Hi everybody, thank you so much for tuning in for this webinar on mitral valve disease in dogs. We are going to talk about when is surgery an option and what does it involve for mitral valve repair specifically. Sorry, it's not fast forwarding.
I'm gonna have to do that again. I think OK. OK, I think it was on the wrong thing.
All right, just gonna start again, sorry. Hi everybody, thank you for tuning in for this edition of the webinar on mitral valve disease in dogs. We're going to be discussing when is surgery an option and what does the surgery involve.
So specifically for mitral valve repair, in regards to myxomatous or otherwise known as degenerative mitral valve disease. As an overview, I'm going to talk to you about the history just in brief of where we've got to in veterinary medicine now and how we've come to that point. We're then going to talk about potential candidates for surgery.
We'll discuss cardiopulmonary bypass, which is essential for these surgeries and the basics of how that works. Then we'll talk about the surgery itself, so the steps and what we're actually trying to achieve. We'll talk a bit a bit about the post-operative care, and then I'll talk to you about the results and the prognosis that we can expect for the average patient.
So just as an overview to begin with, if we look at the surgical history for veterinary medicine, we are very far behind our human counterparts in this discipline specifically, as well as of course in many others. But there really is a huge gap between what human surgeons are currently doing for humans and and what we're trying to do for dogs. And there's multiple reasons as to why this is, but we didn't.
Get started, for a very, very long time. And one of the reasons is that it was initially thought that small dogs, which of course, as we know, is the most common type of dog to be afflicted with myxomatous mitral valve disease, it was thought that they wouldn't actually tolerate being able to go on and off the cardi pulmonary bypass machine, which of course, therefore set everything back and to a large degree. And therefore only a couple of centres were actually performing heart surgery, and that was just the congenital cases.
So those types of cases that affect the large breed dogs because of this thought that it wouldn't it wouldn't be able to be possible in small dogs. But of course congenital heart disease is much, much more rare than myxomatous heart disease and therefore, even if you had a centre or two performing them, they were only doing maybe one a year, sometimes even less. And of course, as with everything in veterinary medicine or practical skills in general.
The less you're doing, you can't get good very quickly and you can't really improve things over time. So again that held things back a lot with success rates, and therefore, of course, owners and veterinarians' willingness to do procedures. Initially, valve replacements were tried, so we're talking both for mitral valve repair, so m valve replacement.
So before repair was tried, this was put in place. Unfortunately, that yielded poor results. So the median survival time in a paper by Autow showed just 4.5 months, and the issue and the reason why is because thrombosis of the prosthesis, so the prosthetic valve was occurring.
The same thing was tried for tricuspid valves and so for congenital tricuspid valve disease, again, very poor success rates. Again, thromboses were forming on the prosthetic valve, and this is a picture on the left hand side. This is a postmortem sample of a tricuspid, and you can see a very, very clearly defined a fibbing clot essentially, and that's rendering that mechanical valve from from functioning.
And so unfortunately, only one in that case series actually survived over a year and the others were much, much shorter. And for both the mitrals and the tricuspis, this was despite using the same anticoagulation drugs and monitoring in the same way as in humans, but unfortunately drugs just weren't responding to those anticoagulations in the same way and had a high propensity therefore to form these clots. So again, that set things back a lot.
When we talk about repair versus replacement, the two words often unfortunately get used a little bit interchangeably, and it's very, very important to distinguish between the two. So what we're discussing here is repairing the valve instead of replacing it. So we just had a brief look at the reasons why replacement hasn't to date worked.
If you take a step back from that, there are actually many advantages of the repair regardless of those results. So this is from the human literature, so of course, in general, if you do a repair rather than a replacement, you don't actually need lifelong anticoagulants. That's because you have much smaller foreign material inserted into the heart and therefore the body will actually be able to cover it in normal cells within probably about 8 to 12 weeks, whereas a replacement is a very large prosthesis, it's always going to be exposed to the coagulation system and therefore, whether you're a dog, whether you're a human, you will need lifelong anticoagulants with a replacement, which is obviously suboptimal.
In addition to that, repairing the valve rather than replace it preserves the heart function a lot better. They have a longer durability as well, a repair versus a replacement, which isn't really an issue in our population of patients sadly. But in humans, for example, most valve replacements will need to be replaced about 15 to 20 years after they've initially been put in because of wear out.
And then importantly as well, it has been shown in several meta-analysis that there's improved both surgical as well as long term survival rates if you repair the valve rather than replace it. This is one example here, where a valve repair was shown to be 21% superior for survival at 10 to 15 years postoperatively. We just look at a couple of graphs now, this is for mitral valve repair versus replacement, so the blue line being repair, the red line being replacement, and you can see that there's a difference between the two in terms of survival.
So that's where we got to, essentially, looking at humans, what they're doing, realising that replacements, although in some ways easier to perform themselves, weren't actually working. And so for a long time, the veterinary world in this regard was quite stark. Then, however, everything really changed quite a few years ago now with Professor Yechi, Dooshi and his team from Japan.
And they actually showed that mitral valve repair is successful in dogs, and importantly, that's for small breed dogs, so those that have a proclivity to have degenerative mitral valve disease, and therefore that you can take these small dogs both on and off bypass successfully, as well as repair their valves successfully. And this is a a graph taken from one of Doctor Wes's papers from 2012. The red line at the top is patients that underwent a mitral valve repair.
The blue line is matched controls essentially with degenerative match or valve disease that underwent medical management. And you can see that there is a significant difference in survival time. So we have that initial drop off actually in both cohorts, but as you would expect with surgery.
