Differential in Inter-atrial Dyssynchrony and Atrial Mechanical Function in Sick Sinus Syndrome with or without Paroxysmal Atrial Fibrillation

Objectives: To investigate the intra- and inter-atrial dyssynchrony in pts with sick sinus syndrome (SSS) combined with paroxysmal atrial fibrillation (PAF). Background: Sick sinus syndrome is associated with an increased incidence of atria fibrillation. However, the atrial electromechanical dyssynchrony, structural remodeling, and contraction for SSS combined with PAF are still remained clear. Methods: 30 pts in SSS with or without PAF and normal left ventricular systolic function were included. 19 pts combined with PAF (PAF group) and 11 without history of AF (SSS group) were divided. Doppler echo with tissue Doppler imaging (TDI) was performed from apical 4, 2 and 3 chambers during in sinus rhythm. The peak atrial contraction velocities (Va) and the timing of mechanical events (Ta) were measured at the mid of left atrial (LA) and right atrial free wall (RA). Intra-atrial delay was defined by the standard deviation of Ta among LA sep/lat/inf/ant/post/antsep wall. Inter-atrial delay was defined by the time difference between LA and RA free wall. Results: There were no significant difference in age (73±9 vs.71±9), body surface area, ECG p wave duration, LV ejection fraction, mitral inflow velocities, LA ejection fraction between PAF and SSS groups. LA volume index was increased both in PAF and SSS groups, but there was no difference (42±14 vs.34±15 ml/m2). However, LA active empting fraction was lower in PAF compared to SSS groups (24±14 vs.36±13 %, p=0.027). Mean Va of LA was significantly decreased in PAF group as well (2.6±0.9 vs.3.4±0.9 cm/s, p=0.028). Va of RA was no difference between PAF and SSS groups (4.1±1.5 vs.4.6±2.1 cm/s). Inter-atrial delay was significantly prolonged in PAF compared to SSS groups (33±25 vs.12±19 ms, p=0.022). Neither the standard deviation of Ta nor the maximum difference of Ta among 6 segments of LA showed difference between two groups. Conclusion: In pts with SSS combined with PAF, worsening of LA mechanical contraction and inter-artrial dyssynchrony occurred even in normal left ventricular systolic function. Appropriate atrial pacing for those patients should be considered