Disproportionate mitral regurgitation: another myth? A critical appraisal of echocardiographic assessment of functional mitral regurgitation

Abstract

The contradictory findings of recent prospective randomized controlled trials assessing the impact of percutaneous edgeto-edge repair in patients with functional or secondary mitral regurgitation have triggered a lively discussion about an "integrated" echocardiographic approach for grading severity of mitral regurgitation. In the MITRA-FR trial, the COAPT trial and the REDUCE-FMR trial echocardiographic assessment of the severity of mitral regurgitation was consistent with principles set forth by the current echocardiographic guidelines and analysed in its best settings by expert international leaders in the field of echocardiography. However, serious inconsistencies appeared in the presented echocardiographic assessments regarding cardiac output and regurgitant fraction. A new term "disproportionate functional mitral regurgitation" was introduced describing a situation where the increase of effective regurgitant orifice area exceeds the enlargement of the left ventricular end-diastolic volumes. Further discussion resulted in the idea of a "new conceptional framework" for distinguishing "proportionate" and "disproportionate" functional mitral regurgitation. The aim of this viewpoint is to dispute conclusions based on the term "disproportionate" mitral regurgitation. A "disproportionate" FMR is highly questionable because disproportionateness of flow in communication vessels cannot exist. In addition, a proposal of echocardiographic assessment based on a conventional comprehensive transthoracic echocardiography is given to avoid obvious hemodynamic contradictions.

Plausible Functional Diagnostics by Rational Echocardiography in the Assessment of Valvular Heart Disease - Role of Quantitative Echocardiography in the Assessment of Mitral Regurgitation

“…Thus, the EROA should theoretically be calculated by the equation CSA MA x VTI MAret = EROA x VTI MRret , where CSA MA is the cross-sectional area of the mitral annulus (MA), VTI MAret is the velocity time integral of the systolic retrograde flow velocities determined at the MA level by pw Doppler and VTI MRret is velocity time integral of the systolic retrograde transmittal flow velocities determined by cw Doppler. However, it is not possible to perform these measurements to analyze EROA in MR patients like in AS patients due to the deceleration of retrograde transmittal flow velocities and the impossibility to assess high regurgitant flow velocities at the mitral annulus (MA) level by pw Doppler ( 6 , 16 ). However, due to physical laws of conservation of mass and energy in communicating tubes, disproportionateness between EROA and LVEDV is impossible provided that LV function is properly assessed.…”

Echocardiographic assessment of mitral regurgitation: discussion of practical and methodologic aspects of severity quantification to improve diagnostic conclusiveness

“…Furthermore, over-and underestimation of LV volumes in humans [64] and phantoms [65,66] have been described comparing different imaging methods, e.g., native 2D-and 3D echocardiography, contrast echocardiography, CMR, and computed tomography. Recently, conclusive LV volume assessment by 2D echocardiography was illustrated if image quality is adequate [67][68][69][70]. The differences in LV volumes between 2D echocardiography Table 2 Proposal to classify primary mitral regurgitation (PMR) more in detail with respect to specific echocardiographic findings, the chronicity of the underlying diseases, and the clinical complaints of the patients and CMR can be minimized by triplane, 3D-, and contrast echocardiography [71,72].…”

Functional mitral regurgitation: a proportionate or disproportionate focus of attention?

“…With reduced ventricular function and low total left ventricular (LV) stroke volume, a low regurgitant volume is obligatory, confirming the observations of quantitative Doppler echocardiographic studies. Reports that suggested a disproportionate regurgitant volume to the LV size 10,11 have been plagued by severe underestimation of ventricular volumes and should be discounted 12 …”