Abstract. There is a good evidence to support atrial based pacing rather than ventricular pacing in sinus node disease (SND) without concomitant atrioventricular conduction disturbances. Nevertheless, there is some risk of the subsequent development of atrioventricular block. The risk of development of AV block may depend on severity of the disease which could be reflected by atrial fibrillation history and on antiarrhythmic drugs used for atrial fibrillation prevention. Double risk of complications caused by implantation of additional lead consist an argument for AAI pacing system use whenever ventricular pacing is not necessary.

The aim of the study was to evaluate the influence of atrial tachyarrhythmia (paroxysmal atrial fibrillation, flutter, tachycardia) history on the risk of AV block development, requiring additional ventricular lead implantation, in patients with SND and permanent atrial pacing system.

Methods. Data of 752 patients with SND who had single chamber atrial pacing system implanted between 1993 and 1997 in our Dept. of Cardiology were identified. The history of atrial tachyarrhythmias (AF) was established on the basis of preoperative exam. The records of patients were examined to find cases that required further procedure to change their pacemaker system to dual chamber or ventricular. The data up to the end of the year 2002 were taken into consideration. Mean observation period was 6.6 years.

Results. Atrial tachyarrhythmia history was noted in 417 pts (55.5%) in the whole group. 144 pts (19.1%) required subsequent ventricular lead implantation procedure. 105 pts had the DDD (or VVI) pacemaker implanted in the AF group (25.2%) and 39 in the group with no AF history (11,6%). Absolute risk increase was 13.6% and relative risk 2.17. Mean time to the “upgrade” procedure was 1090 days in the whole group, 1025 in the AF group and 1263 in pts with no AF history and the difference was statistically significant (Kaplan-Meier product-limit method, test log-rank p<0,00000).

Conclusions. The risk of atrioventricular block occurrence, requiring additional ventricular lead implantation, in patients with sinus node disease and permanent atrial pacing system is increased in patients with history of atrial tachyarrhythmia. The AF history should be taken into consideration when making a decision of DDD pacing system implantation in borderline cases.