Table 2.

Echocardiographic parameters for assessing AR and MR severity, individual cut-offs for severe AR and MR, and their limitations—especially in combined AR and MR

	Severe AR	Severe MR
Jet area	Only qualitative information	Only qualitative information
General limitations	The jet area, the ratio of AR jet diameter and LVOT diameter, the ratio of AR jet area and LV area, as well as the ratio of MR jet area and left atrial area are not recommended for grading the severity of regurgitation in the guidelines. The many confounding factors render these findings unreliable
Monoplane vena contracta	> 6 mm	> 7 mm
General limitations	Not standardizable in variable, non-circular regurgitant orifice areas: not applicable and defined in multiple jet formations; extremely dependent on the sectional plane visualizing the central longitudinal jet formation; only feasible after optimizing image settings (no smoothing of pixel size, individually optimized 2D gain, color gain, color Doppler frequency, low velocity reject, frame rate)
Biplane vena contracta	–	> 8 mm
General limitations		Not standardized in the literature
Doppler techniques	Pressure half time (PHT) by CW-Doppler < 200 ms Reversed end-diastolic flow velocity > 0.2 m/s, determined in the proximal descending aorta or the left subclavian artery	Maximum of transmitral E-velocity by PW Doppler > 1.5 m/s in the absence of other causes of elevated LA pressure and of mitral stenosis Tribouilloy ratio = mitral-to-aortic velocity time integral (VTI) ratio = VTItransmitral/VTILVOT by PW Doppler > 1.4
General limitations	Standardization of the sample volume of the PW Doppler is necessary; alignment of cw-Doppler angulation parallel to the corresponding jet direction is necessary. PHT is influenced by chamber compliance
Special limitations	Both AR and MR affect diastolic LV properties in hard-to-predict ways. Thus, using the PHT of regurgitant flow velocities to grade AR severity is even less reliable in the presence of MR than in isolated AR	Transmitral E-velocity is unreliable in the presence of increased transmitral flow due to mitral stenosis; VTItransmitral/VTILVOT ratio cannot be used in the presence of relevant mitral stenosis and/or AR
EROA by 2D-PISA method	≥ 0.3 cm2	≥ 0.4 cm2  ≥ 0.3 cm2 if EROA is elliptical
General limitations	2D-PISA is reliable only in jet formation with an alignment parallel to the corresponding jet formation; it is error-prone in presumably non-circular orifice areas and highly error-prone in case of incorrect labeling of the PISA radius. 2D-PISA does not consider the dynamic nature of MR
Special limitations	Presumably, 2D-PISA may be reliable only with right coronary cusp prolapse using the parasternal long-axis view—adequate alignment is not possible in all other AR jet formations	2D-PISA is not reliable and error-prone in eccentric jet formations, in multiple jets, in lesions like perforation or cleft, in tenting of the leaflets, and in primary MR
Regurgitant volume	≥ 60 mL	≥ 60 mL  ≥ 45 mL in conditions of low flow
General limitations	The extent of regurgitant volumes depends on the extent of LV total stroke volume; therefore, the parameter of regurgitant volume must be interpreted with respect to LV effective stroke volume
Special limitations	An individual cut-off for isolated severe AR cannot be used if the calculated LV effective stroke volume is in a range that is too low and not plausible	An individual cut-off for isolated severe MR cannot be used if the difference between LV total stroke volume and calculated regurgitant volume results in an LV effective stroke volume in a range that is too low and not plausible
Regurgitant fraction	≥ 50%	≥ 50%
General limitations	Individual assessment of the regurgitant fraction requires a reliable and verifiable assessment of cardiac volumes resulting in plausible hemodynamic scenarios. The estimation of the MR regurgitant fraction in combined AR by calculation of the LV total stroke volume is not reliable and error-prone
Special limitations	In isolated AR, the regurgitant fraction can be assessed by measuring forward stroke volumes in the LVOT and RVOT. However, determining RVOT dimensions is challenging. The cross-sectional area of the proximal pulmonary trunk is easier to measure than the most often elliptical area of the RVOT. The assessment of LV inflow by transmitral VTI and mitral annulus dimension is highly error-prone. The assessment of regurgitant fractions using regurgitant volumes by 2D-PISA method is severely limited by methodological limitations	In isolated MR, the regurgitant fraction can be assessed by planimetric or volumetric measurement of LV total stroke volume and the measuring the LV forward stroke volume in the LVOT. The difference between both volumes represents the MR regurgitant volume which can be used for calculating the regurgitant fraction. The assessment of LV inflow by transmitral VTI and mitral annulus dimension is highly error-prone

AR aortic regurgitation, CW continuous-wave, EROA effective regurgitant orifice area, 2D-PISA method two-dimensional proximal isovelocity surface area method, LV left ventricular, LVOT left ventricular outflow tract, MR mitral regurgitation, PW pulsed wave, RVOT right ventricular outflow tract, VTI velocity time integral