Comparative quantification of primary mitral regurgitation by computer modeling and simulated echocardiography

Abstract

Clinical investigations have demonstrated that mitral regurgitation (MR) quantification using echocardiography (echo) may significantly underestimate or overestimate the regurgitant volume, especially for two-dimensional (2D) echo. Computer modeling and simulated echo were conducted to evaluate the fundamental assumptions in the echo quantification of primary MR that is due to posterior mitral leaflet prolapse. The theoretical flaw of the proximal isovelocity surface area (PISA) method originates from the assumption that the MR flow rate is the product of the isovelocity surface area and aliasing velocity, which is only valid when the velocity vectors are perpendicular to the isovelocity surface. Other factors such as the Doppler angle effect, the view planes of 2D echo, and the single time instant of PISA were also analyzed. We find that the hemielliptic PISA method gives the smallest error for moderate and severe MR cases compared with other PISA methods. Compared with the PISA method, the volumetric technique (VT) is theoretically more robust. By considering correction factors that are caused by nonflat velocity profiles and the closing volume of the aortic valve, the accuracy of the VT method can be significantly improved. The corrected volumetric technique provides more accurate results compared with the PISA methods, especially for mild MR. NEW & NOTEWORTHY We evaluate the accuracy of common echocardiography techniques for the quantification of primary mitral regurgitations using computer modeling. The hemielliptic proximal isovelocity surface area (PISA) method gives the smallest error (within 15%) for moderate and severe mitral regurgitation cases compared with other PISA methods. The volumetric method is theoretically more robust than the PISA method. The accuracy of the volumetric method can be improved by a correction factor around 0.7 because of the nonflat velocity profiles and the closing volume of the aortic valve.

Quantification of regurgitation in mitral valve prolapse with automated real time echocardiographic 3D proximal isovelocity surface area: multimodality consistency and role of eccentricity index

“…Interestingly, despite, 3D-PISA evaluation demonstrated higher values when compared with 2D-PISA; three patients were downgraded one grade MR scale with 3D-PISA. A plausible explanation for that is Doppler angle dependency, as demonstrated in the study from Mao et al [ 19 ]. Basically, 3D-PISA gives an urchinoide shaped FCR due to angle dependence and underestimates compared with 2D-PISA in case of non-elongated proximal flow regions, but overestimates (or 2D-PISA underestimates) in case of elongated FCR because of the hemispheric assumption of the 2D-method.…”

Computational Analysis of Virtual Echocardiographic Assessment of Functional Mitral Regurgitation for Validation of Proximal Isovelocity Surface Area Methods

“…These computer models can be considered phantom models (similar to a benchtop experimental model) for analyzing the relative (theoretical) errors of PISA methods. 30 Using the computer phantom models, 3D blood flow in left atrium, in the left ventricle, and across the MV was extracted, from which the reference values of MR flow rate and regurgitant volume (RVol) could be directly and accurately measured.…”

“…In vitro experimental studies are limited by the complexity of experimental setups and the difficulty of obtaining a detailed interrogation of regurgitant flow field across the mitral valve (MV). Recent advances in image-based computational modeling have substantially enhanced the investigation of patient-specific cardiac dynamics, including studies of echocardiographic measurement in MR. 30 Therefore, the aims of this study were to (1) create and validate computer phantom models for accurate measurements of FMR reference values; (2) perform virtual PISA measurements, including 2D and 3D PISA, with both peak and integrated PISA approaches; and (3) investigate the accuracy of these PISA methods and quantify their sources of theoretical errors.…”

Fluid–Structure Interaction Analyses of Biological Systems Using Smoothed-Particle Hydrodynamics

“…The SPH method was demonstrated and validated in several articles on mitral valve closure [ 30 , 40 , 41 , 42 ]. Subsequently, it was used to assess several diseased mitral valve states [ 43 , 44 , 45 , 46 ] and applications of medical devices designed to correct them [ 47 , 48 , 49 , 50 ]. Besides the mitral valve, other valves have been studied using the same methods [ 42 , 51 , 52 , 53 , 54 , 55 ].…”