Mitral Valve Disease



Mitral Valve Disease


Brian R. Lindman

Suzanne V. Arnold





High-Yield Concepts



  • Discrepancy between the mitral valve area (MVA) and mean gradient in MS may be related to cardiac output or heart rate


  • Wilkins score: Carefully review leaflet mobility, thickening, and calcification and subvalvular thickening to predict efficacy of balloon valvuloplasty


  • Eccentric regurgitant jet: Be suspicious that it might be severe


  • Grading regurgitation severity: Do not rely on one measurement alone



Key Views



  • Parasternal long axis—initial screening for mitral stenosis (MS) and mitral regurgitation (MR) severity; evaluation of subvalvular apparatus


  • Parasternal short axis—planimetry of MVA


  • Apical views—quantitative assessment MS and MR: Mean gradient, proximal isovelocity surface area (PISA) and volumetric assessments, LA and LV size and function


  • TEE—higher resolution views for MR etiology and severity (e.g., PISA, pulmonary vein reversal) and for Wilkins score; important for planning interventions


Severity of Mitral Stenosis

See Table 10-1.








Table 10-1 Criteria for Determining Severity of Mitral Valve Stenosis
























  Mild Moderate Severe
MVA (cm2) >1.5 1.0–1.5 <1.0
Mean gradient (mmHg) <5 5–10 >10
PASP (mmHg) >30 30–50 >50
MVA, mitral valve area; PASP, pulmonary artery systolic pressure.
Adapted from Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. J Am Soc Echocardiogr. 2009;22(1):1–23, with permission from Elsevier.


Severity of Mitral Regurgitation

See Table 10-2.









Table 10-2 Criteria for Determining Severity of Mitral Valve Regurgitation




image



Anatomy



  • Leaflets



    • Anterior and posterior leaflets each have three scallops (Fig. 10-1).


  • Annulus



    • The junction between atrium and ventricle and the place where the mitral leaflets insert.


    • There is an anterior and posterior portion of the annulus corresponding to the respective leaflets. The anterior portion is attached to the right and left fibrous trigones and is structurally more supported.


    • The annulus may dilate leading to functional regurgitation or calcify leading to stenosis.


  • Subvalvular Apparatus



    • Papillary muscles: Anterior–lateral and posterior–medial; the anterior–lateral papillary muscle usually receives dual blood supply (LAD and LCX), whereas the posterior–medial papillary muscle usually has single blood supply (either LCX or RCA).


    • Chordae tendinae: Primary, secondary, and tertiary chords connect the papillary muscles to both valve leaflets; these can elongate, shorten, rupture, calcify, or fuse.


  • Ventricle



    • The ventricular size and shape impact the function of the mitral valve. As the ventricle dilates and becomes more spherical, the papillary muscles become apically displaced and can restrict the closure of the mitral leaflets, leading to MR.






      Figure 10-1. Cartoon of parasternal short axis at the mitral valve level showing the different scallops numbered in ascending order from lateral to medial.



  • Left Atrium



    • If the left atrium dilates, this can lead to annular dilation and affect the closure of the mitral leaflets, leading to MR.



Key Point:

Unlike the tricuspid and pulmonic valve, which is separated by the RV infundibulum the mitral and aortic valve, are in direct continuity, separated only by a fibrous connection. This has ramifications for pathology such as endocarditis, which can therefore spread between both valves and cause annular and aortic root abscess.


Mitral Stenosis



  • Pathophysiology

    See Figure 10-2.


  • Etiology








    Rheumatic (most common)

    • 2/3 are female
    • May be associated with MR
    • Stenotic orifice often shaped like a “fish mouth” (PSAX) (Fig. 10-3) with doming of anterior leaflet (PLAX and apical views) (Fig. 10-4) and marked reduction in posterior leaflet motion
    • Rheumatic fever can cause fibrosis, thickening, and calcification leading to fusion of the commissures, cusps, and/or chordae.
    • As opposed to calcific MS this process starts in the subvalvular apparatus and extends to the leaflets with increasingly severe disease.
    Other causes (less common)

    • Congenital
    • Mitral annular calcification (i.e., calcific MS)—process starts from annulus and extends to the leaflets. Significant calcification is required to impact the larger area of the mitral annulus compared to rheumatic MS which affects the leaflet tips
    • Chest radiation
    • MV prosthesis dysfunction
    • Mucopolysaccharidoses
    • Malignant carcinoid
    • Systemic lupus erythematosus (SLE)
    • Rheumatoid arthritis
    • Iatrogenic due to surgery for MR: Oversewn mitral annuloplasty ring, MV clip/Alfieri stitch
    • “Functional MS” due to restriction of left atrial outflow (MV leaflets are normal):

      • Tumor (typically atrial myxoma)
      • LA thrombus
      • Endocarditis with large vegetation
      • Cor triatriatum (congenital LA membrane)







    Figure 10-2. The pathophysiology of mitral stenosis and associated echocardiographic features.


  • Echocardiographic assessment of MS


  • 2D assessment



    • Leaflets



      • Motion/mobility of the valve


      • Thickening


      • Calcification


    • Subvalvular apparatus



      • Chordal fusion, shortening, fibrosis, and calcification


    • Mitral valve area planimetry



      • The mitral valve orifice is traced in the parasternal short-axis view usually during mid-diastole.







        Figure 10-3. A: A 2D PSAX view at the MV leaflet tips with planimetry of the orifice in mid-diastole. B: 3D PSAX view for planimetry of a mitral valve that is severely stenotic. Note the ability to easily determine the correct position of the orifice in the 3D example by manipulation of the planes in the biplanar TEE images (arrows).







        Figure 10-4. (A) Parasternal long-axis and (B) apical four-chamber views showing doming of the anterior mitral leaflet and a thickened and fixed posterior mitral leaflet consistent with rheumatic mitral valve disease (arrows). (C) M-mode shows the classic features of thickened mitral valve leaflets, “tracking” of the posterior leaflet and reduced E-F slope.



      • This can be an accurate way to assess the severity of MS that is independent of flow, chamber compliance, and other valve lesions; however, it is also prone to error. While in the parasternal short-axis view, scanning should be done from apex to base to ensure that planimetry is being done at the leaflet tips. Sometime, reviewing the anatomy from the parasternal long-axis view can help identify the right plane in the short-axis view. This is a measurement where 3D imaging is particularly helpful in enhancing accuracy (Fig. 10-3).


  • Left atrial dimension



    • Significant MS can lead to substantial dilation of the LA, predisposing the patient to atrial arrhythmias and thrombus formation.


    • Wilkins score is graded as detailed in Table 10-3.


  • Doppler

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Oct 20, 2016 | Posted by in CARDIOLOGY | Comments Off on Mitral Valve Disease

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