Assessment of left atrial volume and function by real-time three-dimensional echocardiography

Background: Determination of left atrial (LA) size and function is important in clinical decision-making. Calculation of LA volume (LAV) is the most accurate index of LA size. Aim: To compare real-time 3-dimensional echocardiography (RT3DE) and 2-dimensional echocardiography (2DE) for calculation of LAV and function. Methods: Fifty patients were studied using 2DE and RT3DE for calculating LAV including: Maximum (V max), minimum (V min) and pre-atrial contraction (V pre A) volumes. For 2DE, the formula: LAV = 8(A1) (A2)/3π (L) was used, while for RT3DE, offline analysis was performed using commercially available software. LA function indices including Total Atrial Stroke Volume (TASV), active ASV (AASV), Total Atrial Emptying Fraction (TAEF), active AEF (AAEF), passive AEF (PAEF), and Atrial Expansion Index (AEI) were calculated. Results: Patients were classified into 2 equal groups: group I with normal V max (< 50 ml) and group II with V max (≥ 50 ml). Good correlation was obtained between RT3DE and 2DE for LAV (r = 0.64, p = 0.001) in group I and (r = 0.83, p < 0.0001) in group II. In group I, LAV and functions showed no significant difference by both techniques, while in group II, the V min and V pre A were significantly lower by RT3DE than 2DE (p = 0.009, 0.006). TAEF, AEI, and PAEF indices were significantly higher by RT3DE than 2DE in group II. Conclusion: RT3DE provides a reproducible assessment of active and passive LA function by volumetric cyclic changes. It is comparable and may be superior to 2DE due to its higher sensitivity to volume changes.