Both type 1 Myotonic Dystrophy (Steinert disease) and Brugada syndrome may be complicated by conduction disturbances and sudden death. ST elevation in the right precordial leads is the hallmark of Brugada syndrome but may be seen in some myopathies. Mutations in DMPK gene in Steinert pts may lead to cytosolic accumulation of muted toxic RNA or altered alternate splicing of some RNA potentially causing sodium channel dysfunctions. The prevalence of Brugada ECG pattern in Steinert disease is unknown.we perform ajmaline challenge test (1mg/kg over 5min) during electrophysiological (EP) testing in a population of 44 Steinert disease pts (27 men, 41±15 years old) without ST elevation at baseline. Left ventricular EF was normal in each case. The presence of type 1 ST elevation (> 2mm J elevation with coved ST and negative T wave) after ajmaline challenge was correlated to clinical, ECG and electrophysiological variables.8 pts (18%) present type 1 ST elevation in the right precordial leads after ajmaline infusion. Brugada pattern was more often seen in men: 7/27 (26%) vs 1/17 (6%) (p=0.09). Patients with negative ajmaline test presented more often with fascicular block: 13/35 (27%) versus none (p=0.03).Brugada pattern was not correlated to age, symptoms, PR interval, QRS, QT or QTc durations, HV interval (at baseline or after ajmaline), presence of bundle branch block, of late potentials at SA-ECG or inducibility of ventricular arrhythmias at EP study.Nine pts were implanted with a pace maker and four with an ICD. Significant or symptomatic bradycardia did not happen in any non implanted pts, while only one pt presented with malignant ventricular arrhythmias during the 6.3±2.6 years follow-up (ventricular fibrillation with hypokaliemia in an ajmaline negative pt).Brugada ECG pattern can be elicited by class 1 drug in 18% of Steinert disease pts and especially in men. Presence of type 1 ST elevation under class 1 drug in Steinert disease do not seem to have some significant clinical or ECG correlations.