Long-term follow-up of arrhythmias in patients with myotonic dystrophy treated by pacing

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 > or =70 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 arrhythmias 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 MD with infrahisian conduction abnormalities. The prophylactic implantation of a pacing system when the HV interval is > or =70 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.