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Know Your DM1 Repeat Length: It’s Important for Your Cardiac Care

Understanding cardiac and other myotonic dystrophy (DM) risk factors and planning for the known complications of DM that may affect you someday can help protect and maintain your quality of life and that of your loved ones. Cardiac complications are the highest-priority care consideration for doctors treating patients with myotonic dystrophy type 1 (DM1) (as identified by expert clinicians in the forthcoming care guideline, "Consensus-based Care Recommendations for Adults with DM1"). As a result, researchers have been trying to understand the factors that may increase the risks of cardiac disease for DM patients.

Dr. Caroline Chong-Nguyen at the Sorbonne Paris Cité University and her colleagues recently published a study in which they looked at DM1 repeat length and its relationship to the risk of cardiac disease. This was a large study of the data in the French patient registry, which tracks patients' symptoms and information over time to understand disease progression and other important information. Eight hundred fifty-five patients with genetically-confirmed DM1 were followed for an average of 11.5 years in order to gain insight into how repeat length could predict cardiac events. Importantly, the research team considered many other factors (such as age, sex, and presence/absence of diabetes) to ensure that their data was not confounded by other variables.

The research team showed that death, sudden death and other adverse cardiac events were linked to DM1 repeat length. Heart rate was higher and conduction system disease was more prevalent in subjects with larger repeats. They found that each 500 repeat increase was associated with 1.5-fold higher risk of death from all causes. Patients with longer repeat lengths also were more likely to have a permanently-implanted pacemaker. 

These findings support taking a more aggressive approach toward screening DM patients for adverse cardiac events, particularly for DM1 patients at the higher end of the range of repeat lengths. Knowing your repeat will help you have discussions with your physician about monitoring and managing your level of risk for cardiac disease.

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