All right, thanks Nishan. So yeah, as Nishan said, I'm really excited to talk to you guys bright and early here from Los Angeles. So I'm going to be talking about adult congenital heart, my slide on the floor, let me just make sure I can control these slides. There we go. So I'm going to be talking about catheter ablation in adult congenital heart disease. This is requested for me and we have a lot of experience at UCLA with a fairly large adult congenital heart disease population. We follow about 4,000, I think, outpatients every year. So hopefully some of the things that we've sort of learned will be useful for everybody here. So first of all, why, you know, the first question is what do we end up ablating in congenital heart disease? It's almost, I mean, the vast majority of the catheter ablation procedures are for supraventricular tachycardia and mostly atrial arrhythmias, organized re-entry atrial arrhythmias. We know that this is a major problem in the adult congenital heart disease population. If you look at some of the data out of Canada here, you know, the reason for admission to the hospital is dominated by supraventricular arrhythmia in the adult congenital heart disease population and is a major public health concern. It's also associated with both increases in morbidity and mortality in terms of stroke, heart failure, and requirement for various interventions, whether these are cardiac or interventional, cardiac surgery or interventional procedures. So it's got a lot of relevance to clinical care for the adult congenital heart disease population. So it's a big concern. Congenital heart disease does affect 1% of children and the vast majority of these patients, these kids are now living into adulthood. And if you look at the survivors into adulthood, there's a 15% prevalence of supraventricular arrhythmia, specifically atrial arrhythmia in adults with congenital heart disease. And in general, the risk is greater than the general population with acquired heart disease or without heart disease. And another sort of rule of thumb is that the anatomy determines the degree of risk. And so there's various categories of anatomical anatomy and congenital heart disease. And I'll go over the ones that are associated with the greatest risk and we'll focus on those. Just to get into a little bit of a historical context, mapping and ablation for congenital heart disease dates back to the early 90s. A lot of this was done at UCSF. And some of the things that were noticed early on were based on fluoroscopy, simple catheter feel, and electrogram recognition. So these are just a couple of the classic papers showing atriotomy circuits with moving a roving catheter around the atriotomy while you're in atriotomy-dependent flutter. And you can see this was described as you have split potentials that are widest at the middle of the atriotomy and then converge at either end. And so, you know, this is one of the first kind of congenital heart disease specific papers to describe this. And then things like recognition of patch material, what changes, what the impedance does when you're touching a patch and how to recognize these kinds of circuits were all described actually very early on in the 90s. Since then, obviously things have changed quite a bit. We've got much better tools available for mapping and for ablation. One of the key papers, I think one of the key sort of features of reentry in congenital heart disease is the central obstacle is important to recognize. And there's a set, there's a limited number of types of obstacle that we see, most common being the AV valve annulus, whether it's a right-sided mitral valve, like you see in CCTGA or a tricuspid valve, but the right-sided AV valve tends to be common. Free wall scar, atriotomy circuits, atriotomy lines, and even the ASD patch. And so this is just a study out of Boston very early, also with 3D mapping, showing the initial experience, looking at the different types of central obstacles for reentry. And they found that, you know, right AV valve tend to be the most common followed by free wall scars. And then chrysotermin alleles in some, and then atriotomy and ASD patches. And this is actually needs to be updated. I think this is pretty much the only paper in congenital heart disease to describe this, but it's still fundamental to the way we map and ablate these patients. Another thing, I'm sure everybody's familiar with dual-loop reentry, first described in France in 2000. But I think it's worth remembering that dual-loop reentry actually was first described in a consecutive series of ASD patients. So they all had atriotomy scars and had dual-loop reentry around the atriotomy and the tricuspid valve annulus. And so again, congenital heart disease, very common to see dual-loop reentry circuits and important not to miss them when you're mapping so that you can ablate all of the reentry circuits in the patient. So this is just an example. I'm gonna go through some of this and it sounds like you guys have talked about excuse me, the different anatomical types, but this is a setting patient with dual-loop reentry around a posterior anastomosis here. So there's a sort of a counterclockwise circuit going around this posterior anastomosis in the pulmonary veins. In a clockwise circuit going around the tricuspid valve, which is on the pulmonary venous side here. This one here is on the right