Quantification of Chronic Functional Mitral Regurgitation by Automated 3-Dimensional Peak and Integrated Proximal Isovelocity Surface Area and Stroke Volume Techniques Using Real-Time 3-Dimensional Volume Color Doppler Echocardiography

Abstract

Background-The aim of this study was to test the accuracy of an automated 3-dimensional (3D) proximal isovelocity surface area (PISA) (in vitro and patients) and stroke volume technique (patients) to assess mitral regurgitation (MR) severity using real-time volume color flow Doppler transthoracic echocardiography. Methods and Results-Using an in vitro model of MR, the effective regurgitant orifice area and regurgitant volume (RVol) were measured by the PISA technique using 2-dimensional (2D) and 3D (automated true 3D PISA) transthoracic echocardiography. The mean anatomic regurgitant orifice area (0.35±0.10 cm 2 ) was underestimated to a greater degree by the 2D (0.12±0.05 cm 2 ) than the 3D method (0.25±0.10 cm 2 ; P<0.001 for both). Compared with the flowmeter (40±14 mL), the RVol by 2D PISA (20±19 mL) was underestimated (P<0.001), but the 3D peak (43±16 mL) and integrated PISA-based (38±14 mL) RVol were comparable (P>0.05 for both). In patients (n=30, functional MR), 3D effective regurgitant orifice area correlated well with cardiac magnetic resonance imaging RVol r=0.84 and regurgitant fraction r=0.80. Compared with cardiac magnetic resonance imaging RVol (33±22 mL), the integrated PISA RVol (34±26 mL; P=0.42) was not significantly different; however, the peak PISA RVol was higher (48±27 mL; P<0.001). In addition, RVol calculated as the difference in automated mitral and aortic stroke volumes by real-time 3D volume color flow Doppler echocardiography was not significantly different from cardiac magnetic resonance imaging (34±21 versus 33±22 mL; P=0.33). Conclusions-Automated real-time 3D volume color flow Doppler based 3D PISA is more accurate than the 2D PISA method to quantify MR. In patients with functional MR, the 3D RVol by integrated PISA is more accurate than a peak PISA technique. Automated 3D stroke volume measurement can also be used as an adjunctive method to quantify MR severity. (Circ Cardiovasc Imaging. 2013;6:125-133.)Key Words: 3D integrated PISA ◼ 3D peak PISA ◼ automated 3D stroke volume ◼ cardiac MR imaging ◼ mitral regurgitation ◼ real-time 3D volume color flow Doppler echocardiography

Quantitative Three-Dimensional Color Flow Echocardiography of Chronic Mitral Regurgitation: New Methods, New Perspectives, New Challenges

“…Another notable feature is that velocities over the duration of the MR are used in computing EROA and RVol, thus avoiding the potential for overestimation of the degree of MR in dynamic and nonholosystolics MR. An alternative 3D CFD approach uses voxel segmentation to identify isovelocity in the FCR and automatically quantify the 3D surface area. 7 Then, using the peak velocity and the velocity-time integral from continuous-wave spectral Doppler of the MR jet, 3D EROA and RVol are computed. When the 3D surface area of the frame with the largest FCR is used along with the peak velocity of the MR jet, we can determine ''peak PISA'' EROA, and when this is combined with the VTI of the MR jet, ''peak instantaneous'' RVol is obtained.…”

“…By integrating these individual peak instantaneous RVol values over the duration of MR, ''integrated PISA''-derived RVol is determined; this measure shows significantly better agreement with RVol measured by CMR. 7,8 Thus, both automated 3D FOM and the 3D voxel segmentation approach to identify the FCR overcome the potential for overestimating MR severity using the single-frame approach. Integration of data from 2D CFD of the FCR over the duration of MR can be done, but it requires manual computation and still suffers from limitations of using 2D images to describe what is essentially a 3D shape.…”

“…and reproducibility. It is now possible to perform real-time (nongated, nonstitched) CFD imaging at temporal resolution not significantly different from that of gated imaging, 7 although there is clearly room for improvement. Furthermore, gated 3D CFD is virtually impossible in atrial fibrillation, which is not uncommon in chronic MR.…”

“…In patients without valvular disease, mitral and aortic stroke volumes are not different, 13 whereas when MR is present, the difference between mitral and aortic stroke volume yields RVol. 7 Initial studies in relatively small numbers of patients have shown good accuracy in normal control subjects and in patients with chronic MR compared with CMR. 7,14 Recently, the automated 3D CFD-based stroke volume measurement also has been extended to transesophageal echocardiography, providing an alternative when conventional transthoracic echocardiography is suboptimal.…”

“…7 Initial studies in relatively small numbers of patients have shown good accuracy in normal control subjects and in patients with chronic MR compared with CMR. 7,14 Recently, the automated 3D CFD-based stroke volume measurement also has been extended to transesophageal echocardiography, providing an alternative when conventional transthoracic echocardiography is suboptimal. The advantages of this method are that it does not depend on analysis of the FCR and that RVol is computed over the duration of MR.…”