Non-Invasive Assessment of Prosthetic Valves

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, 19-33 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, 19-33 mm Hancock Mosaic Stentless porcine

8. Unveiling the arsenalOld 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 1965. 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 • 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 • 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 19-29 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 2.9 m/sec 29 mm 1.9 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