Measurement of left atrial volume by 2D and 3D non-contrast computed tomography compared with cardiac magnetic resonance imaging

Background: Cardiac magnetic resonance imaging (MRI) is considered the gold standard for assessment of left atrial (LA) volume. We assessed the feasibility of evaluating LA volume using 3D non-contrast computed tomography (NCCT). Furthermore, since manual tracing of LA volume is time consuming, we evaluated the accuracy of the LA area using 2D NCCT imaging for LA volume assessment. Methods: MRI and NCCT imaging were performed in 69 patients before and one year after aortic valve replacement. In 3D MRI and 3D NCCT, each slice was manually traced, excluding the pulmonary veins and atrial appendage, and multiplied by slice spacing, thus generating a measure of LA volume. The LA volume was indexed to body surface area. On 2D NCCT, the largest axial cross-section LA area was traced manually. Results: The mean LA volume was 102 ± 28 ml in MRI compared with 103 ± 28 ml in 3D NCCT. 3D NCCT showed good agreement with MRI measurements (mean difference −0.7 ml/m²; 95% confidence interval (CI) −2.2 to 0.9). By Bland-Altman, 3D NCCT also showed good agreement with MRI (limits of agreement: −18.7–17.4 ml/m²). Furthermore, good correlation was found between 2D NCCT and 3D NCCT LA volume (r = 0.93). Conclusion: 2D and 3D measurements of LA volume in non-contrast computed tomography are feasible and accurate.