Geometric Errors of the Pulsed-Wave Doppler Flow Method in Quantifying Degenerative Mitral Valve Regurgitation: A Three-Dimensional Echocardiography Study

Abstract

The aim of this study was to estimate geometric errors made by the two-dimensional (2D) transthoracic echocardiographic (TTE) pulsed-wave Doppler flow (PWDF) method in calculating regurgitant volume (RVol) and effective regurgitant orifice area (EROA) in degenerative mitral regurgitation (MR) by comparison with the three-dimensional (3D) transesophageal echocardiographic (TEE) PWDF method. RVol and EROA were calculated in 22 patients with degenerative MR using the conventional 2D TTE PWDF method on the basis of monoplanar dimensions and a circular geometric assumption of the cross-sectional areas (CSAs) of the mitral annulus (MA) and the left ventricular outflow tract (LVOT) and the 3D TEE PWDF method, in which the CSAs of the MA and LVOT were measured directly in "en face" views. Diameters of the MA and LVOT were also measured in similar views as with TTE imaging in 3D TEE data sets. Both the MA and LVOT were oval. Mean MA diameters were 41 ± 4 mm (3D TEE major axis), 31 ± 4 mm (3D TEE minor axis), 39 ± 5 mm (2D TTE imaging), and 38 ± 5 mm (2D TEE imaging). Mean LVOT diameters were 29 ± 4 mm (3D TEE major axis), 21 ± 2 mm (3D TEE minor axis), 22 ± 2 mm (2D TTE imaging), and 23 ± 2 mm (2D TEE imaging). Compared with 3D TEE measurements, mitral annular CSA was overestimated by 13 ± 12% on 2D TTE imaging and by 7 ± 14% on 2D TEE imaging, while LVOT CSA was underestimated by 23 ± 10% and 17 ± 10%, respectively. Mean values of RVol were 95 ± 43 mL (3D TEE PWDF), 137 ± 56 mL (2D TTE PWDF), 120 ± 45 mL (2D TEE PWDF), and 111 ± 49 mL (flow convergence). Mean EROAs were 69 ± 34 mm2 (3D TEE PWDF), 98 ± 45 mm2 (2D TTE PWDF), 88 ± 42 mm2 (2D TEE PWDF), and 79 ± 36 mm2 (flow convergence). Observer variability for 3D TEE imaging was better than for 2D imaging. The 2D TTE PWDF method overestimates mitral RVol and EROA significantly because monoplanar 2D measurements represent mitral annular major-axis diameter and LVOT minor-axis diameter, and assumed circular CSAs of the MA and LVOT are oval.