Proximal Flow Convergence Method by Three-Dimensional Color Doppler Echocardiography for Mitral Valve Area Assessment in Rheumatic Mitral Stenosis

Background: The two-dimensional (2D) proximal isovelocity surface area (PISA) method has important technical limitations for mitral valve orifice area (MVA) assessment in mitral stenosis (MS), mainly the geometric assumptions of PISA shape and the requirement of an angle correction factor. Single-beat real-time three-dimensional (3D) color Doppler imaging allows the direct measurement of PISA without geometric assumptions or the requirement of an angle correction factor. The aim of this study was to validate this method in patients with rheumatic MS. Methods: Sixty-three consecutive patients with rheumatic MS were included. MVA was assessed using the transthoracic 2D and 3D PISA methods. Planimetry of MVA (2D and 3D) and the pressure half-time method were used as reference methods. Results: The 3D PISA method had better correlations with the reference methods (with 2D planimetry, r = 0.85, P<.001; with 3D planimetry, r = 0.89, P<.001; and with pressure half-time, r = 0.85, P<.001) than the conventional 2D PISA method (with 2D planimetry, r = 0.63, P<.001; with 3D planimetry, r = 0.66, P<.001; and with pressure half-time, r = 0.68, P<.001). In addition, a consistent significant underestimation of MVA using the conventional 2D PISA method was observed. A high percentage (30%) of patients with nonsevere MS by 3D planimetry were misclassified by the 2D PISA method as having severe MS (effective regurgitant orifice area <1 cm(2)). In contrast, the 3D PISA method had 94% agreement with 3D planimetry. Good intra-and interobserver agreement for 3D PISA measurements were observed, with intraclass correlation coefficients of 0.95 and 0.90, respectively. Conclusions: MVA assessment using PISA by single-beat real-time 3D color Doppler echocardiography is feasible in the clinical setting and more accurate than the conventional 2D PISA method.