Quantitative vs Semi-Quantitative Methods
The strong correlation between MR and prognosis underscores that the assessment of MR severity is an important part for the decision making in patients with IMR[14,15]. The recently updated guidelines of the American Society of Echocardiography (ASE) recommended an comprehensive method involving quantitative, semi-quantitative and qualitative methods to confirm the degree of secondary MR, which was divided into mild, moderate and severe[15-17]. The color Doppler is the most commonly used method for quantifying MR. The effective regurgitant orifice area (EROA), regurgitant volume and fraction can be obtained by evaluating the distal MR jet area/left atrium area ratio, vena contracta width and the proximal isovolumetric surface area (PISA)[16]. Hoverer, there are some limitations in using color Doppler to evaluate MR, such as eccentric or multiple or non-holosystolic MR jet, non-circular regurgitant orifice, non-hemispherical PISA, and the influence of load conditions[16].
Three dimensional (3D) imaging can provide supplementary information, which is an adjunct to a comprehensive examination of 2D transesophageal echocardiography (TEE). Specifically, it enhances the spatial orientation and accuracy of linear measurements, allows synchronous visualization of orthogonal views, and allows the volumetric analysis of cardiac chambers without geometric assumptions. 2D imaging can provide a wide range of methods for the identification of cardiac anatomy, physiology and structures of interest, while 3D TEE is used to obtain specific supplementary quantitative and qualitative information from the interested structures at present[18]. It is recommended to use 3D echocardiography to overcome some of the pitfalls encountered in 2D examination: the 3D image acquisition of MR enables the direct planimetry of the vena contracta (i.e., regurgitant orifice area) and thus optimizes the MR assessment in the case of non-hemispherical PISA and multiple jets[16,19,20].