Ambulatory electrocardiographic monitoring in type 1 myotonic dystrophy.

Myotonic dystrophy is a multisystemic disease, in which cardiac involvement is the second most common cause of death. Cardiac conduction tissue involvement is the most frequent, characteristically in a variably progressive and asymptomatic form. Careful surveillance through ambulatory monitoring is therefore needed, but with unknown periodicity. Our aim was to evaluate de novo changes on Holter monitoring performed at eight-month follow-up of a previously studied group of 36 patients with the genetic diagnosis of type 1 myotonic dystrophy, and to correlate them with genetic, neurological, and electrocardiographic data and risk factors for cardiac events. We found a high prevalence and variety of changes between baseline and follow-up Holter that justified permanent pacemaker implantation in 11 patients. In eight these were not documented in previous Holter readings. On the basis of our findings, we suggest that Holter monitoring in type 1 myotonic dystrophy patients should be performed on a regular basis, at intervals not greater than six months. Predictive parameters for the occurrence of these changes were not found.