Mitral Valve

The mitral valve consists of anterior and posterior leaflets, chordae tendineae, anterolateral and posteromedial papillary muscles, and the mitral annulus.

The posterior leaflet is divided into P1, P2, and P3 scallops. The corresponding anterior leaflet segments are A1, A2, and A3.

Routine Assessment¶

Evaluate:

Leaflet thickness, mobility, calcification, and coaptation
Prolapse, flail leaflet, restriction, or perforation
Annular size and calcification
Subvalvular apparatus
Mitral stenosis and regurgitation
LA and LV response
Pulmonary venous flow and pulmonary pressure

Use multiple views because eccentric regurgitant jets and localized leaflet disease may be missed in a single plane.

Mitral Regurgitation¶

Mechanism¶

Carpentier classification describes leaflet motion:

Type	Leaflet motion	Common causes
I	Normal	Annular dilation, perforation
II	Excessive	Prolapse, flail leaflet
IIIa	Restricted in systole and diastole	Rheumatic disease
IIIb	Restricted primarily in systole	Ischemic or functional MR

Primary MR results from structural valve disease. Secondary MR results from ventricular or atrial remodeling with otherwise structurally normal leaflets.

Jet direction can help localize pathology:

Posterior leaflet prolapse → anteriorly directed jet
Anterior leaflet prolapse → posteriorly directed jet
Ischemic restriction → jet directed away from the restricted leaflet

Severity Assessment¶

MR severity requires integration of valve anatomy, color Doppler, spectral Doppler, quantitative measurements, and chamber remodeling.

Parameter	Mild	Moderate	Severe
Vena contracta width	<0.3 cm	0.3–0.69 cm	≥0.7 cm
EROA	<0.20 cm²	0.20–0.39 cm²	≥0.40 cm²
Regurgitant volume	<30 mL	30–59 mL	≥60 mL
Regurgitant fraction	<30%	30–49%	≥50%

Findings supporting severe MR include:

Flail leaflet or large coaptation defect
Large central jet or eccentric wall-impinging jet
Vena contracta ≥0.7 cm
Dense, triangular CW Doppler envelope
Mitral E-wave velocity ≥1.2 m/s
Pulmonary vein systolic flow reversal
Progressive LA or LV enlargement
Elevated pulmonary pressure

Color jet area alone should not determine severity. Eccentric jets may appear deceptively small because of wall impingement.

PISA Method¶

\[ \text{Regurgitant flow} = 2\pi r^2 \times V_a \]

\[ \text{EROA} = \frac{\text{Regurgitant flow}} {\text{Peak MR velocity}} \]

\[ \text{Regurgitant volume} = \text{EROA} \times \text{MR VTI} \]

PISA is most reliable with a hemispheric flow-convergence zone and a single, circular regurgitant orifice. It is less reliable with eccentric, multiple, elliptical, or dynamic jets.

Secondary MR is frequently dynamic and may vary substantially with blood pressure, volume status, ischemia, and medical therapy.

Mitral Stenosis¶

Rheumatic MS typically produces:

Commissural fusion
Leaflet-tip thickening
Diastolic doming of the anterior leaflet
Restricted posterior leaflet motion
Chordal thickening and fusion
LA enlargement

Degenerative MS results from mitral annular calcification extending into the leaflet bases. Commissural fusion is generally absent.

Severity¶

Mitral valve area is the primary measure of stenosis severity.

Severity	Mitral valve area
Progressive MS	>1.5 cm²
Severe MS	≤1.5 cm²
Very severe MS	≤1.0 cm²

A mean transmitral gradient >10 mm Hg often accompanies severe MS but depends heavily on heart rate, rhythm, stroke volume, and concomitant MR.

Always report the heart rate with the mean gradient.

Valve Area¶

Direct planimetry is preferred in rheumatic MS when image quality is adequate. Trace the smallest diastolic orifice at the leaflet tips.

\[ \text{MVA} = \frac{220}{\text{Pressure half-time}} \]

Pressure half-time is affected by LA and LV compliance and may be inaccurate with:

Significant aortic regurgitation
Abnormal LV relaxation or compliance
Immediately after balloon commissurotomy
Tachycardia
Irregular rhythm

Continuity equation:

\[ \text{MVA} = \frac{\text{CSA}_{LVOT} \times \text{VTI}_{LVOT}} {\text{VTI}_{MV}} \]

The continuity method is unreliable with significant MR, AR, or intracardiac shunting.

Suggested Reporting¶

The mitral valve leaflets are structurally normal with normal excursion. No mitral stenosis is present. There is trace mitral regurgitation.

There is posterior mitral leaflet prolapse with an eccentric, anteriorly directed regurgitant jet. Findings are consistent with severe primary mitral regurgitation.

There is restricted systolic leaflet motion related to LV remodeling, producing moderate secondary mitral regurgitation.

The mitral leaflets are thickened with commissural fusion and diastolic doming, consistent with rheumatic mitral stenosis. Mitral valve area is ___ cm² by planimetry, with a mean gradient of ___ mm Hg at ___ bpm.

Key Points¶

Define the mechanism before grading MR.
Use an integrated assessment; no single parameter is sufficient.
Pulmonary vein systolic flow reversal strongly supports severe MR.
Eccentric MR may be substantially underestimated by jet area.
Mitral valve area determines MS severity; the gradient is flow and heart-rate dependent.
Report the heart rate whenever documenting a transmitral gradient.