Comparison of echocardiographic single-plane versus biplane method in the assessment of left atrial volume and validation by real time three-dimensional echocardiography.

BACKGROUND The American Society of Echocardiography recommends calculating left atrial (LA) biplane volume because of its greater accuracy and prognostic value over LA diameter. However, biplane methods are not always feasible. The aim of this study was to assess the correlation between the echocardiographic LA biplane and single-plane volumes and their agreement in the classification of LA size when American Society of Echocardiography cutoffs are applied. METHODS Two-dimensional echocardiography was performed on the participants of the population-based Cardiovascular Abnormalities and Brain Lesions study. LA volume was calculated by the biplane area-length and single-plane modified Simpson's methods and validated against three-dimensional echocardiography. RESULTS The study sample consisted of 527 participants (mean age 69.6 +/- 9.7 years; 61.9% women). Both single-plane and biplane LA volumes correlated well with three-dimensional echocardiography (r = 0.93, P < .001). The correlation between the single-plane and biplane methods was excellent (r = 0.95, P < .001; intraclass correlation coefficient, 0.92; 95% confidence interval, 0.80-0.96). Categorical agreement between the single-plane and biplane methods was modest (kappa = 0.51; 95% confidence interval, 0.45-0.57; disagreement rate, 26.0%), mainly because of overestimation by the single-plane method. The correction of the single-plane volume by a regression equation improved the agreement (kappa = 0.70; 95% confidence interval, 0.64-0.76), but misclassifications remained in 14.0% of cases. CONCLUSIONS Single-plane and biplane LA volume measurements have strong correlations, but their agreement for categorical classification is suboptimal. Specific cutoff points should be developed for the single-plane method.