Mitral Stenosis is the result of narrowing of the valve orifice causing obstruction or restriction of blood flow resulting in an increased flow velocity and pressure gradient across the valve. This change causes an increase in LA pressure and decrease in LV pressure.
ETIOLOGIES:
1. Calcification (age-related or acquired):
- MAC - Mitral Annular Calcification
- Chordal calcification
- Left Atrial Enlargement
- Decrease in diastolic leaflet excursion
2. Rheumatic (acquired post-inflammatory disease)
- Commissural fusion
- Diastolic doming of leaflets (hokey stick appearance)
- Anterior motion of posterior MV leaflet
- Decreased E-F slope (M-mode)
- Reduced maximal diastolic cusp excursion
- Decreased valve area (orifice size)
- LAE
3. Congenital & Other
- Stenotic at birth
- No thickening or commissural fusion
- Examples: Parachute MV and Double Orifice MV (DOMV)
Doppler spectral analysis:
- Increased PW/CW jet profile as restriction increases
- Increased peak inflow velocity
- Decreased E – F slope due to restricted inflow (increased DT)
Quantification of MV Stenosis Severity:
1. Valve area (2D planimetery)
- Tracing the inner MV area in diastole (PSSAX view) with appropriate lower gains. Identify max or largest orifice at tips of MV leaflets at beginning of diastole and trace inner border.
2. Transmitral pressure gradients
- Measure E wave max velocity and trace spectral flow in an aligned apical 4-chamber view. Ensure parallel positioning to vena contracta to obtain highest velocity flow.
3. Continuity equation (Doppler & 2D Diameter)
- LVOT Diameter (PSLAX)
- LVOT VTI (Trace LVOT spectral, same as with AS)
- MV VTI (Trace MV CW spectral trace)
4. Valve area by Pressure Half Time
- P½ Time (ms) - the time interval for maximum mitral pressure to fall by half its original value. MVA (cm²) = 220/P1/2T.
- Increased restriction will prolong blood flow, maintaining higher pressure difference between the two chambers over a longer period of time.
- This decay in pressure will take longer time if valve is stenotic due to increased LA pressures.
5. PISA
MS SEVERITY VALUES:
