Cardiac Genetics -> Clinical Genetics and registries D-MP11 - What's the Latest in Cardiogenetics? (ID 49) Moderated ePoster

D-MP11-06 - Patients With Genetically Confirmed Myotonic Dystrophy Have A High Prevalence Of Undiagnosed Atrial Fibrillation (ID 711)


Background: Myotonic dystrophy (MMD) is the most common inherited muscular dystrophy in adults. Approximately 80% of patients with type 1 MMD (MMD1) and 20% with type 2 MMD (MMD2) have cardiac involvement (CI). Few studies have examined the frequency of arrhythmias among MMD patients with cardiovascular implantable electronic devices (CIEDs).
Objective: Report frequency of arrhythmias detected on CIEDs including implantable loop recorder (ILR) follow-up.
Methods: Retrospective single center IRB-approved study of patients with MMD1 and MMD2 seen from 2007-2019 documenting symptoms at presentation, ECG and echocardiogram findings, and CIED data at follow-up.
Results: One hundred and five genetically confirmed MMD cases were included: 83 (79%) with MMD1 and 22 (21%) with MMD2. Mean (± SD) age was 41.6 (± 14.6) years and 54% were female. Median follow-up was 36.6 (IQR 14.6-71.5) months. At index evaluation, left ventricular (LV) ejection fraction was 59.6% ± 6.7% in MMD1 and 57.3% ± 16.6% in MMD2 patients (p=0.549). Atrial fibrillation (AF) occurred in 24 (23%) over the study period (22 [26.5%] with MMD1; 2 [9%] with MMD2; p=0.084), of whom 83% had normal LA size. Increased CTG repeats in MMD1 correlated with increased left atrial dilation rates (p=0.020), but not with AF risk (p=0.305). Forty-two patients (40%, 36 MMD1 and 6 MMD2) received CIEDs (32 ICD, 1 pacemaker, 11 ILR; some patients had devices changed during the study period), generating 119.1 patient-years of data. Asymptomatic AF was diagnosed in 2 ILR patients. Eleven patients with ICDs had asymptomatic AF diagnosed by CIED detection; of these, one had systemic embolism resulting in limb ischemia and one had a stroke. One symptomatic AF patient had a remote stroke history. Six patients were started on anticoagulation due to CIED findings, none of whom had embolic events.
Conclusion: AF in our series (23%) was significantly more prevalent than the 5% previously reported. Among 42 MMD patients with CIEDs, asymptomatic AF was diagnosed in 13 (31%) patients, two of whom had embolic events. Many arrhythmias were not detected by standard screening and AF risk was not related to CTG repeat number. Decisions about more detailed screening and thromboembolic prophylaxis in this population warrant further study.