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 aortic 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 2000 and seven 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. As many of you know in 2015 the F. D. A. Uh granted approval of the valve with the lower I. NR. And in the Proact trial. And so the valve currently is used with after three months of conventional therapy. An eye on our of 1.5-2.0. Which makes a huge difference in terms of the patient's bleeding risk. It reduces bleeding risks To greater than 60% lower than conventional standard 2.023.0. Um And the data was so solid. Such that the A. J. A. C. C. Guideline update in 2017 allowed for the valve to be given a class two indication for uh an iron are of 1.5 to 2 point oh and I think that is a strong endorsement for the valve um as it currently sits, let me speak for a couple of minutes about patient selection with both the onyx aortic and onyx mitral valve. I think it's very important that guidelines are followed also in patients who you anticipate having a small aortic annual. It's I think it's very important to make a judgment preoperative really those patients and try to identify who you think you may be faced with a small aortic analysts. Those in the operating room you need to have that um one needs to have that all worked out before you get to the operating room and techniques to do that would be studying the trans thoracic echocardiogram pre operatively if need be moved to a trans esophageal echocardiogram preoperative lee. And the reason to do that before you get to the operating room is so that you can be prepared and the patient can be prepared for the fact that they may have to have a mechanical valve if they had chosen to have a bio prosthetic valve. Because of those findings. The other thing that one can do today in the world of tab are is that cT imaging has become very accurate in terms of sizing and so uh to the extent that one wants to be as accurate as possible. A C. T. Scan can be obtained pre operatively to also identify patients that you think you might anticipate having a small aortic and so all those things are very important to consider pre operatively in in planning for the patients operative surgery so that your mindset as a surgeon and the patient's mind set as a patient can be can be ready for that experience. 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 tab are, 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 except 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 uh in a very uh patient friendly manner. So they understand exactly the choices that they're making for themselves and their family. A very exciting aspect to the onyx valve and the aortic position is the pro act in a trial. This is a trial that was started in 2019. Uh and is enrollment of that trial is well underway. It's 1000 patient trial. That's a randomized prospective study and basically randomizing patients who conventional therapy of two point oh 23 point oh versus patients who are on eloquence. Um one tablet P. O. B. I. D. One of the questions that come up about this trial is that why when you wrote randomize it against 1.5 to 2 point oh. The answer was very simple and that the FDA required uh the cry life company to randomize against conventional therapy. So that's the reason why they didn't randomize against 1.5 to 2 point oh. But this is a very exciting trial and honestly will be uh as some have characterized at the Holy Grail in uh cardiac valve replacement. Because if if a patient can be offered an onyx mechanical valve that we know is durable for a lifetime and only take l a quest once. Uh one tablet in the morning and one tablet in the evening. Then many patients will very likely want to go to having this valve implanted in the aortic position, The substantial reduction in risk of patient prosthesis mismatch. We all know that PPM is a very serious issue. Pebereau identified this back in 2010 and has published papers on it subsequently to show that mortality rates are substantially increased if the patient's prosthesis is not matched to the patient's body surface area. So the eo ai becomes a very important factor and one should always keep this in mind when picking a valve for a patient. This can be anticipated. Patients are markedly obese pre operatively. Uh If they are small stature, small frame, typically women are can be a challenging size. And so in those patients, once you're seeing them in the office, you can look at the transfer desk echocardiogram, ask your cardiology colleagues to measure the diameter. Uh if you're still unsatisfied that that's not an accurate measurement, then you can get a. T. E. Pre operatively which can be a bit more accurate and even moved to a ct scan. So all those things are things that you have in your toolbox to try to identify patients that are going to be a problem in the operating room. You want to have a mindset for that going into the, into the operation, as seen on the graph. The effective orifice area index Is quite an important factor and a huge advantage of the annex valve. So, uh patients can be implanted with a 21 valve down to a body surface area or up to a body surface area of 2.1 And a 19 valve up to a body surface area of 1.7, which is a pretty good size individual. So the valve has incredibly good flow dynamics and this is one of the huge advantages of the valve to to make sure that that the patient doesn't suffer from PPM, which carries a very significant mortality risk. Uh these uh flow dynamics are true not only for the isolated aortic valve but also for the ascending aortic prosthesis. So that's