Atrioventricular conduction disturbances in patients with sinoatrial node disease and atrial pacing

In sinoatrial node disease (SND) atrial pacing may be limited by progression of AV block. The incidence of AV block after AAI systems implantation range, according to various authors, from 0% to 12%. The aim of this study was to examine the AV conduction disturbances that forced a change in the mode of pacing in patients with AAI pacemakers. The information was collected retrospectively from a cohort of 122 patients. The follow-up period ranged from 5 to 83 months (mean = 35). Among these patients there were 37 with sinus bradycardia and 85 with bradycardia-tachycardia syndrome. Their mean age was 63 years. Before AAI pacemaker insertion, all patients had normal AV conduction on 12-lead ECG, and all but five had a Wenckebach cycle length shorter than 500 msec. Seven out of these 122 patients (5.7%) developed symptomatic conduction disturbances (second-degree type I AV block in five, second degree type II AV block in one, and third-degree AV block in one), necessitating a change from AAI to another mode of pacing. We conclude that progression of AV block after atrial pacemaker implantation in patients with SND is infrequent and mild in the majority of cases. Intraventricular disturbances such as left anterior hemiblock represent contraindication to AAI pacing particularly in patients who may be in need of antiarrhythmic drugs.