Photon-counting ct evaluation of regional wall thickness and epicardial fat distribution in the left atrium

Achieving sufficient ablation lesions can be challenging, and it has long been suspected that wall thickness plays a significant role in this process, along with the potential influence of epicardial fat. Traditional imaging techniques with a high spatial resolution often lack the resolution necessary for accurate assessment of these anatomical features. The advent of Photon-Counting Computed Tomography (CT) enhances imaging capabilities, allowing for precise evaluation of wall thickness and epicardial fat distribution.

The purpose of this study was to characterize wall thickness and epicardial fat of different regions in the LA with a photon-counting CT.

High-resolution photon-counting CT was performed pre-interventionally in 50 patients undergoing AF ablation as part of a prospective study. After processing the CT scans with the 3D segmentation software to measure wall thickness and epicardial fat thickness, the left atrium was segmented into six regions (anterior, roof, posterior, inferior, lateral, septal) using the Paraview 5.12.0 visualization program. For each region, the mean, median, and standard deviation of wall thickness and epicardial fat were calculated.

The mean wall thickness (± standard deviation) and median with interquartile range (Q1–Q3) were observed in each region of the left atrium as follows: anterior: mean 1.79 ± 0.26 mm, median 1.80 [1.56–1.93] mm; roof: mean 1.58 ± 0.31 mm, median 1.55 [1.34–1.78] mm; posterior: mean 1.79 ± 0.32 mm, median 1.78 [1.57–2.08] mm; inferior: mean 1.74 ± 0.36 mm, median 1.69 [1.50–2.03] mm; lateral: mean 1.76 ± 0.36 mm, median 1.75 [1.51–1.97] mm; and septal: mean 1.81 ± 0.27 mm, median 1.77 [1.65–2.04] mm.

Epicardial fat thickness showed notable regional variability, with mean (± standard deviation) and median with interquartile range as follows: anterior: mean 2.25 ± 0.88 mm, median 2.12 [1.64–2.84] mm; roof: mean 1.94 ± 1.23 mm, median 3.05 [0.93–2.89] mm; posterior: mean 0.23 ± 0.25 mm, median 0.12 [0.03–0.39] mm; inferior: mean 1.34 ± 0.88 mm, median 1.36 [0.67–1.95] mm; and lateral: mean 2.56 ± 1.17 mm, median 2.42 [1.82–3.15] mm.

This study provides a comprehensive evaluation of regional wall thickness and epicardial fat distribution in the left atrium using high-resolution photon-counting CT. Wall thickness is homogeneous within individual patients but shows significant heterogeneity between patients, highlighting the need for high-resolution imaging for accurate assessment. In contrast, epicardial fat distribution is highly heterogeneous within individual patients, particularly in the posterior region. These findings emphasize the importance of considering both regional variations in wall thickness and fat distribution when planning ablation strategies for atrial fibrillation, potentially improving procedural outcomes and patient management.

segmented regions,wall thickness,epi fat