1. Echocardiographic Evaluation of Prosthetic Valves, Part I
Echo Conference
3/16/11
Scott Midwall, MD

2. Objectives Introduction to Prosthetic Valves (PV)
Mechanical
Biological/Tissue
Appearance of Normally functioning Valves
Approach to Evaluating PVs with echo and doppler
Evaluating Prosthetic Aortic Valves
Echo Case/Questions (EchoSap)

3. Overview Prosthetic Valves are classified as tissue or mechanical
Actual valve or one made of biologic tissue from an animal (bioprosthesis or heterograft) or human (homograft or autograft) source
Mechanical
Made 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

4. Valves Biologic (Tissue) Mechanical Stented Stentless
Porcine xenograft
Pericardial xenograft
Stentless
Homograft
Autograft
Ball and cage (Starr-Edwards)
Single tilting disc (Medtronic-Hall)
Bileaflet (St. Jude, CarboMedics)

5. Mechanical Valves
Extremely durable with overall survival rates of 94% at 10 years
Primary structural abnormalities are rare
Most malfunctions are secondary to perivalvular leak and thrombosis
Chronic anticoagulation required in all
With adequate anticoagulation, rate of thrombosis is 0.6% to 1.8% per patient-year for bileaflet valves

6. Biological Valves Stented bioprostheses Stentless bioprostheses
Primary mechanical failure at 10 years is 15-20%
Preferred in patients over age 70
Subject to progressive calcific degeneration & failure after 6-8 years
Stentless 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

7. Biologic Valves Continued
Homografts
Harvested from cadaveric human hearts
Advantages: resistance to infection, lack of need for anticoagulation, excellent hemodynamic profile (in smaller aortic root sizes)
More difficult surgical procedure limits its use
Autograft
Ross Procedure

9. Caged-Ball Valve

10. Single-Leaflet Valve

11. Bileaflet Valve

13. Stentless Aortic Graft Valve

14. Stented Biologic Mitral Valve

15. Approach to Valve Evaluation
Clinical data including reason for the study and the patient’s symptoms
Type & size of replacement valve, date of surgery
BP & 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

16. 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

17. Echo Imaging
Mild thickening is often the 1st sign of primary failure of a biologic valve
Occluder motion of a mechanical valve may not be well visualized by TTE because of artifact and reverberations

18. Evaluation of the Prosthetic Aortic Valve (AV)

19. Imaging Considerations
Identify the sewing ring, valve or occluder mechanism, and surrounding area
Ball 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

20. Doppler of Prosthetic AV
Doppler velocity recordings across normal PVs usually resemble those of mild native aortic stenosis
Maximal velocity usually > 2 m/s, with triangular shape of the velocity contour
Occurrence 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

22. 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

23. 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 < 1
DVI < 0.25 is highly suggestive of significant obstruction
DVI is not affected by high flow conditions through the valve, including AI

25. Doppler & Prosthetic AV
High gradients may be seen with normal functioning valves with:
Small size
Increased stroke volume
PPM
Valve 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

26. Doppler Continued
Other 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

27. 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

29. Suggests Significant Stenosis
Doppler Parameters of Prosthetic AV function in Mechanical and Stented Biologic Valves in Conditions of Normal Stroke Volume
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
<0.25
EOA (cm2)
>1.2
<0.8
Contour of Jet velocity in PV
Triangular, early peaking
Triangular to intermediate
Rounded, symmetrical
AT (ms)
<80
80-100
>100

31. Patient-Prosthesis Mismatch (PPM)
When the EOA of the inserted prosthesis is too small in relation to the patient’s BSA
A 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

32. PPM Continued Commonly 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

33. Evaluation of Prosthetic AI
With color doppler, one can evaluate the components of the color AI jet
Flow convergence, vena contracta, extent in the LVO tract and LV
Normal “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

34. Prosthetic Valve AI
With 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

35. Significant AI, AV Dehiscence

36. AI in PVs
Contrary 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 mild
10-20% suggests moderate
> 20% suggests severe
**Rocking of the prosthesis usually associated with >40% dehisscence