important to keep in mind. You want to make sure that that you anticipate whether or not the patient's going to have a small annual list because it all costs. You want to prevent patient prosthesis mismatch. So in this case we're gonna do a trans versi autonomy here. But you can see if the patient had a small aortic root and you were anticipating needing to do in a uh aortic annular enlargement. Then what you want to do is a hockey stick incision and carry that down into the non coronary sinus, which would be over here. So the incision would go here and carry down into the non coronary sinus. But in this case we're just gonna do a transverse, the autonomy now so that exposure is ideal. In the lab. I'm actually gonna transect the aorta. This of course would be the view that you would see if you were doing and we will be doing a is sending aortic prosthesis placement at a later video. Once one opens the door to of course, you want to identify where the coronaries are. This is the right coronary artery and this is the left main coronary artery. This is the aortic valve. And we're going to excise that in a typical fashion, there's nothing different for the annex valve. With regards to this, the anatomy of the pig is a little bit different also and that the sinuses are quite tend to be a little bit steeper than in the human. So now we've excised the aortic valve and we are going to examine the annual. It's like you always do, of course this is a normal uh pig, normal annual list. And so now we're going to size it so you can see what I've done is actually cut the aorta down. Of course it's been transected and so that we can really see down into the aortic aneurysm. Just to point out, the pig really has a pretty large muscle shelf here, which of course the human does not, but in this case it's not obscuring too much. So we're going to talk about sizing And I'm gonna start with a 23 sizer. Sizing is incredibly important for all valves, but especially mechanical valves. You can see on the 23 here where there's still space is in the annual, obviously that's way too small. So we're now gonna go to the 25 And you can see with the 25 that it's a little tighter and that still is showing quite a bit of space right here. It really shouldn't be. You want to go for some mild, mild smugness, but you don't want it to pop through. So, this is 27 29, which is looking about right for this particular analyst, The 30. This is a replica for the 27 29 and one should always use this to make sure that this will replicate what the valve is gonna look like once it's seated. You see that the coronary, of course the pigs, coronaries are quite high. So here and over here, the coroners are well out of the way. You can also see how the valve is going to sit by twisting that around. What I want to point out is to make sure that the valve isn't oversized. You don't want to feel the, you don't want to feel the size are popping through. You want to feel it too snugly, go through the annual. So this is just about perfect the way this feels here. If in fact, one finds that they are going between the 27 29 possibly being too tight and downsizing to a 25. There's only a one um millimeter mean gradient difference between 27 29 25. So certainly a 25 would be suitable if in fact, this seemed to appear to be too tight. So you can see that we've completed all the future placement. These are non inverting mattress sutures that are pleasant ID There are different featuring techniques that one can use. You can use non inverting um non pledge, it'd futures, a mattress fashion or you can use simple futures if you have a relatively small analysts and the smaller the analysts more likely one would use either non pledge it'd futures or simple futures. Um I'm not sure that it's uh advisable to do a diverting mattress suture technique on the aortic valve because there's increased tension in this area right here. If you divert the mattress future in that fashion, We're gonna resize now now that we have the pledge it's in and the futures in this is a 25 and this actually seems better to me now, we have the futures and of course it will be just some mild person ringing effect from the future placement. The 25 looks quite good in there. To me. It goes in easily with a mild smugness and then I turned it around to put the replica in. And, and then you can see that the coronary arteries, this is the left main and the, excuse me, the right coronary artery and this is the left main. Over here are well away. It's important to note in the human because obviously they're much closer than they are in the pig. Let's just look at the 27, Um, which is what the original thought would be when I first size this and this would might be okay, but it just seems a little too snug to me. I'm a little bit concerned that it might be too big. Uh The point to be made that A 25 only has increased gradient of one millim of mercury over 27 29. So Um either one of these will be fine and I think we'll just go with the 25. So this is the 25 valve. A couple things I want to point out on the valve, You see it comes in a holder, like this is very important that one takes the valve and rotates it like this before you insert it just to make sure sometimes there's a little bit of a seal that must be broken, but this turns pretty well because once you get it in there, even though we're going to place the future so that we don't have to rotate it, it um it would be good to know that it does rotate. I'm gonna fit this in there. Even before we put the suitors in, you can see how it sits in there nicely. I can look down in there, I can even