Dr. Glenn Barnhart provides educational material for young surgeons and surgical trainees so that they may adopt successful techniques related to the implantation of the On-X Mitral Heart Valve .
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On-X® Prosthetic Heart Valves IFU’s
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My name is Dr Glenn Barnhart. And I've been asked by a cryolife too. Uh Talk about the onyx valve and specifically to provide educational material for young surgeons just starting out and surgical trainees. Uh so that they may adopt techniques that are uh successful with the use of the onyx valve. My background is having done training at the Medical College in Richmond Virginia as well as that the National Institutes of Health in Boston Children's Hospital. I practiced at the Medical College of Virginia as well as Sentara Heart Hospital in Norfolk Virginia for nearly 20 years and then was asked to be executive director of the Swedish Heart and Vascular institute and Swedish Medical Center as well as chief of cardiac surgery there in Seattle, where I was for approximately 11 years and recently have retired. So my experience with annex starts in 2000 and six. When I first started in planning the valve, I was the principal investigator at Sentara Heart Hospital where I was at practice at the time. I started using the valve around that time as part of the Proact trial Which was of course under F. D. A. Um clinical trial guidelines and I moved to Swedish medical center in 2007 and continued the use of the valve there. Um I have implanted over 200 onyx valves both in the aortic and mitral position. I certainly think it's the valve of choice. Let me speak for a couple of minutes about patient selection with both the onyx aortic economics mitral valve. I think it's very important that guidelines are followed. Certainly there are tradeoffs for any valve that we use. There's no question about that whether it's mechanical, bio prosthetic or tab are um there are a number of factors that need to come under consideration when one is choosing a valve for a patient. I think the conversation with the patient is also extremely important, patients need to understand and our job I think is job number one is to make sure the patient is completely informed. And part of that informed consent is the longevity of the valve and how long it's going to last. And there is very little question about that in today's world, that mechanical valves will last longer than any bio prosthetic valve on the market and any tab are on the market. The study that we would all like to see is a randomized prospective study lasting 35 to 40 years between mechanical versus bio prosthetic valves versus to bar that is a study that is impossible to do. So we have to extract from the literature what we know about the longevity and the durability of mechanical valves versus bio prosthetic valves versus Tavon. And I think there's no question that mechanical valves wins that race every time. Now there are tradeoffs. Currently, it does require Coumadin therapy and many patients do not like to think of having to take cumin and not having their blood drawn on an interval basis. However, patients need to understand if they are choosing a bio prosthetic valve over a mechanical valve, that they are going to be possibly limiting their lifespan from a statistical standpoint. So it's very important that they understand that I feel as a surgeon job number one is to make sure that that we are providing the patient with as long of a normal lifespan as possible. Additionally, let me comment on the patient's informed consent regarding re operation and further procedures on an interventional basis for tab are I think that all of us, as surgeons accept the fact that having a re operation carries a higher risk. There is no question about that in today's hands. It's a reasonable risk, but still it's a higher risk than the first time operation. So all of those issues I think need to be discussed with the patient in a very uh patient friendly manner. So they understand exactly the choices that they're making for themselves and their family, considering all the aspects when it comes to valve choice regarding mechanical versus bio prosthetic versus to bar. Uh This brings us back again then to consideration of mechanical valve and specifically on X. We know now that the proact trial clearly has shown that the valve can safely be used with an iron are of 1.5 to 2 point oh uh that was approved by the FDA in 2015 and has made it into the updated A. J. A. C. C guidelines in 2017. Uh Also the uh mitral valve is currently on a clinical trial. Uh enrollment in that trial is complete. While that still is being on Coumadin. It is a substantial reduction in the amount of bleeding risk to the patient, reducing that patient from an iron ore of 2.5 to 3.5 down to two point oh 22.5. All of us have taken care of these patients over the years recognized the fact that overshoot occurs commonly with Coumadin. And so if you're over shooting in a range from 2.022.5 versus over shooting at a range from 2.5 to 3.5, the less there is much less likelihood of having a significant bleeding complication uh in the patients who have the lower iron, so I think this is going to be a very significant improvement in patients with mechanical mitral valves. So patients who are Have a mechanical mitral valve being in a lower I and our 2.02.5 will definitely be an improvement for that patient population. In that they're bleeding risk will be substantially reduced. So in this video we're going to demonstrate several aspects of the implantation of the NX micro valve. First, it's very important that one prepare for optimal mitral exposure. One needs to free up the KV on both ends, spc and ibc so that their skeletonized um open the oblique sinus and um open the inter atrial group. Obviously we haven't done that here because this is an atomic specimen of pig heart. The second thing to talk about is that of course in today's world we try to repair as many micro valves as possible, but when one gets to not being able to repair the mitral valve. In many cases one is dealing with calcium and calcification. Not only of the mitral valve but also the mitral annular us as well as uh the left ventricular myocardial. Always in the back of the surgeons, mine is concerned about left atrial left ventricular disruption um with any sort of manipulation and resection of the calcium. One of the things I like to do is