Heart valve disease module 4: diagnosis

Mitral stenosis

Echocardiographic minimum dataset

The echocardiographic minimum dataset for mitral stenosis consists of:

detailed description of the valve appearance and mobility (aetiology and mechanism)
geometric orifice area
mean gradient
left atrial size
effect on the right ventricle and pulmonary artery pressure.

Rheumatic disease causes:

the leaflet tips to become preferentially thickened
commissural fusion
chordal thickening and matting.

Suitability for balloon valvotomy can be gauged by the Wilkins score³⁸ in which a score of 1-4 is given for:

leaflet thickening
leaflet mobility
leaflet calcification
chordal involvement.

A Wilkins score >8 is unfavourable. However the commissure and chordae are the more important elements within this score and valvotomy is not usually feasible if there is one or more of the following:

bicommissural or heavy calcification of one commissure
heavy chordal involvement
more than mild regurgitation
mobile left atrial appendage thrombus.

An approximate idea of orifice area can be obtained using colour Doppler. However, planimetry should be attempted using the parasternal short axis on a mid-diastolic frame and a zoomed in view.² This is facilitated by 3D.³⁹

Grading mitral stenosis (see table 6)

When grading mitral stenosis, the geometric orifice area is the predominant measure. An indirect measure of area is obtained using the pressure T_1/2:⁴⁰

MVA = 220/ T_1/2

(where MVA = mitral valve area)

Table 6. Severity grading of mitral stenosis⁹

This gives only an approximate relationship with area and is particularly inaccurate in mild stenosis or after balloon valvotomy. Mean gradient is dependent on flow (see table 6).

Where there are discrepancies between the planimetered and CW Doppler measurements of stenosis severity, other measurements using the continuity equation and proximal isovelocity surface area methods are recommended, although not generally necessary or widely used.

Advanced echocardiography

3D is increasingly useful to guide planimetry of the orifice which may often be out of the plane of a conventional 2D section.³⁹

TOE is essential before balloon valvotomy to exclude mobile left atrial appendage thrombus, and confirm the other TTE findings.

Stress echocardiography is useful in patients with uncertain symptoms³⁴ looking for:

An increase in mean gradient to >15 mmHg
A rise in pulmonary arterial systolic pressure to >60 mmHg
LV decompensation as a result of coexistent coronary disease.

Cardiac computed tomography in mitral stenosis

For an evaluation of the valve components, a reconstruction at 65% of the R-R interval for the open mitral valve, and a reconstruction at 5% of the R-R interval is recommended for the closed mitral valve.

Figure 13. Cardiac CT showing heavy posterior mitral valve annulus calcification and minor aortic valve calcification. The mid segment of the left circumflex artery is seen on the top of the image and is free of disease (arrow)

In mitral stenosis, CT may be useful for:

excellent anatomical and morphological detail of the mitral valve apparatus
detection of calcium in leaflet, commissure and annulus (see figure 13)
geometric orifice by direct planimetry (correlates well with TEE findings (R=0.88, p<0.001))⁴¹
accurate left atrial size
detection of left atrial thrombus
right ventricular hypertrophy
radiographic evidence of pulmonary oedema and pulmonary hypertension.

Cardiac magnetic resonance imaging in mitral stenosis

CMR imaging may be used for the assessment of mitral stenosis but is considered to be a second-line technique for this purpose. Much as with the aortic valve, mitral inflow turbulence may be seen on SSFP in-plane imaging and the mitral valve area may be measured using carefully placed through plane SSFP imaging. Although this technique has been shown to correlate well with echo derived areas,^42–3 it is often limited by the presence of atrial fibrillation and problems with electrocardiogram (ECG)-gating.

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