Left Atrial Wall Thickness Estimated by Cardiac CT: Implications for Catheter Ablation of Atrial Fibrillation

Abstract

Atrial wall thickness (AWT) is a significant factor in understanding the pathological physiological substrate of atrial fibrillation, with a potentially substantial impact on the outcomes of catheter ablation procedures. Precise measurements of the AWT may provide valuable insights for categorising patients with AF and planning targeted interventions. Objectives: The purpose of this study was to evaluate the characteristics of the left atrium (LA) using non-invasive multidetector computed tomography (MDCT) scans and subsequent three-dimensional (3D) image post-processing using novel software designed to calculate atrial thickness dimensions and mass. Methods: We retrospectively analysed 128 consecutive patients (33.6% females; mean age 55.6 ± 11.2 years) referred for AF ablation (37 with persistent AF and 91 with paroxysmal AF) who underwent preprocedural MDCT. The images were post-processed and analysed using the ADAS software (Galgo Medical), automatically calculating the LA volume and regional wall thickness. In addition, the software employed a regional semi-automatic LA parcellation feature that divided the atrial wall into 12 segments, generating atrial wall thickness (AWT) maps per segment for each patient. Results: This study demonstrated considerable variability in the average thickness of LA walls, with the anterior segments being the thickest across the cohort. Distinct sex-specific differences were observed, with males exhibiting greater anterior and septal wall thickness than females. No significant associations were identified between the average AWT and body mass index, LA volume, or sphericity. Survival analysis conducted over 24 months revealed a meaningful relationship between mean anterior wall thickness and recurrence-free survival, with increased thickness associated with a lower likelihood of AF-free survival. No such relationship was observed for the indexed LA volume. Conclusions: The variability in AWT and its association with recurrence-free survival following AF ablation suggest that AWT should be considered when stratifying patients for AF management and ablation strategies. These findings underscore the need for personalised treatment approaches and further research on the interplay of the structural properties of the left atrium as factors that can serve as important prognostic markers in AF treatment.

Keywords: atrial fibrillation; atrial remodelling; atrial wall thickness; catheter ablation; ganglionated plexi; left atrium; multi-detector computed tomography; personalised treatment; recurrence-free survival; substrate.

Figure 1

Software reconstruction using multidetector computed tomography images and analysis using ADAS 3D™ software generated a 3D map of the atrial wall thickness. Thickness colour map: thickness <1 mm, red; 1–2 mm, yellow; 2–3 mm, green; 3–4 mm, blue; >4 mm, purple.

Figure 2

Schematic illustration of 14 locations where the wall thickness was measured in the left atrium. Posterior (left panel), anterior (middle panel), and left lateral views (right panel) are presented. Legend: Segments 1–4, superior wall; 5–6, posterior wall; 7, septal wall; 8–11, anterior wall; 12, left lateral wall; and 13–14, between superior and inferior pulmonary veins. LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MITRAL, mitral annulus; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein.

Figure 3

Example of LA wall thickness measurement (posterior view). The bar on the right shows the colour code assigned to the thickness variations.

Figure 4

Boxplot of left atrial wall thickness distribution according to region.

Figure 5

Box plot with comparison by sex of the left atrial volume index to the body surface. Legend: LAVI, left atrial volume index; SD, standard deviation.

Figure 6

Mean left atrial wall thickness by region.

Figure 7

Illustration of the 14 locations in the left atrium and corresponding topographic colour maps showing thickness differences. Posterior and anterior views (A,B), right anterior oblique view (C), and left lateral view (D) are shown. Legend: LIPV, left inferior pulmonary vein; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein; MITRAL, mitral annulus; LAA, left atrial appendage ostium.

Figure 8

Log-rank test estimates of recurrence-free survival according to mean anterior wall thickness (optimal cutpoint → 1.69 mm).

Figure 9

Survival curve estimates of arrhythmia recurrence-free survival according to left atrial index volume. Legend: The optimal cut-off point obtained by maximising the sum of sensitivity and specificity was 58.6 mL/m².

Figure 10

Illustration of left anterior wall thickness in different patients. The areas with the highest thickness corresponded to the Bachmann bundle region. Legend: LIPV = left inferior pulmonary vein, LSPV = left superior pulmonary vein, RIPV = right inferior pulmonary vein, RSPV = right superior pulmonary vein, MITRAL = mitral annulus, LAA = left atrial appendage ostium.