Echo Conference 3/16/11 Scott Midwall, MD. Objectives I. Introduction to Prosthetic Valves (PV) I....
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Transcript of Echo Conference 3/16/11 Scott Midwall, MD. Objectives I. Introduction to Prosthetic Valves (PV) I....
Echo Conference 3/16/11
Scott Midwall, MD
ObjectivesI. Introduction to Prosthetic Valves (PV)
I. MechanicalII. Biological/TissueIII. Appearance of Normally functioning Valves
II. Approach to Evaluating PVs with echo and doppler
III. Evaluating Prosthetic Aortic ValvesIV. Echo Case/Questions (EchoSap)
OverviewProsthetic Valves are classified as tissue or mechanical Tissue:
Actual valve or one made of biologic tissue from an animal (bioprosthesis or heterograft) or human (homograft or autograft) source
MechanicalMade of nonbiologic material (pyrolitic carbon,
polymeric silicone substances, or titanium)Blood flow characteristics, hemodynamics, durability,
and thromboembolic tendency vary depending on the type and size of the prosthesis and characteristics of the patient
ValvesBiologic (Tissue) Mechanical Stented
Porcine xenograftPericardial xenograft
StentlessPorcine xenograftPericardial xenograftHomograft Autograft
Ball and cage (Starr-Edwards)
Single tilting disc (Medtronic-Hall)
Bileaflet (St. Jude, CarboMedics)
Mechanical ValvesExtremely durable with overall survival rates
of 94% at 10 yearsPrimary structural abnormalities are rareMost malfunctions are secondary to
perivalvular leak and thrombosisChronic anticoagulation required in all With adequate anticoagulation, rate of
thrombosis is 0.6% to 1.8% per patient-year for bileaflet valves
Biological ValvesStented bioprostheses
Primary mechanical failure at 10 years is 15-20%Preferred in patients over age 70Subject to progressive calcific degeneration &
failure after 6-8 yearsStentless bioprostheses
Absence of stent & sewing cuff allow implantation of larger valve for given annular size->greater EOA
Uses the patient’s own aortic root as the stent, absorbing the stress induced during the cardiac cycle
Biologic Valves ContinuedHomografts
Harvested from cadaveric human heartsAdvantages: resistance to infection, lack of
need for anticoagulation, excellent hemodynamic profile (in smaller aortic root sizes)
More difficult surgical procedure limits its useAutograft
Ross Procedure
Caged-Ball Valve
Single-Leaflet Valve
Bileaflet Valve
Stentless Aortic Graft Valve
Stented Biologic Mitral Valve
Approach to Valve Evaluation Clinical data including reason for the study and
the patient’s symptomsType & size of replacement valve, date of
surgeryBP & HR
HR particularly important in mitral and tricuspid evaluations because the mean gradient is dependent on the diastolic filling period
Patient’s height, weight, and BSA should be recorded to assess whether prosthesis-patient mismatch (PPM) is present
Echo Imaging of Prosthetic Valves Valves should be imaged from multiple views,
with attention to:Opening & closing motion of the moving parts
(leaflets for bioprosthesis and occluders for mechanical ones)
Presence of leaflet calcification or abnormal echo density attached to the sewing ring, occluder, leaflets, stents, or cage
Appearance of the sewing ring, including careful inspection for regions of separation from native annulus & for abnormal rocking motion during the cardiac cycle
Echo ImagingMild thickening is often the 1st sign of
primary failure of a biologic valveOccluder motion of a mechanical valve may
not be well visualized by TTE because of artifact and reverberations
Imaging ConsiderationsIdentify the sewing ring, valve or occluder
mechanism, and surrounding areaBall or disc is often indistinctly imaged,
whereas leaflets of normal tissue valves should be thin with an unrestricted motion
Stentless or homograft may be indistinguishable from native valves
One can use modified views (lower parasternal) to keep the artifact from the valve away from the LV outflow tract
Doppler of Prosthetic AVDoppler velocity recordings across normal
PVs usually resemble those of mild native aortic stenosisMaximal velocity usually > 2 m/s, with
triangular shape of the velocity contourOccurrence of maximal velocity in early systole
With increasing stenosis, a higher velocity and gradient are observed, with longer duration of ejection and more delayed peaking of the velocity during systole
Doppler Velocity Index (DVI)Dimensionless ratio of the proximal velocity in
the LVO tract to that of flow velocity through the prosthesis: DVI= VLVO/ VPrAV
DVI is calculated as the ratio of respective VTIs and can be approximated as the ratio of respective peak velocities
Incorporates the effect of flow on velocity through the valve and is much less dependent on valve size
DVI Helpful measure to screen for valve
dysfunction, particularly when the CSA of the LVO tract cannot be obtained or valve size is unknown
DVI is always < 1DVI < 0.25 is highly suggestive of significant
