PO-03-224 ELECTROPHYSIOLOGY STUDY WITH VENTRICULAR STIMULATION DOES NOT ADEQUATELY RISK STRATIFY PATIENTS WITH MYOTONIC DYSTROPHY

Abstract

Myotonic dystrophy (MD) types 1 and 2 frequently are associated with progressive conduction disease. Furthermore, patients are at risk ventricular arrhythmias (VAs), although prediction of this remains difficult. The 2021 HRS Guidelines give a IIb recommendation to the use of electrophysiology study (EPS) with ventricular stimulation (v-stim) 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. To examine the natural history of MD patients with positive and negative v-stim during EPS. Patients with a history of MD undergoing EPS with associated v-stim from 2007 to present were retrospectively identified. EPS included measurement of baseline conduction intervals. Ventricular stimulation was performed from two sites, most commonly the right ventricular apex and the right ventricular outflow tract, with delivery of up to three ventricular extra-stimuli with a drive cycle length of 600 ms and 400 ms. V-stim was deemed positive when sustained monomorphic ventricular tachycardia (VT) was present or required intervention (pace termination or cardioversion) due to hemodynamic compromise. From 2007-2022, 26 consecutive patients with confirmed type 1 or type 2 myotonic dystrophy presented for EPS with v-stim. Mean age was 51 +/- 12.6 years and mean LV ejection fraction of 63 +/- 9.4%. Eight (31%) v-stim protocols utilized Isoproterenol. Four v-stim protocols were positive for sustained or hemodynamically significant VT, one of which was induced with 600 doubles, the others with triple extra-stimuli. 22 of 26 subjects received a device implant, with 18 receiving pacemakers (PPM) and 4 intracardiac defibrillators (ICD). All four of the patients with positive v-stims underwent ICD implant. After a mean of 5.7 years of follow up, 7 patients with pacemakers 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. In this single center, observational study, v-stim in patients with myotonic dystrophy was not useful in predicting the subsequent development of clinical VAs as a vast majority of MD patients who developed VAs had negative v-stims. Given the changing ventricular substrate in patients with MD, implantation of a dual chamber ICD should be considered without performing an EP study with ventricular stimulation.