Echo assessment of Aortic Stenosis

ECHOCARDIOGRAPHIC
ASSESSMENT OF AORTIC
VALVE STENOSIS

Dr Ranjith MP

Normal Aortic valve
 Three cusps, crescent shaped
3 commissures
3 sinuses
supported by fibrous annulus

3.0 to 4.0 cm2

Node of Arantius

2D Echo-Long axis view
Diastole Systole

2D Echo-Short axis view
Diastole Systole

Y or inverted Mercedes-Benz sign

CAUSES AND ANATOMIC
PRESENTATION

Aortic stenosis- Causes
Most common :-
Bicuspid aortic valve with calcification
Senile or Degenerative calcific AS
Rheumatic AS

Less common:-
Congenital
Type 2 Hyperlipoproteinemia
Onchronosis

Anatomic evaluation

 Combination of short and long axis images to
identify
Number of leaflets
Describe leaf mobility, thickness, calcification

Combination of imaging and doppler allows
the determination of the level of obstruction;
subvalvular, valvular, or supravalvular.

Transesophageal echocardiography may be
helpful when image quality is suboptimal.

Calcific Aortic Stenosis
 Nodular calcific masses on aortic side of cusps
No commissural fusion
Free edges of cusps are not involved
stellate-shaped systolic orifice

Parasternal long axis
view showing
echogenic and
immobile aortic valve

Parasternal short-axis
view showing calcified
aortic valve leaflets.
Immobility of the cusps
results in only a slit like
aortic valve orifice in
systole

Bicuspid Aortic valve
 Fusion of the right and left coronary cusps (80%)
 Fusion of the right and non-coronary cusps(20%)
Schaefer BM et al. Am J Cardiol 2007;99:686–90
Schaefer BM et al.Heart 2008;94:1634–1638.

Two cusps are seen in systole with only two
commissures framing an elliptical systolic
orifice(the fish mouth appearance).
Diastolic images may mimic a tricuspid valve
when a raphe is present.

Parasternal long-axis echocardiogram may show
an asymmetric closure line
 systolic doming
 diastolic prolapse of the cusps

In children, valve may be stenotic
without extensive calcification.

In adults, stenosis typically is due to calcific changes,
which often obscures the number of cusps, making
determination of bicuspid vs. tricuspid valve difficult

 Calcification of a bicuspid or tricuspid valve, the severity
can be graded semi-quantitatively as

0 1+ 2+ 3+ 4+
Schaefer BM et al.Heart 2008;94:1634–1638.
 The degree of valve calcification is a predictor of clinical
outcome. Rosenhek R et al. N Engl J Med 2000;343:611–7.

Aortic sclerosis
Thickened calcified cusps with preserved
mobility

Typically associated with peak doppler
velocity of less than 2.5 m/sec

Rheumatic aortic stenosis
Characterized by
Commissural fusion
Triangular systolic orifice
thickening & calcification

Accompanied by rheumatic mitral valve
changes.

Rheumatic aortic stenosis
Parasternal short axis view showing commissural
fusion, leaflet thickening and calcification, small
triangular systolic orifice

Subvalvular aortic stenosis
(1) Thin discrete membrane consisting of
endocardial fold and fibrous tissue
(2) A fibromuscular ridge
(3) Diffuse tunnel-like narrowing of the LVOT
(4) accessory or anomalous mitral valve tissue.

Supravalvular Aortic stenosis
Type I - Thick, fibrous ring above the aortic
valve with less mobility and has the easily
identifiable 'hourglass' appearance of the aorta.

Supravalvular Aortic stenosis
Type II - Thin, discrete fibrous membrane
located above the aortic valve
The membrane usually mobile and may
demonstrate doming during systole
 Type III- Diffuse narrowing

HOW TO ASSESS AORTIC
STENOSIS

Doppler assessment of AS
The primary haemodynamic parameters
recommended (EAE/ASE Recommendations for
Clinical Practice 2008)

Peak transvalvular velocity

Mean transvalvular gradient

 Valve area by continuity equation.

