Quantification of primary mitral regurgitation by echocardiography: A practical appraisal

Abstract

The accurate quantification of primary mitral regurgitation (MR) and its consequences on cardiac remodeling is of paramount importance to determine the best timing for surgery in these patients. The recommended echocardiographic grading of primary MR severity relies on an integrated multiparametric approach. It is expected that the large number of echocardiographic parameters collected would offer the possibility to check the measured values regarding their congruence in order to conclude reliably on MR severity. However, the use of multiple parameters to grade MR can result in potential discrepancies between one or more of them. Importantly, many factors beyond MR severity impact the values obtained for these parameters including technical settings, anatomic and hemodynamic considerations, patient's characteristics and echocardiographer' skills. Hence, clinicians involved in valvular diseases should be well aware of the respective strengths and pitfalls of each of MR grading methods by echocardiography. Recent literature highlighted the need for a reappraisal of the severity of primary MR from a hemodynamic perspective. The estimation of MR regurgitation fraction by indirect quantitative methods, whenever possible, should be central when grading the severity of these patients. The assessment of the MR effective regurgitant orifice area by the proximal flow convergence method should be used in a semi-quantitative manner. Furthermore, it is crucial to acknowledge specific clinical situations in MR at risk of misevaluation when grading severity such as late-systolic MR, bi-leaflet prolapse with multiple jets or extensive leak, wall-constrained eccentric jet or in older patients with complex MR mechanism. Finally, it is debatable whether the 4-grades classification of MR severity would be still relevant nowadays, since the indication for mitral valve (MV) surgery is discussed in clinical practice for patients with 3+ and 4+ primary MR based on symptoms, specific markers of adverse outcome and MV repair probability. Primary MR grading should be seen as a continuum integrating both quantification of MR and its consequences, even for patients with presumed "moderate" MR.

Keywords: echocardiography; heart valve disease (HVD); primary mitral regurgitation; regurgitant fraction; regurgitant volume; valvular regurgitation.

Figure 1

Central algorithm of the echocardiographic assessment of a patient with primary MR. Freely inspired by Zoghbi et al and Hagendorff et al. (23, 28). 2D, two-dimensional; 3D, three-dimensional; BP, blood pressure; CMR, cardiac magnetic resonance; CPET, cardiopulmonary exercice testing; CWD, Continuous-Wave Doppler; ECG, electrocardiogram; EROA, effective regurgitant orifice area; LA, left atrial; LV, left ventricular; MR, mitral regurgitation; MV, mitral valve; PISA, proximal isovelocity surface area; RegFrac, regurgitant fraction; RegVol, regurgitant volume; RV, right ventricular; S-PAP, systolic pulmonary artery pressure; TR, tricuspid regurgitation; TSV, total stroke volume; TTE, transthoracic echocardiography; TEE, transesophageal echocardiography; VCA, vena contracta area; VTI, velocity-time integral.

Figure 2

Morphological assessment of flail leaflet. (A,B) Patient with posterior flail leaflet visible on TTE (the tip is directed towards the LA). TEE confirms the involvement of segment P2 (white arrow) with chordae rupture (blue arrow). (C,D) Patient with bi-leaflet MV prolapse and P2 flail (red arrow) only visible on 3D-imaging TEE (surgical “en face” view). (E,F) Patient with flail involving the segment A1 (green arrow) visible on TEE imaging using biplane mode from the bi-commissural view (60–90°), and on 3D-imaging (surgical “en face” view). LA, left atrium; TTE, transthoracic echocardiography; TEE, transesophageal echocardiography.

Figure 3

Doppler color approach of primary MR evaluation. (A) Anterior MV prolapse with eccentric MR jet impinging on the posterior LA wall because of Coandă effect. The direction of the MR jet helps in understanding the prolapse's mechanism. (B) Posterior MV prolapse with eccentric jet impinging on the interatrial septum down to the pulmonary veins. Despite a small color flow jet area, a significant MR should be suspected because of the presence of a Coandă effect. (C) Posterior MV prolapse with large spontaneous proximal flow convergence (i.e without modifying Doppler color settings). A significant MR should be suspected. (D,E) Examples of posterior MV flail by TEE where the 3 components of the MR are clearly visualized (proximal flow convergence, vena contracta and distal MR jet). Hence, it is possible to measure 2D-vena contracta width. However, it should be kept in mind that the measurement of 2D-VCW could be less reliable when performed orthogonal to the direction of the ultrasound beam because of lower lateral than axial resolution. (F) Surgical “en face” view with Doppler color mode. A full MV 3D color-coded data set can objectively document MR regurgitant(s) jet(s). However, this method could suffer from markedly decreased framerate, therefore multi-beat acquisition is usually required to obtain an acceptable quality imaging. Herein, the origin of the MR is visualized at the MV anterior commissure (red arrow), and the distal MR jet is impinging on the inter-atrial septal wall because of the Coandă effect. (G,H) Double MR jet with a pattern of “Crossed swords sign”. 3D-TEE imaging revealed a large anterior cleft indentation. 3D, three-dimensional; LA, left atrium; MR, mitral regurgitation; MV, mitral valve; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography; VCW, vena contracta width.