And then essentially, as we'll look at later with our data, is surviving the postoperative period, you then will go on to have a very good long term success rate thereafter. So this is what really changed things and made people realise over time that actually this surgery can be performed and obviously with bypass, which is essential to do it. So if we think about now the candidates for mitral valve repair, we'll look at the A CVIM stages of disease that I'm sure we're all familiar with.
So we have B1 on the left hand side, so basically any cavalier king 12 spaniel sadly. So predisposed to, heart failure or mitral valve disease itself. Up to stage D at the very end, which is where we're refractory to, your standard treatments of heart failure as defined by the ACAM consensus statements.
So B1, of course, is not going to be a candidate. Those dogs may never ever even get into B2. So we typically look at this population here, and you'll see that we've drawn the box from kind of the end of B2 to mid-be beginning of D.
In an ideal world, well, currently in an ideal world, most of our candidates, or all of our candidates would be in stage C. B2 is somewhat of a controversial end stage I would say, because we obviously do not know that every dog in B2, in fact we know that not every dog in B2 will go on to develop stage C of disease and therefore we don't know that those dogs that are in B2 currently will ever actually have much of valve disease as their limiting life condition, potentially quality of life as well. And at the moment it's very hard to predict which dogs will go on to progress into stage C.
On the flip side of that, you obviously have a situation where the healthier the drug is when you operate on it, particularly with such a major surgery involving bypass, the better potentially your chances of success. And that's why we kind of keep B2 in. However, what we're talking here, if we're considering operating the drug in B2 is advanced B2.
And so the cardiologist that I work with, Ankaraawa, she has several criteria to look at very, very specifically on echo to help determine, and this is comparisons over time as well, which patients are more likely or very likely slash imminently about to go into stage C. And if we determine that that's likely the case, then we will put them on our waiting list. Equally, if things remain very static, then we will continue to bump them down the waiting list, and then we ideally operate just as they go into stage C.
We know that sadly once you enter stage C that is then a life limiting condition. And on average you're looking at approximately 10 months, maybe 12 months of life once you've entered stage C. In terms of stage D at the other end, of course, those dogs are essentially in a situation where their life is very, very limited.
Their quality of life is typically pretty poor. And the reason I put the box where it is is because again, in an ideal world you wouldn't be taking dogs at the very end of day. So potentially even in the ICU department, needing intravenous medications to keep them alive, they are obviously not going to be your ideal candidates in terms of survival of surgery coming on and off bypass.
Unfortunately we find that a lot of the time when people inquire about the surgery, they're already in sea, if not been in sea for a long time. We obviously also have a waiting list, which is sadly a few months regardless of, you know, what we do to try and limit that. And so we will sometimes find ourselves in a situation where we are kind of end stage, mid to end stage D.
And that's a conversation of course to have with an owner. So typically actually this is our population of dogs that we operate on, and we'll look at that in some of the results section a little bit later on. In terms of other things to discuss, we talk about comorbidities.
So, there are of course going to be some comorbidities that mean we're going to unfortunately have to deny surgery. So something else that might be very life limiting. And people often ask about Cushing's disease.
Of course that's a reasonably common comorbidity to have in the sort of populations we're talking about. So middle aged, older, smaller breed dogs. Cushing's in itself isn't, it doesn't mean that you can't have surgery, but what we like to make sure is that they are on the standard treatment which they're responding well to and have been on that for some time beforehand.
Otherwise, you know, everything of course is assessed on an individual basis. Age we often get asked about, and that of course plays into it in many ways. It's tricky when your population of dogs are middle aged to older.
But of course you're going to be having a very frank conversation with an owner about whether it's worth doing this, whether they really want to do this, if you have a dog that's significantly older than some of the ones that unfortunately are only 6, maybe 8 years old, when they go into stage C. So age of course is important, but generally speaking, we don't have an exact cut off, and we don't like to think of it as age is a disease in itself. So that's very much an individual discussion to be had with that dog's referring veterinarian, referring cardiologists, and of course their owner.
So when we're talking about again, candidacy, of course it's a very much a balance of weighing up the benefits and the risks. So we'll talk about this in the results section, moving forwards, but generally speaking, some broad benefits. If the surgery is successful and the aftercare's successful, these drugs will be able to continue most, essentially all of their cardiac medications within 3 months after surgery.
They will have a prolonged survival compared to if they had just been medically managed. If we think about risks, there is a low risk of periopererative death if you have an experienced and successful heart team operating. And again, we'll look at this in the results section, but we have shown that there is both improved dog as well as owner quality of life with the surgery.
On the other hand, of course, it is an invasive surgery. It's a big thing to undergo. There is, of course, a significant risk of postoperative complications.
In addition, it is expensive and unfortunately, there's no real getting around that. It requires a huge amount of equipment and a very, very large team of experts. So unfortunately, I can't ever see a world where, you know, that expense is able to be very, very limited to the point where it's accessible to the vast majority of people.
. And then on top of that, in terms of limited availability, you know, we're talking about some people or many people having to potentially fly or somehow get to another country in order to have the surgery, which again, of course for some animals is not going to be feasible or not going to be something that is sensible to do. So as with everything, it's a case of weighing up the benefits and the risks, looking at individual patient and of course ultimately seeing if the owner feels that is something they want to be undertaking or not. So, moving on to the process, so the day of surgery, we give all of our dogs sildenafil, the morning of surgery, and that is to potentially hopefully reduce the pulmonary pressures that will basically be raised during cardiopulmonary bypass.
We admit them that morning just to preclude them getting stressed in the hospital the night before, and we anaesthetize them basically straight after admit, so we don't spend time having them in the cage, getting more stressed. Everything is basically aimed at making everything succinct, minimising the time under general anaesthesia, and also keeping the animals calm as possible. And most of our patients will also receive trazodone from the day before surgery as well now.