Peak transvalvular velocity
Continuous-wave Doppler ultrasound

Multiple acoustic windows
 Apical and suprasternal or right parasternal
most frequently yield the highest velocity
 rarely subcostal or supraclavicular windows
may be required

Three or more beats are averaged in sinus
rhythm, with irregular rhythms at least 5
consecutive beats

AS jet velocity is defined as the highest velocity signal
obtained from any window after a careful examination

Any deviation from a parallel intercept angle results in
velocity underestimation

The degree of underestimation is 5% or less if the
intercept angle is within 15⁰ of parallel.

‘Angle correction’ should not be used because it is likely
to introduce more error given the unpredictable jet
direction.

 The velocity scale adjusted so the spectral doppler signal
fills on the vertical axis, and with a time scale on the x-axis
of 100 mm/s

 Wall filters are set at a high level and gain is decreased to
optimize identification of the velocity curve.

 Grey scale is used

 A smooth velocity curve with a dense outer edge and clear
maximum velocity should be recorded

The shape of the CW Doppler velocity curve is helpful
in distinguishing the level and severity of obstruction.

With severe obstruction, maximum
velocity occurs later in systole and the
curve is more rounded in shape

With mild obstruction, the peak
is in early systole with a triangular
shape of the velocity curve

The shape of the CWD velocity curve also can be
helpful in determining whether the obstruction is
fixed or dynamic

Dynamic sub aortic obstruction
shows a characteristic late-
peaking velocity curve, often with
a concave upward curve in
early systole

Mean transvalvular gradient

 The difference in pressure between the left
ventricle and aorta in systole

 Gradients are calculated from velocity
information

 The relationship between peak and mean
gradient depends on the shape of the velocity
curve.


Bernoulli equations
ΔP =4v²
The maximum gradient is calculated from
maximum velocity
ΔP max =4v² max
The mean gradient is calculated by averaging
the instantaneous gradients over the ejection
period


The simplified Bernoulli equation assumes
that the proximal velocity can be ignored

When the proximal velocity is over 1.5 m/s or
the aortic velocity is ,3.0 m/s, the proximal
velocity should be included in the Bernoulli
equation ΔP max =4 (v² max- v2proximal)

Sources of error for pressure
gradient calculations
Malalignment of jet and ultrasound beam.
Recording of MR jet

Sources of error for pressure
gradient calculations
Neglect of an elevated proximal velocity.

Any underestimation of aortic velocity results in
an even greater underestimation in gradients,
due to the squared relationship between velocity
and pressure difference

The accuracy of the Bernoulli equation to
quantify AS pressure gradients is well established

Pressure recovery
The conversion of potential energy to kinetic
energy across a narrowed valve results in a
high velocity and a drop in pressure.

Distal to the orifice, flow decelerates again.
Kinetic energy will be reconverted into
potential energy with a corresponding
increase in pressure, the so-called PR

Pressure recovery
Pressure recovery is greatest in stenosis with
gradual distal widening

Aortic stenosis with its abrupt widening from
the small orifice to the larger aorta has an
unfavorable geometry for pressure recovery

PR= 4v²× 2EOA/AoA (1-EOA/AoA)

Comparing pressure gradients calculated from
doppler velocities to pressures measured at
cardiac catheterization.

Comparing pressure gradients calculated from
doppler velocities to pressures measured at
cardiac catheterization.

Currie PJ et al. Circulation 1985;71:1162-1169

Aortic valve area
Continuity equation

Aortic valve area
Aortic valve area
Continuity equation concept that the stroke
volume ejected through the LV outflow tract all
passes through the stenotic orifice

AVA= CSA LVOT×VTILVOT / VTIAV

Calculation of continuity-equation valve area
requires three measurements
 AS jet velocity by CWD
 LVOT diameter for calculation of a circular CSA
 LVOT velocity recorded with pulsed Doppler.

Aortic valve area
Continuity equation
LVOT diameter and velocity should be measured at the
same distance from the aortic valve.

When the PW sample volume is optimally positioned,
the recording shows a smooth velocity curve with a
well-defined peak.

Aortic valve area
Continuity equation
The VTI is measured by tracing the dense modal
velocity throughout systole
LVOT diameter is measured from the inner edge to
inner edge of the septal endocardium, and the
anterior mitral leaflet in mid-systole

Aortic valve area-Continuity equation
Level of Evidence

Well validated - clinical & experimental studies.
Zoghbi WA et al. Circulation 1986;73:452-9.
Oh JK et al. J Am Coll Cardiol 1988;11:1227-34.

