Determination of left atrial (LA) size is important in clinical decision-making. The LA anteroposterior dimension (APD) has been routinely reported as LA size assessment. Early studies indicated that the APD may have limited accuracy in quantification. Conventional 3-dimensional reconstruction (C3DR) of the LA has been validated. However, its process is time-consuming and not applicable for daily practice. To explore an accurate and practical approach, we compared different echocardiographic measurements with C3DR in 141 patients with different LA sizes.

LA size was measured with (1) the cubic equation with APD (Cub); (2) the ellipsoidal formula (Ellp); (3) biplane modified Simpson rule (biplane); and (4) simplified 3-dimensional reconstruction from 3 standard apical views with B spline interpolation (S3VR). All four methods were compared with C3DR. S3VR and biplane methods provided a close agreement to C3DR (y = 0.94x + 3.6, r = 0.95, SEE = 7.6 mL, mean difference = −1.3% for S3VR; y = 0.87x + 2.9, r = 0.91, SEE = 9.0 mL, mean difference = −9.4% for biplane). The Cub and Ellp calculations were less accurate, with significant volume underestimation (P < .001).

LA single dimension is not accurate for LA size measurement. Among four different methods of LA size measurement, biplane and S3VR provide the closest agreement to C3DR. The biplane, which is readily applicable with current echocardiographic equipment, should be routinely applied in clinical practice.