rotate it a little bit if I want to and it looks quite good. So I think this will work well for us. There are three super marks here and here, which will help us to place futures. and at one point I want to make with the future placement on the sewing ring, is that the needle needs to go at least halfway out here and not deep because you don't want to touch the titanium down here, you want to come out about halfway. Ah And what I've developed over the years, I like to go in about halfway on the bottom and come out on the edge. The purpose of that is that when you tie it or when you use the core, not the not will actually turn away from the orifice. If you leave the future, If the future gets too long, it can actually go into the orphans of the valve and interrupt and cause conflict with the leaflets, which can be a bad problem. You see how the valve lowers very nicely and sits in there very nicely. And what I'm doing now is looking inside to make sure that I don't see any pledge. It's hanging out and I'm confirming looking at along the Angelus to make sure that it is well seated everywhere before I commit to tying it in and it does look good. one thing I'd like to point out is that um the valve holder has this extension on it and this has worked very nicely to allow for ease of insertion. You can see how easily the valve goes in and it serves basically as a snowplow effect going in, pushing everything out of the way. I think that's one of the big advantages of the onyx valve and that you don't have to worry about that. Some people have been concerned about the flair and in terms of inserting it and getting it um seeding it inside the annual list. That is not a problem because of the, the extensions on the holder. And so now we're just gonna wiggle this and we're gonna pull this out. So what we're gonna want to do now next is to look inside real quickly, we're gonna open this up, We see that there are a couple of pledges that are down in there and I'm gonna make sure confirm before we get started on this, that those pledges will in fact recede like you can see there recede back underneath the housing and all of these I believe will be retracting back behind the flare once they're tied. What I'm demonstrating here is you can see the pledge, it is hanging out underneath the flair and when I pull back on and see how it retracts, you need to make sure you see how the pledge it would be hanging out, but otherwise it retracts, you've got to be able to see down in there, so with the leaflets open while one is tying it in so that when you get finished the pledges not hanging out like that, they will just tie this one. One thing I was talking about before you need to make sure that the future is on a mechanical valve are not cut too long because if they are then you can see how this could get caught up in the functioning of the valve and actually either stick it open or stick it close. So you need to make sure that those futures are not that long when they're cut and the valve, we can rotate as you can see if we I need to see anything down in there. It actually looks quite good because when I looked down with the probe and focus on it 360°.. There are no pledge. It's anywhere except right over here. So the next thing I would do in this case is go to that pledge it and make sure no that mark and make sure that that pledge it, you see how that pledge it now is retracting away before it was there and now it's not. So it's really important to be able to see that all the way around the valve as you can see as I'm tying these in. We are purposefully and deliberately keeping the leaflets open. I think it's very important that each future one ties down, one can see the corresponding pledge. It has receded back behind the flare because any sort of obstruction or encroachment on the outflow track will lead to turbulence, which of course will lead to throw Magennis city. So I'm gonna use a corn nut in the next few suitors and I think the core not actually is quite advantageous in all types of valve replacement. The corn nut when it comes down. This needs to be to the orifice of the valve, but you can really pull up very nicely. And one shot you can see that the corn, it is complete and of course the core not in doing valve replacement surgery or micro valve repair surgery for rings is much quicker than tying. But you can see that corn. It actually helps deceit very nicely. I have that probe in there so that I can actually make sure that all those pledges have retracted. So let's go ahead and tie the rest of these if we wanted to and we're not happy with the position we could take this, insert it and we could rotate the valve like that. So I just rotated 90° from where it was before. So you can see that the implant works quite well if all those little tidbits are followed. So I'd like to talk a few minutes about the aortic valve of the mechanical on X. Aortic valve. And this is a uh demo model of that. The valve like this. Um This is just a demonstration release mechanism here. What you will get in the operating room is one with the future around it and you simply cut that and it releases it. But once you receive the valve you'll receive it from the scrub tech with this holder on it. The first thing one should do is make sure that one can easily rotate the sewing ring on the valve because you don't want to get it down into the orifice and then find out that you're having difficulty. Occasionally, not very often, but occasionally you will find a valve that's a little more difficult to rotate than you'd like. So you want to make sure this is done in terms of sizing The