1. Echocardiographic Assessment of Aortic Stenosis
Dr Julian Johny Thottian

2. Aorta - anatomy
Eur J Echocardiogr 2009;10:i3-10

3. Normal Aortic valve Three cusps, crescent shaped 3 commissures
3 sinuses
supported by fibrous annulus
3.0 to 4.0 cm2
Node of Arantius

4. PLAX

5. ZOOMED PLAX

6. The long-axis view of the left ventricle corresponding with the echocardiographic parasternal long-axis view, demonstrating the extent of the aortic root.
Figure 2. The long-axis view of the left ventricle corresponding with the echocardiographic parasternal long-axis view, demonstrating the extent of the aortic root. AV indicates aortic valve.
Piazza N et al. Circ Cardiovasc Interv 2008;1:74-81
Copyright © American Heart Association

7. M MODE
M MODE

8. PSAX

9. VARIOUS MEASUREMENTS VS 2.8+/- 0.3 STJ 2.4+/- 0.4 AAo AA 2.6+/- 0.3
1.9+/- 0.2
Evangelista A, Flachskampf FA, Erbel R et al. Echocardiography in aortic diseases: EAE recommendations for clinical practice. Eur J Echocardiogr 2010;11:645-58

10. 2D - Apical five chamber view

11. 2D – Suprasternal view

12. 3D ECHO

14. TEE

15. Aortic stenosis- Causes
Most common :-
Bicuspid aortic valve with calcification
Senile or Degenerative calcific AS
Rheumatic AS
Less common:-
Congenital
Type 2 Hyperlipoproteinemia
Oochronosis

16. ANATOMIC CONSIDERATIONS

17. Calcified aortic valve
Most prominent in the central part of each cusp
Commissural fusion absent
Stellate-shaped systolic orifice.
Valve calcification
Mild - few areas of dense echogenicity with little acoustic shadowing Severe- extensive thickening and increased echogenicity with a prominent acoustic shadow.
Valve calcification - predictor of clinical outcome.

18. Calcific Aortic Stenosis
Calcification of a bicuspid or tricuspid valve, the severity can be graded semi-quantitatively as
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.

19. Calcific Aortic Valve

20. Bicuspid Aortic Valve
Fusion of the RCC & LCC -80% of cases Fusion of the RCC & NCC-20% of cases Fusion of the LCC and NCC is rare.

21. Bicuspid Aortic Valve

22. Rheumatic aortic stenosis
Rheumatic AS - commissural fusion
Triangular systolic orifice Thickening and calcification mostly along the edges of the cusps.
Concomitant involvement of mitral valve seen

23. 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.
Long axis view in a patent with a subaortic membrane (arrow).

24. 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.

25. 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

26. AORTIC VALVE ASSESSMENT

27. There are many Echo criteria for assessment of Aortic stenosis

28. Let’s focus on the ones used in daily practice.

29. RECOMMENDATIONS FOR STANDARD CLINICAL PRACTICE LEVEL A- ESC 2009
● AS jet velocity
● Mean trans aortic gradient
● Valve area by continuity equation.

30. AS JET VELOCITY

31. Jet Velocity This is measured with Continuous wave doppler
Multiple windows and “non-standard views” to look for the highest Vmax
Apical and Suprasternal or right parasternal most frequently yield the highest velocity;
Subcostal or Supraclavicular windows may be required.

32. Aortic Jet Velocity
Patient positioning Adjustment of transducer position Angle - velocity measurement assumes a parallel intercept angle between the ultrasound beam and direction of blood flow
AS jet velocity is defined as the highest velocity signal obtained from any window

33. Aortic Jet Velocity Pitfalls
Any deviation from a parallel intercept angle results in velocity underestimation- degree of underestimation is 5% or less if the intercept angle is within 15° of parallel.
“Angle correction” should not be used.

34. Continuous-wave Doppler of severe aortic stenosis jet
showing measurement of maximum velocity and tracing of the
velocity curve to calculate mean pressure gradient.

