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Quantification of Functional Mitral Regurgitation by Real-Time 3D Echocardiography

Comparison With 3D Velocity-Encoded Cardiac Magnetic Resonance

Nina Ajmone Marsan, MD^_*,, Jos J.M. Westenberg, PhD, Claudia Ypenburg, MD^_*, Victoria Delgado, MD^_*, Rutger J. van Bommel, MD^_*, Stijntje D. Roes, MD, Gaetano Nucifora, MD^_*, Rob J. van der Geest, PhD, Albert de Roos, MD, PhD, Johan C. Reiber, PhD, Martin J. Schalij, MD, PhD^_*, Jeroen J. Bax, MD, PhD^_*,_*

^_* Departments of Cardiology, Leiden University Medical Center, Leiden, the Netherlands
Division of Image Processing, Leiden University Medical Center, Leiden, the Netherlands
Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
IRCCS Policlinico S. Matteo, Pavia, Italy

^_* Reprint requests and correspondence: Dr. Jeroen J. Bax, Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands (Email: j.j.bax{at}lumc.nl).

Objectives: The aim of this study was to evaluate feasibility and accuracy of real-time 3-dimensional (3D) echocardiography for quantification of mitral regurgitation (MR), in a head-to-head comparison with velocity-encoded cardiac magnetic resonance (VE-CMR).

Background: Accurate grading of MR severity is crucial for appropriate patient management but remains challenging. VE-CMR with 3D three-directional acquisition has been recently proposed as the reference method.

Methods: A total of 64 patients with functional MR were included. A VE-CMR acquisition was applied to quantify mitral regurgitant volume (Rvol). Color Doppler 3D echocardiography was applied for direct measurement, in "en face" view, of mitral effective regurgitant orifice area (EROA); Rvol was subsequently calculated as EROA multiplied by the velocity-time integral of the regurgitant jet on the continuous-wave Doppler. To assess the relative potential error of the conventional approach, color Doppler 2-dimensional (2D) echocardiography was performed: vena contracta width was measured in the 4-chamber view and EROA calculated as circular (EROA-4CH); EROA was also calculated as elliptical (EROA-elliptical), measuring vena contracta also in the 2-chamber view. From these 2D measurements of EROA, the Rvols were also calculated.

Results: The EROA measured by 3D echocardiography was significantly higher than EROA-4CH (p < 0.001) and EROA-elliptical (p < 0.001), with a significant bias between these measurements (0.10 cm² and 0.06 cm², respectively). Rvol measured by 3D echocardiography showed excellent correlation with Rvol measured by CMR (r = 0.94), without a significant difference between these techniques (mean difference = –0.08 ml/beat). Conversely, 2D echocardiographic approach from the 4-chamber view significantly underestimated Rvol (p = 0.006) as compared with CMR (mean difference = 2.9 ml/beat). The 2D elliptical approach demonstrated a better agreement with CMR (mean difference = –1.6 ml/beat, p = 0.04).

Conclusions: Quantification of EROA and Rvol of functional MR with 3D echocardiography is feasible and accurate as compared with VE-CMR; the currently recommended 2D echocardiographic approach significantly underestimates both EROA and Rvol.

Key Words: cardiac magnetic resonance • functional mitral regurgitation • real-time 3-dimensional echocardiography

Abbreviations and Acronyms   CMR = cardiac magnetic resonance   EROA = effective regurgitant orifice area   L/S = ratio of the longest and shortest diameter of effective regurgitant orifice area   LV = left ventricle/ventricular   MR = mitral regurgitation   PISA = proximal isovelocity surface area   RT3DE = real-time 3-dimensional echocardiography   Rvol = regurgitant volume   VCW = vena contracta width   VE-CMR = velocity-encoded cardiac magnetic resonance   2CH = 2-chamber view   4CH = 4-chamber view