Prosthetic Valves

by Richard Mitchell, MD

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    00:01 One final note about a different kind of valve. These are the prosthetic valves.

    00:05 There are two different flavors of prosthetic valves.

    00:07 There's the mechanical valve demonstrated here.

    00:10 This is the kind of state-of-the-art tilting - bileaflet tilting disc that is the St. Jude prosthetic valve.

    00:19 The disk and the black material that you see there made of pyrolytic carbon, they're pretty much invulnerable. They will last forever.

    00:29 There are other forms of mechanical valves, but this is now state of the art.

    00:34 The other kind of valve is the bioprosthetic valve.

    00:38 These are tissue valves, and we can fashion them out of porcine aortic valves or bovine pericardium.

    00:46 We sew them onto a stent strut material. That's the white thing all the way around the valve.

    00:52 And that allows us to sew it in. We can also use cryo-preserved homographs.

    00:58 These frozen human valves from deceased donors.

    01:01 And both of these have similar functional and degenerative characteristics.

    01:08 These valves work pretty well for up to a decade. They are just - they're wonderful.

    01:13 They're a great solution for what could otherwise be fatal valvular disease, but they have their limitations.

    01:19 An important point, even though they're wonderfully constructed, they're good valves, 60% of substitute valves, regardless of whether it's mechanical or the bioprosthetic, they will develop a prosthesis-related problem within about a decade of surgery, 60%.

    01:35 And by the time they're in place for 15 or 20 years, it's getting closer to 80 to 90%.

    01:41 So, the valves are good, they're not perfect.

    01:45 Endocarditis can occasionally affect either type of valve. That makes sense.

    01:48 You have this sewing ring, and you can have bacteria settle on the sewing ring.

    01:52 The mechanical valves will not fail mechanically.

    01:56 As I said, they're pretty much impervious. They are really well-constructed.

    02:00 They don't typically fail mechanically. But the valves do not have normal pure laminar flow.

    02:07 They have some degree of turbulent flow and are therefore prone to thrombosis.

    02:12 So, patients must be anticoagulated for the rest of their lives with the mechanical valve.

    02:18 That means, however, that within a decade, 60% of them will either develop a thrombus because they're inadequately anticoagulated or they will develop a hemorrhage some place because they are over anticoagulated. So, either way, it's not particularly good.

    02:35 In many cases, the pathology, the complication is relatively minor, but it can be fatal.

    02:41 So, that's one of the downsides - the downside to mechanical valves.

    02:46 On the other hand, bioprosthetic tissue valves, although they have normal flow characteristics, they look just like a normal aortic valve, and therefore don't require anticoagulation, those valves are not viable.

    03:00 The valvular interstitial cells, everything that's in the valve, has been glutaraldehyde fixed.

    03:06 So, it is now essentially dead tissue.

    03:11 And over 10 to 12 to 15 years, those valves will fail mechanically due to degeneration of this non-regenerating valvular tissue or to calcification of that tissue.

    03:25 And so, they'll fail for one of the other of the modalities.

    03:28 And with that rather long discourse, we've covered everything from infective to non-infective endocarditis, normal valve structure and function, stenosis and regurgitation, and even bioprosthetic and prosthetic valves. I hope you've enjoyed it.

    About the Lecture

    The lecture Prosthetic Valves by Richard Mitchell, MD is from the course Valvular and Hypertensive Heart Disease.

    Included Quiz Questions

    1. They are at risk of thrombus development due to turbulent flow around the valve.
    2. They are more likely to have a clotting disorder.
    3. They are more likely to have had a previous stroke.
    4. They are at increased risk for SLE endocarditis.
    5. They are at increased risk for mechanical valve failure.
    1. They are made up of non-regenerating tissue that degrades and becomes calcified over time.
    2. They are made up of non-human tissue that is at risk of autoimmune rejection.
    3. They are more likely to result in thrombus around the valve.
    4. They are more prone to infective endocarditis.
    5. They are more difficult to surgically implant correctly.

    Author of lecture Prosthetic Valves

     Richard Mitchell, MD

    Richard Mitchell, MD

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