1. Paul Nolan, Galway University Hospitals
Aortic stenosis – when echo and cath (or even echo and echo) don’t matcH

2. Echo evaluation of AS Define aetiology Quantitation of the severity
Assessment of LV function
Assessment of co-existing valvular lesions
Assessment of secondary effects
Pulmonary pressures
Aortic dilatation

3. Quantification of AS by echo
Peak velocity
Mean velocity
Peak gradient
Mean gradient
Aortic valve area
Continuity equation
Insert graph of Max V vs outcome

4. Jet velocity – too simple?
Otto 1997
123 asymptomatic patients
End point
Death
Aortic valve surgery
Jet velocity > 4m/s is an independent predictor of clinical outcome

5. Quantification of AS by Cardiac Cath
Maximum instantaneous gradient
Equivalent to peak gradient by echo
Mean gradient
Equivalent to mean gradient be echo
Peak to peak gradient
Not equivalent to any echo measure
?not physiological
Insert fig 11.9

6. Quantification of the AVA in the Cath Lab
Gorlin formula
AVA = Cardiac output
44.3 (SEP)(HR) √pressure gradient

7. So why sometimes do they not agree?
Cath lab vs echo image

8. Technical sources of error in Echo
Doppler angle

10. Technical sources of error in Echo
Doppler angle
Accuracy of the LVOT measurement
Any error is squared
Average of a number of measurements
Same measurement retained for serial echos
Placement of sample volume within LVOT
Non-simultaneous measurement of Ao and LVOT Doppler profiles
Especially important in irregular rhythms
Average of number of beats
Use max Ao and max LVOT velocities

11. The “Gold Standard”
DMcF

12. Sources of error in the lab
Assessments of Cardiac Output can be prone to error
Common practice of comparing LV to femoral/radial pressure
Damped pressures
Positioning of LV catheter
Alignment of LV and Ao trace

13. Effect of incorrect alignment
Mean grad =47mmHg
Mean grad =26mmHg

14. So where is the error?
“we are constantly seeing these discrepancies between Cath Lab and echo gradients
Consultant Cardiologist
“on occassion we see these discrepancies, particularly in asymptomatic patients”
Physiologist rebuttal
“Do not trust the echo report unless you have personally seen the quality of the study”
“In many patients, echo will provide discordant data necessitating confirmatory hemodynamics in the cath lab”
Susheel Kodali, Columbia Univ Medical Centre

15. Case 1

16. Case 1

18. Case 2
AVA=0.8cm2
Mean grad=54mmHg

20. Pressure gradients are dependent on volume flow rate

21. When gradient and AVA don’t match
Low gradient, severe AVA
High gradient, moderate AVA
Poor LV systolic function
Small LV cavity
Reduced SV
Reduced flow
Concomitant significant MR
Significant AI
Sepsis
Anaemia
High output states
Pressure recovery phenomenon
In theory the AVA should reflect the severity of the stenosis better than the gradient

22. AS and poor LV function Reduced LV function
Reduced cardiac output and stroke volume
Reduced volume flow rates
Reduced gradient across aortic valve
Discordance between AVA and gradient
Severe AS by AVA but low gradient may reflect
Truly severe AS
Psuedo-severe AS

23. Role of dobutamine Dobutamine Gradual infusion of dobutamine (20ug/kg)
Increase stroke volume
Gradual infusion of dobutamine (20ug/kg)
Truly severe AS
LVOT and Aortic velocities increase proportionally
AVA remains constant
Pseudo-severe AS
LVOT velocity increases disproportionally Ao velocity
AVA increases

24. Role of dobutamine Main role is to assess for inotropic reserve
Increase in stroke vol of >20% with dobutamine
Clinical question
Is the severe AS leading to poor LV function
Will replacing the valve improve function
Lack of inotropic reserve is an independent predictor of mortality post AVR

25. Small LV cavity Newer concept Small LV cavity
Paradoxical low flow AS
Low flow/low grad severe AS with preserved EF
Small LV cavity
Hypertrophy
Reduced LV filling
Reduced stroke volume
Discordance between gradient and AVA
PLF AS patients have worse outcome

26. We are measuring different things
Cath lab and echo measure different things
Doppler
Max flow velocity at the level of the vena contracta
Cath
Net pressure gradient between the LV and the aorta

27. Pressure recovery Conservation of energy
Blood flow decelerates as it goes through valve
Kinetic energy - velocity is “lost”
Converted into potential energy – pressure
Therefore we get a recovery of Ao pressure distal to the valve

28. Pressure recovery
Extent of pressure recovery inv proportional to Ao CSA
Thus the max gradient by echo will over estimate the severity compared to the max grad by cardiac cath
Echo reflect the true valve orifice area
Cath reflects the physiological valve area

29. So where are we now Is there anything extra that echo can add
Can we aid in the clarification of these discrepancies

30. Jet velocity – too simple?
Otto 1997
123 asymptomatic patients
End point
Death
Aortic valve surgery
Jet velocity > 4m/s is an independent predictor of clinical outcome

31. Dimensionless Index
Potential error in echo calculation is determining LVOT diameter
Dimensionless index removes LVOT diameter from the assessment
DI= LVOT VTI/Ao VTI
Value of less than 0.25 represents severe AS

32. Indexed aortic valve area
Body size can lead to an incorrect classification of AS severity based on AVA
Has been demonstrated that an iAVA of <0.6cm/m2 is a marker of mortality
Guidelines classify severe AS as iAVA of <0.6cm/m2

33. Indexed aortic valve area
Case 1
AVA of 1.2 cm2
moderate
BSA = 2.1 m2
iAVA=0.57 cm2/m2
Case 2
AVA of 0.9 cm2
Severe
BSA= 1.3 m2
iAVA=0.7 cm2/m2

34. Remember Pressure recovery?
Cath reflects the physiological valve area
Can we somehow correct for pressure recovery

35. Energy loss index
[(AVA x Aa)/(Aa-AVA)]
BSA

36. Prognostic Value of Energy Loss Index in Asymptomatic Aortic Stenosis
Aortic valve events
AVR, HFH, CV mortality

37. What about the third dimension?
Continuity eqn
Assumption that LVOT is circular
LVOT more elliptical
3D TOE
Allows direct measurement of LVOT CSA

38. Conclusion There are sources of error in echo assessment of AS
Take care
Averaged values for LVOT
There are also sources of error in the Cath Lab
So be careful there too
And try and get the Consultants to be careful

39. What I would take away Use the suite of measurements/assessments
Use new measurements
Indexed AVA
Consider new techniques if available
If your gradient and AVA don’t match think about/explain why?
Poor LV
Small LV cavity/low stroke volume
Concomitant AI or MR