Abstract 2307: Rate of Progression of Electrocardiographic Conduction Disease in Myotonic Dystrophy Type 1 Patients
Background: Myotonic Dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disorder with cardiac involvement including conduction disease, arrhythmias, and sudden death (SD). The severity of electrocardiographic conduction disease independently predicted the occurrence of arrhythmias and sudden death in DM1 patients (pts). In this study, we quantified the rate of progression of cardiac conduction disease in DM1 pts.
Methods: A cohort of clinically-and genetically confirmed adult DM1 pts were recruited and followed at 23 U.S. neurology centers. All patients underwent a study entry ECG with conduction disease categorized as: not significant (NS) if SR, PR ≤ 200 ms, and QRS ≤ 100 ms; moderate (MOD) if SR, PR >200, <240ms, or QRS>100, <120 ms; and severe (SEV) if rhythm other than SR, or PR ≤ 240 ms, or QRS≤120 ms.
Results: 406 DM1 pts (205 male, age 42±12 yrs) were followed for 5.1±2.1 yrs. Entry ECG showed NS conduction disease in198 (49%), MOD conduction disease in 112 (28%), and SEV conduction disease in 96(24%). During follow-up, 342 pts had one or more serial annual ECGs. The mean annual rate of progression over 5 yrs from an ECG showing NS conduction disease to MOD conduction disease was 18.3± 4.2%. The mean annual rate of progression over 5 yrs from an ECG showing MOD conduction disease to an ECG showing SEV conduction disease was 24.2±4.3%. It was rare for pts to progress from NS to SEV over a one-year period occurring on average in just 1.8±2.7% of pts.
Conclusion: The rate of progression of electrocardiographic conduction disease in DM1 pts was very significant in our study over 5-year follow-up. And because ECG conduction disease increased the risk of sudden death and arrhythmias, The ECG in DM1 pts should be evaluated at least yearly.