Eccentric opening possible in bicuspid aortic valve or in
asymmetric commissural fusion.
Spectral
Doppler
Patients with suspected aortic stenosis should have a thorough
examination with continous wave Doppler. It is important
to evaluate the valve with the Pedoff probe from the apex
and suprasternal notch, and also at the right sternal border
with the patient in the right decubitus position. The
Pedoff, or "blind", transducer provides more accurate measurements
because it doesn't share bandwidth with the imaging component
of the "inline" transducer and may detect significantly higher
gradients across the valve.
Increased
Peak Systolic Velocity - > 3.5 m/sec
Note: Obtain maximal velocities in apical and suprasternal
views
Decreased
fractional shortening in chronic aortic stenosis
Aorta
2D
Echocardiography
Post
Stenotic Dilatation of Aorta
Possible
presence of coarctation with bicuspid aortic valve
Anatomy
- altered valve profile in acuspid (no leaflets)
Estimation
of Severity
Imaging
direct
measurement of aortic valve area in the parasternal short
axis is difficult that with the mitral valve due to the smaller,
more irregular and coarsely calcified valve. The aortic valve
moves more rapidly through the scan plane than the mitral
valve. The range from mild to severe stenosis is small (.25cm2).
evaluation
of leaflet motion as maximal aortic cusp separation (MACS)
may be diminished when seen in the parasternal long axis view.
Imaging should include the technique of "sweeping"
through the scan plane to note valve irregularities. When
MACS is <11mm, stenosis may be inferred as severe and valve
surface area is ~.75cm2. Then MACS is >13mm, stenosis is
considered to be mild with aortic valve surface area ~>1cm2.
Doppler
Peak
Pressure Gradient - Use the Bernoulli equation:
Beam should be parallel to blood flow so that the cosine theta
angle should be no greater than 20 degrees to avoid underestimating
the gradient. Seek the maximal velocity from apical, suprasternal,
supraclavicular, left parasternal, right parasternal, and
subcostal. Pressure gradients may be higher in patients with
elevated cardiac output due to exercise, pregnancy, or acute
anxiety states. Also, in patients with both aortic stenosis
and aortic regurgitation, the augmentation of the forward
stroke volume with the regurgitant volume will increase the
pressure gradient.
Mean
Pressure Gradient – if instrument does not planimeter
the gradient, you can use the manual method:
1) measure the velocity of the envelope at equal spacing.
2) square each velocity
3) average the velocities by adding all of the values and
dividing the number of values
4) multiply value by 4 to get gradient in millimeters of
mercury.
Aortic
Valve Area - use the Continuity Equation to determine the
aortic valve surface area in cm2.
AVA
= CSA(LVOT) * (Vmax LVOT) / (Vmax AV)
Steps in Determining the values:
1)
measure the LVOT diameter just below the aortic valve
in the parasternal long axis view.
2) Calculate the CSA : CSA=.785(D2)
3) Measure the velocity of the LVOT with PW Doppler from
the apical 5 chamber to the maximal velocity just beyond
the Aortic Valve.
4) Measure the velocity of the LVOT with CW Doppler from
the apical, suprasternal, supraclavicular, left parasternal,
right parasternal, and subcostal positions
Normal Aortic Doppler Values
peak
velocity
valve
surface area
Normal
1.35m/s
(1.0 to 1.7)
2-4cm2
Mild
<3.5m/s
>1cm2
Moderate
3.5m/s
to 4.0m/s
.75-1cm2
Severe
>4.0m/s
<.75cm2
Differential Diagnosis in Patients with both AS and MR –
the aortic Doppler envelope occurs later and ends earlier
than the envelope of mitral regurgitation. Also, the peak
velocity of mitral regurgitation is always higher than that
for aortic stenosis.
Cardiac
Catheterization
Pressure
Data
Left
Ventricular Pressure
Elevated
left ventricular pressure occurs due to the greater effort
of the ventricle to force blood through the narrowed opening
of the aortic valve.
Elevated
end diastolic pressure may occur as ventricle adapts to
the pressure overload condition.
Left
Atrial Pressure
Elevated
left atrial pressure increases as atrium adapts to changes
in left ventricular pressures.
Prolonged
elevated left ventricular pressures may cause mitral regurgitation.
Aortic
Valve Gradient
Peak
to peak pressure gradient is calculated by measuring the
peak left ventricular systolic pressure minus the peak aortic
systolic pressure. This illustration shows an LV-to-AO pullback
recording of the change in pressure across the valve.
CALCULATOR