And overall, we look to be going to our intensive care unit around about 2 o'clock in the afternoon, all being well. So in terms of the procedure itself. As I've said a few times, it obviously is undertaken under Cardiopulmonary bypass, and that is to enable us to have a steer a still and clear bloodless field essential as bloodless as possible in order to perform the mitral valve repair.
So we have a couple of videos here of our cardiopulmonary bypass machine. On the right hand side is the one playing now is just showing the blood draining from the patient, going around the machine and then being pushed back into the patient again. And now you can see here, this is the heart beating, so this is just after we've done the repair and the heart is restarting.
But we'll go on to talk about that in more detail. So in terms of the role of cardiopulmonary bypass, we need it to empty the heart. And this is a schematic taken from a human paper.
So the cannulas are in slightly different places, which you'll see when we come on to talk about that in a moment. But essentially what we have is we have a large venous cannula with a line attached to it draining venous blood from the patient, which then goes into the reservoir of a cardiopulmonary bypass machine. When it's in the reservoir and it's passing through, we have an oxygenator and a heat exchanger.
So the perfusionist, who is the person running the Cardiprimary bypass machine, is able to add oxygen to that venous blood that we've drained from the patient and then control the heat. So sometimes we're gonna need to cool them down in order to do the procedure, and then at the end of the procedure we're going to be able to warm them up again, so they can manipulate the animal's body temperature via the cardiopulmonary bypass machine. Once it's had that oxygen added, which also includes anaesthetic gases, they are all given from the cardio primary bypass machine at this stage.
It goes through the pump. And it's pushed back up to the arterial side of the patient. Along the way, the other things that perfusionist can adjust are the chemical and electrolyte contents.
So they will take a blood sample about every 30 minutes, see what our electrolytes, our blood gases are doing, and we can add drugs directly to the bypass machine in order to provide a very quick manipulation of the patient. The other thing to mention is we have a 2nd pump or a 3rd pump actually, on the machine to deliver something called cardioplegia into the patient as well. So cardiaplegia, and we'll come on to talk about this in a little bit more detail, but that is a solution we use to actually stop the heart.
So that will chemically stop the heart. It has a very high potassium content to it and it's very cold, so it's typically given between about 4 to 6 °C. And we actually deliver that directly into the aortic route.
So when we're ready to do the surgery, we have that cannula in place. We put a cross clamp across the aorta, the other side, so away from the heart, which means when we're ready, the perfusionist, once we've placed that clamp, will deliver the cardioplasia up one of these pumps straight into the patient. And because the aorta is cross clamped the other side of that, the cardioplegia solution has no choice other than to instil down.
And through the coronary arteries into the heart itself, and the high potassium will cause cessation essentially of muscular activity. So the heart at that stage will then be stopped and the heart will be isolated from the rest of the body, which is having its blood instilled via this line in the arterial side. One of the things to mention, it might seem a bit strange, we put it in the carotid cannula in the carotid artery, which is obviously quite small, but just bear in mind that because the arterial system doesn't have any valves in, you can instil it into an artery like that, and it will actually go throughout the whole body other than the heart, which is now isolated.
So quick run through of Cardiop ponary bypass. One of the first things we do when we move through to theatre is our cardiologist will perform a transesophageal echo. What we're doing on that is getting some additional images like this one you can see on the top left, and this is a 3D essential 4D reconstruction.
And you can just about make out almost looks like a tarantula. So we have our mitral valve here which is very thickened. We're looking basically like a bird's eye view straight down onto the valve, and you can see that we've got several, art or several cord ruptures, and those are like the little spider legs coming up towards us.
So that's what we can look at with the TOE. And our cardiologist can just tell us as well if there's any other abnormalities that we haven't picked up on transthoracic echo. So if you look on the bottom left, one of the things we see nowadays, which we didn't use to appreciate or didn't used to realise was maybe part of this disease process, is actually, it's quite common.
To see clefts in the valve. And that's really important information for our cardiologist to pass on to us. So if she says to us, OK, you have a cleft in this position, we're going to obviously examine the valve more carefully, and we're gonna know we're gonna need to repair that as well as the normal steps of a mitral valve repair in order to reduce the amount of mitral regurgitation as much as possible and therefore get the best outcome we possibly can for the patient.
The other purpose of the TOE is that, our cardiologists will measure the diameter of aorta, so much more accurately than in transthoracic echo. And then we will know, based on our ratio of like 1 to 1.2 to 0.4, how wide we need to make sure that the annulus of our valve is going to be narrowed down to with our surgery.
And we'll come on to talk about that in a second. So the TOE is performed. Once the tear is performed, our patient's draped and we're gonna start the surgery.
So we start with a small incision on the left hand side of the neck. And the reason we do this is to start thinking about our cannulation. So we talked about needing to cannulate both the venous side of the body and the arterial side of the body in order to drain the blood into the heart lung machine.
Before we cannulate, it's really important that we thin the blood. Otherwise, the blood will go through the cannulas, it's exposed to foreign material, and it will just instantly clot, which will mean that we can't circulate the blood. So we administer heparin and we're waiting until we have an activated clotting time of over 360 seconds.
Once we've achieved that, with the heparin administration, then we know we're safe to start cannulation. We place the arterial cannula first, which is in the carotid, as I mentioned, and the reason we do this is because it's a large cannula on the arterial side. So if from this point onwards, for example, when we're dissecting the jugular, we're dissecting around the heart, the aorta, if there was to be a bleed, we can use suckers that go directly to the bypass machine.
We can suck the blood from the surgical site and the perfusionist can push that blood straight back into the arterial site. So that would buy us a little bit more time to save that patient's life if there was to be a severe emergency. We then put the venous cannula in and in our patients we put that in the left jugular.
