Identification of left atrial wall thickness in substrate mapping of atrial fibrillation

The objective of this study was to assess the clinical relevance of left atrial wall thickness (LAWT) in identifying electrophysiological substrate abnormalities.

Eighty-two patients with atrial fibrillation undergoing first-time catheter ablation at Xuzhou Central Hospital between March 2016 and May 2023 were enrolled in this study. The left atrium was anatomically segmented into five regions, with all patients undergoing delayed gadolinium-enhanced magnetic resonance imaging (LGE-MRI) for quantitative assessment of parameters including left atrial wall thickness (LAWT, epicardial fat excluded). Bipolar voltage mapping was systematically performed to delineate low-voltage zones (LVZs) and calculate their relative area proportion within the total atrial surface for each patient. The regional segmentation method for left atrial voltage mapping was consistent with that used in late gadolinium-enhanced magnetic resonance imaging (LGE-MRI). Univariate and multivariate logistic regression analyses were conducted to identify clinical factors associated with LVZ formation. Receiver operating characteristic (ROC) curve analysis was employed to determine the optimal LAWT cutoff value for LVZ prediction, along with its corresponding sensitivity and specificity. Additionally, regional comparative analyses were performed between LGE-MRI-derived wall thickness measurements and their corresponding low-voltage zones identified by three-dimensional electroanatomic mapping.

The study cohort comprised 82 atrial fibrillation patients (44 paroxysmal AF, 38 persistent AF). Mean LAWT significantly differed between paroxysmal and persistent AF groups (2.6 ± 0.5 mm vs. 2.3 ± 0.4 mm, P = 0.02). Multivariate analysis identified age (OR = 1.111, 95% CI:1.03-1.19, P = 0.007), left atrial volume (OR = 1.029, 95% CI:1.003-1.055, P = 0.026), and LAWT (OR = 0.044, 95% CI:0.007-0.272, P = 0.001) as independent predictors of LVZs. Regional analysis revealed the septal wall was thinnest (1.76 ± 0.9 mm), followed by posterior (1.95 ± 0.4 mm) and bottom walls (2.62 ± 0.6 mm), with roof (2.89 ± 0.5 mm) and anterior walls (3.0 ± 0.4 mm) being thickest. Correspondingly, septal LVZ area was most extensive (22.5 ± 10.2%), exceeding posterior (15.3 ± 10.6%), bottom (12.6 ± 12.0%), roof (11.8 ± 10.0%), and anterior walls (10.8 ± 12.1%). ROC analysis demonstrated LAWT ≤ 2.3 mm predicted LVZs with 71% sensitivity and 68.2% specificity (AUC = 0.723, P < 0.001). Additional predictors included age >64.5 years (AUC = 0.722, sensitivity 65.9%, specificity 73.7%) and left atrial volume >119.2 ml (AUC = 0.682, sensitivity 61.4%, specificity 78.9%).

This study demonstrate that LAWT significantly correlate with both atrial fibrillation progression and electroanatomical remodeling. Notably, regions exhibiting LAWT ≤ 2.3 mm predict more extensive LVZs. Our findings suggest that non-invasive LGE-MRI-based measurement of LAWT may enhance the detection rate of left atrial pathological substrates.