Measures the effective valve area, the weight
of the evidence now supports the concept that
effective, not anatomic, orifice area is the
primary predictor of clinical outcome.
Baumgartner et al. J Am Society Echo 2009; 22,1 , 1-23.

Limitations of continuity-
equation valve area
Intra- and interobserver variability
AS jet and LVOT velocity 3 to4%.
LVOT diameter 5% to 8%.
When sub aortic flow velocities are abnormal
SV calculation at this site are not accurate

Sample volume placement near to septum or
anterior mitral leaflet

Limitations of continuity-
equation valve area
Observed changes in valve area with changes
in flow rate

AS and normal LV function, the effects of flow
rate are minimal

This effect may be significant in presence
concurrent LV dysfunction.

Left ventricular systolic
dysfunction
Low-flow low-gradient AS includes the
following conditions:

Effective orifice area < 1.0 Cm2
LV ejection fraction < 40%
 Mean pressure gradient < 30–40 mmHg
Severe AS and severely reduced LVEF
represent 5% of AS patients
Vahanian A et al. Eur Heart J 2007;28:230–68.

Dobutamine stress Echo
Provides information on the changes in aortic
velocity, mean gradient, and valve area as flow rate
increases.

Measure of the contractile response to dobutamine

Helpful to differentiate two clinical situations
Severe AS causing LV systolic dysfunction
Moderate AS with another cause of LV dysfunction

A low dose starting at 2.5 or 5 ủg/kg/min with
an incremental increase in the infusion every 3–
5 min to a maximum dose of 10–20 ủg/kg/min

The infusion should be stopped as soon as
Positive result is obtained
Heart rate begins to rise more than 10–20 bpm
over baseline or exceeds 100bpm

Role in decision-making in adults with AS is
controversial and the findings recommend as
reliable are
Stress findings of severe stenosis
AVA<1cm²
Jet velocity>4m/s
Mean gradient>40mm of Hg
Nishimura RA et al. Circulation 2002;106:809-13.
Lack of contractile reserve-
Failure of LVEF to ↑ by 20% is a poor prognostic sign
Monin JL et al. Circulation 2003;108:319-24..

Serial measurements
During follow-up any significant changes in
results should be checked in detail:

Make sure that aortic jet velocity is recorded from
the same window with the same quality (always
report the window where highest velocities can be
recorded).
 when AVA changes, look for changes in the
different components incorporated in the
equation.
 LVOT size rarely changes over time in adults.

Alternate measures of
stenosis severity

(Level 2 EAE/ASE Recommendations )

Simplified continuity
equation.
Based on the concept that in native aortic
valve stenosis the shape of the velocity curve
in the outflow tract and aorta is similar so that
the ratio of LVOT to aortic jet VTI is nearly
identical to the ratio of the LVOT to aortic jet
maximum velocity.
AVA= CSA LVOT×VLVOT / VAV
This method is less well accepted because
results are more variable than using VTIs in
the equation.

Velocity ratio
Another approach to reducing error related to
LVOT diameter measurements is removing CSA
from the simplified continuity equation.

This dimensionless velocity ratio expresses the size
of the valvular effective area as a proportion of the
CSA of the LVOT.

Velocity ratio= VLVOT/VAV

In the absence of valve stenosis, the velocity ratio
approaches 1, with smaller numbers indicating
more severe stenosis.

Aortic valve area -Planimetry
Planimetry may be an acceptable alternative
when Doppler estimation of flow velocities is
unreliable

Planimetry may be inaccurate when valve
calcification causes shadows or reverberations
limiting identification of the orifice

Doppler-derived mean-valve area correlated
better with maximal anatomic area than with
mean-anatomic area.
Marie Arsenault, et al. J. Am. Coll. Cardiol. 1998;32;1931-1937

Aortic valve area - Planimetry

Experimental descriptors
of stenosis severity

(Level 3 EAE/ASE Recommendations -not
recommended for routine clinical use)