35. Mean transvalvular gradient
The difference in pressure between the left ventricle and aorta in systole
Gradients are calculated from velocity information
It is the mean of different instantaneous velocities recorded

36. Mean transvalvular gradient
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

37. 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- v2proximal)

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

40. Other 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

41. 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

42. 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)

43. Cath Vs Echo

44. Comparing pressure gradients calculated from doppler velocities to pressures measured at cardiac catheterization.
Currie PJ et al. Circulation 1985;71:

45. Continuity Equation
Schematic diagram of continuity equation. The assumption is that SV LVOT = SV Aortic Valve

46. Continuity Equation
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.

47. Continuity Equation
LVOT diameter and PW of the LVOT needs to taken from the same location in the LVOT.
LVOT diameter measured- PLAX view
LVOT velocity (or VTI) is measured apically – beware of distance error.
The pulsed-Doppler sample volume is positioned just proximal to the aortic valve so that the location of the velocity recording matches the LVOT diameter measurement.

48. LVOT Diameter
Left ventricular outflow tract diameter is measured in the parasternal long-axis view in mid-systole from the white–black interface of the septal endocardium to the anterior mitral leaflet, parallel to the aortic valve plane and within 0.5–1.0 cm of the valve orifice.

49. Velocity or VTI measurement
LVOT velocity is measured from the apical approach either in an apical long-axis view or an anteriorly angulated four-chamber view An optimal signal shows a smooth velocity curve with a narrow velocity range at each time point. Maximum velocity is measured as shown. The VTI is measured by tracing the modal velocity (middle of the dense signal)

50. Pitfalls of the Continuity Equation
Depends on the variability in each of the three measurements, including both the variability in acquiring the data and variability in measuring the recorded data.
AS jet and LVOT velocity measurements - intra- and inter-observer variability (3–4%)
The measurement variability for LVOT diameter ranges from 5% to 8%.
When trans-thoracic images are not adequate for the measurement of LVOT diameter then TEE used.

51. Pitfalls of the continuity Equation
When subaortic flow velocities are abnormal, for example, with dynamic subaortic obstruction or a subaortic membrane, SV calculations at this site are not accurate.
Another limitation of valve area as a measure of stenosis severity is the observed changes in valve area with changes in flow rate.
In adults with AS and normal LV function, the effects of flow rate are minimal and resting effective valve area calculations are accurate.
This effect may be significant when concurrent LV dysfunction results in decreased cusp opening and a small effective orifice area even though severe stenosis is not present.

52. Alternate measures of stenosis severity
(Level 2 EAE/ASE Recommendations )

53. Simplified continuity equation AVA= CSA LVOT×VLVOT / VAV
Considering 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
Less well accepted because results are more variable than using VTIs in the equation.

54. 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.

55. 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;

56. Planimetered Aortic VAvle

57. Aortic valve area - Planimetry

58. Experimental descriptors of stenosis severity
(Level 3 EAE/ASE Recommendations -not recommended for routine clinical use)

59. 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

60. 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

61. 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.
Damien Garcia.et al. Circulation. 2000;101:

62. Energy loss index Damien Garcia.et al. Circulation. 2000;101:765-771.
Energy loss coefficient (EOA × AA)/(AA - EOA) accurately predicted the energy loss.
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%).

63. Classification of AS severity (a ESC & b AHA/ACC Guidelines)
Aortic Sclerosis
Mild
Moderate
Severe
Aortic jet velocity (m/s)
≤ 2.5 m/s
> 4
Mean gradient (mm Hg)
< 20b(<30a)
20 – 40b (30 -50a)
> 40
AVA (cm²)
> 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

64. Effects of concurrent conditions
ASSOCIATED LV SYSTOLIC DYSFUNCTION
AS gradient becomes low, despite a small valve area- ‘low-flow low-gradient AS’
Defined as Effective orifice area 1.0 cm2
2. LV ejection fraction< 40% Mean pressure gradient <30–40 mmHg

65. Dobutamine stress echo
Measures contractile response
2. changes in aortic velocity, mean gradient, and valve area as flow rate increases
Helps to find out
Severe AS causing LV systolic dysfunction
Moderate AS with another cause of LV dysfunction

66. Protocol
Low dose or 5 mg/kg/min with an incremental increase in the infusion every 3–5 min to a maximum dose of 10–20 mg/kg/min.
The infusion is stopped-
1. As soon as a positive result is obtained Heart rate begins to rise more than 10–20 bpm over baseline or exceeds 100 bpm Symptoms, blood pressure fall, or significant arrhythmias

67. RESULTS
AS velocity, MG, valve area, and EF preferably at each stage (to judge reliability of measurements) but at least at baseline and peak dose
An increase in valve area to a final valve area 1.0 cm2 suggests that stenosis is not severe.
Severe stenosis is suggested by an AS jet 4.0 or a mean gradient 40 mmHg provided that valve area does not exceed 1.0 cm2 at any flow rate.
Absence of contractile reserve (failure to increase SV or EF by 20%) is a predictor of a high surgical mortality and poor long-term outcome although valve replacement may improve LV function and outcome even in this subgroup.