37. Spectral Doppler and PVAI
PHT is useful when the value is <200 ms, suggesting severe AI, or > 500 ms, consistent with mild AI
Intermediate ranges may reflect other hemodynamic variables such as LV compliance and are less specific
Holodiastolic flow reversal in the descending thoracic aorta is indicative of at least moderate AI
Severe is suspected when the VTI of the reverse flow approximates that of the forward flow
Holodiastolic flow reversal in the abdominal aorta is usually indicative of severe AI

38. Parameter Mild Moderate Severe
Valve Structure/Function
Normal
Abnormal
LV size
Normal or Mild Dilation
Dilated
Jet width (%LVO diameter)
Narrow (≤25%)
Intermediate (26-64%)
Large (≥ 65%)
Jet density (CW doppler)
Incomplete or Faint
Dense
PHT, ms (CW doppler)
>500
Variable ( )
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

39. Part II-Evaluation of Prosthetic Mitral Valve

40. Evaluation of Prosthetic MV
A major consideration with echo is the effect of acoustic shadowing by the prosthesis on assessment of MR
Problem is worse with mechanical valves
On TTE, LV function is readily evaluated, but the LA is often obscured for imaging and doppler interrogation
TEE provides visualization of the LA and MR but shadowing limits visualization of the LV
Thus, comprehensive assessment of PMV requires both TTE & TEE when valve dysfunction is suspected

41. Prosthetic MV Imaging Considerations
In the parasternal long-axis view, the prosthesis may obscure portions of the LA and its posterior wall
MR 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 valves
May allow detection of thrombus or pannus
Vegetations can be seen but are often masked by acoustic shadowing

42. Doppler Evaluation of PMV
Complete exam should include:
Peak early velocity
Estimate of mean pressure gradient
Heart Rate
Pressure half-time (PHT)
Determination of whether regurgitation is present
DVI and/or EOA as needed
LV/RV size and function
LA size if possible
PA systolic pressure

43. Peak Early Mitral Velocity
Peak 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

44. 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

45. Mean Gradients of MV Normally less than 5-6 mm Hg
Values up to mm Hg have been reported in normally functioning mechanical valves
High gradients can be due to: hyperdynamic states, tachycardia or PPM, regurgitation, or stenosis

46. 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: obstruction
PHT seldom exceeds 130 ms across normal pv
Minor changes in PHT occur as a result of nonprosthetic factors including:
Loading conditions
Drugs AI
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

49. EOA of PMV
Calculation 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

50. Prosthetic MV and DVI DVI= 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

51. Suggests Significant Stenosis
Doppler Parameters of Prosthetic MV Function
Parameter
Normal
Possible Stenosis
Suggests Significant Stenosis
Peak Velocity (m/s)
<1.9
≥2.5
Mean Gradient (mm Hg) ≤5
6-10
>10
DVI
<2.2
>2.5
EOA (cm2) ≥2
1-2
<1
PHT (ms)
<130
>200

52. Prosthetic MV Regurgitation
Since 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 output
Elevated mitral E velocity
Elevated DVI
Dense CW regurgitant jet with early systolic maximal velocity
Large zone of systolic flow convergence toward the prosthesis seen in the LV
Clinical symptoms & presence of the above findings represents a clear indication for TEE

53. Prosthetic MV Regurgitation
Assessment 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

54. Echo & Doppler Criteria for Severity of Prosthetic MR from TTE/TEE
Parameter
Mild
Moderate
Severe
LV size
Normal
NL or Dilated
Usually Dilated
Valve
Usually Normal
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
Jet Contour: CW
Parabolic
Usually Parabolic
Early peaking, triangular
Pulm Vein Flow
Systolic Dominance
Systolic Blunting
Systolic Flow Reversal
VC Width (cm)
<0.3
≥0.6
R vol (ml/beat)
<30
30-59
≥60
RF (%)
30-49
≥50
EROA (cm2)
<0.2
≥0.50

55. TTE of Prosthetic MV

56. TEE of Same MV