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 Insert graph of Max V vs outcome

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 Insert fig 11.9

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? Cath lab vs echo image

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” DMcF

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 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

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 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

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 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

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 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

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