Mitral regurgitation echocardiography

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Varun Kumar, M.B.B.S.; Lakshmi Gopalakrishnan, M.B.B.S.'; Mohammed A. Sbeih, M.D.[3]

Overview

The echocardiogram is commonly used to confirm the diagnosis of mitral regurgitation. Color doppler flow on the transthoracic echocardiogram (TTE) will reveal a jet of blood flowing from the left ventricle into the left atrium during ventricular systole.

Because of the inability in getting accurate images of the left atrium and the pulmonary veins on the transthoracic echocardiogram, a transesophageal echocardiogram may be necessary to determine the severity of the mitral regurgitation in some cases.

Factors that suggest severe mitral regurgitation on echocardiography include systolic reversal of flow in the pulmonary veins and filling of the entire left atrial cavity by the regurgitant jet of MR.

The 2006 ACC/AHA guidelines included recommendations for echocardiographic monitoring in asymptomatic patients with chronic MR . Echocardiography is performed to assess the left ventricular ejection fraction and end-systolic dimension.

Determination of the degree of mitral regurgitation

Degree of mitral regurgitation	Regurgitant fraction	Regurgitant Orifice area
Mild mitral regurgitation	< 20 percent
Moderate mitral regurgitation	20 - 40 percent
Moderate to severe mitral regurgitation	40 - 60 percent
Severe mitral regurgitation	> 60 percent	> 0.3 cm2

Assessment of Severity of Mitral Regurgitation

The degree of severity of mitral regurgitation can be quantified by the percentage of the left ventricular stroke volume that regurgitates into the left atrium (the regurgitant fraction).

Methods that have been used to assess the regurgitant fraction in mitral regurgitation include:

• Echocardiography.
• Cardiac catheterization.
• Fast CT scan.
• Cardiac MRI.

The echocardiographic technique to measure the regurgitant fraction is to determine the forward flow through the mitral valve (from the left atrium to the left ventricle) during ventricular diastole, and comparing it with the flow out of the left ventricle through the aortic valve in ventricular systole.

This method assumes that the aortic valve does not suffer from aortic insufficiency. The regurgitant fraction would be described as:

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Another way to quantify the degree of mitral regurgitation is to determine the area of the regurgitant flow at the level of the valve. This is known as the regurgitant orifice area, and correlates with the size of the defect in the mitral valve.

One particular echocardiographic technique used to measure the orifice area is measurement of the proximal isovelocity surface area (PISA). The flaw of using PISA to determine the mitral valve regurgitant orifice area is that it measures the flow at one moment in time in the cardiac cycle, which may not reflect the average performance of the regurgitant jet.

Colour Flow Mapping

• Size of flow recruitment is noted.
• Jet base width at the valve level.
• Intra atrial jet area if it is a central jet.
• Jet direction is usually away from a prolapsing leaflet and behind a restricted leaflet.

Continuous Wave Doppler

• Shape and density of signal - In severe Mitral regurgitation, the flow is dense and triangular.
• If as dense as forward flow, it is severe.

Pulse Wave Doppler(PW)

• PW in apical-4-chamber view.
• E wave more than 1.2m/s indicates severe MR.
• Even minor mitral stenosis or hyperdynamic circulation can increase E wave.
• If A-wave dominant, severe MR is virtually ruled out.

Vena Contracta

• vena contracta is the narrowest region of regurgitant jet (usually just below the valve in LA).
• >0.7 cm - severe MR.

Pulmonary Venous Flow

• Usually forward throughout cycle.
• Systolic dominant.
• As MR worsens, there is a blunting of systolic flow.
• If severe MR - systolic flow reversal.

Regurgitant Volume

• Mitral regurgitant volume = Mitral inflow volume - LV outflow volume.

Mitral inflow volume = Vti * Cross sectional area of mitral valve.

LV outflow volume = Vti * Cross sectional area at LV outflow.

• Regurtitant volume - <20% - mild , >50% severe

PISA (Proximal Isovelocity Surface Area)

The radius of Proximal isovelocity surface area or flow convergence zone which is a 3-dimensional surface area proximal to a narrowed orifice at which all the blood velocities are equal, can be used to calculate the severity of mitral regurgitation. The principle is that if the mitral regurgitation is mild, only the blood nearer to the valve orifice accelerates towards the atrium while in severe regurgitation, blood farther away from the valve moves back.

PISA radius

A simple method to determine severity of mitral regurgitation is to measure the PISA radius. Regurgitation is mild if radius is <0.4 cm and severe if >1 cm.

Regurgitant Flow (Instantaneous)

The instantaneous regurgitant flow can be calculated from the PISA radius and can be used to assess the severity of mitral regurgitation.

Regurgitant flow = 2π * r² * V_aliasing

Effective Regurgitant Orifice Area (EROA)

Effective regurgitant orifice area can be calculated using the instantaneous regurgitant flow. The formula can be derived from the following:

V_aliasing * 2πr² = V_max * EROA

hence:

• EROA = PISA (2πr²) * V_aliasing / V_max

Mild = 0-20 cm², moderate = 20 - 40 cm², severe = >40 cm²

Regurgitant volume can be calculated from this.

