• Philippe Maury, Mathieu Audoubert, Pascal Cintas, Anne Rollin, Alexandre Duparc, Pierre Mondoly, Ana-Maria Chiriac, Blandine Acket, Xinran Zhao, Jean Luc Pasquié, Christelle Cardin, Marc Delay, Marie Sadron, Didier Carrié, Michel Galinier, Jean-Marc Davy, Marie-Christine Arne-Bès, and Franck Raczka.
• Department of Cardiology, University Hospital Rangueil Toulouse, France. Electronic address: mauryjphil@hotmail.com.
• Heart Rhythm. 2014 Oct 1; 11 (10): 1721-7.

BackgroundBoth type 1 myotonic dystrophy (MD1) and Brugada syndrome (BrS) may be complicated by conduction disturbances and sudden death. Spontaneous BrS has been observed in MD1 patients, but the prevalence of drug-induced BrS in MD1 is unknown.ObjectiveThe purpose of this study was to prospectively assess the prevalence of type 1 ST elevation as elicited during pharmacologic challenge with Class 1C drugs in a subgroup of MD1 patients and to further establish correlations with ECG and electrophysiologic variables and prognosis.MethodsFrom a group of unselected 270 MD1 patients, ajmaline or flecainide drug challenge was performed in a subgroup of 44 patients (27 men, median age 43 years) with minor depolarization/repolarization abnormalities suggestive of possible BrS. The presence of type 1 ST elevation after drug challenge was correlated to clinical, ECG, and electrophysiologic variables.ResultsEight of 44 patients (18%) presented with BrS after drug challenge. BrS was seen more often in men (26% vs 6%, P = .09) and was related to younger age (35 vs 48 years, P = .07). BrS was not correlated to symptoms, baseline ECG, HV interval, results of signal-averaged ECG, or abnormalities on ambulatory recordings. MD1 patients with BrS had longer corrected QT intervals, greater increase in PR interval after drug challenge, and higher rate of inducible ventricular arrhythmias (62% vs 21%, P = .03). Twelve patients were implanted with a pacemaker and 5 with an implantable cardioverter-defibrillator. Significant bradycardia did not occur in any patients, and malignant ventricular arrhythmia never occurred during median 7-year follow-up (except 1 hypokalemia-related ventricular fibrillation).ConclusionBrS is elicited by a Class 1 drug in 18% of MD1 patients presenting with minor depolarization/repolarization abnormalities at baseline, but the finding seems to be devoid of a prognostic role.Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

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