Aim: Two-dimensional echocardiography may not correctly indicate size in nonspherical atria. The present study compares different parameters of left atrial size evaluated by standard two-dimensional echocardiography with left atrial volume measured using three-dimensional echocardiography (3DE).

Methods and results: One hundred seventy consecutive patients with a history of atrial arrhythmias were studied by standard two-dimensional and by real time 3DE. Of these 166 (98%) recordings were of sufficient quality for interpretation by both imaging techniques. The following parameters of left atrial size were measured: parasternal long axis diameter (PLAX), apical 4-chamber short-axis diameter (4CH short axis), apical 4-chamber (4CH long axis), and 2-chamber long-axis diameters and planimetry areas. Two-dimensional-derived left atrial volumes were calculated by using both single plane (4CH area-length) and biplane area-length methods. The 2D parameters were then correlated with left atrial volume measured by 3D echocardiography. Linear regression analysis showed moderate correlation for 4-chamber planimetry area (r = 0.76, P < 0.0001) and 2D-derived volume calculations (r of 4CH single plane area-length LA volume = 0.74 and biplane area-length LA volume = 0.78, P < 0.0001). Diameters correlated less well with 3DE volume (r of PLAX = 0.67, 4CH short axis = 0.68, 4CH long axis = 0.63, P < 0.0001 respectively).

Conclusion: The results demonstrate that measurements of dimensions using standard echocardiography are of limited accuracy to assess left atrial volume. If 3DE is not available, 4-chamber planimetry area is a valid simple parameter for evaluating left atrial size in clinical practice. Two-dimensional-derived volume by biplane area-length method was only slightly better correlated with 3DE volume than 4-chamber planimetry area.