Risk of Cardiac Disease in a Population-Based Cohort of Myotonic Dystrophy Type 1 and Type 2 in the United States.

Background and Objectives: Myotonic dystrophy type 1 and type 2 (DM1/DM2) are multisystemic disorders that may affect heart function in addition to the progressive skeletal muscle weakness and myotonia that occur. There are limited population-based studies on the prevalence and risks associated with cardiac symptoms in DM1 and DM2. Methods: Cardiac data were abstracted from the medical records of 429 individuals with DM1 and DM2 with a health care encounter between 2008 and 2019. The frequencies of cardiac arrhythmias and of cardiomyopathy were assessed along with relationships to demographic data and age at onset. Results: A total of 429 individuals from MD STARnet were included in the analyses, with 82.3% having DM1. Overall, cardiac arrhythmias were observed in 44.5% and cardiomyopathy in 9.1%. The risk of developing a cardiac arrhythmia was much higher in DM1 than in DM2. Repeat length was not a risk factor for the development of a cardiac arrhythmia. Developing DM1 in childhood or adulthood as opposed to congenital onset was a risk factor of both cardiac arrhythmia and cardiomyopathy in multivariable analysis. Discussion: This study confirms the increased risk of cardiac arrhythmias in individuals with DM and DM2 and identifies the development of cardiomyopathy as a low-frequency event. Notably, the risk of cardiac arrhythmias is particularly elevated in DM1. The study reaffirms the need for serial cardiac monitoring in individuals with DM1/DM2.