1. Non-Invasive Assessment of Prosthetic Valves
November 21, 2007
Alex Morss

2. Terms and definitions
Prosthetic valves: manmade replacements of heart valves, either mechanical (nonorganic) or bioprosthetic (organic materials used in construction, i.e. animal or human parts)
Assessment: visual evaluation
Non-invasive: taking pictures of hidden things without using sharp objects (i.e., essentially nonviolent means of seeing them undressed)

3. Main Characters (Protagonists)
Mechanical Valves
Ball-cage
Tilting disc
Bileaflet
Bioprosthetic Valves
Stented
Unstented (aortic root)
Homograft, allograft

4. The Antagonists Endocarditis +/- vegetations
Paravalvular leak (+/- dehiscence)
Thrombosis
Pannus formation
Degeneration, +/- calcific stenosis or leaflet tear
Strut fracture, disc embolization
Unseating of valve

5. The Arsenal Roentgenography (X-Ray) Fluoroscopy Cardiac MRI (?)
Echocardiography
TTE will often best allow optimal Doppler angles
TEE will often best allow optimal direct visualization
Intangibles

6. The Main Characters Mechanical Valves
Ball-cage (Starr-Edwards)
Tilted-disc (Bjork-Shiley, Medtronic-Hall)
* Note: the convexoconcave version of the Bjork-Shiley valve earned a bad name due to cases of strut fracture and disc embolization
Bileaflet (St. Jude, Carbomedics)
All valves are sized by diameter, mm
O’Neill NEJM 1995

7. Main Characters, Part Deux
Bioprosthetic Valves
Stented: Carpentier-Edwards, Hancock, Ionescu-Shiley, St. Jude Mosaic
Stentless: Biocor.
Homografts/autografts: may not be able to detect noninvasively
Also sized by diameter, mm
Hancock
Mosaic
Stentless porcine

8. Unveiling the arsenal Old School: Roentgenography
Mechanical and many stented bioprosthetic valves are radiopaque, allowing determination of valve type and position on chest X-ray.
May be used to assess for device fracture in some cases
Starr-Edwards valve seen in aortic position
in From Nery, Heart 2004

9. Up a Notch: Fluoroscopy
Best methodology to assess mechanical leaflet motion due to outstanding spatial and temporal resolution.
May be used to assess stability of valve ring with the cardiac cycle
May optimally position angle to best assess subtle fracture
O’Neill NEJM 1995

10. Disc embolization
disc
O’Neill NEJM 1995

11. Cardiac MRI
Cardiac MRI may visualize mechanical valves, but lacks the temporal resolution and Doppler capablities of echocardiography
May show gross valve position, function, and regurgitation

12. More cardiac MRI

14. Echocardiography Transthoracic Transesophageal
Allows assessment of valve area and regurgitation via Doppler, which is generally adequate to exclude significant obstructive or regurgitant change. Flow velocity is the crucial measurement.
Inadequate to assess infection or small structural changes (e.g. strut fracture, small vegetation, paravalvular leak)
Transesophageal
Ideal for visual inspection of valve apparatus and seating; may not accurately quantify valve flow velocities. May directly measure aortic valve area via planimetry

15. Echo by valve position Aortic Mitral Tricuspid Pulmonic
Accurate TTE assessment relies on accurate Doppler assessments in multiple views
Often many TTE views partially obscured by shadowing. Often TEE required to view leaflets
Mitral
Among the best positions for TTE visualization, usually able to see leaflets via apical views
Tricuspid
Also usually adequately visualized by TTE directly and via Doppler
Pulmonic
Rarest position for valve replacement. Difficult to visualize for both TTE and TEE, no clear advantage

16. Aortic Prostheses
Focus on Doppler imaging of aortic outflows to determine mean and peak gradients
Can identify prosthesis type by direct visualization
As with all prostheses, need to know their SIZE to allow assessment of normal vs. pathologically increased transvalvular gradient.
Size varies from mm in diameter
Normal gradients for each valve type and size may be found on reference tables

17. Normal aortic bileaflet valve

21. Peak gradient 20mmHg, mean 12 mmHg
Normal bileaflet gradients are dependent on valve size

22. Normal mechanical aortic valve peak gradients
Bileaflet
19mm: 33 +/- 11
29mm: 13 +/- 5
Tilting disc
19mm: 46
29mm: 12+/- 8
Ball-cage
23mm: 33+/-13
29mm: 29+/-9
Approximate flow velocities:
19mm m/sec
29 mm m/sec
(+/- 0.5 m/sec)
Feigenbaum 2005
Full tables are available in echo texts or on fellowship echo website

23. Normal aortic bioprosthetic valve

26. Peak gradient 17mm- need valve size and ideally baseline gradient at time of valve implantation to assess for normal value
May also use continuity equation with measurement of LVOT to calculate effective aortic valve area

27. Tilting disc AVR

32. Ball-cage AVR

36. Name the AVR type

39. Aortic bioprosthetic valve with paravalvular leak, valvular regurgitation

40. What’s wrong?

46. Tilting disc valve with thrombosis causing partial obstruction
Talley, Can J Card 1986

47. Mitral prosthetic valves
Better visualization on TTE
Much lower normal gradients than aortic valves due to lower flow velocities and larger size overall
Sizes generally vary from 25-33mm in diameter

48. Normal bioprosthetic MVR

51. Peak mitral velocity of 1
Peak mitral velocity of 1.30 m/sec, peak gradient 8 mmHg, mean 5mmHg (normal ~ 5 depending on valve size)

52. Bileaflet MVR

55. Appropriate regurgitation shown- 2 jets in bileaflet valve
By design in mechanical valves to minimize thrombosis risk

57. Ball-cage MVR

60. Cage-ball valves
have the highest nomal
valve gradients due to
design

63. Mean gradient 9 mmHg
Standard mean gradient for ball-cage MVR is 5-7 +/- 3, depending on size

64. Mitral endocarditis
Kort, JASE 2006 (from Gelfand)

65. Mitral unpleasantries, part II

70. A league of its own

75. Summary Valve type and position often easily determined on CXR
Fluoroscopy optimal for assessing mechanical valve leaflet motion, unable to see bioprosthetic leaflets
TTE may identify flow velocities and gross structure, best suited for MVR and exclusion of obstruction due to good Doppler views. Doppler velocities and valve gradients are likely better than calculation of valve area due fewer variables
TEE allows better visualization of smaller structural changes, vegetations, and paravalvular leaks. It is the study of choice for concerns of endocarditis in any prosthetic valve.
CMR limited role and not generally used to assess prosthetic valves.

76. Thank you!