Valve resistance
Relatively flow-independent measure of stenosis
severity
Depends on the ratio of mean pressure gradient
and mean flow rate

Resistance = (ΔPmean /Qmean) × 1333

There is a close relationship between aortic valve
resistance and valve area
The advantage over continuity equation not
established

Left ventricular stroke work loss
Left ventricle expends work during systole to
keep the aortic valve open and to eject blood
into the aorta
SWL(%) = (100×ΔPmean)/ ΔPmean+SBP

A cutoff value more than 25% effectively
discriminated between patients experiencing
a good and poor outcome.
Kristian Wachtell. Euro Heart J.Suppl. (2008) 10 ( E), E16–E22

Energy loss index
Damien Garcia.et al. Circulation. 2000;101:765-771.

Fluid energy loss across stenotic aortic valves is
influenced by factors other than the valve effective
orifice area .
An experimental model was designed to measure
EOA and energy loss in 2 fixed stenoses and 7
bioprosthetic valves for different flow rates and 2
different aortic sizes (25 and 38 mm).
 EOA and energy loss is influenced by both flow rate
and AA and that the energy loss is systematically
higher (15±2%) in the large aorta.

Energy loss index

Energy loss coefficient (EOA × AA)/(AA - EOA) accurately
predicted the energy loss in all situations .
It is more closely related to the increase in left ventricular
workload than EOA.
To account for varying flow rates, the coefficient was indexed for
body surface area in a retrospective study of 138 patients with
moderate or severe aortic stenosis.
The energy loss index measured by Doppler echocardiography
was superior to the EOA in predicting the end points
 An energy loss index #0.52 cm2/m2 was the best predictor of
diverse outcomes (positive predictive value of 67%).

Classification of AS severity
(a ESC & bAHA/ACC Guidelines)

Aortic Sclerosis Mild Moderate Severe

Aortic jet velocity (m/s) ≤ 2.5 m/s 2.6 -2.9 3.0 - 4 >4

Mean gradient (mm Hg) < 20b(<30a) 20 – 40b (30 -50a) > 40

AVA (cm²) > 1.5 1.0 - 1.5 < 1.0

Indexed AVA (cm²/m²) > 0.85 0.60 – 0.85 < 0.6

Velocity ratio > 0.50 0.25 – 0.50 < 0.25

Effects of concurrent
conditions on assessment
of severity

Effect of concurrent conditions ……

Left ventricular systolic dysfunction

Left ventricular hypertrophy
Small ventricular cavity & small LV ejects a
small SV so that, even in severe AS the AS
velocity and mean gradient may be lower than
expected.
 Continuity-equation valve area is accurate in
this situation

Effect of concurrent conditions contd…

Hypertension
35–45% of patients
primarily affect flow and gradients but less AVA
measurements
Control of blood pressure is recommended
The echocardiographic report should always
include a blood pressure measurement


Aortic regurgitation

 About 80% of adults with AS also have aortic
regurgitation
High transaortic volume flow rate, maximum
velocity, and mean gradient will be higher than
expected for a given valve area
In this situation, reporting accurate quantitative
data for the severity of both stenosis and
regurgitation


Mitral valve disease

With severe MR, transaortic flow rate may be
low resulting in a low gradient .Valve area
calculations remain accurate in this setting

A high-velocity MR jet may be mistaken for the
AS jet. Timing of the signal is the most reliable
way to distinguish


High cardiac output
Relatively high gradients in the presence of
mild or moderate AS
The shape of the CWD spectrum with a very
early peak may help to quantify the severity
correctly
Ascending aorta
Aortic root dilation
Coarctation of aorta

M Mode- Aortic Stenosis
Maximal aortic cusp separation (MACS)
Vertical distance between right CC and non CC
during systole
Aortic valve area MACS Measurement Predictive value

Normal AVA >2Cm2 Normal MACS >15mm 100%

AVA>1.0 > 12mm 96%

AVA< 0.75 < 8mm 97%

Gray area 8-12 mm …..

