Left Atrial Volumes Assessed by Three- and Two-dimensional Echocardiography Compared to MRI Estimates

Objectives: The aim of the present study was to establish the accuracy and reproducibility of left atrial volume measurements by three-dimensional (3D) echocardiography compared to 2D biplane and monoplane measurements.

Background: No echocardiographic technique is generally accepted as optimal for estimation of left atrial size.

Methods: Left atrial volumes of 18 unselected cardiac patients were obtained with magnetic resonance imaging (MRI) (volumes 145 +/- 58 ml). These volumes were compared with those obtained with different echocardiographic methods: a multiplane 3D method based on 90 images acquired by apical probe rotation, a simplified 3D method using only the three standard apical views, and 2D biplane and monoplane methods based on area-length, disc summation and spherical formulas.

Results: The echocardiographic methods significantly underestimated maximum left atrial volumes as obtained by MRI by 14-37% (p < 0.001). Accuracy, expressed as 1 SD of individual estimates around this systematic underestimation, was 25 to 27% for all methods, except for the 2D 2-chamber monoplane method (37%). Interobserver coefficient of variation was between 14 and 20% for all methods (n.s.).

Conclusion: All echocardiographic methods significantly underestimated left atrial volumes as obtained by MRI. A minor non-significant improvement in individual echocardiographic estimates by the 3D methods was obtained at the cost of more time consumption. In unselected patients ultrasound image quality precludes significant improvement of left atrial volume measurements by the applied 3D methods.