Evaluation of left atrial volumes using multidetector computed tomography: comparison with echocardiography

Abstract

Objective: To prospectively assess the relationship between the two different measurement methods for the evaluation of left atrial (LA) volume using cardiac multidetector computed tomography (MDCT) and to compare the results between cardiac MDCT and echocardiography.

Materials and methods: Thirty-five patients (20 men, 15 women; mean age, 60 years) underwent cardiac MDCT angiography for coronary artery disease. The LA volumes were measured using two different methods: the two dimensional (2D) length-based (LB) method measured along the three-orthogonal planes of the LA and the 3D volumetric threshold-based (VTB) method measured according to the threshold 3D segmentation of the LA. The results obtained by cardiac MDCT were compared with those obtained by echocardiography.

Results: The LA end-systolic and end-diastolic volumes (LAESV and LAEDV) measured by the 2D-LB method correlated well with those measured by the 3D-VTB method using cardiac MDCT (r = 0.763, r = 0.786, p = 0.001). However, there was a significant difference in the LAESVs between the two measurement methods using cardiac MDCT (p < 0.05). The LAESV measured by cardiac MDCT correlated well with measurements by echocardiography (r = 0.864, p = 0.001), however with a significant difference (p < 0.01) in their volumes. The cardiac MDCT overestimated the LAESV by 22% compared to measurements by echocardiography.

Conclusion: A significant correlation was found between the two different measurement methods for evaluating LA volumes by cardiac MDCT. Further, cardiac MDCT correlates well with echocardiography in evaluating the LA volume. However, there are significant differences in the LAESV between the two measurement methods using cardiac MDCT and between cardiac MDCT and echocardiography.

Keywords: 2D and 3D measurements; Echocardiography; Left atrial volume; Multidetector computed tomography; Simpson method.

Fig. 1

Measurement of left atrial size using 2D length-based method of cardiac multidetector CT. A. Oblique axial image of left atrium. Transverse diameter of left atrium was measured at distance between right and left pulmonary veins. Anterior-posterior diameter of left atrium was measured at midpoint of transverse diameter. B. Sagittal view of left atrium. Longitudinal diameter of left atrium was measured at midpoint of transverse diameter.

Fig. 2

Measurement of left atrial volume using 3D volume threshold-based method of cardiac multidetector CT. A-C. Axial, sagittal, and coronal views of left atrium. Endocardial contours of left atrium were traced on axial slices. Lowest value of CT attenuation was applied to cover contrast-enhanced whole left atrial cavity within region of interest. Included left atrial volume was confirmed by CT attenuation in three-orthogonal planes. D. Volume-rendering threshold image of left atrium. Pulmonary vein confluences and atrial appendage were excluded from left atrial volume measurement.

Fig. 3

Measurement of left atrial volume using modified biplane Simpson's rule method by echocardiography. A, B. Apical four-chamber and apical two-chamber views at ventricular end-systole for measurement of maximum left atrial volume.

Fig. 4

Bland-Altman plots for determining left atrial volumes and function between two measurement methods of cardiac multidetector CT. A-C. Plots show relationships between 2D length-based method (2D LBM) and 3D volumetric threshold-based method (3D VTBM) of cardiac multidetector CT for measurement of left atrial end-systolic volume (A), left atrial end-diastolic volume (B), and left atrial ejection fraction (C). Mean differences (y-axes) between each pair ([mean 2D LBM] - [mean 3D VTBM]) are plotted against average values (x-axes) of same pair ([{mean 2D LBM} + {mean 3D VTBM}]/2). The mean differences between the two measurement methods by cardiac multidetector CT were significant for left atrial end-systolic volume and left atrial ejection fraction (p < 0.05), but not for left atrial end-diastolic volume (p > 0.05). LAESV = left atrial end-systolic volume, LAEDV = left atrial end-diastolic volume, LAEF = left atrial ejection fraction

Fig. 5

Linear regression analysis and Bland-Altman plots for left atrial end-systolic volume between cardiac multidetector CT and echocardiography. LAESV = left atrial end-systolic volume, ECHO = echocardiography A. Left atrial end-systolic volumes were plotted by linear regression for cardiac multidetector CT with 3D volumetric threshold-based method (3D VTBM) and echocardiography. Slope, correlation coefficient, and p value were 0.949, 0.864, and less than 0.001 (Y = 20.536 + 0.949X, r = 0.864), respectively. B. Bland-Altman plots showing relationship between cardiac multidetector CT with 3D volumetric threshold-based method and echocardiography with modified biplane Simpson's method (MBSM) for left atrial end-systolic volume. Mean differences (y-axes) between each pair ([mean 3D VTBM] - [mean MBSM]) are plotted against average values (x-axes) of same pair ([{mean 3D VTBM} + {mean MBSM}]/2). Results showed that echocardiography underestimated left atrial end-systolic volume by 22% compared to cardiac multidetector CT (p < 0.05).