DeMaria A N et al. Circulation.Suppl II. 58:232,1978

M Mode- Aortic Stenosis
Limitations
Single dimension
Asymmetrical AV involvement
Calcification / thickness
↓ LV systolic function
↓ CO status

Approach
 Valve anatomy, etiology
 Exclude other LVOTO
 Stenosis severity – jet velocity
 mean pressure gradient
 AVA – continuity equation

 LV – dimensions/hypertrophy/EF/diastolic fn
 Aorta- aortic diameter/ assess COA
 AR – quantification if more than mild
 MR- mechanism & severity
 Pulmonary pressure

MCQ -1
Which is false about Severe AS?

a) Aortic jet velocity > 4 m/s
b) Velocity ratio > 0.50
c) Indexed AVA < 0.6 cm²/m²
d) Mean gradient > 40 mm Hg
e) None of the above

MCQ-2
By definition Low-flow low-gradient AS
includes the following conditions except

a) Anatomic orifice area < 1.0 Cm2
b) LV ejection fraction < 40%
c) Mean pressure gradient < 30–40 mmHg
d) None

MCQ-3
Characteristic feature of calcific aortic stenosis
is ………….

a) Nodular calcific masses on ventricular side of
cusps
b) Calcium deposition at free edges of the cusp
c) Commissural fusion
d) None of the above

MCQ- 4
False about Maximal aortic cusp separation?
a) MACS of normal aortic valve is >15 mm
b) AVA <0.75 corresponds to MACS <8mm
c) Vertical distance between right CC and non CC
during systole
d) Gray area is 8-12mm

MCQ 5
All are true about standard dobutamine stress
echocardiography for evaluation of AS severity in setting
of LV dysfunction except?
A) Uses low dose of dobutamine starting at 2.5 or 5ủg/kg/min

B) Maximum dose of dobutamine used is 10–20 ủg/kg/min

C) The infusion should be stopped when the heart rate
begins to rise more than 10–20 bpm over baseline

D) Failure of LVEF to ↑ by 40% is a poor prognostic sign


MCQ 6
In a patient with aortic valve area of 0.6 sq
cm(not a low flow low gradient AS) continuous
wave Doppler velocity will be:

a) 1-2 m/sec
b) 2-3 m/sec
c) 3-4 m/sec
d) > 4 m/sec

MCQ-7
True about doppler assessment of AS is all
except ?
a) With severe obstruction, maximum velocity
occurs later in systole
b) Angle correction is likely to reduce errors in
measuring peak transvalvular gradient
a) Apical and suprasternal windows most
frequently yield the highest velocity
c) None of the above

MCQ-8
True a bout Bicuspid valve is?

a) Fusion of the right and non-coronary cusps occurs in
80% of cases
b) Fusion of the right and non-coronary cusps is more
commonly associated with mitral vale myxomatous
disease
c) Parasternal short axis view in diastole always
demonstrate bicuspid anatomy
d) Calcification usually occurs along the edges of cusp

MCQ -9
True about Supravalvular aortic stenosis is all?

a) Type 2 shows doming in systole
b) Type 3 hourglass appearance of aorta
c) Type 1is thin discrete fibrous membrane
d) Type 3 is localized disease just above aortic
valve

MCQ- 10
All are true except

a) accuracy of the Bernoulli equation to quantify AS
pressure gradients is well established
b) The relationship between peak and mean gradient
depends on the shape of the velocity curve.
c) Gradients are calculated from velocity information
d) Dynamic sub aortic obstruction shows a characteristic
early peaking velocity curve
e) None

MCQ-3
Characteristic feature of calcific aortic stenosis
is ………….

a) Nodular calcific masses on ventricular side of
cusps
b) Calcium deposition at free edges of the cusp
c) Commissural fusion is common and early
d) None of the above

MCQ-8
True a bout Bicuspid valve is?

a) Fusion of the right and non-coronary cusps occurs in
80% of cases
b) Fusion of the right and non-coronary cusps is more
commonly associated with mitral vale myxomatous
disease
c) Parasternal short axis view in diastole always
demonstrate bicuspid anatomy
d) Calcification usually starts along the edges of cusp

MCQ -9
True about Supravalvular aortic stenosis is all?

a) Type 2 shows doming in systole
b) Type 3 shows hourglass appearance of aorta
c) Type 1 is thin discrete fibrous membrane
d) Type 3 is localized disease just above aortic
valve

Echo assessment of Aortic Stenosis

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