Variations of the ellipsoid method in estimating three-dimensional echocardiographic left atrial volume in dogs with myxomatous mitral valve disease: comparison with left atrial-to-aortic root ratios and planar volumetric methods.

INTRODUCTION/

OBJECTIVES

The ellipsoid method estimates left atrial (LA) volume using only linear diameters and may offer a practical volumetric alternative to the left atrial-to-aortic root ratio (LA/Ao). The aim of this study was to compare variations of the ellipsoid model with LA/Ao and planar volumetric methods, using real-time three-dimensional echocardiography (RT3D) as the reference standard.

ANIMALS, MATERIALS, AND

METHODS

Seventy dogs with myxomatous mitral valve disease (43 stage B1, 17 stage B2, and 10 stages C/D) were prospectively imaged; 32 (17 stage B1, 10 stage B2, and five stages C/D) were re-imaged by another sonographer. In addition to long-axis and short-axis LA/Ao, body weight-indexed maximal LA volumes obtained using the spherical (right parasternal and left apical), monoplane ellipsoid (right parasternal and left apical), biplane ellipsoid, monoplane area-length and Simpson's method of discs (right parasternal and left apical), biplane area-length method and Simpson's method of discs, and real-time triplane methods were compared to those of RT3D.

RESULTS

The LA/Ao methods showed the lowest correlation (Spearman's coefficient [rs] < 0.800). Based on concordance correlation coefficients (rc), the monoplane ellipsoid (right parasternal: rc = 0.901, left apical: rc = 0.924), biplane ellipsoid (rc = 0.947), biplane area-length (rc = 0.921), biplane Simpson's method of discs (rc = 0.947), and real-time triplane (rc = 0.972) volumetric methods demonstrated at least moderate agreement. However, only the left apical monoplane ellipsoid method exhibited no systematic bias (median of the differences [95% confidence interval]: 0.00 [-0.10 to 0.07]).

STUDY LIMITATIONS: Reproducibility was assessed against a novice observer or measurer who was not involved in image acquisition.

CONCLUSION

The left apical monoplane ellipsoid method provides an effective linear option for estimating RT3D-derived maximum LA volume.