side of the screen is a Fontan patient, Bjork Fontan, who had an anastomosis between the right atrial appendage and the tricuspid valve and had this linear scar on the free wall here with a circuit in a counterclockwise direction around that and then clockwise around the Bjork anastomosis. So just a couple of examples of dual-loop reentry, but we see this very frequently. I did a case yesterday with dual-loop reentry in a viral tunnel Fontan. So it's very, very common to see this. Let me see here. So other things to think about specifically with congenital heart disease are, so we talked a little bit about central obstacles, but isthmus locations tend to be relatively preserved among the different anatomical subtypes because they're based on prior surgical lesions. Obviously, if they have a diffuse scar or bad hemodynamics over time, they can develop alternate scars, but in general, surgical lesion sets tend to be preserved. Another thing to recognize in congenital heart disease is the altered AV conduction anatomy in some of the subcategories. So for instance, this is actually a prior paper just describing the AV conduction system in congenital heart disease. And you can see this is sort of a description of a AV canal patient with the primum ASD and inlaid VSD, and the conduction system is displaced posteriorly by necessity, inferiorly down towards the tricuspid valve annulus, sort of closer to the CTI than normal. So you gotta be really careful when you ablate the AV canal not to damage the AV conduction system because it's displaced. This middle one here is CCTGA, and these patients actually have a duplicated conduction system, but usually the dominant route of conduction is through a anterior AV node near the right atrial appendage, pulmonary valve, sort of connection there, continuity there, and with a long, tenuous conduction system that's very susceptible to AV block. And then one of the more rare forms of altered conduction system anatomy is in heterotaxy syndrome, which we'll talk about if there's time, but essentially you can get a conduction sling here that can cause forms of SVT. So it's very important to recognize the AV conduction system and the different forms of congenital anatomy. And then finally, tachycardia mechanisms tend to be diverse. Focal tachycardias and re-interatrial tachycardias dominate, but we certainly see lots of, especially with Epstein's anomaly, things like Maheim fibers and other kinds of pathway-mediated tachycardias. And then finally, tissue architecture is important, especially, I think, the Fontan patients, probably the most important ones, where longstanding venous hypertension can cause atrial muscle hypertrophy and very thick tissue in some cases, up to almost a centimeter in thickness on the venous side. So getting transmurality may be very difficult with some of the Fontan patients, and you have to be very aggressive sometimes. So here's another publication. This is also out of Canada, I believe, but this is just showing you the prevalence of SVT in a large population of congenital heart disease defects. And the ones I'm gonna focus on are the ones that sort of surpassed the others here in this bar graph. So transposition of the great arteries after the musculature sending operation, very common to have SVT. The univentricular hearts, also known as basically Fontan patients, have a very high incidence of SVT as well. And then finally, Epstein's anomaly, probably the highest in congenital heart disease. I'll also speak about, if we have time to get through that today. So DTGA and mustard and sending. So the mustard and sending operation was introduced very early on as the surgical approach for physiologic correction of transposition of the great arteries. Without surgery, these patients, it basically is a fatal lesion within days to months after birth. The ultimate goal was to achieve an arterial switch operation, but just due to technical issues and bypass issues, early attempts failed. So there was a real push to do atrial redirection surgery. And in 1959, Senning proposed the first full atrial redirection surgery and that became the predominant operation until the mustard operation was introduced in 1964, at which point the mustard actually took over. So I think you've already heard this earlier this week, but the sending operation involves a complex baffling of the SVC and IVC flow across an atrial septal communication over to the mitral valve. And this is done with native tissue. So the atrial septum is essentially used as a flap and sutured around the pulmonary veins. And then a counter-incision around the right side of pulmonary veins is anastomosed. After this is closed off, this is anastomosed over to the atriotomy to create a route of blood for the pulmonary venous return to go around the SVC and IVC into the tricuspid valve. And so very elegant, very creative design without any extra material, but it does involve a lot of suture lines. If you also think about where the sinus node sits, the sinus node oftentimes ends up inside of the pulmonary venous baffle. So I think that's important to recognize that it becomes an internal structure after the sending operation. And so it's susceptible to trauma from catheter ablation if you're not aware of that. The mustard operation, which was again approximately five years later, conceptually a lot simpler. Basically, you make a big