• Regurgitant volume = Effective regurgitant orifice area * V_{time integrale}

Diastolic Mitral Regurgitation Secondary to Severe Aortic Stenosis

Diastolic mitral regurgitation due to severe aortic stenosis

Diastolic mitral regurgitation due to severe aortic stenosis

Diastolic mitral regurgitation due to severe aortic stenosis

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Severity (Summary)

Severity of Mitral Regurgitation

Severity	mild	severe
Jet area	<4 cm2	>8 cm2
Jet width	thin	>0.6
vena contracta	<0.3	>0.7
PISA radius	<0.4	>1
Pulmonary venous flow	systolic dominant	systolic flow reversal
Mitral inflow	can be A wave dominant	E wave dominant >1.2m/s
Continuous wave doppler	soft and parabolic	dense and triangular
LV and LA	normal size	enlarged (in chronic MR)
duration	can be short	holosystolic
Regurgitant volume	<30 ml	>60 ml
EROA	0-20 cm2	>40 cm2

ACC/AHA Guidelines- Indications for Transthoracic Echocardiography (DO NOT EDIT)

“

Class I 1. Transthoracic echocardiography is indicated for baseline evaluation of LV size and function, RV and left atrial size, pulmonary artery pressure, and severity of MR (Table 4) in any patient suspected of having MR. (Level of Evidence: C) 2. Transthoracic echocardiography is indicated for delineation of the mechanism of MR. (Level of Evidence: B) 3. Transthoracic echocardiography is indicated for annual or semiannual surveillance of LV function (estimated by ejection fraction and end-systolic dimension) in asymptomatic patients with moderate to severe MR. (Level of Evidence: C) 4. Transthoracic echocardiography is indicated in patients with MR to evaluate the MV apparatus and LV function after a change in signs or symptoms. (Level of Evidence: C) 5. Transthoracic echocardiography is indicated to evaluate LV size and function and MV hemodynamics in the initial evaluation after MV replacement or MV repair. (Level of Evidence: C) Class IIa 1. Exercise Doppler echocardiography is reasonable in asymptomatic patients with severe MR to assess exercise tolerance and the effects of exercise on pulmonary artery pressure and MR severity. (Level of Evidence: C) Class III 1. Transthoracic echocardiography is not indicated for routine follow-up evaluation of asymptomatic patients with mild MR and normal LV size and systolic function. (Level of Evidence: C)

”

ACC/AHA Guidelines- Indications for Transesophageal Echocardiography (DO NOT EDIT)

“

Class I 1. Preoperative or intraoperative transesophageal echocardiography is indicated to establish the anatomic basis for severe MR in patients in whom surgery is recommended to assess feasibility of repair and to guide repair. (Level of Evidence: B) 2. Transesophageal echocardiography is indicated for evaluation of MR patients in whom transthoracic echocardiography provides nondiagnostic information regarding severity of MR, mechanism of MR, and/or status of LV function. (Level of Evidence: B) Class IIa 1. Preoperative transesophageal echocardiography is reasonable in asymptomatic patients with severe MR who are considered for surgery to assess feasibility of repair. (Level of Evidence: C) Class III 1. Transesophageal echocardiography is not indicated for routine follow-up or surveillance of asymptomatic patients with native valve MR. (Level of Evidence: C)

”

Aetiology and Morphological Features in 2-D Echocardiography

Rheumatic Mitral Regurgitation

In rheumatic mitral regurgitation, there is some degree of commissural fusion and thickening of the tips visible in 2 dimensional echocardiography. The movement of the valve leaflets is restricted.

Myxomatous Mitral Valve

The leaflets and chordae are thick and reduntant. Reduced tensile strength leads to progressive elongation or rupture of chordae. Ruptured chordae appear as flail segments. To diagnose mitral valve prolapse, the following criteria should be fulfilled during echocardiography - Movement of any part of either leaflet more than 2mm behind the annular plane in parasternal long axis view and movement of point of co-aptation behind the annular plane in apical 4 chamber view.

Annular Calcification

Mitral annulus is usually smaller in systole. The increased rigidity due to annular calcification impairs contraction. In 2D- echocardiography, there is increased echogenicity on the LV side immediately adjacent to the attachment of the posterior mitral valve leaflet. Region of anterior mitral leaflet is only rarely involved. This is common in elderly subjects and younger ones with chronic renal failure and hypertension.

Ischaemic Mitral Regurgitation

Mitral regurgitation can occur in ischemia as a result of regional left ventricular dysfunction with abnormal contraction of papillary muscle or underlying ventricular wall. Myocardial infarction can result in MR at rest while if the underlying cause is ischemia the MR may be intermittent. The echocardiogram is characterized by restricted valve leaflet motion and tenting of mitral valve in systole.

Papillary Muscle Rupture

This is usually a complication of myocardial infarction. If entire papillary muscle is disconnected from the left ventricle severe MR results and few survive. Partial rupture is more common.

Functional Mitral Regurgitation

Functional MR results due to LV dilatation and systolic dysfunction in those with a structurally normal mitral valve apparatus.

Flail Posterior Mitral Leaflet M Mode

• Mitral Ring Dehiscence Post Repair With Severe Mitral Regurgitation

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• Severe Mitral Regurgitation From Ring Dehiscence Pulmonary Vein Pulsed Wave Doppler

• Severe Mitral Regurgitation Pulmonary Vein Pulsed Wave Doppler

Sources

• 2008 Focused Update Incorporated Into the ACC/AHA 2006 Guidelines for the Management of Patients With Valvular Heart Disease .