size ear's come in, the corresponding sizes of the valve and 19 through 25 coming what we call a cylindrical or like this that is perfectly symmetric from the beginning from the bottom to the top. And then on the other end is the corresponding size of what they, what we call the replica or what is called the replica um uh portion of the Sizer. So let's take these one at a time. So this is a sizer that when it goes through the orifice, one should feel some snug nous, but it shouldn't really pop through. You don't want that feeling of popping through because it likely means it's too tight. So you want to feel a little bit of friction as it's passing a little bit of snow Agnes. But you don't want it to, you don't have to push it hard to pop through and then you have difficulty getting it out. That could mean that that Sizer is too large. So that's very important. You want to make sure that when you look at the Angelus, um that's when you look down inside the analysts, then one is not seeing a whole lot of space around it like that, that obviously is too large. Or there any areas where if the annual asses asymmetric you want to accommodate for that. So all of those things need to be taken into consideration when sizing for the valve. The replica end is something that is very important to use and I've found in in my practice and experience of talking services, this is somewhat overlooked the importance of this. This really, as you can see how this is formed, this really replicates or duplicates what the valve is going to look like once it's in the Angeles. So again, once you see it in the Angeles, you can take this. And the, the reason the company made this was to make sure that the coronary ostia are going to be free of any evidence or suggestion of obstruction. But it also really gives you a good final feel for what that valve is gonna look like and what it's gonna feel like in the annual stuff. You start with this to choose that size and then you some and you sort of confirm That size with this end. That's true for sizes 19 through 25. This is the 27 29 sizer. And you can see how this is uh not uh cylindrical but its conical, so it's smaller here than it is up here and that thus um the measurement of 27 29. So the only difference here is that it's where it's going to be sitting in the Angeles as you begin to feel the the smugness on the valve again, you don't want it to pop through. But if you have an analyst that's large enough, this will be one of the most uncommon that you use because you know, most of the patients we operate on don't have an annual this large, but you begin to feel the snuggles and you've already felt like the 25 was was not big enough. So you have this in your hand and that's sort of the feeling you want to get again, there is a replica end and you always use the replica end and once again assessed for the coronary ostia um especially if you have a low lying left main, which can happen um and to make sure that the vibe was gonna is gonna seek properly. So those are the main issues that one needs to um, the cognizant of uh, in terms of mechanical, uh, aortic valve replacement, there's a couple of specific issues I want to address and this is sort of valve replacement in general. One is with bicuspid valves, one needs to be cautious about sizing and not getting not over sizing with bicuspid valves because true bicuspid valves have a very high um ca matures and they can actually be deceptive in terms of the size that you can actually get in. In most cases. In many cases, especially if you have a are the valve sizer will go through very easily but it may not accommodate that size valves and you just need to keep that in mind. And if it's suitable in terms of the valve size, in terms of your uh you ai chart and you've assessed that you might want to downsize that valve just a little bit in my opinion. That's that's what should be done in that situation. Should just keep that in the back of your mind with by custody already pounds. The other thing that I would like to talk about about valve aortic valve replacement and in general, and these comments are important, especially with mechanical valves because mechanical valves in general and the onyx included are unforgiving their rigid. And so the by prosthetic valve rings. The by uh by prosthetic valve sewing rings are um more forgiving and more accommodating to the angelus. Not so with mechanical valve. So sizing becomes a very critical issue for any mechanical valve when you're dealing with aortic regurgitation and you're replacing the valve. Again, be cautious about over sizing the valve. Those annually are very accommodating to the sizer but may not be for the actual valve itself. Someone needs to keep that in mind and be in your mind, be ready to downsize one size in those situations, let's speak to the different types of sewing cuffs that are available with onyx, mechanical aortic valve. So there are actually three different types. There is the conform acts, which is this cuff here. There is a standard cuff which you see here and then there is an, an atomic cuff and sewing ring which you can see here. Now the difference between these two, let's go into detail. You can see in the can for max, there's more sewing ring, but it's still in the same plane all the way around the an atomic sewing ring, as you can see here has been made to accommodate the scalloped nature and the an atomic nature of the aortic aneurysm. So that these areas that stooped down as you can see in here or slope slope down, uh conformed to the narrator and these areas with the marks conform to the commissars. So