation (v-stim) during EPS.

Methods: Patients with a history of DM1 undergoing EPS with associated v-stim from 2008 to present were retrospectively identified.

Results: From 2008 to 2022, 26 consecutive DM1 patients presented for EPS with v-stim. Four v-stim protocols were positive for sustained or hemodynamically significant ventricular tachycardia (VT), one of which was induced with 600 doubles, the others with triple extrastimuli. A total of 22 of 26 subjects received a device implant, with 18 receiving permanent pacemakers and 4 implantable cardioverter-defibrillators. All 4 of the patients with positive v-stims underwent ICD implantation. After a mean of 5.7 years of follow-up, 7 patients had sustained VT, 6 of whom had negative v-stims. Of the 4 patients with positive v-stims, only 1 developed sustained VT in follow-up. Other than baseline QT interval at time of EPS, no baseline characteristics were significantly different between patients with and without subsequent VT.

Conclusion: In this single center, v-stim in DM1 patients did not predict clinical VAs, as a vast majority of DM1 patients who developed VAs had negative v-stims.