Non invasive assessment of prosthetic valves
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Non-Invasive Assessment of Prosthetic Valves. November 21, 2007 Alex Morss. 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)

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Non-Invasive Assessment of Prosthetic Valves

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Non invasive assessment of prosthetic valves

Non-Invasive Assessment of Prosthetic Valves

November 21, 2007

Alex Morss


Terms and definitions

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)


Main characters protagonists

Main Characters (Protagonists)

  • Mechanical Valves

    • Ball-cage

    • Tilting disc

    • Bileaflet

  • Bioprosthetic Valves

    • Stented

    • Unstented (aortic root)

    • Homograft, allograft


The antagonists

The Antagonists

  • Endocarditis +/- vegetations

  • Paravalvular leak (+/- dehiscence)

  • Thrombosis

  • Pannus formation

  • Degeneration, +/- calcific stenosis or leaflet tear

  • Strut fracture, disc embolization

  • Unseating of valve


The arsenal

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


The main characters

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


Main characters part deux

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


Unveiling the arsenal old school roentgenography

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


Up a notch fluoroscopy

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


Disc embolization

Disc embolization

disc

O’Neill NEJM 1995


Cardiac mri

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


More cardiac mri

More cardiac MRI


Echocardiography

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


Echo by valve position

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


Aortic prostheses

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


Normal aortic bileaflet valve

Normal aortic bileaflet valve


Non invasive assessment of prosthetic valves

  • Peak gradient 20mmHg, mean 12 mmHg

  • Normal bileaflet gradients are dependent on valve size


Normal mechanical aortic valve peak gradients

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


Normal aortic bioprosthetic valve

Normal aortic bioprosthetic valve


Non invasive assessment of prosthetic valves

  • 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


Tilting disc avr

Tilting disc AVR


Ball cage avr

Ball-cage AVR


Name the avr type

Name the AVR type


Non invasive assessment of prosthetic valves

  • Aortic bioprosthetic valve with paravalvular leak, valvular regurgitation


What s wrong

What’s wrong?


Non invasive assessment of prosthetic valves

Tilting disc valve with thrombosis causing

partial obstruction

Talley, Can J Card 1986


Mitral prosthetic valves

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


Normal bioprosthetic mvr

Normal bioprosthetic MVR


Non invasive assessment of prosthetic valves

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


Bileaflet mvr

Bileaflet MVR


Non invasive assessment of prosthetic valves

  • Appropriate regurgitation shown- 2 jets in bileaflet valve

  • By design in mechanical valves to minimize thrombosis risk


Ball cage mvr

Ball-cage MVR


Non invasive assessment of prosthetic valves

Cage-ball valves

have the highest nomal

valve gradients due to

design


Non invasive assessment of prosthetic valves

  • Mean gradient 9 mmHg

  • Standard mean gradient for ball-cage MVR is 5-7 +/- 3, depending on size


Mitral endocarditis

Mitral endocarditis

Kort, JASE 2006 (from Gelfand)


Mitral unpleasantries part ii

Mitral unpleasantries, part II


A league of its own

A league of its own


Summary

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.


Non invasive assessment of prosthetic valves

Thank you!


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