 Thank you all very much for having me here today, a little bit different topic I suppose and we've started with so far, but I'd like to talk to you today about continuous flow bad support in the fontan patient objectives today I'd like to talk about a little bit of the anatomy lesson of what the fontan looks like issues we see with the fontan circulation. And then what we kind of describe as fontan failure, we'll go over some experience from Dell Children's, then also talk about what's coming down the pipe, excuse me. Starting off kind of how we get to the fontan circulation we'll use hypoplastic left heart syndrome as an example. I mean that's where we utilize the norwood procedure, and then also deliver pulmonary blood flow via the blade left tussig common shot. Just as a kind of side note there's a great movie to watch if you'd like to something Lord made. It's a great story about the three kind of developers of this process. Vivian Thomas is kind of one of my, you know, kind of heroes, if you will, a guy that self taught and raised himself up to basically invent the procedure and show Dr. Blaylock how to do it. And as we are in hallowed ground here, Dr. Cooley himself participated in that very first surgery. He's in that picture somewhere I'm not sure which character. So moving on, sorry, focus. Going back to the next phase of the kind of a trio of surgeries, the Glenn circulation is set up by attaching the SBC to the pulmonary artery, further offloading the ventricle and advancing the patient to the next phase, then next phase with final variation of the hyperphysically tart syndrome surgery pathway is the total cable pulmonary connection or the IBC is eventually connected to the pulmonary artery with the Glenn procedure separating running in parallel those surgeries there, the those circuitries they're providing a fully oxygenated patient. So this procedure so the fontan procedure was originally described by Dr. Fontan in Paris in 1971, later refined and described by Kutcher in Argentina and 73. This is a paliation for the functional or an anatomical single ventricle. Some of those examples are hypoplastic left heart syndrome, tricuspid atresia pulmonary atresia intact ventricular septum son of the original procedure was really focused on tricuspid atresia described the process as connecting the right atrial appendage to the pulmonary artery the thought was behind this was the contractile function of the right atrium augment flow through this process. What was discovered over time and Dr. Frazier and I have personally done many of the fontan conversions if you will. The right atrial distention thrombus formation in that and eventually leading to a rhythm is really landed this procedure to many problems. Later on developed was the inter cardiac fontan where the baffle was placed within the common atrium where the IBC was then baffle through to the SVC that was connected to the pulmonary artery. This later became known as the total cable pulmonary connection which developed later and the one we use most commonly now is the extra cardiac fontan using a PTFE graph from the IBC to the pulmonary artery. The benefit of this it kind of remove the suture lines in the right atrium and maybe made much more kind of a continual pathway there. So a little bit about fontan mechanics that kind of cause some of our problems here if you think about the normal heart ejecting from the LV coming across through the aorta delivering pressure and flow to the systemic circulation passing through the pulmonary beds, and then eventually coming to the right atrium and pressure of, you know, two to eight relatively low coming through the right ventricle pressurizing and being Val. Going through the valve pathway, you increase your pressure to the pulmonary arteries to that, you know, 18 ish pressure, then therefore providing a gradient from the pulmonary artery or cross along to once again a low pressure left atrium, and then starting to cycle over again. With the fontan circulation, you're creating a situation where you're increasing your central venous pressure to that pulmonary artery pressure required once again to create that gradient across your lungs. And this is kind of the the net of all the problems of the fontan circulation required, but can cause problems. What are all the problems. The complications we see in the fontan circulation. The one most noting mind you this isn't all fontans but is a good chunk of these patients. And when we're talking about circulatory support to transplant this is some of the things we definitely see in this population. You're losing interopathy where that lymphatic leak into the gut due to higher than normal venous pressures in in the environment of a low pressure lymph system pours off that fluid into into those organ systems, those proteins being albumin coagulation factors in you know, and then of course immune compromise and then leading to poor healing. So an exacerbation of many problems. Guess what this happens in the lung. So, so the cells back on itself coagulopathy is due to factor loss growth delay albumin one of the primary carriers transport mechanisms for calcium for bone density, and then of course immune compromise, and then leading to poor healing. So, an exacerbation of many problems. So what this happens in the lungs to so plastic bronchitis. So that once again that spillage of protein rich lymph into the airways causes developing of thick cast and the limit of the airway. This can lead to severe I mean this is blocking of the airways progressively so severe hypoxia X fees this is a that word. And also potentially I even leading to death. These can typically or sometimes be removed from bronchoscopy, or even patients can cough these up. Now if you cough that up I might just be I don't know if I could pass through that. Other problems we see with these patients once again do the higher venous pressures we have fontan associated liver disease so lymphatic overflow and congestion of the liver as well. It can lead to esophageal varices societies, fibrosis and cirrhosis of the liver. And once again because of the poor sense system disease of the liver we can have coagulation abnormalities. You