Dysfunction of any of the components of the mitral valve apparatus can result in mitral regurgitation and should prompt a comprehensive 2D evaluation of the valve. When mitral valve disease is to be addressed by means of surgery, the 2D evaluation of the mechanism of pathology plays an important role in deciding whether either valve repair or replacement is indicated, and in the case of repair, which technique will be more appropriate.17 Mitral regurgitation results in volume overload of the left-sided cardiac chambers with subsequent dilatation.18 The right ventricle and atrium may also be affected secondary to the development of pulmonary hypertension. Chamber dilatation is usually seen in long-standing hemodynamic significant mitral regurgitation, but might not be present in the case of sudden-onset severe mitral regurgitation. When mitral valve morphology is abnormal on 2D examination, the chances of dealing with a more severe degree of mitral regurgitation are much greater than when the valve appears normal. Indications of more severe mitral regurgitation on 2D evaluation include flail leaflets such as in chordal or papillary muscle rupture, severe prolapse as in myxomatous degeneration of the valve, leaflet perforation, or the presence of leaflet tenting with a large coaptation defect.
With the aliasing velocity set to between 50 and 60 cm/s and the color gain settings adjusted to eliminate noise, a midesophageal four-chamber view is obtained. Position the color Doppler sector to include the whole of the mitral valve. If mitral regurgitation appears to be present, reduce the size of the Doppler sector to the smallest size that still includes the entire mitral regurgitation jet. This will help to improve temporal resolution by increasing frame rate. After recording a number of cardiac cycles, scroll back and forth and identify the frame where the jet area appears at its biggest. Using the trace function, planimeter the surface area of the regurgitant jet and the surface area of the left atrium. Keep in mind that only the mosaic area of the regurgitation jet should be included when determining jet area. For grading of mitral regurgitation using jet area, see Table 7–1.
Table 7–1. Parameters for the Determination of the Severity of Mitral Regurgitation. ||Download (.pdf)
Table 7–1. Parameters for the Determination of the Severity of Mitral Regurgitation.
Normal or dilated
Normal or dilated
Mitral leaflets or support apparatus
Normal or abnormal
Normal or abnormal
Abnormal or flail leaflet, or ruptured papillary muscle
Color flow jet areac
Small, central jet (usually <4 cm2 or <20% of LA area)
Large central jet (usually >10 cm2 or >40% of LA or variable size wall-impinging jet swirling in LA
Mitral inflow: PWD
E-wave dominantd (E usually >1.2 m/s)
Jet density: CWD
Incomplete or faint
Jet contour: CWD
Early peaking, triangular
Pulmonary vein flow
Systolic flow reversalf
VC width (cm)
In the case of eccentric jets, the greatest surface area may fall outside the tomographic plain imaged and may result in underestimation of the severity of mitral regurgitation. Eccentric wall-hugging jets (Coanda effect) also lead to underestimation of the severity of mitral regurgitation. On the other hand, conditions that cause excessive pressures in the left ventricle such as severe systemic hypertension and aortic stenosis can lead to overestimation of mitral regurgitation due to a very high-velocity jet extending far into the left atrium. For these reasons, it is recommended that jet area not be used as the sole method for quantification of mitral regurgitation.19
Visualize the mitral valve in the ME LAX view and zoom in to optimize image size. With the aliasing velocity (Nyquist limit) set to between 50 and 60 cm/s and color gain settings adjusted to reduce background noise, position the color Doppler sector over the mitral valve and visualize the regurgitant jet. When the tomographic plane is aligned with the regurgitant orifice, color Doppler should display an area of systolic flow convergence proximal to the valve, a color jet into the left atrium, and a narrow neck of color as the jet passes through the regurgitant orifice. This narrowest part as it emerges from the coaptation site of the leaflets is referred to as vena contracta, and its width, measured perpendicular to the direction of regurgitation, correlates well with mitral regurgitation severity determined by means of regurgitant volume and effective regurgitant orifice area. The maximal diameter during any portion of systole is recorded (Figure 7–15). Once again, the color Doppler sector should be kept as small as possible to obtain maximal temporal resolution. Measurement of the vena contracta should be made perpendicular to the coaptation line formed by the anterior and posterior leaflets in order to avoid a false increase in vena contracta from a tangential imaging plane. Thus, the midesophageal long-axis view, which transects the mitral valve perpendicular to the line of coaptation, is the optimal view to measure vena contracta. Repeating the measurement over several cardiac cycles will also increase the accuracy of this method. Vena contracta was proposed to be a load-independent measure of mitral regurgitation, but subsequent data have proven that alterations in afterload can affect the apparent severity in an unpredictable fashion.21 It is therefore recommended that hemodynamic parameters be adjusted during measurement to approximate awake conditions.
Vena contracta seen with two-dimensional (A) and three-dimensional (B) imaging. In the 3D image, the en face view (right panel) revealed a wider vena contracta than that seen with 2D imaging.
