Indications for Cardiac Pacemaker Implantation in Myotonic Dystrophy.

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.