Effects of right low atrial septal vs. right atrial appendage pacing on atrial mechanical function and dyssynchrony in patients with sinus node dysfunction and paroxysmal atrial fibrillation.

Aims: To study the effects of right low atrial septum (AS) and right atrial appendage (RAA) pacing on atrial mechanical function and dyssynchrony in patients with sinus node disease (SND) and paroxysmal atrial fibrillation (AF).

Methods And Results: Detailed echocardiographic examination was performed on 30 patients with SND and paroxysmal AF and a dual-chamber, dual sensing, dual response pacemaker with atrial lead implantation at AS(n= 15) or RAA(n= 15). Peak atrial velocities were recorded by pulsed tissue Doppler spectrum. The timing of atrial contractions (Ta) was measured at the middle of the left atrial (LA) and right atrial (RA) free wall. Intra-[standard deviation (SD) of time of Ta (Ta-SD)] and inter-atrial delay(Ta-RL) was measured as the SD of time interval among LA six segments and time difference between the LA and RA wall, respectively. The baseline clinical statuses were similar between groups. Indexes of LA function, and intra- or inter-atrial dyssynchrony were also similar during intrinsic sinus rhythm in both groups (all P> 0.05). During atrial pacing, LA ejection fraction (52 ± 16 vs. 39 ± 14%, P= 0.029) and LA active emptying fraction (34 ± 7 vs. 23 ± 15%, P= 0.012) were higher in patients with AS than RAA pacing. Atrial velocity was also higher at the RA free wall (14.3 ± 3.1 vs. 10.3 ± 4.4 cm/s, P= 0.009), LA septal (7.5 ± 2.1 vs. 5.2 ± 1.7 cm/s, P= 0.004) and lateral wall (8.6 ± 2.4 vs. 6.3 ± 3.0 cm/s, P= 0.024) during AS compared with RAA pacing. There was no difference in Ts-SD during atrial pacing, nevertheless Ta-RL was significantly prolonged in patients with RAA compared with those with AS pacing (42 ± 36 vs. 27 ± 25 ms, P= 0.011).

Conclusion: In patients with SND and paroxysmal AF, right low AS pacing significantly improved global and regional atrial mechanical function and synchronized inter-atrial electromechanical contraction compared with RAA pacing.