obstructionDVI is not affected by high flow conditions
through the valve, including AI
Doppler & Prosthetic AV High gradients may be seen with normal
functioning valves with:Small sizeIncreased stroke volumePPMValve obstruction
Conversely, a mildly elevated gradient in the setting of severe LV dysfunction may indicate significant stenosis
Thus, the ability to distinguish malfunctioning from normal PVs in high flow states on the basis of gradients alone may be difficult
Doppler ContinuedOther qualitative and quantitative indices
that are less dependent on flow should be evaluated
Contour of the velocity:In a normal valve, even in high flow, there is a
triangular shape, with early peaking of the velocity and short acceleration time (AT)
With PV obstruction, a more rounded velocity contour is seen, with velocity peaking almost in mid-ejection, prolonged AT
Cutoff of AT of 100 ms differentiates well between normal and stenotic PVs
Effective Orifice Area (EOA)EOA PrAV = (CSA LVO x VTI LVO) / VTI PrAV EOA is dependent on size of inserted valve
Should be referenced to the valve size of a particular valve type
For any size valves, significant stenosis is suspected when valve area is < 0.8 cm2
However, for the smallest size valve, this may be normal because of pressure recovery
Largest source of variability is measurement of the LVO tract
Parameter Normal Possible Stenosis
Suggests Significant Stenosis
Peak Velocity (m/s)
<3 3-4 >4
Mean Gradient (mmHg)
<20 20-35 >35
DVI ≥0.30 0.29-0.25 <0.25
EOA (cm2) >1.2 1.2-0.8 <0.8
Contour of Jet velocity in PV
Triangular, early
peaking
Triangular to
intermediate
Rounded, symmetrical
AT (ms) <80 80-100 >100
Doppler Parameters of Prosthetic AV function in Mechanical and Stented Biologic Valves in Conditions of Normal Stroke
Volume
Patient-Prosthesis Mismatch (PPM)When the EOA of the inserted prosthesis is
too small in relation to the patient’s BSAA given valve area acceptable for a small,
inactive person may be inadequate for a larger physically active individual
Main consequence is the generation of higher than expected gradients through a normally functioning valve
PPM ContinuedCommonly seen in:
Patients with small aortic annulus sizes, particularly women
Patients whom indication for AVR was AS as opposed to AI
Young patients, who outgrow their initially inserted prosthesis
Failure of post-op regression of LV mass index at 6 months may be clue to presence of PPM
For patients with exertional symptoms without evidence of primary valve dysfunction, stress echo should be entertained to further evaluate
Evaluation of Prosthetic AIWith color doppler, one can evaluate the
components of the color AI jetFlow convergence, vena contracta, extent in
the LVO tract and LVNormal “physiologic” jet are usually low in
momentum, depicted by homogenous color jets that are small in extent
Ratios of jet diameter/LVO diameter from parasternal long-axis imaging and Jet area/LVO area from parasternal short-axis imaging are best applied for central jets
Prosthetic Valve AIWith eccentric AI
jets, measurement of jet width perpendicular to the LVO tract will cut the jet obliquely and risk overestimation
Entrainment of jet in the LVO tract may lead to rapid broadening of the jet just after the vena contracta-> overestimation
Significant AI, AV Dehiscence
AI in PVsContrary to native valves, the width of the vena
contracta may be difficult to accurately measure in the long-axis in the presence of a prosthesis
Imaging of the neck of the jet in short-axis, at the level of the sewing ring allows determination of the circumferential extent of the regurgitation
Approximate guide:< 10% of sewing ring suggests mild10-20% suggests moderate> 20% suggests severe**Rocking of the prosthesis usually associated
with >40% dehisscence
Spectral Doppler and PVAIPHT is useful when the value is <200 ms, suggesting
severe AI, or > 500 ms, consistent with mild AIIntermediate ranges may reflect other hemodynamic
variables such as LV compliance and are less specificHolodiastolic flow reversal in the descending thoracic
aorta is indicative of at least moderate AISevere is suspected when the VTI of the reverse flow
approximates that of the forward flowHolodiastolic flow reversal in the abdominal aorta is
usually indicative of severe AI
Parameter Mild Moderate Severe
Valve Structure/Function
Normal Abnormal Abnormal
LV size Normal Normal or Mild Dilation
Dilated
Jet width (%LVO diameter)
Narrow (≤25%)
Intermediate (26-64%)
Large (≥ 65%)
Jet density (CW doppler)
Incomplete or Faint
Dense Dense
PHT, ms (CW doppler)
>500 Variable (200-500)
Steep (< 200)
Diastolic Flow Reversal (Descending
Aorta)
Absent or Brief early
diastolic
Intermediate Prominent, holodisatolic
Regurgitant Volume (ml/beat)
< 30 30-59 >60
Regurgitant Fraction (%)
<30 30-50 >50
Evaluation of Prosthetic MVA major consideration with echo is the effect of