at the end of the day, this is somewhat surgeon preference as to what one is comfortable with, what one has gotten used to in my practice, I used this cuff which is the standard uh standard cuff. But either one of these other two cuffs are used very frequently out in the field, but just for the surgeon to be aware that to study that a little bit as one begins to use the onyx valve to decide which one is her or his preference, one of the important aspects of the aortic valve replacement in today's world is making sure the patient gets an adequately sized aortic valve prosthesis. It doesn't matter whether it's mechanical, bio prosthetic or tab are. I think one of the areas that we need to make sure that we're doing the right thing for the patient is that they are getting an adequately sized aortic prosthesis. One can anticipate in certain patients that are at risk for patient prosthesis mismatch. And those are patients that are small framed, typically smaller women or patients who are obese in which there be S. A. Is somewhat out of proportion to their um to the aortic analyst. One can anticipate this pre operatively by the transparency echocardiogram. If one feels that the echocardiogram uh is not adequate in terms of the accuracy of measurement of the diameter, uh imaging quality may not be good. That's especially true in obese patients. Um then one can move to a. T. E. Or even getting a ct scan. Our radiology imaging colleagues today in today's world with the tab are have become quite accurate in terms of sizing. So all of those modalities exist pre operatively. So that when you get into the operating room, you're not faced with a surprise as a surgeon and that you can pre operatively talk with your patient about the realities of possibly having to put in a mechanical valve. If the patient's preferences of bio prosthesis or um having to do any aortic root enlargement. Um Let's talk about that for a minute. So if you get into the operating room and find that the way I want you measure the valve because you're not going to really know until you exactly what you can get in, until you get there and you're on cross clamp, you cut out the valve and you're sizing the valve. Um You're gonna go then to the eo a chart and and look at that to see if the size that you can get in will be suitable for that patient. If you cannot get in a suitably sized valve and that patient then one must consider doing an aortic root enlargement and that's covered in a separate chapter in the library here. But suffice it to say that I ordered through enlargement should be done in that situation. It only adds about 20-25 minutes to the operation. And for the benefit of the patients. Long term survivability. It's important to do that. Um So all of those considerations need to be made when it comes to uh sizing and picking the appropriate prosthesis for the patient. I think most cardiac surgeons today have uh converted to a non inverting suture so that the sutures are placed from the left ventricular aspect through the sewing ring or the the analyst to the aortic aspects. So if you're using pledges, the pledges will end up on the ventricular aspect. If you're not, then of course you end up with a use a U shaped mattress future in those areas averting mattress sutures um Historically have been used. I think they're probably not as good. Most studies would show because there's increased tension uh in the in the version of the tissue number one and number two, it actually makes the annual is smaller so frequently as surgeons were dealing with patients that have um small or borderline, small aortic cannula and you don't want to be doing inverting futures that make that situation even worse. So I think um it's been years since I've done diverting mattress sutures. Honestly, I don't really know of any circumstances in which that would be advantageous to be using that. And um non inverting suit, you should be used virtually in all cases. Let me speak for a moment about the types of uh future that that can be used in aortic valve replacement. And in my opinion, uh when certain types of future should be used. So there are basically three different types of uh suture technique. One is non inverting pledges futures. The second is non inverting non pledge it'd futures and the third is a simple future. And so let's go and reach one of those pledges futures, which is frankly what I used most of the time in my practice um orient the pledges to the ventricular aspects of their non inverting and they're a mattress future uh and they're used primarily to bolster the tissue so that when you tie down with uh not uh and you're tying the future in place, it provides a bit more of a bolster or a cushion for the tension that's being placed on that future. Um That is a situation in most cases where the ambulances um friable and in in many cases today that is the case. Every typically an aortic valve replacement can be one in which the tissue is quite uh quite quite friable. And then once you've to breed it all the calcium mountain. The second technique is non uh pledge it'd diverting mattress sutures and again in the future is oriented so that the U. Shape is on the ventricular aspect and the pledge it comes up through the aortic side of the analyst. And I think that's a perfectly suitable technique. Um You lose the aspect of the bolster, you lose the aspect of the cushion when you're tying it down. But certainly very fine surgeons I know use that technique that have used it successfully without any concern about a perry valvular league. The third technique is simple futures. Simple structures can be