[Symptomatic bradycardia with amiodarone in patients with pre-existing conduction disorders]

Amiodarone has been shown to improve survival in patients with impaired left ventricular function and ventricular trachyarrhythmias. The clinical applicability, however, is limited by numerous often serious adverse effects. 70 patients receiving the treatment with amiodarone for ventricular tacharrhythmias were investigated regarding the development of symptomatic bradycardia. Group 1 consisted of 25 patients with preexisting conduction disorders, 5 had first degree heart block, 10 had right bundle branch block, and 7 had left bundle branch block on electrocardiographic examination. The 3 remaining patients showed asymptomatic sinus node dysfunction defined as sinus arrest or sinuatrial block. Amiodarone caused symptomatic bradycardia in 6 of the group 1 patients (II degrees-III degrees AV block in 3 patients with preexisting I degree AV block or right bundle branch block; intermittent sinus arrest or SA block in the 3 cases with previous sinus node dysfunction). 45 patients had no conduction disorders before the administration of amiodarone (group II). None of these patients developed symptomatic bradycardia. The difference to group I was significant (p < 0.0005). Thus, patients with preexisting conduction disorders have a substantial risk of developing symptomatic bradycardia under amiodarone therapy, with an incidence of 24% in group I patients of our collective.