Development of sinus node disease in patients with AV block: implications for single lead VDD pacing

Objective-To investigate the incidence of sinus node disease after pacemake r implantation for exclusive atrioventricular (AV) block. Design-441 patients were followed after VDD (n = 219) or DDD pacemaker (n = 222) implantation for AV block over a mean period of 37 months. Sinus node disease and atrial arrhythmias had been excluded by Holter monitoring and treadmill exercise preoperatively in 286 patients (group A). In 155 patient s with complete AV block, a sinus rate above 70 beats/min was required for inclusion in the study (group B). Holter monitoring and treadmill exercise were performed two weeks, three months, and every six months after implanta tion. Sinus bradycardia below 40 beats/min, sinoatrial block, sinus arrest, or subnormal increase of heart rate during treadmill exercise were defined as sinus node dysfunction. Results-Cumulative incidence of sinus node disease was 0.65% per year witho ut differences between groups. Clinical indicators of sinus node dysfunctio n were sinus bradycardia below 40 beats/min in six patients (1.4%), intermi ttent sinoatrial block in two (0.5%), and chronotropic incompetence in five patients (1.1%). Only one of these patients (0.2%) was symptomatic. Cumula tive incidence of atrial fibrillation was 2.0% per year, independent of the method used for the assessment of sinus node function and of the implanted device. Conclusions-In patients undergoing pacemaker implantation for isolated AV b lock, sinus node syndrome rarely occurs during follow up. Thus single lead VDD pacing can safely be performed in these patients.