Direct Measurement of Proximal Isovelocity Surface Area by Single-Beat Three-Dimensional Color Doppler Echocardiography in Mitral Regurgitation: A Validation Study

Background The two-dimensional (2D) proximal isovelocity surface area (PISA) method has some technical limitations, mainly the geometric assumptions of PISA shape required to calculate effective regurgitant orifice area (EROA). Recently developed single-beat, real-time three-dimensional (3D) color Doppler imaging allows direct measurement of PISA without geometric assumptions. The aim of this study was to validate this novel method in patients with chronic mitral regurgitation (MR). Methods Thirty-three patients were included, 25 (75.7%) with degenerative MR and eight (24.2%) with functional MR. EROA and regurgitant volume were assessed using transthoracic 2D and 3D PISA methods. The quantitative Doppler method and 3D transesophageal echocardiographic planimetry of EROA were used as reference methods. Results Both EROA and regurgitant volume assessed using the 3D PISA method had better correlations with the reference methods than conventional 2D PISA. A consistent significant underestimation of EROA and regurgitant volume using 2D PISA was observed, particularly in the assessment of eccentric jets. On the basis of 3D transesophageal echocardiographic planimetry of EROA, 14 patients had severe MR (EROA ≥ 0.4 cm2 ). Of these 14 patients, 42.8% (6 of 14) were underestimated as having nonsevere MR (EROA ≤ 0.4 cm2 ) by the 2D PISA method. In contrast, the 3D PISA method had 92.9% (13 of 14) agreement with 3D transesophageal planimetry in classifying severe MR. Good intraobserver and interobserver agreement for 3D PISA measurements was observed, with intraclass correlation coefficients of 0.96 and 0.92, respectively. Conclusions Direct measurement of PISA without geometric assumptions using single-beat, real-time 3D color Doppler echocardiography is feasible in the clinical setting. MR quantification using this methodology is more accurate than the conventional 2D PISA method.