can kind of see kind of some recurrent themes of feedback mechanisms that cause some of these problems so the fontan failure can kind of be described in two different pathways the circulatory failure where we have these elevated pvrs and mind you all these are much of these patients end up being on high levels of phosphodescase five inhibitors and the subgenophils that the dialyphils and even both sent in to get those pvr and the resistance down through the lungs. Hydrostatic pressures, the pressures within the fontan circulation are very variable to standing and laying and so on and so forth obstructions within the circuit itself these are not straightforward surgeries. There can be a lot of energy loss, especially in the, the extra cardiac or the inter cardiac fontan where the atrial wall can be very modular and change shapes. Some, sometimes there's a lot of stasis when these, in these circuits, and with this we have potential progressive cyanosis and the development of auto pulmonary collateral. So on the other end of things, not the circuit or the plumbing of the process, the pump itself can become a problem. Many of these patients, especially in the hyperplastic left heart syndrome pathway. We're using a systemic RV RV to create the higher pressures that an LV would be accustomed to. This is not a long term strategy and we almost always see some kind of dysfunction in these LVs long term. We have developed some of the low cardiac output, we can develop cyanosis in this. And of course, with low cardiac output develop endorphin dysfunction they can lead to other problems so you can see there's kind of feedback mechanisms here that we can't really get around. The one thing we can do or try to do is fix this problem. And we can do that with mechanical circulatory support. We share kind of our, some of our experience Dell Children's Hospital in Austin, and keep our kind of motto in in check. Our last two four years we are excuse me two years we've done four patients, all of them single ventricle for our continuous flow devices. We had an 11 year old with a herotexilla and balanced AB canal. We poured a heart where in 19 year old extra cardiac fontan with a heart where 12 year old with a extra cardiac on time with the heart and three. And then now we currently still have on a 13 year old with extra cardiac fontan awaiting transplant. All the previous patients have been transplanted successfully. I'm going to go over the first patient real quick, because she was unique. So we had a 11 year old with heterotaxi unbalanced AB canal. She had a fontan in 2019 about 10 years after that she came to us with worsening heart failure during her stage you kind of be evaluating worked up for transplant, but she had a cardiac arrest. It was a great deal. We had really hard time getting access. She had scar and every vessel in her body. So they're very prolonged CPR event she did get on successfully onto ECMO. We did take her to CT to kind of check some of the boxes make sure okay, we did see some sub acute cerebral infarcts, but nothing that kind of really indicated that it was a no go. We even woke her up on ECMO to make sure we could get some level of neurologic exam. Another challenge. We actually implanted this from the right atrium to the aorta. We did this for a few different reasons. One, I just say we had 120 minutes of CPR. So the chest was really beat up a lot of hemorrhaging in there already should have been on ECMO for seven days. And also the fact that this is all these patients are 345 time redo sternotomies. So the scar level the adhesion level within this chest was immense and everything was bleeding. So to dig out the ventricle to implant this in a normal fashion was was really not an option. So that was one problem. Also part of the problem is because of this heterotaxi and the unusual kind of structure and architecture of the aorta or excuse me AB valve, we really couldn't fit something into a apex on this relatively small heart. So the choice was to go through the right atrium to the ascending area. This is kind of in a unique way because we didn't do it on bypass. We were already on ECMO so utilize our bypass pump on standby as kind of a dairy mechanism so my colleague Tiffany Rob wrote this up nicely last year. So the rest of our patients we did implant in what the relatively normal pathway, we did put the pump in the systemic ventricle. What the systemic ventricle was a right ventricle, which is full of heavy tribulation, kind of a perfect night is for one pump occlusion, and also for thrombus within that ventricle, low heart failure patient, low cardiac output patient, a lot of the ventricle, we had to be very careful to kind of make sure we didn't have any to make our excuse me thrombus within there. So the second problem we see in these patients is we're going to put the aortic anastomosis, this whole ascending order has been mutilated. It's full of suture lines, unusual connections of the pulmonary artery and the original aorta making a neo aorta for materials whether that be catabaric tissues or Dachron or whatever. So you have to find a place to fit this graph so that's a challenge as well. So also challenge you to see this, see with these patients, for example, our patients three and four aortic insufficiency of that unacceptable you just create a feedback loop within the heart and within the bad is unacceptable anything other than mild, we have to address. You can address that with aortic valve repair, aortic valve replacement, or you can even just close the aortic valve LBOT that definitely increases the risk of thrombus formation. The problem with this once again like I just said, this aortic root this ascending area is a God awful mess so we have to think about what that looks like it to skeletonize the aortic outflow track to be able to do a aortic repair, which causes another level of a hemostatic problems, and also just the different tissues so we think about that and time on bypass. So what did we do, we employed a park stitch for two of these patients so that's a central stitch proximal nodules or Antias, I was kind of like saying or Antias is fun. So what this does is due to this large