atriotomy, you recept the atrial septum, you suture on this special, what they called a pantaloon-shaped patch that redirects blood flow, like the sending from the SVC and the IVC over to the mitral valve, but it's sewn around the pulmonary veins so that the pulmonary venous drainage is directed around that towards the tricuspid valve. And the whole thing's just closed off with a big patch. So it's actually surgically easier to do this operation than the sending, and this actually became more favored, this was more favored after it was introduced in 1964 out of Toronto. If you look at follow-up after these operations, there's a really disappointing propensity to basically atrial flutter with about 25% of patients in the longest follow-up at 20 years out after the mustard operation. So if you look at the Kaplan-Meier curves, they're pretty dismal looking here. So about 25% of patients at 20 years. So it's pretty, and it's a progressive sort of problem with these patients. The arrhythmias most commonly observed are, this is a schematic. So the pink is the pulmonary venous flow here. You got the pulmonary veins coming in, wrapping around the systemic venous atrium, going to the tricuspid valve here on the left, and then your SVC and IVC over to the mitral valve here on the right. The isthmus between the tricuspid valve and the IVC, despite the altered surgical anatomy, still is the most common site of ablation. So basically CTI-dependent flutter is the most common target for these patients. And we saw that in this study in the vast majority, but you see some, especially the mustards around the free wall patch or atriotomy, and then focal tachycardias along the baffle are pretty common as well, as well as a few AVNRTs you see from time to time. But the vast majority are CTI-dependent flutters. We actually looked at patients who had recurrences and where they were, and we saw only a few in the CTI, and actually these had not necessarily been ablated the first time. A couple of focal tachycardias, and then this posterior anastomosis for the sending operation. If you recall, there's a counter-incision along the right pulmonary veins for the sending operation, and this is a site for recurrence in these patients. And so we've taken to always going after the anastomosis really carefully at the index procedure. So how do you get there? We're talking about the CTI in most cases, but the CTI is in the opposite chamber, separated from you, from the IVC by this baffle. So to get there, you basically need to, there's two ways. You can go retrograde through the aorta into the RV and back to the trapezoid valve, but the direct route is to do a transbaffle puncture, and that's favored in most centers. So that's what I'll show you next. But basically you come up from the IVC and you do this puncture more anteriorly than usual and superiorly. And if you look at the fluoroscopic images here, this is a contrast injection from the IVC that fills the systemic venous baffle over to the mitral valve. And then here are the operators staining the baffle with a needle. And you can see this is directed basically superiorly, and there should be an anterior bend to this in most cases. And so after staining that, you can get across as any kind of typical transeptal procedure, but the difference is really the orientation of the needle and the trajectory. And sometimes this baffle material can be quite thick and difficult to puncture through because it's surgically placed. So here's just an example of a patient we had at our center with, I didn't mention this, but a lot of these patients have sinus node dysfunction as well. This patient had sinus node dysfunction, had recurrent episodes of atrial flutter. He was from, I believe, Las Vegas and came out to see us. We always do a hemodynamic cath on these patients before the catheter ablation procedure. Very important because they do develop problems with the SVC and IVC baffle. They also tend to develop baffle leaks. So you basically have atrial level shunting. And a lot of them have abnormalities in their valves and pressures due to the RV being a systemic RV. So anyway, this patient had a baffle stenosis here, which I think is important when you take a look at the angiograms. This is the baffle stenosis. So you can see the IVC is filled here, a baffle stenosis, but the baffle drains over to the mitral valve. And then to get to the circuit, which for him was in this chamber here, the pulmonary venous chamber, we did a trans baffle puncture, as I mentioned a second ago. So here's the trans baffle puncture. Do with ice, using ice is the way to engage the needle location. And then this is the map. This is really a map we've been using a lot of high-definition mapping for these patients. But you can see here on this right side of view, this right lateral view, this patient's pulmonary veins are coming in here. It has a large patch along the right atrial free wall, which you see typically with mustard patients. And then there's some scarring along the septum between the morphologic left atrium and the morphologic right atrium. All of this is pulmonary. We call this pulmonary venous atrium because it's draining the pulmonary veins to the tricuspid valve. So there's some scar along here, and especially a dense scar along the right atrial free wall. This is just putting the SVC and IVC on as well as the mitral valve. And then pretty