place a pericardial patch. Especially this works very nicely in the post interior uh Manulis. And what I do is I take simply this card that we all know very familiar and I use that as a pattern. This is done once one decides that you really need to cover the posterior annuals. When one goes to cut the patch for that area and whether you use bovine pericardium or photo fix either one of those two substances is fine. Then you have something to work off. But that would then be suited to the um left ventricular myocardial along here and then carried around on both edges up to the annual S and then up onto the left atrial wall. And of course it will be saddle shaped like that. And then once you have this then one can take the photo fix or again you can either be that move on pericardium. I found this substance to be very nice and you can lay the pattern on this and then simply cut the photo fix to the pattern that you have developed. I'm gonna go ahead and remove the anterior leaflet. We have already made a decision that we're going to do a micro valve replacement. And so I'm going to detach the anterior leaflet. I'm going to leave a little rim of anterior leaflet but you can see there and I'm actually going to leave the posterior leaflet. Now obviously if we had significant calcification in the post here, analysts, or the poster leaflet or the left ventricular myocardial. Then the next step here would be to cut out the post here leaflet and then use our photo fix and patch that area like that. And then once this is patched in place, the futures for the mitral valve simply come along this area in the in the neo Angeles here and then carried on around up here. But I think I want to make a point about coral sparing, coral sparing as we know today is very important. However, if you notice from from this point say the nine o'clock point over 23 pm point um we have divided the anterior leaflet and I'm actually going to cut out the portion of the leaflet from nine o'clock to 12 o'clock and I think that especially in a mechanical valve should not be left in place. And the reason for that is because once the mechanical valve gets down in there, this portion of the anterior leaflet can become draped across the left ventricle outflow track, which of course is up in here and can actually obstruct the left ventricle outflow track with this segment of the anterior leaflet. We're going to actually incorporate um fixation of this to the analyst uh with the valve futures and I think you can see where I am grabbing that leaflet and then going through the Angelus. That way it saves a step actually serves to bolster that segment. obviously in this area of P 1, 1 needs to be a bit cautious about how deep to go because the sir complex coronary is in this region. If you have resected the leaflet, you really need to be cautious here. I'm actually just grabbing leaflet on the bike, going in and endless on the bite, coming out and around the left, commit. Sure. one needs to be cautious about not going too deep with this future because if you go too deep in this area here, you can actually grab leaflet of the aortic valve. So that's why I leave this rim of tissue here to ensure that that doesn't happen. This completes the suitors. Let's talk a bit about sizing. So this is a 25 micro sizer and I want to make a point. You see how that looks way too small, but in terms of my trolls, one does not need to oversize with the onyx valve. The flow dynamics are fantastic. You will see gradients across the onyx micro valve are quite nice. It's important to understand that. So one does not oversize. There's no need to oversize this valve or be concerned that much about sizing. This obviously is too small. So we're gonna size for a um 27 29 and this here is a 31:33 And this actually looks about right, would be one of the other 27, Or 31 33. So let's talk a little bit about the two different types of valve choices. With the NX. We have the conform acts here, which you can see works very nicely if the annuals is heavily calcified and you need to have the cuff, the sewing cuff to conform to the annual is because there's a lot of cuff out here. This is the more conventional standard valve Um that comes in sizes. This comes in just the one size, 25, So today we're gonna be using this valve, we use the can for max 25 33. It's very nice valve sits very nicely uh in there, we have 13 suitors. So now we're going to simply place these in the usual manner. Again, not wanting to get too close to the housing for the valve, so now we're gonna insert of ours first, going to make sure that all the suitors are pulled up and I'm looking down below, making sure that everything is taught. Yes. So we're going to just let it sit in there like that and I'm gonna go ahead and turn this. Now, we're gonna want to leave the valve in the anti an atomic position, which is going to be about like that. And that will be demonstrated better once the holder comes out. And so now we're going to pull this up and pull this out and we can see down in there to check and make sure everything looks good. I'm going to use a technique here to show you and to make sure that the valve isn't popping out. So we're gonna tie that there and then we're gonna go across over here and we're going to uh yeah, this one, here's what I want because I can see this pledge it down in here. I'm going to make sure that that's going to come up. You can see how now that pledge, it has disappeared behind the housing. And now I'm going to tie these futures just beside where I've tied and then I'm gonna go 180° across the valve to ensure that it is getting completely into the Angelus. Just for demonstration purposes, I'm gonna put in a corner lot, which I think works very nicely for all valve replacements. So, we're gonna this down here. I believe that the corn, it actually is more superior, not more secure, not then um surgeon's knot because you're pulling on both suitors simultaneously when you secure the core. Not. So we're gonna, yeah, but they're just not here. Good. All right, so we're now completed the valve. You can see now the valve implant has been completed. So one of the questions that comes up frequently is what type of cuff should be used with the nX micro valve. There is a standard cuff and then there's a con form X cuff. The con form X cuff actually is a very nice cuff. If you have a heavily calcified mitral annular because it's quite broad, it's quite wide and set super annular on top of that area, covering