So a video here now, we have the carotid artery isolated. This is an incision in the neck which is around about 2 centimetres, so not very big. We have it isolated and suspended between two ligatures as you can see, and we've just made a little cut with some scissors transversely in the carotid itself.
So it's slightly out of focus, this is a head camera. So then what we're doing is we're just pulling the sides of the arterial wall. We're inserting the cannula.
We've flushed it with saline to enable a smooth transition. We'll release that tourniquet and we'll push that cannula in. Once it's in place, it's secured with that rum on and then it's attached to the arterial line of the bypass machine.
The same thing is then repeated for the jugular. So just before we talk about the actual surgical technique itself, if we just review the anatomy that we're talking about. So, and this is obviously a cadaver specimen, and this is from Foxed paper in 2012.
And you can see really nicely the mitral valve apparatus that we're talking about. So we have the two valve leaflets. We also then have the corer tendinna marked with CT on this, and they attach to the edge mainly of the mitral valve, and they secure it down to the papillary muscle marked P on this image, which is essentially a muscular projection of the left ventricle wall.
And the cord tender are those parachute strings that essentially stop the valve from prolapsing up into the atrium, so they will make sure they stop at the level of the annulus, in order to create a watertight seal or a blood tight seal. So we have the valve, the cord of tendinne, and then the annulus itself that we've mentioned a few times, that is essentially the sort of ring, so to speak, of where the mitral valve is sitting suspended in the atrium itself. So it's basically the atrial blends into that.
So we talk about the annulus a lot and you'll come on to see why that is in a second, but that is the suspension point, of the valve. So the two steps of the actual repair are the annuloplasty on the left hand side, which is depicted. This is a tricuspid anioplasty.
But this is the closest diagram I can find of what we actually do with the mitral valve annuloplasty. And so we use Gore-Tex material for all of this section of the repair. And we run essentially similar to a purse string around the annulus, around the suspension of the mitral valve.
And we know, with degenerativeomatous mitral valve disease, that one of the first things that happens is as we're getting that mitral regurgitation leaking back, is we start to get dilation of the left atrium and the ventricle. And as that left atrium dilates, because the mitral valve is suspended within it, it will actually pull the two leaflets further and further apart from each other. That will obviously result in more mitral regurgitation.
Dilation of the left atrium further, further pulling a part of the mitral valve, and you're in this vicious cycle, as well as with a few other components, to enable unfortunately, many dogs to end up in C and then D of disease. So it's really, really important. One of the main steps of the surgery is that we bring that annulus back down to the normal size in order to bring those valves back into position with each other.
So we do the annuloplasty for that reason. And then we also place artificial cords, and we do this, as you'll see from a schematic in a moment. We're basically supporting all aspects of the main valve leaflets.
If we were to go in, examine the valve and say, OK, there's only 2 cords that are ruptured, or there's only 2 cords that are very stretched. And we just put artificial cords in there because this is a degenerative condition, what we would find very quickly, weeks, months, for example, is we'd be back in the same situation when another cord is more diseased. So it's really important that all main valve leaflets are suspended.
So if we look at the schematic here, drawn by Ankara so, we can see on the top since before surgery we have much bigger annulus because the valve leaflets have been pulled apart. We've got a couple of ruptured cords. If we have a look, we're going to place and spread them out, but we're going to put artificial cords roughly like this.
So we typically, for example, a chihuahua, would typically place maybe 4 cords, sometimes 5, sometimes more, depends on the individual on and the main valve segment, and then 2 on the other side. And occasionally, as I mentioned, we also have a cleft that needs repairing, and we usually use polyprolene for that. But if the artificial cords and the annuloplasty, we use Gore-Tex suture material.
Gore-Tex is a great material because it's the most sort of antithrombogenic we can get. So we are less likely for the body to form clots on that, which of course would be disastrous if they formed on the left side of the heart. So if a clot was to dislodge, that would go to the brain, potentially a limb, for example, would have some severe neurological impacts, if not, unfortunately, death.
So that's what we're using for those. So if we have a look now, we are looking now straight down bird's eye view onto the mitral valve that's just been pulled up there. It should be completely transparent.
Instead, it's very, very thickened. And we're just starting the first bit of the annularplasty here. So this is the Gore-Tex material.
It has two needles on it. So we'll take one needle, this is a tiny patch of Gore-Tex that we've cut to size, and that is just to strengthen the start and the end of the suture in order to reduce the risk of it pulling out. So we'll run that first needle around as you saw on the schematic.
We'll then take the second needle, do the same thing. So we have these two strands running like a purse string to the other side. So we place that first.
We don't tie it at this point because you can imagine these valves are very dilated, the anus is very diluted. If we were to tie it back down to the normal size, we would end up with a much smaller orifice, and we'd still need to place our artificial cords further through. So once we've done that, we leave it long and we then come to place our artificial cords.
So this is the same view, so we're looking straight through the atrium, down mitral valve, and in this picture you can see these ring forceps grasping a very abnormal looking cord, and they're pulling up on the cord to expose the papillary muscle a bit better. So if we look here, there's a little mountain caps in more fibrous tissue at the top of the papillary muscle, and that's why we want to anchor our artificial cordon, because it's likely to be stronger than the actual more muscular process itself. So again, Gore-Tex material, two needles on this.
Two bites with one needle of the papillary muscle. This is a bit, out of centre, but this is the edge of the mitral valve, again, very, very abnormal, very thickened, and this is what all of our cases will obviously look like. We'll then take 2 bites of the valve with the first needle, 2 bites with the second, which has given us 4 contact points on the valve, which again, we hope to try means that it reduces the risk of the artificial cord pulling out.
