Atrial pacing improves atrial mechanical function only in patient with sinus nodes disease with paroxysmal atrial fibrillation existing atrial dyssynchrony

BACKGROUND: Minimizing ventricular pacing for bradycardia reduces 40% risk of developing persistent atrial fibrillation (AF) in sinus node disease (SND). However, the impact of atrial pacing on atrial mechanical dyssynchrony and function in SND pts with paroxysmal AF (PAF) remains unclear. METHODS: 19 SND pts with PAF (mean age 71±9 years, 13 F) implanted with DDDR pacemaker for symptomatic bradycardia and normal left ventricular ejection fraction (>60%) were enrolled for study. Detailed echo with tissue Doppler imaging (TDI) during intrinsic sinus rhythm when backup AAI 40 bpm (AsVs mode) and atrial pacing at 10 bpm above sinus rhythm (ApVs mode) were performed. The peak atrial contraction velocities (Va) and the timing of mechanical events (Ta) were measured at the middle of left atrial (LA) and right atrial (RA) free wall by TDI. Intra-atrial delay was defined by the standard deviation of Ta among six segments of LA (Ta-SD >40ms). RESULTS: During AsVs mode, 13 pts were found Ta-SD 40ms (mean age 71±9 years, 4F). In pts with Ta-SD >40ms, ApVs mode significantly increased in LA filling fraction (25±8 vs. 39±11, p=0.035), trended to improve in LA active emptying fraction (14±8 vs. 25±11, p=0.07), and also significantly improved Va of LA (2.0±0.8 vs. 2.6±0.7, p=0.02) compared to AsVs mode. However, there were no changes in PAF pts with Ta-SD