classic for him, I mean, for these patients, had a pretty classic circuit. So he had a counterclockwise flutter circuit using, actually in this case, portions of the morphologic right atrium that are in the pulmonary venous chamber, as well as portions on the systemic venous chamber down here. And then he also had this clockwise, what looked like it was gonna be a clockwise circuit around this atriotomy, but colliding with the other circuit here backed by the pulmonary veins. So not a true, I guess, dual-loop circuit here, but what looks like, if you didn't have this faster circuit driving the secondary circuit, this could potentially operate independently, and which turned out to actually be the case. So after we ablated the CTI-dependent flutter, we induced a much slower tachycardia. Whenever we tried to map it, it terminated. Whenever we tried to entrain this area, it terminated. It had this just really long fractionated signal. So we ablated this atriotomy site here, and the tachycardia slowed and terminated. It was not inducible. So I think, keep in mind that these dual-loop reentries are pretty common in congenital heart disease. I'd say probably 50% of cases seem to have some sort of dual-loop mechanism. So this is just where we put the lesions for that patient, and then had a focal tachycardia as well that we went over afterwards, went after. This patient got a pacemaker, and then, I'm not talking about pacemakers today, but obviously this is not the usual location for pacemaker wires. But this is where we end up in these patients. Again, baffle leaks, very common. We should be doing TEEs with these cases because you don't want to get any embolization, and you potentially wanna close these off as you're there anyway. So we often involve our interventionalists. If you look at combining interventional procedures with electrophysiology procedures in congenital heart disease, it makes a lot of sense in terms of cost, as well as things like anesthesia time, contrast dose, and hospital length of stay, but especially these mustards in sending patients. They are all kinds of issues that can be addressed by interventionalists, and so we oftentimes will get advanced imaging ahead of time and do a comprehensive cath at the time of the EP study, just to make sure that we don't have anything else to address beyond the EP issues, which is very common. All right, Fontan, the next category, Fontan operation. The rationale here for this surgery is essentially you have a single functional ventricle, and you need to use that ventricle for the systemic pump. And so because pulmonary blood flow can occur, generally can occur passively, you simply need, not simply, but you need to bypass the heart to establish pulmonary blood flow from the systemic venous return. The major types of Fontan are your atrial pulmonary Fontan, lateral tunnel Fontan, and extracardiac Fontan. This is actually just a few of them. There's actually several others. These are, these dominate the types that we see. And in general, this operation has saved, you know, thousands of lives, but it is complicated by arrhythmias as these patients age, as well as other forms of Fontan failure, which arrhythmia is only one of them. This is the classic Fontan operation as described by Fontan in 1971. It's also known as the cross your heart Fontan because the SVC flow is directed exclusively to the RPA, and the IVC flow through the right atrium is directed to the valve conduit to the LPA. Turns out these patients don't have hepatic factor reaching the right lung, and so they develop pulmonary AVMs. So nowadays we use, actually following that at least, a modified atrial pulmonary Fontan was used where you have direct connection of the right atrium to the pulmonary artery. And this was the preferred approach for the Fontan for many, many years until the, basically in the late 80s. Unfortunately, this right atrial chamber dilates progressively with time and becomes extensively hypertrophied due to high, just generally high pressure. Fontan pressures are typically in the range of 10 to 15 millimeters of mercury, which causes the artery right atrium to progressively enlarge and hypertrophy. And so these patients have all any, I mean, multiple different forms, multiple potential re-entrant circuits based on the surgical anastomosis that's used, as well as some of the natural barriers. So there's actually a baffle that's placed from the right atrium here so that the right atrium doesn't, so the blood flow does not enter the heart. So there's a baffle here that can serve as a central obstacle. The AV valve annulus can serve as a central obstacle. The patch from the RA to PA can serve as one. An atriotomy scar can serve as one, and you can even get re-entry on the SVC and IVC. This is one of the ones, this is one we had a year or two ago, which was quite difficult to ablate because it was going around this patch to the pulmonary artery and a very large circuit. And then this isthmus here, which we targeted, was very resistant to catheter ablation. I think the tissue was extremely thick. We did hundreds of lesions before finally terminating here, and fortunately it remained durable, but this was a very difficult line to create with lots of trabeculation and lots of thick tissue. This is another example of a patient who had basically, almost a complete intercable line here, but had a gap and the