Mitral Stenosis

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Mitral stenosis is a valvular heart disease resulting from the narrowing of the mitral valve orifice. Echocardiography is the most important investigation in confirming the diagnosis and assessing severity.


Source(s): Mitral Stenosis


Contents

Pathophysiology

The normal mitral valve orifice area is 4-6 cm2. Mitral stenosis occurs when the orifice area is reduced to at least 2.2 cm2. This result in a gradient across the mitral valve which is the haemodynamic hallmark of the disease.

40px Mitral stenosis


Source(s): Mitral Stenosis


Aetiology


Source(s): Mitral Stenosis


Mitral Stenosis Echocardiography

Mitral valve assessment with echocardiography should include:

  • Diagnosis from the pattern of valve involvement and calcification.
  • severity of mitral stenosis
  • Associated mitral regurgitation
  • Other co-existent valve lesions
  • Chamber dilatation and function

M-mode echocardiography

M-mode echocardiographic assessment of the valve reveals slow early diastolic closure of the mitral valve. The mid-diastolic closure velocity or E-F slope is remarkably reduced. This can be used to assess the severity of the mitral stenosis and to determine re-stenosis from serial measurements after surgical or percutaneous treatment. E-F slope can also be flat in subjects with normal mitral valve if the left ventricular compliance is reduced.

Another M-mode feature of mitral stenosis is the anterior movement of posterior mitral valve leaflet in early diastole.


Source(s): Mitral Stenosis


2D - Echocardiography

As with any stenotic valve, the main diagnostic feature in the parasternal long-axis view is the doming of the anterior mitral valve leaflet in diastole. This is due to the reduced mobility of the valve tips compared to the base of the leaflets.

Thickening of the valve leaflets with or without calcification can be visualised with echocardiography. This can also involve the annulus and the chordae which can be shortened.

Other associated features may include markedly enlarged left atrium, pulmonary hypertension, right heart enlargement and tricuspid regurgitation. There may be involvement of other valves as well.


Source(s): Mitral Stenosis


Orifice area by planimetry

  • A well validated technique for assessing severity
  • In parasternal short axis view
  • The mitral valve is funnel shaped, so the area needs to be measured at the tip of the valves (the narrowest portion).
  • Be sure to turn the gain down to have low overall 2D gain.
  • Trace the inner edge of the valve orifice during the maximum opening in diastole.
  • Not useful if heavily calcified valves or after valvotomy
  • Sometimes chordae can mimic the valve orifice.


Source(s): Mitral Stenosis


Doppler echocardiography

Mean transmitral valve gradient

Can be measured by tracing the outline of mitral diastolic inflow and the mean pressure gradient is automatically calculated. The severity can be assessed as mild (<5), moderate (5-10) and severe (>10).


Source(s): Mitral Stenosis


Continuity equation Mitral valve area

Mitral valve area = transmitral stroke volume / velocity time integrale of the MS jet.


Source(s): Mitral Stenosis


Assessment of severity

Severity of mitral stenosis
Severity mild moderate severe
Mitral valve area 2.2 - 1.5 1- 1.5 <1
Pressure Half time (msec) 100 - 150 150 - 220 >220
Mean Pressure Gradient <5 5-10 >10
TR velocity <2.7 >3
Pulmonary artery pressure <30 >50

Factors favouring successful percutaneous mitral valvuloplasty

Mitral stenosis is amenable to percutaneous mitral valvuloplasty if the echocardiography demonstrates :

  • Thickening confined to valve tips
  • Good mobility of Anterior mitral valve leaflet
  • Little chordal involvement
  • not more than trivial mitral regurgitation
  • no left atrial thrombus
  • no commissural calcification.


Source(s): Mitral Stenosis


Wilkins score

A scoring system exists to grade the morphological changes in the mitral valve during assessment with echocardiography. This takes into account 4 characteristics: leaflet mobility, leaflet thickening, valve calcification and involvement of the subvalvular apparatus. The involvement is graded from 0-4. A total score of more than 8 is predictive of a low success post percutaneous mitral valvuloplasty.[1]


Source(s): Mitral Stenosis


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References

  1. Wilkins GT, Weyman AE, Abascal VM, Block PC, Palacios IF. Percutaneous balloon dilatation of the mitral valve: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation. Br Heart J. 1988;60:299–308. doi: 10.1136/hrt.60.4.299
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