amount of AI during diastole, it brings those that center portion of the valve together and makes it competent so that the the aortic insufficiency is solved, and it also allows some level of opening of the aortic tractors to wash the valve out and allow some flow in there reducing potential thrombus around that outflow. So we employ that in two of our patients. So how do you know where you end up being on RPMs and flow in these patients. So typically, especially described in the adult population, you do a ramp study. So you do this using echocardiography, you observe the septum position so moving left or right depending on the offloading of the LV, LV size to understand if you're properly offloading. How often is the already valve opening determining the pressures across that area right valve and increase RV pressures if you're not offloading the LV properly, then it backs up into your RV you're going to have problems with that. Only one ventricle. There's no septum blow gap for position, very little reference on what size ventricles are going to be proper, and you very well may have a park stitch in place so you can observe that area valve opening properly. So, we took these kids to the cat club. So wanting to make sure that we had therapeutic anticoagulation in place and anti or platelet inhibition properly want to make sure there's no thrombus within the LVOT that we're going to mobilize. So we had a lot of realization between these changes we had to make sure and kind of sit on our hands in a little bit and let them let things stabilize with the very kind of compliance of the Venus system. These changes take a little while to kind of get to where they're going to end up being so we started by lowering the RPMs of the devices until the AV valve opens or every every beat or looking at the AV valve research increases. So all these values and documented them and trend them throughout the process looking at the bad settings. Pulsatility index on so forth, looking at pressures along the fontan circuit, and also looking at saturations and then actually looking at those structures and seeing how they react to these changes. So these are the 20 results to be very straightforward and honest so this is our hardware patient we weren't able to kind of stimulating circumstances with our first patient weren't able to do a ramps a second hardware patient. We ramp them all the way from 2400 to 2900. I don't know if you notice though, pretty flat lines, we really didn't see any exciting changes that we could dial this into the similar things with our heart mate three patients. You can see the CVP or the fontan pressure stayed pretty much flat. The capillary wedge pressure your left atrial pressure stayed pretty flat, and we didn't get a huge bump out of any saturations as well. So our fourth patient very similar process. So one thing we kind of had to go by was that AV valve regurg since also we can really look at the aortic valve so we looked at the aortic AV valve regurg and then dial back just appropriate to keep that in check. So sometimes we have to always think about kind of these feedback loops. So we have this relatively fixed PBR in these patients. Like I said they are on pulmonary vascular resistance reduction meds. We can't be too aggressive to overflow the pulmonary system and create pulmonary edema in by going faster and faster and kind of sucking the fontan dry, if you will, we increase those Venus pressures and cause more problems and always have to think about what's downstream from all this. So we have higher Venus pressures by increasing the flow of the bad we can't decompress the lymph system as well. If you remember the thoracic duct dumps right into the inominate vein, which if we're pressurizing that valving system can't work properly and decompress the the lymph system. So where is the sweet spot of the QPQS with these with these bags. I hate to tell you that I can't tell you. There's not perfect place to be the key points that we found in these patients to get them in that sweet spot, make sure we're offloading the AV valve regurg ample cardiac output to maintain an end organ function, primarily renal make sure and balance their volume volume or volume status and also get to make sure we get quality nutrition in there, and also that we're not overflowing the lungs. So the good news is, hopefully there are some things down, down in the future that will help us with this, the group of chop has reported successful use of total artificial heart and failing fontan circulation. And this is quite the undertaking those of you participated in these. But that does solve the problem there's a pump and there are valves on the side of the circulation now, the taste care of this but this is definitely a one way pathway to transplant. So in the lab there's still some work that's very exciting stuff there's some centrifugal pump systems that kind of decompress the SVC and IVC circulations and and push into the pulmonary circulations. So far so good but they came across a few problems that were nicely defined by the road fell group that has been working on this I remember seeing the first presentation, I think in like 2002. So, this group has been working on this long and hard. One thing they really define in their processes and their research was that you have to have a passive system as well. So if the system, the pumped mechanism or the artificial portion of this fails for any reason, you still have to have open pathway and passive pathway for your blood flow. We're coming out coming down the road, but I'm excited to be here to be talking about this because I know for a fact that there's some of this work going on right here in the Texas Medical Center. So hopefully we can see some advancing of some of this as well. I encourage you to come visit us in Austin sometime we're growing in a fantastic program. I'd like to give a big thank you to Texas or and this is exciting that we're at a 60th anniversary of Texas our Institute and 50th anniversary of TTI perfume. What I learned here and what I was exposed here, and I see a lot of really familiar faces that learned me brought me to where I am today. So thank you all very much.