PRE-CLINICAL INVESTIGATIONS Color Doppler Jet Area Overestimates Regurgitant Volume when Multiple Jets are Present Ben A. Lin, MD, PhD, Arian S. Forouhar, PhD, Niema M. Pahlevan, MS, Costas A. Anastassiou, PhD, Paul A. Grayburn, MD, James D. Thomas, MD, and Morteza Gharib, PhD, Pasadena and Menlo Park, California; New Haven, Connecticut; Dallas, Texas; Cleveland, Ohio Background: Color Doppler jet area (CDJA) is an important measure used to classify mitral regurgitation (MR) severity. The investigators hypothesized that the presence and configuration of multiple regurgitant jets can alter CDJA quantification for fixed regurgitant volumes. This has relevance to MR assessment prior to the treat- ment of valves with multiple regurgitant orifices or after surgical or percutaneous double-orifice mitral valve repair. Methods: An in vitro model was developed to create jets flowing through a simulated mitral orifice into an im- aging chamber. The flow loop was driven with a pulsatile pump at 60 beats/min containing a water-glycerol solution approximating the viscosity of blood. At the orifice, simulated regurgitant stroke volumes of 2.5 to 25 mL were created through plates having either single openings with orifice areas from 0.125 to 0.50 cm 2 or two to four openings with total orifice area of 0.25 cm 2 and varied linear spacing. An 8-MHz transthoracic two-dimensional ultrasound probe was used to acquire jet velocities by continuous-wave Doppler as well as color Doppler for offline analysis. CDJA values were obtained with custom automated pixel-counting software. Results: Peak jet velocities ranged from 30 to 550 cm/sec. For single jets, normalized average CDJA values in- creased nonlinearly as a function of average Reynolds number. Peak CDJA values were up to 62% higher for multiple jets compared with single jets with similar total orifice areas and simulated regurgitant stroke volumes. The presence or absence of multiple jets, rather than the total number of jets, appeared to have a greater effect on maximum CDJA. In addition, peak CDJA values for multiple jets increased with increased linear spacing. Conclusions: A fixed regurgitant volume involving multiple jets will have a larger CDJA value than the same total volume from a single jet. The source of this discrepancy appears to be increased ambient fluid entrain- ment from adjacent regurgitant jets. This potential overestimation of MR severity using color Doppler flow jets should be taken into consideration when assessing MR prior to treatment or when assessing residual MR after double-orifice mitral valve repair. (J Am Soc Echocardiogr 2010;23:993-1000.) Keywords: Mitral regurgitation, Mitral regurgitation severity, Color Doppler jet area, Double-orifice repair, Edge-to-edge repair, Multiple jets Because each of the surrogate measures of mitral regurgitation (MR) severity has limitations, the American Society of Echocardiography suggests using an integrative approach for classifying MR. 1 One of the recommended metrics (the easiest to acquire and most com- monly used) is the size of the color Doppler jet area (CDJA) in the left atrium created by the regurgitant jet. The challenge in assessing MR severity using CDJA is estimating volumetric flow from the spatial distribution of velocity-encoded pixels. This becomes much more dif- ficult when flow is turbulent and fast enough to cause multiple aliasing artifacts, as is the case with MR. 2 CDJA estimates of MR severity are often confounded by several factors independent of the regurgitant volume. 1 These factors include instrument settings, 3 the shape and size of the regurgitant orifice, 4 blood viscosity, 5 jet momentum, 2 jet velocity, 4 jet direction, 6 and driving pressure. 4 To the best of our knowledge, studies demonstrating the limitations of CDJA measurements have reported only on flow through a single regurgitant orifice. However, given the complex three-dimensional geometry of the mitral valve coaptation surface, it is common for dis- eased mitral valves to have multiple regurgitant lesions (e.g., in Barlow’s disease 7 or endocarditis). In addition, mitral valve repair or replacement techniques that alter mitral valve geometry may also alter the spatial distribution of residual regurgitation at the mitral valve orifice. In particular, double-orifice repair, in which the scallops of the anterior and posterior leaflets are approximated, converts From the Option of Bioengineering (B.A.L., N.M.P., M.G.) and the Division of Biology (C.A.A.), California Institute of Technology, Pasadena, California; the Section of Cardiovascular Medicine, Yale University School of Medicine, New Haven, Connecticut (B.A.L.); Abbott Vascular, Menlo Park, California (A.S.F.); the Baylor Heart and Vascular Institute, Baylor University Medical Center, Dallas, Texas (P.A.G.); and the Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio (J.D.T.). This study was funded by Evalve, Inc. (Menlo Park, CA), prior to its acquisition by Abbott Vascular. Drs. Lin and Forouhar contributed equally to this work. Reprint requests: Ben A. Lin, MD, PhD, Yale University School of Medicine, Section of Cardiovascular Medicine, 333 Cedar Street, P.O. Box 208017, New Haven, CT 06520 (E-mail: ben.lin@yale.edu). 0894-7317/$36.00 Copyright 2010 by the American Society of Echocardiography. doi:10.1016/j.echo.2010.06.011 993