Automated border detection (ABD) echocardiography is a convenient and objective tool in the estimation of left atrial (LA) area and function when compared to the off-line, two-dimensional echocardiographic method that requires manual tracing of the endocardial border. In addition, the applicability of the ABD system to instantaneously derive LA area and function may provide a noninvasive method to assess the diastolic interaction between the left ventricle and the left atrium.

53 patients with a normal sinus rhythm and an apical four chamber view of LA area (in which at least 75% of the endocardium was clearly visible) were selected for this study. The on-line echocardiographic assessment of LA areas and function with automated boundary detection was performed and compared with the off-line estimation. From the instantaneous cavity area displayed by the ABD system, the extents of left atrial area decrease resulting from rapid ventricular filling (D) and atrial contraction (AC) were measured. The D/AC ratio was compared with the transmitral Doppler flow velocity E/A ratio.

1) The end-systolic area (ESA) and the end-diastolic area (EDA) of the left atrium, diastolic atrial emptying index (AEMI) and the systolic atrial expansion index (AEXI) with the ABD system were not different from those with the off-line, manually trace method. 2) ESA, EDA, AEMI and AEXI determined by the ABD system and the off-line method showed strong correlations (r=0.87, 0.79, 0.52 and 0.49 respectively). 3) D/AC ratio with the ABD system correlated significantly with the transmitral Doppler velocity E/A ratio (r=0.70).

The ABD system may be used in the assessment of LA area and LA function and the diastolic interaction between the left atrium and the left ventricle.