challenging a bit from, From a future management technique because you end up with a lot of suitors, the typical already valve replacement and a 25 valve, I would say it would be 12-15 futures With simple futures. It's going to be at least 20 plus futures, 20-24 suitors. And so you have to have a mindset for that. And how you set that up in the tray for holding the futures also is a bit different. So those are the three techniques that are used, their different circumstances in which you want to use that. Uh and just to be complete, I should mention that the simple future technique is quite helpful if the patient is has a small aortic aneurysm because if the annual list is small there with either one of the mattress techniques, either pleasant or non pledge, it'd suit you. You're going to end up with a slight per stringing effect. Not completely, but there will be a little bit of a purse string effect all the way around. Which of course are the simple future technique. You eliminate that as a possibility so small aortic analysts tissues are adequate um tissue integrity is adequate, then you it's suitable and probably preferable to use um Simple future technique when one is deciding what is the oriented, correct orientation of the valve. Um There is in the aortic position. Um some literature albeit soft in which the valve should be oriented and that is to say that the leaflets um middle orifice should be directed Toward the left, right, commit. Sure and they're on one aspect and of course the other aspect 180° across should be in the middle portion will be in the middle portion of the non coronary sinus. There is some data to suggest that the coronary flow is optimal with that. And also there's less turbulence with that. Um That's not to say though that you can't orient the valve differently from that if in fact there's sub valvular tissue or heaven forbid the pledge it is sticking out somewhere so that you want to not have any chance that the leaflets will be um leaflet function will be impinged upon by the occurrence of that sub valvular tissue. We try to cut out all the tissue, Try to get everything right. But occasionally that'll still happen so you can orient the valve differently from what I just talked about. If in fact that circumstance occurs. The other thing I would like to say is that one should um in the process of doing an aortic valve replacement with especially with the mechanical prosthesis is that the valve is excised. The angelus is debris. Did futures are, The valve is in sized for proper selection, but the valve is not brought out yet because you place the futures and then you size again after the futures replaced. Occasionally, that the valve choice can change. And you certainly don't want to have the valve on the table and decide. You need to decide that you need to go one valve uh smaller. Uh Of course, there's no preparation for this valve. There's no two minute wait or anything like that. So you can wait right till that moment to choose the valve. But that's an important thing to remember is to is to size initially, but size again after the futures replaced. One thing is imperative with the NX mechanical valve. Of course this is pure paralytic carbon and it can be uh scraped and it can be um injured if you will with any sort of metallic objects. So never ever touch the valve leaflet or the housing with any sort of um uh metal uh hemostat. Any sort of probe or anything needs to always be plastic like this that comes in the kit uh when one is testing the leaflets, checking to make sure the leaflets are opening and closing properly. Always always use this and never use anything that's metallic or metal. The reason for that is if you get a slight injury to the surface of this and a scrape in this, the net can become obviously a the night is for a throbbing Jenness city and dramas can get in that area and of course can then go on to become uh Rambo bolic and cause a. T. I. Or stroke. Let me address an issue that's been around for a number of years about the onyx aortic valve and a concern uh that the valve is difficult to insert. Typically, what could happen is the valve could pop up out of the, out of the animals even though it was appropriately sized. That problem has been completely eliminated. With the new extended holder, you can see that these arms come down much further and it's essentially act as a snowplow as one is going into the annuals. Everything is being pushed away and the seating is quite accurate and quite proper so that that issue has been, has been taken off the table completely. The other thing to say is that the size, others are actually um, One millim larger than the actual valve. So when you're sizing for a 25, the size is actually a 26. And so that's important to remember uh as you're, as you're doing that, that you're actually going to get one millimeter benefit. And the final thing to say about uh, any sort of difficulty is that the, the pledge, it's that essentially, uh, most surgeons use can very easily be seen through the valve. Uh, if the valve remains open the entire time that you're structuring in first, you, once the valve goes in and you still have it on the holder, then you can see down inside the valve to make sure that the pledges have receded. And if they haven't, one can go to those areas and uh, directly and address those pledges first to make sure that they are receding back behind the housing. So, all of those issues in today's world, uh, in terms of the quote difficulty of uh, sizing and seeding the aortic valve have been eliminated by all of those uh, issues that I've just addressed.