Prosthetic Valves

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.