So again, all of these are pre-placed. You can see a variety here. This is from a little cavalier, who had 8, artificial cords placed.
8 is a very common number, pretty average number to place in a cavalier. Sometimes they might even need 10. Again, as I said, it's very much on an individual basis.
So all of those are pre-placed, and then for me, I, I come back and I tie the annuloplasty that we've left long. Just a picture here before we tie the annuloplasty of an artificial, sorry, a ruptured cord, a native ruptured cord here. And you can see in this dog, the valve is so diseased that it's actually yellow in appearance, it's not just that white, colouring.
And now here we have a different dog and the angioplasty tide. So we have those two Gore-Tex little pledgets that I talked about at the beginning and the end of the angioplasty just to bolster that up, that are now in situ, and they are now meeting or, you know, not far off meeting, whereas before they would have been much further apart. Once that anaplasty is tied to the diameter that the cardiologist has told us to tie it to, we'll then go and tie the artificial cords one by one.
And of course a really important component of that is making sure that the artificial cords aren't too long and allowing prolapse of the valve still, or that segment of the valve, but of course also that they're not too tight and restricting the valve and therefore allowing leakage in mitral regurgitation that way. So it's a little bit of an art when it comes to that and getting used to what's the right length for each patient. So, once we've done the repair, we're going to start closing the atrial incision, and we just use polypropylene for that.
We typically have these dogs at a body temperature of around about 28 to 29 degrees when the heart's open, so when we're doing the repair. So once we start closing the atrium, we want to start warming them up again. It's really important when we're doing a mitral valve because we're on the left side, as we talked about earlier, just like when we open the abdomen, the thorax, we're gonna be introducing air into the heart.
And so we obviously need to evacuate that air, otherwise it's going to be pushed around the body and and have consequences like we discussed earlier. So we actually use a Foley, urinary catheter and we pop that through our atrial incision. We mentioned earlier about the suckers that help us suck blood from the surgical site straight back to the bypass machine, so we're minimising any blood loss.
So we'll turn one of those suckers onto the Foley, and that will mean we're providing constant low rate suction, and we'll agitate the heart, try and dislodge any, bubbles before we allow it to restart, so before we take the cross clamp off. So we'll do that as much as possible. When we get to 30 degrees, and we think we've de-aired it, quite a lot, we will take that cross clamp off.
Remember that cross clamp is stopping blood, is stopping perfusion going to the heart. So as soon as that's off, we will now have blood going to our heart perfusing our coronaries as well. And usually within a few minutes, our heart will start to beat again.
It will initially be very slow. You have a very cold patient, you have a heart that's been, what's diseased, and it's been stopped and then restarted. But we just allow the heart to start essentially in its own time, as long as the electrolytes are normal.
As we continue to actively rewarm that patient, then the bypass machine is still in process. We'll be aiming for a body temperature of 36 °C at that point, and we'll have the bear hugger on, etc. Sometimes the heart will defibrillate, it's not that common, but obviously if it's fibrillating, we need to stop that.
So what we do nowadays is we administer a high dose of potassium into the bypass machine, which will quickly stop the heart. And what we typically find, we call that chemical defibrillation, we typically find that that will stop the heart very instantaneously and then almost always that patient will restart once the potassium is a bit more out of its system, without fibrillating again. If they continue to fibrillate when they restart again, despite that potassium being given, then we will typically, of course, administer an electrical defibrillation internally at that point.
Occasionally we might put temporary pacing leaves directly onto the heart itself, and we would typically do this if we had a patient that was very slow to restart. So, restarting but very, very bradycardic, despite being warmed up. We just want to get things going.
We want to get the blood pumping around the body, pumping around the heart effectively. So we might just make them, you know, maybe a heart rate of 60, 80, for example, a little bit sooner rather than just waiting for a long time, in order to kick things off. When the heart has restarted, one of the first things we're then going to do is repeat the TOE, so our transesophageal echo.
And at this stage, it's really important that we assess the repair. We wanna make sure that we've achieved what we want to achieve. So we wanna make sure that we've got much, much better movement of the valves, and a huge reduction in the amount of mitral regurgitation that we had.
So we're making sure that the cords aren't too long, they're not too short. You can see here on the left hand side we have a preoperative or pre-repair, I should say, image. We've got quite significant MR.
On the right hand side you can see we're quite bradycardic because we're just weaning from bypass, and but you can see that there's a huge reduction in the amount of mitral regurgitation. A very small amount is OK. To be honest, that would typically resolve over time anyway, and we'll look at an example of that a little bit later.
But obviously these valves are very, very thickened, so we expect, in most cases, a trivial amount still to remain, and that's OK. The heart will still be able to reverse, remodel, shrink back down to a normal size. And as it does that and kind of everything tightens up, we typically find where with most cases, absolutely no, MR within a few days or a few weeks at all.
So that's what we're looking for on the iOE as well as making sure we don't have any residual air. We also can do a 4D again. We looked at an example of this earlier.
On this image on the left hand side, this is the same dog. And on the left you can see I was talking about the annulus being so dilated that sometimes the two valve leaflets don't even meet. So you can see here they've probably not been in contact for quite a long time.
On the right hand side, you can see how much we have to reduce the annualist down by occasionally. So, you know, this has probably gone over 50%, we've had to reduce this down by. And now you can see that those valve leaflets are back to being friends again.
So we're meeting again and that in itself, even without the artificial cords, which obviously we're going to do, but you can see how that even on its own, would make a big impact to the amount of MR that that patient has had. It's a really important step. So once we've assessed the TOE we're happy that the repairs looking good, the heart's looking fine.
