Comparison of left atrial size by freehand scanning three-dimensional echocardiography and two-dimensional echocardiography.

Aims: As the left ventricular (LV) dimension is a poor indicator of LV volume, there are well-known limitations of left atrial (LA) antero-posterior dimensions as indicators of chamber size. LA volume has been shown to provide a more accurate assessment of LA size than LA dimension. To evaluate two-dimensional (2D)-derived LA volume in assessing LA size, we compared LA dimension and 2D LA volume with three-dimensional (3D)-derived LA volume.

Methods: We performed transthoracic freehand scanning 3D echocardiography (3D EchoTech, Germany) using magnetic fields and a harmonic imaging system in 32 patients. We collected a series of LA tomograms by slowly tilting the probe (fan-like scanning) in the parasternal position. The 3D LA volume was calculated by using the multiplanar Simpson's method. The 2D LA volume was measured by using the modified biplane Simpson's rule.

Results: LA antero-posterior dimensions and 2D volumes showed a significant positive correlation with 3D LA volumes. However, the correlation coefficient was significantly greater for the relationship between 2D LA volumes and 3D LA volumes than for that between LA dimensions and 3D LA volume.

Conclusions: The 2D LA volumes provide a more accurate measure of the true size of the LA and are more sensitive to changes in LA size.