ABSTRACT
OBJECTIVES: To determine risk factors for cardiac complications in patients with myotonic dystrophy, and to determine whether permanent cardiac pacemakers may be beneficial in the treatment of myotonic dystrophy heart disease. BACKGROUND: Myotonic dystrophy affects the cardiac conduction system. Cardiac pacemakers are easily implanted and can be life-saving in patients with severe or complete heart block. METHODS: A total of 94 patients with myotonic dystrophy were examined; 46 were followed for a mean of 6.4 (+/- 3.5 SD) years to determine predictors of the end point events of sudden death, Stokes-Adams attacks, or onset of atrial fibrillation. The end points were chosen to determine when cardiac pacemakers should be implanted (Fig. 1). RESULTS: Four out of 5 patients (and all 4 patients >60 years of age) with PR intervals longer than 275 msec had sudden death (n=1), Stokes-Adams attacks (n=1), or onset of atrial fibrillation (n=2). Conversely, only 1 of 89 patients with a PR interval shorter than 275 msec had end point events; 1 patient, aged 63 years, developed left bundle branch block and palpitations accompanied by dyspnea, which responded to a pacemaker. CONCLUSIONS: We recommend that patients with myotonic dystrophy and any indication or a family history of myotonic heart disease have at least a yearly electrocardiogram, particularly if they have a prolonged baseline or progressively increasing PR interval, or symptoms suggestive of heart block.
