Standardised computed tomographic assessment of left atrial morphology and tissue thickness in humans

Abstract

Aims: Left atrial (LA) remodelling is a common feature of many cardiovascular pathologies and is a sensitive marker of adverse cardiovascular outcomes. The aim of this study was to establish normal ranges for LA parameters derived from coronary computed tomographic angiography (CCTA) imaging using a standardised image processing pipeline to establish normal ranges in a previously described cohort.

Methods: CCTA imaging from 193 subjects recruited to the Budapest GLOBAL twin study was analysed. Indexed LA cavity volume (LACV_i), LA surface area (LASA_i), wall thickness and LA tissue volume (LATV_i) were calculated. Wall thickness maps were combined into an atlas. Indexed LA parameters were compared with clinical variables to identify early markers of pathological remodelling.

Results: LACV_i is similar between sexes (31 ml/m² v 30 ml/m²) and increased in hypertension (33 ml/m² v 29 ml/m², p = 0.009). LASA_i is greater in females than males (47.8 ml/m² v 45.8 ml/m² male, p = 0.031). Median LAWT was 1.45 mm. LAWT was lowest at the inferior portion of the posterior LA wall (1.14 mm) and greatest in the septum (median = 2.0 mm) (p < 0.001). Conditions known to predispose to the development of AF were not associated with differences in tissue thickness.

Conclusions: The reported LACV_i, LASA_i, LATV_i and tissue thickness derived from CCTA may serve as reference values for this age group and clinical characteristics for future studies. Increased LASA_i in females in the absence of differences in LACV_i or LATV_i may indicate differential LA shape changes between the sexes. AF predisposing conditions, other than sex, were not associated with detectable changes in LAWT.Clinical trial registration:http://www.ClinicalTrials.gov/NCT01738828.

Keywords: AF, atrial fibrillation; BSA, body surface area; CCTA, cardiac computed tomography; Computed tomography (CT); DZ, dizygotic; LA, left atrium; LAA, left atrial appendage; LACV, left atrial cavity volume; LASA, left atrial surface area; LATV, left atrial tissue volume; LAWT, left atrial wall thickness; Left atrium; MZ, monozygotic; PV, pulmonary vein; Tissue thickness.

Fig. 1

Standardization of identification of pulmonary vein ostia prior to removal from atrial wall mesh. Panel A: Posterior-anterior view of semi-transparent segmentation of left atrium with vessels and appendage attached. Seeds dropped at the left atrial appendage (LAA), left superior pulmonary vein (LSPV), left inferior pulmonary vein (LIPV), right superior pulmonary vein (RSPV) and right inferior pulmonary vein (RIPV) are used to calculate centre line to centre of mass of segmentation (red lines). Discs (yellow) identify position along centre line corresponding to criteria used to identify PV/LAA ostia. Panel B: Same segmentation as panel A, yellow discs indicate position along centre line identified as ostia of vessels. Panel C: Anterior-posterior view of mesh generated from segmentation after standardized cropping of pulmonary veins and LAA. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Atlas generated from atrial wall thickness measurements. Panel A: Anterior view of left atrium showing increased tissue thickness measurements in the septum. Panel B: Posterior view of the left atrium, in which increased tissue thickness measurements are seen in the superior aspect compared to the inferior aspect.

Fig. 3

Comparison of CT derived left atrial parameters between female and male subjects.