Mitral Stenosis

• Related:
  • Rheumatic Heart Disease

The analogy that is often used to describe stenotic lesions is covering a hose with your finger, you can sense the increased pressure when doing so. Further, this causes the jet of water to travel a greater distance.

• Auscultation
  • Opening snap (OS)
    • forceful opening of the MV when the pressure in the LA is greater than the pressure in the LV → OS of MS is a high-pitched early diastolic sound due to sudden tensing of the valve leaflets and subvalvular apparatus at the end of the opening excursion (Source)
    • occurs 40-120 milliseconds after A2
    • A2-OS interval varies inversely with the severity of mitral stenosis
• In a patient with rheumatic MS who has Sx, but there is a discrepancy with resting echo hemodynamics, then do exercise testing with hemodynamics
  • exercise is preferred to dobutamine stress because it provides a more physiologic assessment
• Screening surveillance
  • Asymptomatic patients with mild or moderate MS should have surveillance echocardiograms every 3-5 years
  • Severe, but asymptomatic:
    • if MVA <1 cm2 → exercise treadmill testing should be performed yearly
    • if MVA 1-1.5 cm2: every 1-2 years

	Mild	Moderate	Severe
Valve area (cm2)	>1.5	1.0-1.5	<1.0
Mean gradient (mmHg)	<5	5-10	>10
PA pressure (mmHg)	<30	30-50	>50
Diastolic PHT (ms)		<150	≥150
The above criteria are based on a HR between 60 to 80 bpm and in sinus rhythm.

📝 Because of the variability of the mean pressure gradient with HR and forward flow, you may not see it included in the criteria for severity.

Stage	Definition	Valve Anatomy	Valve Hemodynamics	Hemodynamic Consequences	Symptoms
A	At risk of MS	Mild valve doming during diastole	Normal transmitral flow velocity	None	None
B	Progressive MS	Rheumatic valve changes with commissural fusion and diastolic doming of the mitral valve leaflets Planimetered mitral valve area >1.5 cm2	Increased transmitral flow velocities Mitral valve area >1.5 cm2 Diastolic pressure half-time <150 ms	Mild to moderate LA enlargement Normal pulmonary pressure at rest	None
C	Asymptomatic severe MS	Rheumatic valve changes with commissural fusion and diastolic doming of the mitral valve leaflets Planimetered mitral valve area ≤1.5 cm2	Mitral valve area ≤1.5 cm2 Diastolic pressure half-time ≥150 ms	Severe LA enlargement Elevated PASP >50 mm Hg	None
D	Symptomatic severe MS	Rheumatic valve changes with commissural fusion and diastolic doming of the mitral valve leaflets Planimetered mitral valve area ≤1.5 cm2	Mitral valve area ≤1.5 cm2 Diastolic pressure half-time ≥150 ms	Severe LA enlargement Elevated PASP >50 mm Hg	Decreased exercise tolerance Exertional dyspnea
Source: Table 16 of Otto et al.

Severe MS

• Mitral valve area (MVA) is considered significantly narrowed when <1.5 cm2

Wilkins Score for Balloon Valvuloplasty

• Wilkins Echo score can predict the procedural success for mitral valvuloplasty based on valve structure.
• Grades each of the following components from 1 to 4:
  • leaflet mobility
  • leaflet thickness
  • calcification
  • abnormalities of the subvalvular apparatus
• Wilkins score ≤ 8 predicts a more favorable procedural, short, intermediate and long-term outcome (including survival).

Echo in MS

• MS severity is assessed in 3 ways:
  • Doppler pressure gradient
    • Mean gradient is more important than peak gradient
    • ⚠️ may overestimate severity when transmitral flow is ↑ (e.g., with concomitant MR) and may also be misleading when ventricular compliance is abnormal
  • Direct planimetry of MVA
    • Preferred approach as it is it is independent of loading conditions
  • Pressure Half Time (PHT) method
    • The more severe the MS, the slower the emptying into the LV and the longer the PHT will be.
    • ⚠️ may be inaccurate in patients with abnormalities of LA or LV compliance, those with associated aortic regurgitation, and those who have had recent mitral valvuloplasty.
    • ⚠️ has not been validated in patients with calcific MS

Echo Math for MS

MVA using PHT

$$\text{Mitral Valve Area (MVA)}=\frac{220}{\text{PHT}}$$

MVA using PISA method

$$\text{MVA}=\left(\frac{2\pi \cdot {r_{\text{PISA}}}^2\cdot \text{Aliasing velocity}}{V_{\text{max}}}\right)\times \frac{\alpha }{180}$$

Management