ECHOCARDIOGRAPHIC ASSESSMENT OF AORTIC VALVE STENOSIS

1. ECHOCARDIOGRAPHIC ASSESSMENT OF AORTIC VALVE STENOSIS Dr Ranjith MP

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

3. 2D Echo-Long axis view Diastole Systole

4. 2D Echo-Short axis view Diastole Systole Y or inverted Mercedes-Benz sign

5. 2D - Apical five chamber view

6. 2D – Suprasternal view

7. M Mode- Normal aortic valve

8. CAUSES AND ANATOMIC PRESENTATION

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

10. 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.

11. 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

12. Calcific Aortic Stenosis • Parasternal long axis view showing echogenic and immobile aortic valve

13. 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

14. 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.

15. Bicuspid Aortic valve • 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.

16. 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 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

17. 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.

18. Aortic sclerosis • Thickened calcified cusps with preserved mobility • Typically associated with peak doppler velocity of less than 2.5 m/sec

19. Rheumatic aortic stenosis • Characterized by • Commissural fusion • Triangular systolic orifice • thickening & calcification • Accompanied by rheumatic mitral valve changes.

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

21. 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.

22. 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.

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

24. HOW TO ASSESS AORTIC STENOSIS

25. 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.

26. 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

27. Peak transvalvular velocity • 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.

28. 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

29. 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 the curve is more rounded in shape • With mild obstruction, the peak is in early systole with a triangular shape of the velocity curve

30. Peak transvalvular velocity • 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

31. 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.

32. 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

33. 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)

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

35. 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

36. 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

37. 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)

38. Comparing pressure gradients calculated fromdoppler velocities to pressures measured at cardiac catheterization.

39. Comparing pressure gradients calculated fromdoppler velocities to pressures measured at cardiac catheterization. Currie PJ et al. Circulation 1985;71:1162-1169

40. Aortic valve areaContinuity equation

41. 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=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.

42. Aortic valve areaContinuity 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.

43. Aortic valve areaContinuity 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

44. Aortic valve area-Continuity equationLevel of Evidence • Well validated - clinical & experimental studies. Zoghbi WA et al. Circulation 1986;73:452-9. Oh JK et al. J Am CollCardiol 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.

45. 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

46. 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.

47. 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.

48. 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

49. 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 bpm over baseline or exceeds 100bpm

50. Dobutamine stress Echo • 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..