Echocardiographic measurement of left atrial volume: Does the method matter?

Four two-dimensional echocardiographic methods (cube, ellipsoid, Simpson's and area-length) can be used to assess left atrial volume (LAV).

To compare absolute LAV measurements and evaluate agreement regarding the semiquantitative assessment of degree of left atrial (LA) enlargement, between methods.

We prospectively measured LAV in 51 healthy volunteers using the four methods, and defined thresholds for moderate (mean+2 standard deviations [SDs]) and severe (mean+4 SDs) LA enlargement for each method. In 372 patients referred for echocardiography, we compared absolute LAV measurements and agreement between methods.

LAV was significantly different between methods in the healthy volunteer group (11 ± 4, 17 ± 3, 26 ± 6 and 28 ± 7 mL/m(2), respectively; P<0.0001), resulting in different thresholds for moderate and severe LA enlargement. LAV was also significantly different in the 372 patients (30 ± 20, 47 ± 27, 61 ± 34 and 65 ± 36 mL/m(2), respectively; P<0.0001). Agreement regarding degree of LA enlargement (none, moderate, severe), using the area-length method as reference, was modest with the cube method (kappa=0.41), correct with the ellipsoid method (kappa=0.60) and excellent with Simpson's method (kappa=0.83).

The choice of the method had a major effect on assessment of degree of LA enlargement. Our results suggest that the cube and ellipsoid methods, which significantly underestimated LAV and provided modest agreement, should be disregarded. In contrast, Simpson's method and the area-length method were slightly different, but showed close agreement, and should be preferred, using dedicated thresholds (50 and 56 mL/m(2) respectively).