Atrial Fibrillation and Flutter in a Contemporary Cohort of Patients With Myotonic Muscular Dystrophy

Literature on the prevalence and management of atrial arrhythmias in patients with myotonic muscular dystrophy type 1 (MMD1) or myotonic muscular dystrophy type 2 (MMD2) is limited.

This study sought to describe incidence, prevalence, and predictors of atrial fibrillation (AF) and atrial flutter (AFL) in a contemporary cohort of patients with myotonic muscular dystrophy (MMD).

Associations between patient factors and incident AF/AFL were analyzed in patients with MMD referred for routine electrophysiology evaluation between January 2013 and September 2023.

We identified 120 patients (96 MMD1, 24 MMD2) seen for new electrophysiology clinic visits for MMD cardiac evaluation. Median age at MMD diagnosis was 34.6 years (Q1-Q3: 21.8-51.0 years), with a younger age at diagnosis for MMD1 patients (P < 0.001). AF or AFL was diagnosed in 31% of patients (31 of 96 MMD1 patients vs 6 of 24 MMD2 patients; P = 0.656) during the study period. AF occurred in 34 (28%) patients, AFL in 9 (8%), and 6 of 37 had both AF and AFL. Anticoagulation (AC) was prescribed at initial AF/AFL diagnosis in 41% (n = 15 of 37) of patients. The CHA₂DS₂-VASc score was higher in patients who received AC (P < 0.001). Twelve (32%) patients underwent catheter ablation. One stroke occurred in the AF/AFL group (no AC, CHA₂DS₂-VASc score 0). Female MMD1 patients were less likely to develop AF/AFL (HR: 0.08). Diagnosis of MMD1 at a younger age (HR: 0.95 per year) and greater CTG nucleotide repeats (HR: 1.09 per 50 repeats) were associated with incident AF/AFL.

There was a high prevalence of AF/AFL in this single-institution MMD cohort. The CHA₂DS₂-VASc score may not be an effective tool in this population.