We basically decrease the amount of flow going through the bypass machine. So we're basically allowing the heart to take on more and more work, so more and more blood volume itself. We do that very, very.
Gradually, just to make sure that the heart can cope with that. Some patients take a little bit more time than others for their heart to take on more of the work, and that's OK, we just, you know, ride that out. So we decrease the flow until the point where we can turn it off and the heart's doing all of the work now.
Once bypass machine is off, the patient's blood pressure is OK, then we're going to start taking out our cannulas. We do that in the reverse order of how we place them so that cardiopplegia cannula, which is in the aortic root comes out first. We're then going to take out our venous line, and we leave that arterial line in place for the same reason we talked about at the very beginning.
So if there was to be a bleed at this point, we have access to the arterial system directly and we can instil large volumes of blood, fluids, etc. In order to help our patient quicker. The other thing we have to do at this stage, when we're happy that the patient is stable, the blood pressure is good, so we talked about administering heparin at the start, in order to thin the blood to allow the patient to tolerate the blood going through the cannulas, going through the heart lung machine.
Of course, if we just left them anticoagulated, we now have multiple incisions, some one even intracardiac, where the patient would just ooze and ooze and ooze because they're not able to clot, and of course that would end up being life threatening itself. So now we have to think about reversing the effects of that heparin, that anticoagulant. So in order to do that, we have to give a drug called protamine.
Unfortunately, protamine is quite a risky drug. It has a reasonable chance of inducing anaphylaxis, similarly in humans, although we found that dogs seem to react poorer to it, so a higher risk of that. So we have to watch them very, very carefully.
If we have any reaction, we have to stop the protamine, and we have to administer more blood, from the bypass machine, so that's left over in our reservoir, and support them as much as we can. Sometimes you're not able to administer any protamine, that would be quite an extreme situation. And then you've got a patient that's anticoagulated with these incisions, which obviously are going to be harder to manage and will need some blood products.
And other times patients will tolerate a full dose of protamine, and they will go back to an ACT that's within normal limits. So, once the protamine's been administered, the patient's stable, we're going to move back to the intensive care unit and we're going to extubate. They typically are placed either in an oxygen cage or if we want more access out in a cot like this with high flow nasal oxygen, providing their oxygen supplementation for them.
And at this stage they're gonna be having 1 to 1 monitoring with a nurse. So we talked about hypho nasal oxygen or oxygen cage. We have a chest strain in place, of course, from the thoracotomy, which we remove as soon as possible.
Typically it's about 12 hours after surgery, so we expect to have a fair bit, depending on some pleural effusion anyway, which initially might be a bit of a hemothorax. Even if they tolerated protamine, you might get a few mLs of blood. Obviously you're also vacating air from the fracture down the thoracotomy.
But we've got that chest drain in place to make sure that we don't have a significant bleed and that we're allowing the lungs to expand fully. And once we're happy that we've drained all the air, there's no increased buildup in fluid or blood, and then we'll take that out as soon as possible. The same with the other instrumentation.
So we have our arterial line in, this is not the cannula, this is just a normal arterial line in the dorsal pedal to monitor direct blood pressure. We have a urinary catheter in place to monitor urine output during perfusion, and we'll take that out the next morning, and we have two IV cannulas in and a central line. So again, we get the basically what we can out as soon as possible.
Anything going into that patient obviously is increasing the risk of an infection, which in a dog with a valve problem and who's just had a valve repair, it could potentially mean an endocarditis, which unfortunately would obviously be life threatening. So we de-instrument as soon as we can. The following morning, after the surgery, when we're definitely happy that all the bleeding or any residual bleeding has stopped, we then need to start blood thinners.
So we talked about having foreign material in the bloodstream being recognised and therefore forming clots. So we have to then start blood thinners, so we tend to do low molecular weight heparin, subcutaneous injections, oral aspirin and oral clopidogrel. And we're balancing that out over the first few days to make sure they're on the right dose so that they're not bleeding and equally they're not forming clots.
So it's really important steps. So it's obviously a big surgery, it involves a lot. However, I think what's important to understand is that obviously we all know that dogs are very resilient in general, and these are some of our patients on the morning after surgery.
So you can see we've got central line in. We've taken the IV canyons out, the urinary catheter out, chest drain out, and these patients should be walking around the next morning. So the vast majority will be.
We obviously just let them do a very, very gentle walk, shift everything along. It's also nice for them just to be able to get outside, and I think just from a mentality point of view as well. We offer them food, most owners will want to come and visit at that point.
And so you can see that really the vast majority of patients will bounce back very quickly. Otherwise, we then stop the diuretics immediately, postoperatively. We have them on blood thinners for 3 months and we actually also keep our patients on immobendan for 3 months.
The reason being, we know Pimabbendan helps when you're in B2 of disease, we also think it probably does something to help with reverse remodelling of the heart as it's shrinking back down again after the repair. We start rivaroxabam, so we switch out fragment injections on day 3 or day 4, and we do rivaroxabam instead, which just means that they can go home earlier, so they can go home on day 4, rather than having to stay and to have the heparin injections. So again, average patient nowadays will go home day 4 after surgery.
We will, however, see them back every couple of days. We do repeat echoes, repeat haematology, repeat biochemistry, make sure everything's progressing as normal. So, some examples here, of one of our cavaliers, so we have pre-surgery, echo on the top left, we just replay that.
We can see we've got our MR then we've got immediately post-op, 7 days post-op, 1 month post-op, and hopefully you can appreciate that the left atrium is significantly smaller already between pre-surgery and a couple of days after surgery, at 1 month, and we have a normal sized atrium, normal sized ventricle, and no MR. If we look at thoracic radiographs, again, plastic case, of course, these dogs have significantly enlarged left atriums. You can see on the top X-ray that we have compression on the trachea, and this is a patient that was coughing a huge amount preoperatively.