69. LVH
Small ventricular cavity with thick walls and diastolic dysfunction
Small LV ejects a small SV so that, even when severe stenosis is present, the AS velocity and mean gradient may be lower
Continuity-equation valve area is accurate indexing valve area to body size

70. Hypertension Associated in 35-40%
HT increases LV pressure load may cause changes in ejection fraction and flow
Mascherbauer J, Fuchs C, Stoiber M, Schima H, Pernicka E, Maurer G et al. Systemic pressure does not directly affect pressure gradient and valve area estimates in aortic stenosis in vitro. Eur Heart J 2008;29:
presence of hypertension may therefore
primarily affect flow and gradients but less AVA measurement.

71. Aortic regurgitation
Severe AR accompanies AS, measures of AS severity remain accurate including maximum velocity, mean gradient, and valve area
High transaortic volume flow rate, maximum velocity, and mean gradient will be higher than expected for a given valve area.

72. Mitral valve disease
Severe MR, transaortic flow rate may be low resulting in a low gradient even when severe AS is present
A high-velocity MR jet may be mistaken for the AS jet as both are systolic signals directed away from the apex.

73. High cardiac output Ascending aorta
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

74. 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

75. THANK YOU

76. QUIZ

77. Question 1
A patient with severe aortic stenosis has MR. Which one of the following statements is incorrect?
The peak mitral regurgitation jet velocity is higher than the peak trans-aortic valve flow velocity.
The aortic transvalvular flow duration is shorter than the MR jet duration.
The LVOT flow duration is longer than the MR jet duration.
MR signal is not obtained in suprasternal window

78. Question 2
Which of the following is not a marker of severe aortic stenosis?
1. Vmax across the Aortic valve is > 4m/s
2. Calculated aortic valve area of 1.34 cm2
3. LVOT Vmx / AV Vmx ratio < 0.25
4. Mean gradient = 55 mmHg

79. Question 3
Which is not recommended in level A in assessing aortic stenosis
1. AS jet velocity
2. Mean trans aortic gradient
3. Valve area by continuity equation.
4. Planimetry

80. Question 4 False about severe AS Mean gradient above 30 mm Hg
Velocity ratio < 0.25
3. Indexed valve area < 0.6 cm/ m2
4. Peak velocity > 4m/sec

81. Question 5
At maximal dobutamine infusion, in an AS patient, the peak LVOT velocity increased from 50 to 90 cm / sec., while the peak transaortic valve velocity increased from 2 to 2.3 m/sec. The LVOT diameter is 2 cm. This study suggests that:
1. The baseline ejection fraction was < 20%.
2. There is significant AR.
3. AS is not severe.
4 LV motion did not improve.

82. Question 6 Which cannot be used for calculating area of aortic valve ?
1. MV annular diameter
2. MV annular VTI
3. AV VTI
4. LVOT diameter

83. Question 7
False about Maximal aortic cusp separation? 1. MACS of normal aortic valve is >15 mm
2. AVA <0.75 corresponds to MACS <8mm
3. Vertical distance between left CC and non CC during systole
4. Gray area is 8-12mm

84. Question 8
False about standard dobutamine stress echocardiography for evaluation of AS severity in setting of LV dysfunction
1 Uses low dose of dobutamine starting at 2.5 or 5ủg/kg/min
2 Maximum dose of dobutamine used is 10–20 ủg/kg/min
3 The infusion should be stopped when the heart rate begins to rise more than 10–20 bpm over baseline
4 Failure of LVEF to ↑ by 40% is a poor prognostic sign

85. Question 9 Continuity equation obeys Bernoulli`s principle Ohm`s law
Law of conservation of energy
Poiseuille`s law

86. Question 10
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