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

2D - Apical five chamber view

2D – Suprasternal view

M Mode- Normal aortic valve

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

Combination of short and long axis images to identify

Number of leafletsDescribe 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.

Anatomic evaluation

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

Calcific Aortic Stenosis

Parasternal long axis view showing echogenic and immobile aortic valve

Calcific Aortic Stenosis

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.

Bicuspid Aortic valve

Bicuspid Aortic valve

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

In children, valve may be stenoticwithout 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

Calcific Aortic Stenosis

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.

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

Rheumatic aortic stenosis

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.

Type II - Thin, discrete fibrous membranelocated above the aortic valve

The membrane usually mobile and may demonstrate doming during systole

Type III- Diffuse narrowing

Supravalvular Aortic stenosis

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 parasternalmost 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.

Peak transvalvular velocity

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

Peak transvalvular velocity

Peak transvalvular velocity

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 thecurve is more rounded in shape

With mild obstruction, the peakis in early systole with a triangularshape 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 obstructionshows a characteristic late-peaking velocity curve, often with a concave upward curve inearly systole

Peak transvalvular velocity

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

Mean transvalvular gradient

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- v2

proximal)

Mean transvalvular gradient

Sources of error for pressure

gradient calculations

Malalignment of jet and ultrasound beam.

Recording of MR jet

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

Sources of error for pressure

gradient calculations

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)

Pressure recovery

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

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

AVA= CSALVOT×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

Aortic valve area

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

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.

Aortic valve area-Continuity equation

Level of Evidence

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

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.

Limitations of continuity-

equation valve area

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.

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 situationsSevere AS causing LV systolic dysfunction

Moderate AS with another cause of LV dysfunction

Dobutamine stress Echo

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 bpmover baseline or exceeds 100bpm

Dobutamine stress Echo

Role in decision-making in adults with AS is controversial and the findings recommend as reliable areStress findings of severe stenosis

AVA<1cm²

Jet velocity>4m/s

Mean gradient>40mm of HgNishimura 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..

Dobutamine stress Echo

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 )

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.

Simplified continuity

equation.

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.

Velocity ratio

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 areaThe 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 indexDamien 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.

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

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%).

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

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

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

Effect of concurrent conditions contd…

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

Effect of concurrent conditions contd…

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

Effect of concurrent conditions contd…

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

Effect of concurrent conditions contd…

Maximal aortic cusp separation (MACS)

Vertical distance between right CC and non CC during systole

M Mode- Aortic Stenosis

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

M Mode- Aortic Stenosis

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

Approach

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

e) None of the above

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

e) None of the above

MCQ 5

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/secb) 2-3 m/secc) 3-4 m/secd) > 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 myxomatousdisease

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 -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 is common and early

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

e) None of the above

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

e) None of the above

MCQ 5

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/secb) 2-3 m/secc) 3-4 m/secd) > 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 myxomatousdisease

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

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