So not due to pulmary edoema, actually that was well controlled, but just from traquil compression. Again, a lot of these patients, because of the breeds they are, are predisposed to a tracheal collapse, and most of them have been asymptomatic for that before their heart got to a significant size, and then we find that they are often quite affected by that. And, but you can see it's 6 weeks postoperatively on the bottom radiograph that that left atrium, at least radiographically, is now normal and we don't have tracheal compression.
And this dog went from coughing so many times a day that it was actually fainting to them within a few days of surgery, a hugely improved cough, barely coughing at all, 6 weeks postoperatively, not coughing whatsoever. We obviously will warn owners that we can't guarantee the cough will completely disappear if it's related to your collapse, we could still have some issues with that. But it's amazing how basically hardly any of them will actually have that, so the vast, vast vast majority will go back to a resolved cough now.
So, run through what that involves. What I wanted to then do was show you some data. So obviously it's all very well telling you about the surgery but it's important to think about what we're actually achieving or what we can achieve with this.
So at my last hospital where we set up a programme, I've just got some data from you from that. So that was over pretty much all this data is from a 2 year period then and from when when we started to when we finished. So we did 43 dogs we operated on with stage C or D.
And the largest breed or the most common breed, sorry, was Cavalier King Charles at 24%, which is no surprise, median age of 10. And the majority were in stage C, so 72%, 28% were in stage D. So as I said to you, we don't operate really on B2 dogs.
We don't really feel that it's. Ideal. And even with the markers we use, we'll put them on our waiting list, but we wait till they've just tipped in to see.
Otherwise, you know, the surgery and the aftercare associated with it has risks, and you could be taking a dog that could have had many, many months, if not longer, of reasonable quality of life if not good quality of life, and, and undergo that. So all Cs and D's. In terms of survival results, our surgical survival was 98% in this cohort, that was just one patient, that unfortunately, it was our first one there who died due to a severe, anaphylaxis to the protamine.
So the drug I mentioned earlier that reverses the heparin. Everybody else survived the surgery. Survival to discharge in this cohort was 81%.
So for 2022, that was 75%. We were a lot lower at the end of 22, because we had multiple patients or several patients in a row have severe reactions to protamine. Only one died of it, which was the first one I just mentioned, but these other drugs were unable to have their full dose, which meant they were receiving, they were oozing a lot, they were receiving lots of blood transfusions and unfortunately died of complications related to that.
And in 2023, and we changed our protocol again. We'd already done many, many things to try and reduce this risk, but we were able to do several things, which meant that we fortunately, touch wood, and don't really see this as a consistent problem nowadays, and that meant in 2023, and once we'd altered this, our survival rates and to discharge from the hospital were then 91%. So if we just look at this on a graph looking at AIM stage C of disease and D of disease, so, our survival overall this whole cohorts that includes 2022 was 78% for C, 91% for D.
Obviously we're not going to read into this. We talked earlier that of course the sicker your heart is, the higher risk you are at, . We just operate in quite a lot of stage D's, the protamine reaction dogs, were typically the ones in C just because low numbers, and that's why there's a difference, and we would never obviously say to an owner, that you're more likely to survive in D, that's not going to be the case.
So other outcome measures, obviously we can't just look at survival, although it's very, very important. We also need to look at what else are we actually achieving. So in this cohort, they all discontinued their diuretics from the day of surgery.
One of these dogs still kept on the Pima Bendan just because their heart hasn't completely gone back to normal, size based on breed and dimensions. So we therefore just keep them on the Pimabendan because it's a drug with hardly any side effects at all. Handful of minor complications, post discharge, and all able to be resolved.
And we did in this cohort sadly have one dog, who actually presented with a rupture of the gallbladder 3 weeks after surgery, and that was operated on successfully and then unfortunately not long after developed a refractory IMTP and was sadly euthanized. So very unusual case and one that we're actually just writing up as a case report . The essentially overall message is that surviving to discharge, you're extremely unlikely to die of something related to the surgery or your heart condition after that stage.
If we look at per operative complications and post-operative complications, there are obviously probably in a way an exhaustive list. The more you do, the more things you see. We talked about protamine reaction, we talked about Amy.
We expect to see arrhythmias. This is a diseased heart. A lot of them have preoperative arrhythmias, and then you've restarted a heart.
So it'd be very, very normal to get a degree of arrhythmias, but of course here we're really talking about potentially more sinister ventricular ones. So we keep them on an ECG for quite some time, just to make sure we don't need to start medication. IVSH this is something that's very unusual.
We saw this on our last hospital before this one, a few times actually, we haven't seen it since, touch wood. This stands for intraventricular septal hematoma, and there is an echocardiographic still at the bottom here. And you would be forgiven to think that this is a ventricle on the right side, but this is actually a hematoma that's developed in the wall of the left ventricle itself.
And you can see that of course what it means is that you've hardly got any blood volume allowed in the ventricle. So you're going to be hypotensive and cascade of issues. So this is something, another thing that they're looking for on the TOE, the cardiologist, to make sure we don't have that.
If we do, we could open the heart up again and incise it, but actually, we don't think that's really necessary. We just have to give more volume of drugs in order to bolster up that left ventricle and maintain the blood pressure a bit better. And in those cases, you are, most of the time they, they can be fatal sadly, but, as our understanding of this disease process has got better, We find typically that if you bolster them up with medications, fluids, then typically you will have a resolution of this condition.
Fortunately it's very rare to see. Post operatively, lots of things that can go wrong. So it's a complicated process in animals with significant disease, bleeding, of course, arrhythms we talked about, thromboembolisms, be that air, be that clots from the repair.