circuit was going through that gap and went around through the isthmus between the SVC and the PA anastomosis. And we've seen that a number of times as well, where you have this re-entry through this area. And you can target it here or you can target it along the free wall. So something to keep in mind. The other thing, I think just looking at the physiology here, remember how this right atrium dilates, the same thing happens to the IVC over time. And so the IVC dilation can be so dramatic that you can see pericabral re-entry as well. And pericabral re-entry was described a while back by Ravi Mandapati back in 2003. And it is a real mechanism. We see this from time to time in these Fontan patients. So it's worth keeping in mind as well. So with all the problems that were associated with atrial pulmonary Fontan, people thought, okay, we need to find a better way to get better fluid dynamics through the heart without causing this progressive right atrial dilation. It's actually a lot of energy loss in the right atrium when you have a direct connection to the PA. And then also, how do we get less arrhythmia? And so it was proposed that we do what's called a lateral tunnel Fontan, which essentially involves a small baffle through the right atrium from the IVC up to the SVC. And then the SVC would be then anastomosed to the PA. This was generally accepted pretty quickly and became the preferred approach. It was also associated with less arrhythmia and even some of the early studies looking at this within the first five to 10 years after the operation was introduced showed reduced arrhythmia as compared to the atrial pulmonary Fontan that we talked about earlier. These patients still get arrhythmia. The predominant mechanism, I think, this is not really necessarily published, but in our own experience at least is circuits around the AV valve annulus are very common, as well as the patch between the lateral tunnel Fontan and the rest of the atrium tends to be a central obstacle for circuits and finally the atriotomy. So those three mechanisms are very common and those three mechanisms are most common with lateral tunnel Fontan. This is a case where we had gone retrograde with stereotaxis to do the left-sided deblation. This is another case, actually. This is a kind of a nice one showing both atria. This is the SVC and IVC lateral tunnel Fontan on the, this is especially at situs inversus. So lateral tunnels on the right here, the pulmonary venous chambers on the left, I guess the patient's right and this is on the left. And there's a circuit using this atriotomy, actually used part of the pulmonary venous chamber as well. But you can see that there's this nice isthmus between the atriotomy and the IVC here where there was a first burn termination here that was really nicely shown with this mapping system. So keep in mind atriotomy, patch and AV valve annulus for these patients. This is just showing, this is actually just one of the studies we had put together a while back showing that this ultra high definition mapping can be useful for quickly identifying what we call troughs in this histogram so you can identify conduction isthmuses. All right, so the most recent form of Fontan is the extracardiac Fontan. This was further proposed to even improve the hemodynamics of the Fontan further, as well as to completely eliminate any kind of alteration of the atrium with the surgery so that you can potentially avoid any arrhythmias altogether. And most centers are now doing the extracardiac Fontan for the past 20 years, 20 to 30 years. Some centers are still using the lateral tunnel Fontan. I know Boston still use lateral tunnel Fontan, but this is probably the most common approach now. Early studies did not show a difference though with the extracardiac versus lateral tunnel and other Fontans. Probably because they're underpowered and they're very early publications. But if you look at this more recent study, I guess not that recent at this point anymore, but the combined experience out of Australia and New Zealand they did see that if you look down here at the bottom here with extracardiacs as the reference group, lateral tunnels had three times the incidence of SVT and atrial pulmonary Fontans had almost 11 times the incidence of SVT. So extracardiac Fontans are significantly less likely to have supraventricular tachycardia as compared to the other subtypes. So unfortunately we still see SVT with extracardiac Fontans. And the challenge now is that the SVT is relatively remote from the approach that we take, which is obviously from the IVC. These two structures are no longer in continuity and it can be a real challenge to get to the arrhythmia substrate. We published this a few years, this is a multicenter study looking at is this feasible to do in extracardiac Fontans? There was actually some question of whether we can even do conduit punctures, et cetera, to get to the substrate safely. Turns out it does seem to be safe in experienced centers. We also looked at the substrates that these patients have for re-entry. And it's, interestingly, it tends to be very simple. In most cases, periannular substrates tend to dominate as well as atriotomy circuits tend to dominate this group. As far as how people were getting, this is from 2016, how these people were getting there, it was direct conduit puncture in the majority. In some patients, like with