Aortic Stenosis (AS) 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.
ETIOLOGIES:
1. Calcification (age-related or acquired):
- Increased echogenicity of cusps
- Sclerosis - Areas of focal thickening on cusps
- Decrease in valve/orifice size
- Decrease in systolic leaflet excursion
2. Rheumatic (acquired post-inflammatory disease)
- Commissural fusion
- Fibrosis of the valve apparatus
- Increased echogenicity of cusps
- Systolic doming of cusps
- Reduced maximal systolic cusp excursion (< 1.5 cm)
- Decreased valve area (orifice size)
3. Congenital & Other
- Stenotic at birth
- Unicuspid (single cusp)
- Quadricuspid (four cusps)
- Bicuspid (two cusps) - gradual thickening/calcification over time
Bicuspid Aortic Valve (BAV)
- PSLAX will depict eccentric closure line, doming in systole and redundant diastolic closure.
- PSSAX will show only 2 cusps (fish mouth or raphe appearance), decreased valve area size with increased echogenicity.
Doppler spectral analysis:
- Aliasing LVOT flow with PW Doppler.
- Laminar high velocity jet seen with CW Doppler
Secondary findings of AS:
- Left Ventricular Hypertrophy
- Left Atrial Enlargement
- Mitral Stenosis
- Post stenotic dilation of aorta
- MAC - Annular Calcification
- Aortic insufficiency
Quantification of MV Stenosis Severity:
1. Continuity equation (AVA = Aortic Valve Area)
- LVOT Diameter (PSLAX)
- LVOT VTI, V1 max (Trace LVOT PW flow)
- AoV VTI, V2 max (Trace AoV CW flow, *Use PEDOF/blind probe)
- AVA = π(LVOT/2)² x V1/V2
2. Dimensionless Index (DI) - Velocity Ratio
- V1 = Subvalvular velocity (LVOT)
- V2 = Maximum veloctiy across aortic valve
- DI = V1/V2
3. Planimetry of the AoV
Imaging techniques to quantify AS:
1. LVOT Diameter
- Measure using the PSLAX view
- Measure during mid-systole using zoom function
- Proximal to aortic annulus (0.5 - 1.0 cm)
2. V1 (LVOT Flow)
- Views - Apical 5 and/or 3 chamber views
- PW Doppler proximal to aortic annulus (0.5 - 1.0 cm)
- Sample volume is advanced up the outflow tract until rapid acceleration is noted then withdrawn slightly.
3. V2 (AoV Flow)
- Use multiple views - Apical 5/3, SSN, Right Parasternal
- Use PEDOF/blind probe
- Trace spectral display with complete maximal velocity envelope, avoid over or under gaining.
AS SEVERITY VALUES:
