RESUMO
PURPOSE: The purpose of this study was to do better than the simple maximal axial area (MAreaax) and to validate simple, fast and robust orthogonal methods for determining the left atrium volume (LAV) with cardiac CT (CCT). MATERIAL AND METHODS: A total of 60 patients who underwent CTT were retrospectively included. There were 30 men and 30 women with a mean age of 59±12 (SD) years (range: 27-80 years), using four methods to assess LAV beyond the MAreaax: two orthogonal methods requiring the measurements of axial, coronal and sagittal planes of 3 diameters LAV3diam or 3 area LAV3Areas; Area-length biplane method LAVbiplane; and volumetric method LAVvolumetric using a semi-automated tool that served as the reference standard. The orthogonal methods were applied on contrast-enhanced (IV+) and unenhanced (IV-) CCT images. Comparisons were performed using Pearson correlation test (r) and Bland-Altman analysis. Inter- and intra-observer variability were assessed using intraclass correlation coefficient (ICC) with a two-way mixed-effects model. RESULTS: On IV+ CCT, LAVbiplane, LAV3diam-IV+, LAV3Areas-IV+ underestimated LAV (-15±1.99mL; -21±1.37mL; -15±1.98mL; all P<0.001). LAV3diam-IV+, LAV3Areas-IV+ better correlated with reference standard (r=0.97 and 0.98) than LAVbiplane (r=0.79) as well as MAreaax (r=0.90). Estimating LAV on IV- further showed high correlation against the reference (r=0.93 and 0.95 for LAV3diam-IV- and LAV3Areass-IV-, respectively). Intra- and inter-observer ICC increased from LAVvolumetric (2.43% and 3.09%); LAV3Areas-IV+ (3.04 and 3.30%); LAV3Areas-IV-(3.34 and 4.23%), LAV3diam-IV+ (3.36 and 5.11%); LAV3diam-IV- (5.16 and 6.90%); to LAVbiplane (9.65 and 10.28%). CONCLUSIONS: Better than MAreaax, orthogonal methods using either diameter or surface are fast and reproducible methods to assess LAV on CCT when performed with or without intravenous administration of contrast material.