Figure 4

Patient with primary MR with typical features of Barlow's disease. Presence of a MV valve prolapse (A3P3) with mitral annulus dilatation and disjunction (A). The MR jet is very eccentric with small color jet size (B). The best CWD MR envelope is obtained in the long-axis parasternal view, revealing a mid-late systolic MR (C). Using the PISA method, the proximal flow convergence area displays an oblong shape in apical-4-chamber view because being constrained by the LV lateral wall (D). The proximal flow field is better delineated in long-axis parasternal view (E), with an “urchinoid” shape because of loss of Doppler signal on its angles. CWD, Continuous-Wave Doppler; LV, left ventricular; MR, mitral regurgitation; MV, mitral valve; PISA, proximal isovelocity surface area.

Figure 5

Echocardiographic assessment of MR severity grading. Illustrative example of a 50-year-old male patient with primary MR. Posterior MV flail leaflet is seen on apical-3-chamber view (A). The mitral VTI is measured at 28.7 (B: the sample volume is positioned at the tip of the mitral leaflets). The LVOT VTI is measured at 17.7 (see Figure 7), thus resulting in a high MAVIR (1.62). A short LV ejection time is observed (<260 ms, C). The 3 components of the MR jet (proximal flow convergence, vena contracta and distal jet) are not clearly identified (D), therefore the 2D-VCW cannot be measured accurately. The PISA radius is measured at 1.2 cm for an aliasing velocity of 31 cm/s, thus suggesting significant MR. The MR EROA and MR RegVol estimated by the PISA method are of 0.51 cm2 and 81 ml, respectively. (E) However, the proximal flow convergence is partly constrained by the posterior LV wall (white arrow). Also there is a dropout of MR signal on the other side of the hemisphere (green arrow) because of a “Doppler angle effect”. Then, the MR is mainly mid-late systolic as shown by the CW Doppler MR signal (F). Hence, the MR RegVol by the PISA method is likely to over-estimate the true MR RegVol. All taken together, the MR is likely to be significant. CWD, Continuous-Wave Doppler; MAVIR, mitral-to-aortic velocity-time integral ratio; MV, mitral valve; VTI, velocity-time integral; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography.

Figure 6

Examples of pitfalls of the PISA method. (A) Patient with anterior MV prolapse. A clear hemispheric-shaped proximal flow convergence is seen on parasternal long-axis view (A). However, this is not the most common situation encountered in clinical practice. (B) Wall-constrained proximal flow convergence with a oblong shape. This is frequently observed in case of posterior MV prolapse or commissural MR. There is a risk of over-estimation of MR EROA and RegVol by the PISA method. (C) Late-systolic MR. As shown in Doppler color coupled to M-mode, the MR is only present in the latter part of systole. Therefore the MR EROA which depends on a single time point measurement (the PISA radius) is not reliable to grade MR. (D) Multiple MR jets. The PISA method is not reliable to grade MR. Indirect quantitative methods should be considered. (E) Bi-leaflet prolapse with extensive MR from one commissure to another. The PISA method is inapplicable. Indirect quantitative methods should be considered. EROA, effective regurgitant orifice area; LV, left ventricular; MR, mitral regurgitation; MV, mitral valve; PISA, proximal isovelocity surface area.

Figure 7

PW Doppler quantitative method. Same patient as Figure 5. The LV total stroke volume is computed by the Doppler method as follows: LVTSV_(MV) = π x (Δ_MV)2 x VTI_MV/4. Importantly, the Δ_MV must be measured at early diastole. Also the sample volume must be positioned at the level of the mitral annulus (not that of the leaflet tips). The aortic systolic forward stroke volume is computed by the Doppler method as follows: LVSV(Ao) = π x (Δ_LVOT)2 x VTI_(LVOT)/4. The Δ_LVOT must be measured at mid systole. The MR RegVol_(MV) is computed as the difference between the LVTSV_(MV) and the LVSV(Ao). Consequently, the MR RegFrac_(MV) is obtained by dividing the MR RegVol_(MV) by the LVTSV_(MV). Δ, diameter; LV, left ventricular/ventricle; LVOT, LV outflow tract; LVSV(Ao), LV systolic aortic forward stroke volume by Doppler method; LVTSV(_MV), LV total stroke volume by the PW Doppler quantitative method; MR, mitral regurgitation; RegVol, regurgitant volume; RegFrac, regurgitant fraction; PW, Pulsed-Wave; VTI, velocity-time integral.

Figure 8

Indirect volumetric method. Same patient as Figures 5, 7. The LV total stroke volume is computed as the difference between LV end-diastolic and end-systolic volumes according to the 2D-biplane Simpson's method [LVTSV_(2D)] or 3D-volumes [LVTSV_(3D)]. The LV borders should be traced at the interface between the LV cavity and the compacted myocardium, and not at the blood-tissue interface (that is at the tip of the trabeculation). The aortic systolic forward stroke volume is computed by the Doppler method (see Figure 7). The MR-RegVol_{(2D, 3D)} is computed as the difference between the LVTSV_{(2D, 3D)} and the LVSV(Ao). The MR-RegFrac_{(2D, 3D)} is obtained by dividing the MR RegVol_{(2D, 3D)} by the LVTSV_{(2D, 3D).} The congruence between MR RegVol and RegFrac values obtained by the different indirect quantitative methods as well as LV hemodynamic and cardiac output should be carefully checked. Δ, diameter; BP, biplane; EDV, end-diastolic volume; ESV, end-systolic volume; LV, left ventricular/ventricle; LVSV(Ao), LV systolic aortic forward stroke volume by Doppler method; LVTSV_(2D), LV total stroke volume by 2D-indirect volumetric method; LVTSV_(3D), LV total stroke volume by 3D-indirect volumetric method; MR, mitral regurgitation; RegVol, regurgitant volume; RegFrac, regurgitant fraction.