Objective: To examine the association between the presence of arrhythmia in type 1 myotonic dystrophy (DM1) and clinical-genetic variables, evaluating their role as predictors of the arrhythmic risk.
Methods: Two hundred and forty five patients with genetically proven DM1 underwent clinical and non-invasive cardiological evaluation. Severity of muscular involvement was assessed according to the five point muscular disability rating score (MDRS). Data were analysed by univariate and multivariate models.
Results: We examined 245 patients and found cardiac arrhythmias in 63 subjects ,40 of which required a device implant. Statistical analyses revealed that men had a more than double risk to develop arrhythmias compared to women (p = 0.018). The addition of each year of age caused an increased risk of arrhythmia equal to 3% (p=0.030). Subjects with MDRS 5 had a risk of arrhythmia 12 times higher than patients with MDRS 1-2 (p<0.001). Although all these variables were significantly associated with cardiac rhythm dysfunction, they had a low sensitivity for the prediction of the arrhythmic risk.
Conclusion: Male sex, age and muscular disability are strongly associated with development of arrhythmia in DM1. However, all these variables are weak predictors of the arrhythmic risk. These results suggest that other factors may be involved in the development of cardiac conduction abnormalities in DM1.