In Vitro Validation of Real-Time Three-Dimensional Color Doppler Echocardiography for Direct Measurement of Proximal Isovelocity Surface Area in Mitral Regurgitation

Abstract

The 2-dimensional (2D) color Doppler (2D-CD) proximal isovelocity surface area (PISA) method assumes a hemispheric flow convergence zone to estimate transvalvular flow. Recently developed 3-dimensional (3D)-CD can directly visualize PISA shape and surface area without geometric assumptions. To validate a novel method to directly measure PISA using real-time 3D-CD echocardiography, a circulatory loop with an ultrasound imaging chamber was created to model mitral regurgitation (MR). Thirty-two different regurgitant flow conditions were tested using symmetric and asymmetric flow orifices. Three-dimensional-PISA was reconstructed from a hand-held real-time 3D-CD data set. Regurgitant volume was derived using both 2D-CD and 3D-CD PISA methods, and each was compared against a flowmeter standard. The circulatory loop achieved regurgitant volume within the clinical range of MR (11 to 84 ml). Three-dimensional-PISA geometry reflected the 2D geometry of the regurgitant orifice. Correlation between the 2D-PISA method regurgitant volume and actual regurgitant volume was significant (r 2 = 0.47, p <0.001). Mean 2D-PISA regurgitant volume underestimate was 19.1 ± 25 ml (2 SDs). For the 3D-PISA method, correlation with actual regurgitant volume was significant (r 2 = 0.92, p <0.001), with a mean regurgitant volume underestimate of 2.7 ± 10 ml (2 SDs). The 3D-PISA method showed less regurgitant volume underestimation for all orifice shapes and regurgitant volumes tested. In conclusion, in an in vitro model of MR, 3D-CD was used to directly measure PISA without geometric assumption. Compared with conventional 2D-PISA, regurgitant volume was more accurate when derived from 3D-PISA across symmetric and asymmetric orifices within a broad range of hemodynamic flow conditions. Accurate quantitation of regurgitant volume is an ongoing challenge in the assessment of patients with valvular heart disease. The flow convergence or proximal isovelocity surface area (PISA) method is derived from the principle that as blood approaches a regurgitant orifice, its velocity increases, forming concentric shells of increasing velocity and decreasing surface area. 1,2 This surface area (PISA) can be estimated during 2-dimensional (2D) color Doppler (CD) echocardiography (2D-CD) assuming a hemispheric distribution of velocity vectors proximal to the regurgitant orifice. Under the principle of flow continuity, the severity of valve dysfunction can be quantified using PISA to determine the effective regurgitant orifice area and regurgitant volume. 3

A three-dimensional insight into the complexity of flow convergence in mitral regurgitation: adjunctive benefit of anatomic regurgitant orifice area

“…Such altered morphology of the orifice is likely to lead to either under-or overestimation of EROA (6,12,15,21,27), as evidenced by the greater discrepancy between the 3D and FC measurements in patients with eccentric MR jets. FC analysis described previously (30) demonstrated reduced accuracy of MR severity evaluation compared with catheterization, when applied clinically to patients with MV prolapse who likely had complex, nonplanar, noncircular regurgitant orifices and where the assumptions regarding jet orientation, planarity of the orifice and leaflets, and, therefore, the symmetry of hemispherical isovelocity profiles break down (7, 29 -31, 34, 36).…”

Three-Dimensional Ultrasound Imaging Model of Mitral Valve Regurgitation: Design and Evaluation

“…Unlike a comparison of methods in the clinical setting, these methods were compared in an in vitro setting against a flow meter gold standard for assessment of actual regurgitant volume. Employing the model described here, we have recently reported (Little et al 2007) that the classic 2D color Doppler method was associated with greater underestimation of regurgitant volume for both asymmetric regurgitant orifice shape and larger regurgitant volume. In contrast, the 3D-CD method demonstrated excellent correlation with the flow meter standard.…”

“…Measurements were performed off-line, blinded to the flow measurements, regurgitant orifice characteristics and 3D data. As previously reported, the spectral Doppler data were used in conjunction with both 2D color Doppler and novel 3D color Doppler assessments of the proximal flow convergence zone to compare the relative accuracy of either 2D or 3D method to estimate effective regurgitant orifice area and regurgitant volume (Little et al 2007). …”

Índice de dissincronia ventricular: comparação com a fração de ejeção bidimensional e tridimensional

“…Real-time three-dimensional transthoracic echocardiography is a novel method of structural and functional analysis of the heart that permits real-time three dimensional investigation of the heart without using ionizing radiation, and is highly reproducible and easy to obtain [5][6][7][8][9][10][11][12][13][14][15][16] . It has a good cost-benefit ratio when compared with methods such as magnetic resonance imaging and also increases the possibility of identifying patients with advanced heart failure who can benefit from cardiac resynchronization therapy using biventricular pacemaker implantation.…”

“…Three-dimensional echocardiography is more improved in relation to twodimensional echocardiography because it is not based on geometric inferences for the calculation of volumes of cardiac chambers, ventricular mass, and left ventricular ejection fraction, considering a limited number of observation planes [9][10][11][12][13][14][15][16] . An application of three-dimensional echocardiography that may have a great clinical impact is related to the indication and clinical follow-up of patients with NYHA functional class III and IV CHF undergoing cardiac resynchronization therapy with biventricular pacemaker.…”