Long‐Term Arrhythmia Follow‐Up of Patients with Myotonic Dystrophy

<jats:title>Arrhythmias in Myotonic Dystrophy Patients</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Myotonic dystrophy (MD) is the most common muscular dystrophy in adults and is associated with sudden death. Reported predictors of sudden death in this population include atrial tachyarrhythmias, a PR interval greater than 240 milliseconds, aberrant QRS conduction, and any degree of AV block.</jats:p></jats:sec><jats:sec><jats:title>Objective</jats:title><jats:p>We sought to report on the arrhythmic outcome of a cohort of patients with a new diagnosis of genetically proven MD.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We performed a retrospective review of 37 patients with genetically confirmed MD referred to our electrophysiology clinic for primary cardiac screening.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>There were 25 patients with MD type 1 (MD1) and 12 patients with MD type 2 (MD2). Eight patients with MD1 (32%) had atrial fibrillation, compared to only one patient with MD2 (8.3%). Patients with MD1 were more likely to have evidence of conduction disease abnormalities (40% vs. 8.3%, P = ns) and had a higher all‐cause mortality (16% vs. 0%) than those with MD2. Criteria for recommending ICD implantation were based on sudden death risk factors suggested by published literature. Eleven patients were offered an ICD, 2 refused and died within the next year. Of the 9 patients who received an ICD, 8 had MD1. Three patients received appropriate shocks, 2 for monomorphic VT, and one for polymorphic VT.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>The presence of AV conduction disturbance in MD patients is associated with a greater risk for ventricular arrhythmias. MD1 was more likely to be associated with cardiac arrhythmias than MD2. The incidence of ventricular arrhythmias among those who received a primary prevention ICD was 33% over 22 months, with 2 patients experiencing monomorphic VT and one experiencing polymorphic VT.</jats:p></jats:sec>