Transcript Aortic stenosis – when echo and cath don’t match

Paul Nolan, Galway University Hospitals
AORTIC STENOSIS – WHEN ECHO
AND CATH (OR EVEN ECHO AND
ECHO) DON’T MATCH
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
Quantification of AS by echo
 Peak velocity
 Mean velocity
 Peak gradient
 Mean gradient
 Aortic valve area
 Continuity equation
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
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
Quantification of the AVA in
the Cath Lab
 Gorlin formula
 AVA =

Cardiac output
44.3 (SEP)(HR) √pressure gradient
So why sometimes do they not
agree?
Technical sources of error
in Echo
 Doppler angle
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
The “Gold Standard”
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
Effect of incorrect alignment
Mean grad =47mmHg
Mean grad =26mmHg
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
Case 1
Case 1
Case 2
AVA=0.8cm2
Mean grad=54mmHg
Pressure gradients are
dependent on volume flow
rate
When gradient and AVA don’t
match
Low gradient, severe AVA
High gradient, moderate AVA
 Poor LV systolic function
 Significant AI
 Small LV cavity
 Sepsis
 Reduced SV
 Anaemia
 Reduced flow
 High output states
 Concomitant significant
MR
 Pressure recovery
phenomenon
In theory the AVA should reflect the severity of
the stenosis better than the gradient
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
Role of dobutamine
 Dobutamine
 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
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
Small LV cavity
 Newer concept
 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
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
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
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
So where are we now
 Is there anything extra that echo can add
 Can we aid in the clarification of these
discrepancies
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
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
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
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
Remember Pressure recovery?
 Cath reflects the
physiological valve
area
 Can we somehow
correct for pressure
recovery
Energy loss index
 [(AVA x Aa)/(Aa-AVA)]

BSA
Prognostic Value of Energy Loss Index in
Asymptomatic Aortic Stenosis
 Aortic valve events
 AVR, HFH, CV mortality
What about the third
dimension?
 Continuity eqn
 Assumption that LVOT is
circular
 LVOT more elliptical
 3D TOE
 Allows direct
measurement of LVOT
CSA
Conclusion
 There are sources of
 There are also sources
error in echo
assessment of AS
of error in the Cath Lab
 So be careful there too
 Take care
 Averaged values for
LVOT
 And try and get the
Consultants to be
careful
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