Introduction: AAI is the pacing mode recommended in patients with sinus node dysfunction (SND) but is the less used in our country. Progression to high grade atrioventricular block (AVB) is argued as the reason to implant VVI or DDD pacemakers. We used AAI pacemakers in patients with SND only if Wenckebach AVB appeared at atrial pacing rates > or = 120 beats/min before implantation.
Patients and methods: A series of 45 patients with permanent atrial pacemaker (AAI-PM) systems, were prospectively followed and retrospectively analyzed to investigate the incidence of atrioventricular (AV) conduction disturbances and chronic atrial tachyarrhythmias. AAI-PM were implanted in patients with sinus node dysfunction (SND) in the absence of bundle branch block, only if Wenckebach AV block appeared at atrial pacing rates > or = 120 beats/min. Four patients were lost during follow-up. In 41 patients (23 males, mean age 68 +/- 12 years) the mean follow-up time was 56 months (10 to 110). There was one case of lead failure but no case of dislodgement.
Results: 28 of the 41 patients are still successfully paced in AAI mode after a mean of 68.5 months (44-110). Five patients presented chronic atrial fibrillation at a mean of 23 months (10-39) after PM implantation and remained chronically in this situation. Of these, 4 patients had paroxysmal atrial fibrillation documented before PM implantation. Eight patients died during follow-up (range 10-78 months post PM implantation) at mean age 84 years. Causes of death were noncardiovascular in 5 patients, and a cerebrovascular accident in 3 patients. One patient on digoxin and amiodarone had asymptomatic Wenckebach AV block during night sleep. The AV conduction normalized after cessation of drug therapy. Progression to high degree AV block was not documented in any patient.
Conclusion: AAI is a reliable and safe mode of pacing in patients with SND. If appropriate indications for AAI pacing are followed, progression to high degree AV block is rare and the need to implant additional ventricular lead seems unlikely.