The Left Atrio-Vertebral Ratio: a new simple means for assessing left atrial enlargement on Computed Tomography.

ABSTRACT

OBJECTIVE: The purpose of this study is to describe a new method to quickly estimate left atrial enlargement (LAE) on Computed Tomography. METHODS: Left atrial (LA) volume was assessed with a 3D-threshold Hounsfield unit detection technique, including left atrial appendage and excluding pulmonary venous confluence, in 201 patients with ECG-gated 128-slice dual-source CT and indexed to body surface area. LA and vertebral axial diameter and area were measured at the bottom level of the right inferior pulmonary vein ostium. Ratio of LA diameter and surface on vertebra (LAVD and LAVA) were compared to LA volume. In accordance with the literature, a cutoff value of 78 ml/m2 was chosen for maximal normal LA volume. RESULTS: 18% of LA was enlarged. The best cutoff values for LAE assessment were 2.5 for LAVD (AUC 0.65; 95% CI 0.58-0.73; sensitivity 57%; specificity 71%), and 3 for LAVA (AUC 0.78; 95% CI 0.72-0.84; sensitivity 67%; specificity 79%), with higher accuracy for LAVA (P=0.015). Inter-observer and intra-observer variability were either good or excellent for LAVD and LAVA (respective intraclass coefficients 0.792 and 0.910; 0.912 and 0.937). CONCLUSION: A left atrium area superior to three times the vertebral area indicates LAE with high specificity. KEY POINTS • Left atrial enlargement is a frequent condition associated with poor cardiac outcome. • Left atrial enlargement is highly time-consuming to diagnose on CT. • The left atrio-vertebral ratio quickly assesses left atrial enlargement. • A left atrial area > three times vertebral area is highly specific.