an interrupted IVC, a transpulmonary puncture was used in a case. And then we had started doing transcable puncture, so basically puncturing through a small area of overlap between the IVC and the pulmonary venous atrial wall in a few cases back then, which I'll talk about in a little bit. But this is how people are getting back there. We didn't have any complications related to access to the pulmonary venous chamber for these patients. So the transcable cardiac puncture, I want to talk about a little bit. This has been our preferred approach at UCLA for the past five to 10 years or so. It turns out that when these patients are operated on as children, which is almost always the case, the conduit length is not the size of a full-grown adult heart, and so as the heart grows, the IVC is typically pulled up around the pulmonary venous chamber, and there's almost always at least some overlap between the IVC and the pulmonary venous chamber. And so you can take advantage of that. If you recognize it, you can take advantage of it because a puncture in this area is much easier than through conduit material, which can be extremely difficult, often calcified, nearly impossible sometimes to get across. And so with careful evaluation, usually we do a preoperative CT scan, which shows the conduit very nicely. You can determine this is there and go after it at the time of the procedure using either TE or eyes. And this is just a recent, we just published this, I think like a month ago, showing that, you know, this is definitely a feasible approach for extracardiac Fontan patients to get to the pulmonary venous chamber, which is where these arrhythmias are coming from in these patients. So again, you do a venogram, look at the edges of the conduit on fluoroscopy. You can figure out where you're going to kind of probably target the puncture and then use eyes to make sure that you're in the right spot or TE in some cases, especially in the older cases we had done. So here's an example of eyes just showing the conduit border right about here and the transepal puncture performed right below the level of the conduit into the morphologic right atrium. The other advantage of the, you have a direct approach. So some people will go retrograde and use stereotaxis for this. I think the advantage of the prograde approach is you can get multipolar catheters into the pulmonary venous chamber for high-definition mapping of complex arrhythmia circuits. And in some cases, even, we found this useful for cryoballoon, PBI in extracardiac Fontan patients with atrial fibrillation. So again, the direct approach does have some benefit in terms of mapping and also ablation for these patients. And so it's been our preferred approach. And we basically found that if you have preoperative CT scan that demonstrates definite overlap between these structures, we're able to do this transcardiac, or transcable cardiac puncture in the majority of patients without any real complications or issues. This is just a case showing this where we've done a conduit, or a transcable puncture here right below the conduit. And we had this re-atrial re-entry, likely related to where this IVC had previously been oversewn here. It's actually pretty, it's also something we see. And on the left side of the screen here, there's a, this patient also had what's called twin AV note tachycardia, which I'll talk about briefly. But it's a fascinating form of tachycardia mechanism where you have duplicated conduction systems, duplicated AV nodes. And in tachycardia, you have anti-grade conduction over one AV node and hysperkinesis system, and then retrograde conduction over the other. So you form a complete circuit using the two conduction systems. That mechanism is seen in, almost exclusively in the heterotaxy patients. Heterotaxy syndrome patients have duplication of either right or left-sided heart and thoracodominal structures. So for twin AV note tachycardia, we see this really in the right atrial isomerism patients where you have duplication of right atrial structures. This is seen outside the heart by aortic cable juxtaposition, excuse me, down in the abdomen, typically a midline liver. And then in the chest, you see eparterial bronchi on both sides, basically bilateral right-sidedness in terms of the arteries and bronchi. In terms of the heart, complete AV canal is common, total anomalous pulmonary venous drainage, double outlet right ventricle and pulmonary atresia are very common. And what you see, and this is a, this is just a recent map. This is only from a few weeks ago. But with these right atrial isomerism patients, you have duplication of the electrically, electrical structures in the heart, meaning the sinus node and the AV node. So the sinus node is a right atrial, a right-sided structure. You typically have bilateral sinus nodes and twin AV nodes in these patients. So if you look at this, this is a high-definition map of mapping the conduction, mapping His-Purkinje conduction. So all of these represent His and His-Purkinje electrograms. And you can see there's activation. This is the right-sided ventricle and the left-sided ventricle. This is the ventricular septal defect here. And there's conduction along the His-Purkinje system coming from the superior AV node. And then simultaneously, this inferior AV node has His-Purkinje conduction, you know, that it kind of just meet in the