Interatrial septal thickness as a marker of structural and functional remodeling of the left atrium in patients with atrial fibrillation

Background/Aims: There have been reports that interatrial septal (IAS) thickness is increased in patients with atrial fibrillation (AF). This study was performed to investigate whether IAS thickness determined by transthoracic echocardiography (TTE) represents the amount of left atrium (LA) structural and functional remodeling. Methods: The study population consisted of 104 consecutive patients who underwent catheter ablation (CA) for AF (paroxysmal atrial fibrillation [PAF], 82; persistent atrial fibrillation [PeAF], 22). IAS thickness and left atrium volume (LAV) using TTE, and LA voltage ($LA_{VOL}$) using 3-dimensional electroanatomical mapping system were assessed during sinus rhythm. Results: IAS thickness was significantly correlated with maximal LAV ($LAV_{max}$) (r = 0.288, p = 0.003), mean $LA_{VOL}$ (r = -0.537, p < 0.001), total left atrium emptying fraction ($LAEF_{total}$; r = -0.213, p = 0.030), and active LAEF ($LAEF_{active}$; r = -0.249, p = 0.014). IAS thickness was greater in the high-risk group (${\geq}2$) compared to other groups according to $CHA_2DS_2$-VASc score (p = 0.019). During a follow-up of 19.6 months, 23 subjects (22.1%; PAF, 17; PeAF, 6) had recurrence of arrhythmia. Univariate analysis showed that $LAV_{max}$, minimal LAV, mean $LA_{VOL}$, $LVEF_{total}$, $LVEF_{active}$, and IAS thickness were associated with recurrence of arrhythmia. However, on multivariate analysis, only mean $LA_{VOL}$ and $LAEF_{active}$ were independent risk factors for recurrence. Conclusions: Although IAS thickness showed significant correlations with parameters for LA structural and functional remodeling, this parameter alone could not independently predict recurrence of arrhythmia after CA for AF.