Should we perform systematic electrophysiological study in Steinert's disease?

Myotonic dystrophy type 1 (DM1 = Steinert's disease) is a multisystem disorder with autosomal dominant inheritance. This disease is caused by an unstable expansion mutation of the cytosine thymine-guanine (CTG) trinucleotide repeat situated in the 3' non-coding exon of a gene that encodes a serine-threonine protein kinase (DMPK). The incidence of DM1 is estimated to be 1/8000 births [1]. Patients disclose features muscular disorder including myotonia, progressive muscular weakness and wasting associated to a multi-systemic disorder (cataract, hypogonadism, gastrointestinal disorders, and diabetes). Patients with DM1 have a high incidence of sudden cardiac death (SCD) because of ventricular arrhythmias and/or complete heart block [2,3]. Histopathology studies disclose fibrosis in the conducting system and in the sino-atrial node associated with myocyte hypertrophy and fatty acid infiltration.Groh WJ et al. reported in a mean follow-up period of 5.7 years, 27 sudden deaths in a study including 406 adults' patients with DM1. There is a consensus to explore symptomatic patients with DM1. Electrophysiological study (EPS) is an invasive procedure for assessing conduction abnormalities and risk of SCD (with ventricular stimulation). This procedure should be considered in case of syncope, family history of sudden death, sinus node dysfunction (sinus pause > 3 seconds), ventricular arrhythmias and electrocardiogram (ECG) abnormalities suggesting intra or infrahissian conduction disturbances [4,5]: left bundle branch block, bifascicular or trifascicular block, second or third degree atrio-ventricular (AV) block. Pacemaker implantation should be considered in symptomatic patients with conduction abnormalities. Implantable cardioverter defibrillator (ICD) has proved its efficacy to prevent SCD due to ventricular arrhythmias. An ICD implantation should be considered if spontaneous sustained VT was noted.In asymptomatic patients, prediction of cardiac events is not easy. About as