a lot of the Angelus. The standard micro cuff is also a very nice cuff, intends to expand a bit once the valve is seated into place. But if you have a heavily calcified um Angeles, the an ex con form X actually works quite well in that situation. So one of the issues that comes up with the mitral uh next mitral valve is sizing and in terms of valve choice um as it turns out that 25 mitral onyx valve flow dynamics is very competitive with any other valve and is large enough. One needs to keep in mind not trying to oversize the mitral valve, it's unnecessary. This is especially important when one is doing a double valve replacement because there's one increases the size of the mitral valve in a double valve replacement. You begin to not necessarily decrease the size of the aortic annual ist, but you tend to stiffen the aortic mitral curtain with that valve and the bigger the valve becomes in the mitral orifice, the more stiffening that area becomes and therefore the smaller aortic prosthesis one can get in place. So I think in terms of the type of valve to use or the size of valve to use in the in the micro position, I think standard um sizing is appropriate with a tendency not to oversize. So let me address the issue of the 25 33 con form X valve in terms of sizing. If one size is safe in a smaller patient, uh the the annual is to be 25 millimeters. Can one put in a 25 33. How does that work? Well, As it turns out the way the valve is designed, the valve basically is uh is eight realized so that it actually sets up into the left atrium and the cuff is below that area. So that really doesn't become a significant factor in terms of the sizing. The flow dynamics are uh very competitive with larger valves and will be quite satisfactory. So that's the reason why if you size For 25 and 25, is chosen, it will work quite well. A frequent question that is asked about the annex mechanical mitral prosthesis is why just one size, namely 25. And the answer for that is actually quite simple and based on engineering principles. If you look at me in gradients going from 25 and larger valves and compared to other products on the market, you can see that there really is hardly any improvement in gradient. The gradient are already so low that it's meaningless to try to reduce the gradients any further. Secondly, there are two other important points that need to be made. When you start making that valve larger. In the micro position, number one, you increase the homogeneous city because you've got sluggish flow across that valve uh and you don't have the washing effects that you have in a situation where the flow is greater. And thirdly something that's often unappreciated is the fact that you have um uh increased leakage or increased micro regurgitation because the office is so large. So all three of those components, uh the lack of need for increased, decreasing the mean gradient, the throne ethnicity and the increased micro regurgitation. All three of those reasons are the reasons why the 25 is uh large enough in all patients that are undergoing mechanical micro valve replacement with the annex other attributes to the mitral mechanical valve. Uh Made bionics is that with the con form X cuff, it's quite large and patients that have significant michael annular calcification. This could be quite advantageous to sort of cover that area where the valve is uh setting up in the in the atrium and so it helps quite a bit on MAC management. Uh The other aspect that is important is that um when one is doing a micro valve replacement in today's world, one really needs to consider doing um coral sparing technique. And with the way the mitral valve is designed by annex, the entire posterior leaflet can be retained as well as a portion of the anterior leaflet. In my opinion, the anterior leaflet should always be resected in a mitral valve replacement, whether it's by a prosthetic or mechanical From 9 to 12:00. The reason for that is that uh if you push the prosthesis in, whether it's by a prosthetic or mechanical and stretch out that leaflet if it's large enough and bill away enough, it can actually obstruct the left ventricular outflow track And cause significant obstruction uh to left ventricular outflow immediately coming off pump. I've actually seen 2-3 cases of that in my career, so I always would respect that area of the valve. But the anti relief from 12 to 3 and the entire post relief, it can be remained in place for Kordell sparing technique which we know augments and preserves left ventricular function. Long term for that patient with the mechanical onyx valve to clarify a bit more about coral sparing technique. Uh This is a plastic model of the onyx valve and you can see how the leaflets are all uh within the housing of the valve so that as the valve is inserted into the mitral annular lists and the chords are retained and spared in this area. Then the leaflet tissue as well as the cords are actually pushed away. And there is no way that you can have any uh Kordell uh involvement with the leaflets. That's very important because that can happen with a cordial sparing technique. Again, the one thing that I think is important is to resect this portion here from nine o'clock to 12 o'clock of the anterior leaflet of the mitral valve. Because if that is not done that area there could obstruct left ventricular outflow uh and can become immediately apparent. I've seen 2 to 3 cases of that. The other thing I would like to uh to comment on if this situation is the valve in the micro position should always be left in the anti an atomic position if possible you want these leaflets to be vertical like this because that really augments and facilitates flow dynamics. So that's very important. The valve again is rotate herbal and so one can, if valve gets implanted and ends up like this, one can insert a rotator and turn it back this way so the valve is left anti anatomical. An important aspect of the use of the mechanical annex mitral valve is the proact trial in the mitral arm of the product trial. Of course this trial looked at reducing the iron are of patients from 2.5 to 3.5 uh down to two point oh 22.5 while the patients are still on component. Uh There's a significant reduction in lowering the iron are from the 2.5 to 3.5. Range down to two point oh 22.5. All that being said I think it's going to be very important That um patients are able to safely go down to a range of 2.022.5 once this trial is completed and um should be approved by the FDA.