Long-term follow-up of arrhythmias in patients with myotonic dystrophy treated by pacing - A multicenter diagnostic pacemaker study

OBJECTIVES We hypothesized that pacemaker (PM) implantation in patients with myotonic dystrophy (MD) with a prolonged HV interval, even asymptomatic, may protect them against sudden death related to atrioventricular (AV) block. We sought to prospectively document the true incidence of AV block episodes in this high-risk population and accurately trace, in the long term, by the PM, the occurrence of arrhythmias that may remain undetected during conventional follow-up. BACKGROUND Myotonic dystrophy is associated with a high risk of sudden death, commonly attributed to AV block or ventricular arrhythmias, but cardiac pacing is only recommended as a secondary prevention. METHODS Patients with MD with an HV interval greater than or equal to70 ms, even in the absence of related symptoms, prospectively received a cardiac PM, including an algorithm capable of diagnosing episodes of bradycardia and tachyarrhythmias. RESULTS The population consisted of 49 patients (45.5 +/- 8.9 years old) followed for 53.5 +/- 27.2 months. Paroxysmal arrhythimas were recorded in 41 patients (83.7%), consisting of complete AV block (n = 21), sino-atrial block (n = 4), or atrial (n = 25) or ventricular (n = 13) tachyarrhythmias. No patient died of AV block during follow-up, but 10 deaths occurred, 4 of them sudden. An arrhythmic cause could be excluded by postmortem PM interrogation in two cases of typical sudden death. CONCLUSIONS Arrhythmias are common in patients with MID with infrahisian conduction abnormalities. The prophylactic implantation of a pacing system when the HV interval is greater than or equal to70 ms seems appropriate. The PM protects the patient against the clinical consequences of paroxysmal profound bradycardia and facilitates the diagnosis and management of frequent paroxysmal tachyarrhythmias. (C) 2002 by the American College of Cardiology Foundation.