We expect some electrolyte disturbances that would be very normal after bypass. Endocarditis fortunately is very uncommon, but it's something of course we're always on the lookout for because it would be life threatening if it occurred. And we have seen this a few times.
Acute kidney injury, that is possible after bypass. We did a paper several years ago where about 20% of dogs technically got an AKI. Only one was actually azotemic, that is AKI defined with the Irish grading system.
You could get SARS, you could get hyper hypotension, so lots and lots of things we're monitoring for. And pancreatitis, again, you can have this as a complication post bypass. It's something that we clinically see very infrequently, though some dogs can take quite a few days to start eating again.
It's hard to know occasionally if that's potentially some pancreatitis, or if that's that dog's personality, for example, of being hospitalised, etc. But, you know, they're on pain relief, they're on fluids if they're not eating, etc. So we essentially do treat that pancreatitis for those situations regardless.
And pancreatitis is something we've actually seen more commonly a, a little bit since we started sending them home earlier. So we have to be very, very strict with our clients and make sure that they only feed, a low fat, brand of food that we've provided, otherwise, and they are more predisposed to getting pancreatitis. So if people give them a treat, or something a bit more fatty, we're probably more likely to see a clinical pancreatitis compared to a normal or a more standard postoperative patient.
So we looked at survival, we looked at medications, obviously it's incredibly important quality of life, so we know we can extend their life with successful surgery, but what about the quality? It's a big undertaking. You need a lot of 1 to 1 care that first night.
So this is a little dog called Titch, and this is Titch's first night. This is Titch at 4 days after surgery, joining me in the office, because he doesn't like to be in a cage. And this is Titch living his best life, back home, a couple of months later.
So, If we look at quality of life, we, a few years ago now, used the fetch questionnaire, which is, was designed from Tufts University in the States, who kindly let us use it to look at our actual mitral valve patients. And what we found, we use this in a cohort of patients, and 54 dogs. We looked at their quality of life with this questionnaire preoperatively and then at several time points postoperatively.
So 136, and 12. And we found that there was a significant improvement in quality of life preoptively versus every single postoperative time point, which, you know, you would expect and hope for. We also, in this paper looked at a number of medications, so you can see by 3 months, so we have our aspirin and clopidogrel for 3 months and we stop it.
Our immobendan we do for 3 months and then we stop it. As I said in the vast majority of patients. Occasionally we might need immobendin a bit longer.
So in this cohort, median number of medications at 3 months was 0, range of 0 to 3. So immobendan occasionally you might need antiarrhythmics, as well, but that's not common. We also then looked at, owner quality of life, again, using questionnaire.
So we looked at 26 owners of dogs, the same time points, so preoptively compared to 136, and 12. 7 questions as listed down here, which basically gives you an overall scale from 0 to 35. Based on the answers.
We found that at preoperatively, those whose dogs were in stage D had a worse quality of life to those in stage C, which wouldn't be unusual. Obviously you have much more intense, medication regimes most of the time, a lot more owner anxiety often as well. And we saw that there was a statistically significant improvement from preoperatively to T1, which is 1 month postoperatively, and then between 1 month postoperatively and 3 months postoperatively.
So you can see here, if we look at it, median score and pre-op was 25.5, that was out of a possible 35, and a big drop off, even at 1 month after surgery down to 6. And these are just some of the areas, .
Where there was a significant difference, social, sleep, costs, worry, etc. As you would expect. So, as I mentioned, post discharge, we're gonna have Pimmovean, aspirin, clopidogrel for 3 months.
At 3 months we should be free of all of our medications, and at that point we're gonna start to let them off the lead. So we have very strict exercise restriction up to that point, very short, toilet purposes lead walks initially, building to 5 minutes, 10 minutes, 15 minutes, etc. Over time.
But we don't allow them off the lead till about 3 months after surgery. They see a cardiologist at 136 and 12 months then annually. Some owners like to go more frequently than annually, which is understandable given everything they've been through, but if everything's going well, then annually is sufficient.
So to wrap up, in conclusion, we expect a high survival rate with an experienced and successful team, with a significant improvement to the dog's quality of life as well as the owner's quality of life. We should be free of all medications, cardiac medications, at 3 months postoperatively in the vast majority of cases. And I just wanted to mention as well that there are quite a few cardiac diseases that can be managed surgically nowadays.
So this talk is of course on mitral valve repair for myxomatous disease, congenital, there can be candidates for mitral valve repair too, trachoscopy valve repair as as well as a few others. So if you have any cases, that you're wondering if there is potentially a surgical, solution, please feel free to reach out. It's always worth discussing an individual case, just to seeing if there is something that can be done.
So a few of our little, patients here, and finish with a couple of videos. This is Faith on the left hand side who was, end stage D preoperatively. She was in ICU on nitroproide of various other CRIs, and, her owners decided to go for the surgery, even though obviously we want the prognosis is very poor.
This is her back in America. I think 6 weeks, 2 months maybe after surgery. And then this is Jeffrey on the right hand side, lovely, lovely Jeffrey, who is having his first off lead walk, has his muzzle because, as you might expect with his breed, he likes to chase rabbits at his 3 month postoperative points and off he goes.
So I put my email on the bottom, although we've left our last institution, that is because we are starting a new hospital which is currently in the process of being put together. So, if anybody wants. Any updates, we will at some point start to provide those.
But in the meantime, this is the Gmail address on which we can be reached if you have any questions about the talk and about anything to do with, surgical heart disease, or anything you'd like to discuss. Thank you very, very much for listening. It's been a pleasure, being able to do the webinar today.