Mitral regurgitation assessment
From Echocardiography in ICU
Mitral valve regurgitation is very frequent. It can be caused by primary disease of the mitral leaflets or can occur secondary to left ventricle or mitral apparatus dysfunction. The tolerance of mitral regurgitation will depend upon its acuteness and upon the left ventricle function.
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Positive diagnosis of mitral regurgitation (MR)
The positive diagnosis of MR is made with color Doppler. MR appears as a systolic regurgitation from the left ventricle to the left atrium.
In parasternal long axis the jet can be either directed toward or away from the probe, then its color can be yellow-red (toward the probe) or green-blue (away from the probe).
In apical 4 or 2 chamber, MR will appear as a blue-green systolic jet going away from the probe.
When you are looking for MR, it is important to visualize properly the mitral leaflets before activating color Doppler. If the image quality is not good, the sensitivity of color Doppler to detect the regurgitant flow will not be sufficient and you will underdiagnose MR.
Methods of grading MR severity
Semi-quantitative estimation
The semi-quantitative assessment relies on the estimation of the regurgitant jet extension in the left atrium, and the comparison of the jet extension to the left atrium area. It is important to evaluate the MR in at least two different views.
This is the easiest method of MR evaluation. With limited experience, it is reliable only for the distinction between mild to severe regurgitation.
Please go to the images library to see more examples of MR.
! Be careful !
-excentric jets are very difficult to assess, you must ask for referent echo
-in patients with dilated right atrium, the severity of MR is often underevaluated
-in patients with high right atrium pressure, MR can be underestimated
► ALWAYS ASSESS MR FROM 2 DIFFERENT VIEWS AT LEAST
Quantitative estimation
Proximal Isovelocity Surface Area (PISA). Not to be used for goal-directed TTE. Please go to specific chapter for explanations.
Fluctuations in MR severity
In a same patients, severity of MR can fluctuate, depending on
- loading conditions. Higher pre and/or after-load will increase the amount of MR
- ischemic conditions. Ischemia can prevent the dynamics and geometry of the mitral apparatus, thus increasing the MR severity. The posterior papillary muscle is only supplied by the posterior descending branch of the right coronary artery, whereas the anterior papillary muscle has dual blood supply and is less prone to ischemia.
MR consequences
The consequences of MR on the left ventricle and right ventricle pressures will depend on its acuteness and mechanism.
Acute MR
-reduction of forward stroke volume
-increase in end-diastolic volume
→ hyperkinetic LV
→ reduced LA compliance
→ elevation LA pressure
→ pulmonary edema
→ elevation RVSP
Chronic MR
- LA dilatation
- hyperkinetic LV
- LV dilatation (increased telediastolic volume)
- elevation RVSP
Clue to distinguish acute from chronic MR
LV and/or LA dilatation point toward chronic MR. They are evidence of chronic remodeling in response to increased LA pressure and LV pre-load.
Determination of MR mechanism
The determination of MR mechanism can be important for the patient's management, and to guide a possible treatment. The diagnosis of MR mechanism is done on two-dimensional images, mainly in parasternal long axis.
Prolapse
Mitral valve prolapse (MVP) is defined when one or both leaflets goes further than the plane of the mitral anulus in a nonsymmetric manner. MVP corresponds to Carpentier type 2 MR.
Parasternal long axis view. You can see a prolapse of the anterior mitral leaflet:
Restriction
When the leaflets dynamics is restricted, MR can appear. Restriction is caused by thickening and calcification of the leaflets or chordae. Aging and rhumatismal disease can lead to restriction. This mechanism corresponds to Carpentier type 3 MR.
Parasternal long axis, restriction of anterior and posterior leaflets. You can see that the leaflets are very thickened, specially the anterior leaflet, and their motion is restricted, leading to moderate MR.
Annulus dilatation
In cardiomyopathy, remodeling and dilatation of the LV occur, stretching the mitral annulus and leading to apical and lateral displacement of the papillary muscles. It is also called "tenting" of the mitral leaflets. It corresponds to Carpentier type 1.
Parasternal long axis. Dilatation and spherisation of the LV, with poor coaptation of the mitral leaflets leading to mild to moderate MR. You can note the severe LV systolic dysfunction
Ischemia
Two acute ischemic mechanisms can lead to MR:
-partial or complete papillary muscle rupture creates severe acute MR with poor hemodynamic tolerance. Since it has only one blood supply, the postero-medial papillary muscle is more prone to ischemic rupture than the antero-lateral papillary muscle. Papillary muscle rupture can occur even during very limited infarct.
-acute MR secondary to acute LV remodeling and wall akinesis changing MV dynamics
Chronic ischemic MR is secondary to LV remodeling and altered submitral apparatus function.
Endocarditis (vegetation, perforation)
Endocarditis can lead to MR by 2 mechanisms:
-vegetation is the characteristic lesion of endocarditis. It appears as a hyperechoic mobile mass attached to localized thickening of the mitral leaflet, on the atrial side of the valve. Positive diagnosis is difficult with TTE, with poor sensitivity and specificity.
-valve perforation appears as a regurgitant jet originating from the body of the mitral leaflet.
References
Carpentier A. Cardiac valve surgery-the "French correction". J Thorac Cardiovasc Surg 1983; 86:323-37