acoustic shadowing by the prosthesis on assessment of MRProblem is worse with mechanical valves
On TTE, LV function is readily evaluated, but the LA is often obscured for imaging and doppler interrogationTEE provides visualization of the LA and MR but
shadowing limits visualization of the LVThus, comprehensive assessment of PMV requires
both TTE & TEE when valve dysfunction is suspected
Prosthetic MV Imaging Considerations
In the parasternal long-axis view, the prosthesis may obscure portions of the LA and its posterior wallMR may be difficult to evaluate
Parasternal long-axis views allows visualization of the LVO tract, which can be impinged by higher profile prostheses
Apical views allow visualization of leaflet excursion for both bioprosthetic and mechanical valvesMay allow detection of thrombus or pannusVegetations can be seen but are often masked by
acoustic shadowing
Doppler Evaluation of PMVComplete exam should include:
Peak early velocityEstimate of mean pressure gradientHeart RatePressure half-time (PHT)Determination of whether regurgitation is
presentDVI and/or EOA as neededLV/RV size and functionLA size if possiblePA systolic pressure
Peak Early Mitral VelocityPeak E velocity is easy to measure
Provides simple screen for prosthetic valve dysfunction
Can be elevated in: hyperdynamic states, tachycardia, small valve size, stenosis, or regurgitation
Inhomogeneous flow profile across caged-ball and bileaflet prostheses can lead to doppler velocity measurements that are elevated out of proportion to the actual gradient
For normal bioprosthetic MVs, peak velocity can range from 1.0 to 2.7 m/s
MV Peak Velocity In normal bileaflet mechanical valves, peak
velocity is usually < 1.9 m/s but can be up to 2.4 m/s
As a general rule, peak velocity < 1.9 m/s is likely to be normal in most patients with mechanical valves unless there is markedly depressed LV function
Mean Gradients of MVNormally less than 5-6 mm HgValues up to 10-12 mm Hg have been
reported in normally functioning mechanical valves
High gradients can be due to: hyperdynamic states, tachycardia or PPM, regurgitation, or stenosis
MV Pressure Half-time (PHT)A large rise in PHT on serial studies or a markedly
prolonged single measurement (>200 ms) may be a clue to the presence of:obstructionPHT seldom exceeds 130 ms across normal pv
Minor changes in PHT occur as a result of nonprosthetic factors including:Loading conditionsDrugsAI
PHT should not be obtained in tachycardic rhythms or 1st degree blocks when the E & A velocities are merged or the diastolic filling period is short
EOA of PMVCalculation from PHT, as traditionally applied
in native MS, is not valid in prosthetic valves due to its dependence on LV and LA compliance and initial LA pressure
EOAPrMV= stroke volume/VTIPrMV
Usually reserved for cases of discrepancy between information obtained from gradients and PHT
Prosthetic MV and DVIDVI= VTIPrMV/ VTILVO
DVI can be elevated with stenosis or regurgitation
For mechanical valves, a DVI < 2.2 is most often normal
Higher values should prompt consideration of prosthesis dysfunction
Parameter Normal Possible Stenosis Suggests Significant Stenosis
Peak Velocity (m/s)
<1.9 1.9-2.5 ≥2.5
Mean Gradient (mm Hg)
≤5 6-10 >10
DVI <2.2 2.2-2.5 >2.5
EOA (cm2) ≥2 1-2 <1
PHT (ms) <130 130-200 >200
Doppler Parameters of Prosthetic MV Function
Prosthetic MV RegurgitationSince direct detection of prosthetic MR is often not
possible with TTE, particularly with mechanical valves, one must rely on indirect signs suggestive of significant MR
Such signs include:Hyperdynamic LV with low systemic outputElevated mitral E velocityElevated DVIDense CW regurgitant jet with early systolic maximal
velocityLarge zone of systolic flow convergence toward the
prosthesis seen in the LVClinical symptoms & presence of the above findings
represents a clear indication for TEE
Prosthetic MV RegurgitationAssessment of severity of prosthetic MR can
be difficult at times because of the lack of a single quantitative parameter that can be applied consistently in all patients
Currently, best method is to integrate several findings from both TTE and TEE that together suggest a given severity of regurgitation
Parameter Mild Moderate Severe
LV size Normal NL or Dilated
Usually Dilated
Valve Usually Normal Abnormal Abnormal
Color Flow Jet Area
Small, central jet (usually <4 cm2
or <20% of LA area)
Variable Large, central jet
(usually >8cm2 or
>40% of LA area)
Flow Convergence
None or Minimal Intermediate
Large
Jet Density: CW Incomplete/Faint Dense Dense
Jet Contour: CW Parabolic Usually Parabolic
Early peaking,
triangular
Pulm Vein Flow Systolic Dominance
Systolic Blunting
Systolic Flow Reversal
VC Width (cm) <0.3 0.3-0.59 ≥0.6
R vol (ml/beat) <30 30-59 ≥60
RF (%) <30 30-49 ≥50
EROA (cm2) <0.2 0.20-0.49 ≥0.50
Echo & Doppler Criteria for Severity of Prosthetic MR from TTE/TEE
TTE of Prosthetic MV
TEE of Same MV