Adult myotonic muscular dystrophy (Steinert's disease) is the most common inherited neuromuscular disorder. Cardiac rhythm disturbances occur frequently in this disease state and may be responsible for up to one-third of deaths. In this study, we intend to evaluate the utility of non-invasive electrocardiographic screening methods and history in predicting serious arrhythmic events.

The long term objectives of this population study is a more defined natural history, optimal diagnostic testing methodology, and methods of therapy for arrhythmias in individuals with myotonic muscular dystrophy. The goal is a more adequate definition of appropriate diagnosis and therapy for arrhythmias in order to decrease the likelihood of cardiac morbidity and mortality in this disorder.

The specific aims of the study involve an initial survey of individuals with myotonic muscular dystrophy detailing multiple factors. Non-invasive electrocardiographic testing will be done. Using this initial data and subsequent follow-up data collected yearly the cohort of patients will be followed as to arrhythmia development over a minimum of five years and likely longer with a long-term registry and evaluation of National Death Records and Ancestry.com. This project is unique in that it characterizes a non-neurologic abnormality associated with a neuromuscular disease, myotonic muscular dystrophy.

Inclusion Criteria:

1. Age 18 and over
2. Willing to sign informed consent
3. Have a previous diagnosis of myotonic muscular dystrophy

Exclusion Criteria:

1. Under age 18.
2. Unwilling to sign consent.
3. Unwilling to commit to long-term follow-up.

Patient Recruitment: Will take place at the 230 hospital-affiliated MDA neuromuscular clinics. Individuals with myotonic dystrophy will be identified in the MDA clinics these will be asked to participate in the study.