Regurgitant Volume, Regurgitant Fraction, and Effective Regurgitant Orifice area
Flow across an incompetent valve is always greater than the effective forward stroke volume. In mitral regurgitation, the difference between forward stroke volume and flow across the mitral valve is equal to regurgitant volume. The effective forward stroke volume can be measured in the left ventricular outflow tract or across the pulmonic valve in the absence of significant regurgitation of the aortic or pulmonic valves.
RVolMitral = SVMV − SVLVOT
SVMV = MV Annulus Area × VTIMV (at the level of the MV annulus)
(Mitral Annulus Diameter)2 × 0.785
Another method used to calculate the MV annulus area is based on the fact that the mitral valve annulus is elliptical in shape rather than circular. Determination of the area requires that 2 measurements of the mitral annulus are made in perpendicular planes in mid-diastole:
MV Annulus Area = π/4 × AB
A = annular diameter in one plane (cm)
B = annular diameter in a plane perpendicular to plane A (cm)
SVLVOT = LVOT Area × VTILVOT
LVOT = Left ventricular outflow tract
VTI = Velocity-time integral
RF = Regurgitant fraction
RVol = Regurgitant volume
EROA = Effective regurgitant orifice area
MR = Mitral regurgitation
The result must be carefully interpreted because a small operator error in measurement will have a major impact on the squared calculation. For quantitative parameters of mitral regurgitation as determined through the above formulae, refer to Table 7–1.
Proximal Isovelocity Surface Area (Pisa)22
In mitral regurgitation, flow accelerates when approaching the regurgitant orifice. This results in concentric hemispheric shells of increasing velocity as the valve is approached. The area of one such hemisphere is referred to as proximal isovelocity surface area (Figure 7–16). By applying color Doppler to the mitral valve in the midesophageal views, the regurgitant jet can be displayed. As determined by convention, flow towards the mitral valve in the ME LAX view will be displayed as differing intensities of red. When the Nyquist limit is reached, as invariably happens with high velocities achieved in mitral regurgitation, the direction of flow apparently reverses, a phenomenon referred to as aliasing. This apparent reversal is not a true reversal, but rather an inability to measure high velocities. By adjusting the baseline of the color Doppler scale upwards (in the direction of regurgitant flow), the velocity at which aliasing will occur can be adjusted in order to alter the radius of the aliasing hemisphere. It is recommended that the color Doppler baseline be adjusted in order to achieve an aliasing contour with a radius of 11 to 15 mm. Smaller radii result in flattening of the aliasing hemisphere and larger radii result in a cone-shaped aliasing contour.23 The radius of the hemisphere should be measured from the narrowest part of the jet to the contour where aliasing occurs first, and the velocity of blood at the aliasing contour is obtained from the top of the color Doppler scale (see Figure 7–16). The area of the hemisphere is then calculated with the following formula:
Surface Area of Hemisphere (cm2) = 2πr2
where π = 3.14 and r is the radius of the aliasing contour, measured from the narrowest part of the color jet.
Flow acceleration in the region proximal to a regurgitant orifice forming concentric hemispheres of increasing velocity. The radius of the hemisphere should be measured from the narrowest part of the jet to the contour where aliasing occurs.
The flow at the surface area where aliasing occurs can then be calculated using the following formula:
where Va is aliasing velocity from the top of the color legend.
The maximal isovelocity surface area should occur at the instant of maximal velocity through the regurgitant orifice. This can be measured by applying continuous-wave Doppler to the regurgitant jet and measuring the peak velocity (Figure 7–17). The principle of conservation of mass states that flow in a closed system should be equal at all points; therefore, flow rate at the effective regurgitant orifice area (EROA) should equal the flow rate at any given isovelocity surface area. Thus, the effective regurgitant orifice area can be calculated by the following equation:
where r is the radius of the first contour of aliasing, Va is the aliasing velocity, EROA is the effective regurgitant orifice area, and Vmax is the maximal regurgitant velocity obtained with continuous-wave (CW) Doppler.
The maximal systolic velocity through the regurgitant orifice can be measured by applying continuous-wave Doppler to the regurgitant jet. Together with the area of the PISA hemisphere, it is used to calculate the effective regurgitant orifice area and subsequently the regurgitant volume.
Once the effective regurgitant orifice area has been determined, regurgitant volume can also be calculated by using the velocity-time integral of the mitral valve regurgitant jet.
RVol = EROA × VTIMitral Regurgitant Jet
where RVol is the regurgitant volume and VTIMitral Regurgitant Jet is the velocity-time integral of the mitral regurgitant jet as measured with CW Doppler trace.
The examiner should keep in mind that the proximal isovelocity surface area method assumes a flat surface area proximal to the regurgitant orifice. In the case of an angled ventricular surface area of the mitral valve, a correction factor should be used to improve the accuracy of this method. The effective regurgitant orifice area should be multiplied by α/180, where α is the angle of the proximal converging surfaces (Figure 7–18).
Image demonstrating the determination of the angle α in a patient with a regurgitant jet that has eccentric convergence.
