Bachmann's bundle pacing not only improves interatrial conduction but also reduces the need for ventricular pacing

Background: Patients treated for sick sinus syndrome may have interatrial conduction disorder, what often leads to atrial fibrillation. Moreover, up to 20% of them have atrioventricular conduction delay which worsens over time and is responsible for the need of ventricular pacing. Implantation of atrial lead in right atrium appendage (RAA) is the reason for longer interatrial and atrioventricular conduction time even in patients without prior disorders. Purpose: The aim of this study was to assess influence of atrial pacing site on interatrial and atrioventricular conduction and the percentage of ventricular pacing in population with SSS implanted with DDD pacemaker. Methods: The study group consisted of 107 patients (64 F, 43 M) aged 71,2±18,7 years. Patients were divided in two groups: group I (n=51) with RAA pacing, group II (n= 56) with Bachmann's area pacing. Differences in atrioventricular conduction in sinus rhythm and AAI 60 and 90/min pacing were assessed. Also P wave width at sinus rhythm and during atrial pacing as well as percentage of ventricular stimulation were compared. P wave morphology was studied in surface ECG leads I and II. Results: There were no differences in baseline P wave duration in sinus rhythm between the groups (99.7±16 ms vs 103.0±28 ms, p=n.s.). Atrial pacing 60 bpm revealed longer P wave duration with atrial lead location in RAA in comparison to Bachmann's bundle region (141.1±24.3 vs 107.2±14.2 ms, p<0.01). In group II the P wave morphology was more comparable with sinus P wave. The differences between atrioventricular conduction time during sinus rhythm and atrial pacing at 60 and 90 bpm were significantly longer in patients with RAA vs. Bachmann's pacing (42.1±16 vs 8±7 ms p<0.01 and 68±32 vs 22±11 ms p<0.005, respectively). The percentage of ventricular pacing was higher in group I (19±1 vs 3±3%, p<0,01). Conclusions: 1. Right atrium appendage pacing in SSS pts promotes atrioventricular conduction disorder which results in higher percentage of ventricular pacing in DDD mode. 2.The Bachmann's bundle region pacing of right atrium results in less pronounced interatrial and atrioventricular conduction delay.