24 h holter monitoring in myotonic dystrophy type 1 follow-up: is it really needed?

Myotonic dystrophy (DM1) is a hereditary neuromuscular disease with frequent cardiac involvement. Cardiac conduction tissue involvement is frequent and is often progressive and asymptomatic. Therefore, regular 24h-Holter monitoring is recommended to identify conduction disturbances and arrhythmias.

In this study, we aimed to evaluate the clinical effectiveness of 24h-Holter monitoring to screen for de novo conduction disturbances and arrhythmias in patients with genetic diagnosis of DM1 and evaluate its impact in patients’ treatment.

A retrospective single-centre study was conducted including all adult patients with DM1 who received a 24h-Holter from January 2013 to September 2023. Holter findings were compared with the results of cardiac screening based on history taking and electrocardiography. Arrhythmias and/or conduction abnormalities that would have remained otherwise undiagnosed were considered de novo findings.

A total 46 genetically confirmed DM1 patients were included, 52.2% were male (mean age was 48,0 ± 10,0 years). All patients were asymptomatic. A total of 144 Holter recording was analysed. An average of 3,1 ± 1,7 Holter recordings per patient was performed.

Abnormal Holter results were found in 31 (67,4%) patients, including first and second-degree atrioventricular block, atrial fibrillation/flutter and non-sustained ventricular tachycardia, after a mean follow-up of 70,8 ± 34,9 months. Abnormalities mainly consisted of conduction disorders (80,6%) such as AV block. Out of the 31 patients with abnormal Holter findings, 23 (74,2%) patients had de novo Holter findings, with clinical treatment consequences in five of them.

These results suggest that 24h-Holter monitoring may improve routine cardiac screening in patients with DM1. De novo Holter findings added value to disease management in 10,9% of our patients.

Cardiac involvement screening in this population is challenging and DM1-specific recommendations are still needed to improve cardiac care of this population.