In spite of relatively low frame rates, 3D color Doppler imaging allows for a more accurate determination of the proximal isovelocity surface area (Figure 7–19).24 For instance, in functional mitral regurgitation the proximal isovelocity surface area is not hemispherical but a hemiellipsoid. Three-dimensional color Doppler may avoid underestimation of severity of mitral disease using the proximal isovelocity surface area method.
Two-dimensional (A) and three-dimesional (B) imaging of the proximal isovelocity surface area. Three-dimensional color Doppler imaging allows for a more accurate determination of the proximal isovelocity surface area and avoids underestimation of EROA and regurgitant volume.
Pulmonary Venous Flow Patterns
Pulsed-wave (PW) Doppler can be used to assess pulmonary venous flow patterns in order to quantify mitral valve regurgitation. In order to visualize the left upper pulmonary vein, the probe is pulled back and turned to the left from the midesophageal four-chamber view until the left atrial appendage is observed. The left upper pulmonary vein will be superior and posterior to the left atrial appendage, and parallel alignment for Doppler analysis could be optimized by rotating the multiplane angle forward to between 20° and 60°. The right upper pulmonary vein can be visualized by obtaining the bicaval view and then rotating the probe towards the right, beyond the aortic root. Slight withdrawal of the probe will allow visualization of the right upper pulmonary vein. Placement of the color Doppler cursor over the pulmonary veins showing flow predominantly towards the probe will help to correctly identify these vessels. Pulmonary venous flow patterns are obtained by placing the cursor of the pulsed-wave Doppler approximately 1 cm into the pulmonary vein under interrogation.
A normal pulmonary venous flow pattern has a large forward systolic component (S-wave), a slightly smaller forward diastolic component (D-wave), and a small reversed component (A-wave) caused by atrial contraction. Should reversal of the systolic component occur, severe mitral regurgitation can be diagnosed with a specificity of 100% and sensitivity of 90% (Figure 7–20).25 However, systolic blunting of flow (S < D), as seen with atrial fibrillation or diastolic dysfunction, is diagnostic only of an elevation in left atrial pressure.26 In the case of severe eccentric mitral regurgitation, the wall-hugging jet may cause systolic flow reversal in only some of the pulmonary veins. It is therefore important to assess pulmonary venous flow in both left- and right-sided pulmonary veins.
Pulsed-wave Doppler interrogation of pulmonary venous flow exhibiting systolic reversal (arrow) in a patient with severe mitral regurgitation. (A, atrial contraction flow; S, systolic flow; D, diastolic flow.)
Other Doppler Measures for Determining MR Severity
Pulsed-wave Doppler assessment of transmitral inflow patterns can also aid in the grading of mitral regurgitation. In the midesophageal four-chamber view, the pulsed-wave Doppler cursor should be positioned at the level of the leaflet tips during ventricular filling. A spectral Doppler trace of the transmitral inflow pattern should then be recorded. Large regurgitant volumes such as in severe mitral regurgitation result in increased left atrial pressures at the end of systole. The subsequent high diastolic gradient between left atrium and left ventricle results in an E-wave dominant inflow pattern, with the E-wave velocity typically exceeding 1.2 m/s.27,28 In the case of the transmitral inflow pattern being dominated by the A-wave, severe mitral regurgitation can be excluded.28
Continuous-wave (CW) Doppler interrogation of the mitral regurgitant jet also contributes to the grading of mitral regurgitation. The normal spectral Doppler trace of lesser degrees of mitral regurgitation is parabolic in shape and follows the pressure gradient between the left ventricle and left atrium during systole. Large regurgitant volumes result in a rise in the left atrial pressure during systole and also results in an inability of the left ventricle to achieve normal peak systolic pressures. The resultant decrease in pressure gradient between the left ventricle and atrium causes an early peaking, truncated spectral Doppler trace seen in severe mitral regurgitation (Figure 7–21). The quality of spectral Doppler trace is also helpful. In mild mitral regurgitation the jet is faint, but in severe mitral regurgitation a very dense spectral Doppler trace can be obtained. A faint trace results from small numbers of red blood cells passing through the regurgitant orifice, but large regurgitant volumes cause a dense representation of the jet.27
The continuous-wave Doppler trace contributes to the grading of mitral regurgitation. A large regurgitant volume results in this dense jetpattern which is early peaking and truncated.
When grading mitral regurgitation with TEE under general anesthesia, one should consider the effect of altered loading conditions on the circulation and the effect it will have on the indices used to grade mitral regurgitation. Reduction in ventricular filling, systemic vascular resistance, and blood pressure typically occurs in anesthetized patients and can decrease the apparent degree of mitral regurgitation compared to preoperative assessments. In order to gain more reliable information it may be necessary to simulate awake loading conditions by maintaining preload or increasing afterload through the administration of a vasopressor.29 Cancellation of mitral valve surgery based on intraoperative findings after preoperative assessment indicated a need for surgery should therefore be made with great caution.