Validation of Left Atrial Volume Estimation by Left Atrial Diameter from the Parasternal Long-Axis View

Measurement of left atrial (LA) volume (LAV) is recommended for quantification of LA size. Only LA anteroposterior diameter (LAd) is available in a number of large cohorts, trials, or registries. The aim of this study was to evaluate whether LAV may be reasonably estimated from LAd.

One hundred forty consecutive patients referred to our outpatient clinics were prospectively enrolled to measure LAd from the long-axis view on two-dimensional echocardiography. LA orthogonal dimensions were also taken from apical four- and two-chamber views. LAV was measured using the Simpson, area-length, and ellipsoid (LAV_e) methods. The first 70 patients were the learning series and the last 70 the testing series (TeS). In the learning series, best-fitting regression analysis of LAV-LAd was run using all LAV methods, and the highest values of F were chosen among the regression equations. In the TeS, the best-fitting regressions were used to estimate LAV from LAd.

In the learning series, the best-fitting regression was linear for the Spearman method (r² = 0.62, F = 111.85, P = .0001) and area-length method (r² = 0.62, F = 112.24, P = .0001) and powered for the LAV_e method (r² = 0.81, F = 288.41, P = .0001). In the TeS, the r² value for LAV prediction was substantially better using the LAV_e method (r² = 0.89) than the Simpson (r² = 0.72) or area-length (r² = 0.70) method, as was the intraclass correlation (ρ = 0.96 vs ρ = 0.89 and ρ = 0.89, respectively). In the TeS, the sensitivity and specificity of LA dilatation by the estimated LAV_e method were 87% and 90%, respectively.

LAV can be estimated from LAd using a nonlinear equation with an elliptical model. The proposed method may be used in retrospective analysis of existing data sets in which determination of LAV was not programmed.