Normal left atrial function determined by 2-dimensional echocardiography.

To obtain normal values for left atrial function noninvasively, volumes of the left atrium and ventricle were calculated in 52 volunteers by 2-dimensional echocardiography. A light pen digitizing and computation system, controlled by a microprocessor, was used to outline the left atrium and ventricle in orthogonal apical views. Then, to calculate end-systolic and end-diastolic atrial and ventricular volumes, a modified Simpson's rule formula was used. End-systolic left atrial volume (mean +/- standard deviation) was 37 +/- 11.7 ml or 21 +/- 6.6 ml/m2. The change in left atrial volume from end-systole to end-diastole was 24 +/- 7.6 ml or 13.5 +/- 4.3 ml/m2, which represented 37 +/- 12.9% of left ventricular stroke volume. The mean fractional emptying of the left atrium was 65 +/- 8.9% and the conduit volume was 41 +/- 14.0 ml or 23 +/- 7.9 ml/m2. These values are similar to those reported in studies in which left atrial function was calculated from contrast angiography.