middle. So this is the substrate for this twin. So if you basically have refractory tissue here and a timed extra stimulus, you can get reentry. You can get one of these to conduct, integrate, and then recovery. So you can conduct retrograde and get sort of reentry through these twin AV nodes. The treatment for this is to ablate one of the AV nodes essentially. And typically, what you want to do is identify the weaker of the two and ablate the weaker AV node. Also, preferably ablate the one that has the wider QRS complex associated with it. So this is an example of ablation for a patient with twin AV node tachycardia. And we're atrial overdrive pacing, so you don't see the accelerated. You see, typically, you see accelerated junctional rhythm with this. But with atrial overdrive pacing, basically, you see you go from an inferior QRS complex to a superior QRS complex when you're ablating the anterior AV node. This is just a quick plug. We actually are doing a study on twin AV node tachycardias because there's not a lot of data on these patients. And so if anybody is at a center that has experience with twin AV node tachycardia ablation, feel free to reach out to me at some point because we're actually enrolling centers right now. We've got, I think, 12 centers so far that have enrolled and are submitting patients. This is just a quick plug. All right, so as these patients get older, we do see a predominance of reentrant atrial tachycardias, atrial flutter. But as these patients get older, we do see an increase in atrial fibrillation, essentially. And then once these patients are around 50 or so, atrial fibrillation seems to become the predominant atrial supraventricular arrhythmia. And it's becoming a bigger and bigger problem, actually, in congenital heart disease patients. This is actually, I showed you this patient earlier where we had done a transceival cardiac puncture to get a cryo balloon and to do a PVI on a patient, which, you know, maybe 10 years ago we would not really have thought about doing. But it's becoming a bigger issue now. And there's a lot of ongoing efforts to look at how best to, you know, how to approach these patients in terms of ablation technology and what kind of substrate to avoid. All right, so the last category I talk about today is Epstein's anomaly. This is a fascinating, it's very rare, it makes up only about 1% of all congenital heart disease. But it's fascinating in terms of the different forms of arrhythmia that these patients manifest. It's been termed by Ed Walsh, who's known to be sort of the father of congenital heart physiology, to be a natural laboratory for reentrant arrhythmia. And if you look at this list, this is just out of a review article that he wrote, these patients have accessory AV pathways, 20 to 30% of patients have accessory pathways. They do also have a fair number of atrial fascicular fibers. AV node reentry is not uncommon. They do have monomorphic VT, although it's very uncommon. And then when these patients get older, atrial MAC reentry, so atrial flutters, focal atrial tachycardiasis, and atrial fibrillation are all common. So you can see any number of different mechanisms of these patients, and they're probably the most affected by arrhythmia as they get older. This is just showing an anomaly, an Epstein's anomaly. So you have displacement of the septal leaflet of the tricuspid valve, and then on the right side here, you can see this is the inferior leaflet of the tricuspid valve, which is massively displaced. This leads to a third chamber here, which we call the atrialized right ventricle. So it's under atrial pressure, but it's right ventricular myocardium, and it tends to become very thin-walled and fibrotic over time. And this is a source for arrhythmogenesis in terms of VT for these patients. And sudden death for these patients. Really, you know, interesting to look at how these patients were diagnosed early on. Some of the early investigators used transducers with an electrode on them, so they can measure simultaneous pressure and electrograms. And you can see as they're towards the RV apex, you have this RV pressure and a kind of a late electrogram in the QRS. As they pull back into the atrialized RV, the electrogram gets earlier. This is actually what you see with these patients sometimes with their accessory pathways, too, as they get earlier in the atrialized RV. The HV intervals were noted to be on the long side because most likely because the septum is very involved in the fibrotic process. And there is a difference in the conduction pattern in the atrialized right ventricle in these patients depending on whether or not they have a WPW pathway. So the proximal atrialized right ventricle may have a very early electrogram or early activation rather in the presence of WPW, whereas typically it's very late if there's no accessory pathway conduction into that area. Because it's sort of the latest area to be activated. I'm going to skip ahead. So I think that kind of leads us to the next topic, which is just the EKG. And I think everybody knows that an examination of the EKG is very important for determining whether these patients have WPW or not. Because WPW in Epstein's is classically a very atypical pattern. You expect to see a complete right bundle branch block in Epstein's anomaly without an accessory pathway because conduction is activating this atrialized right ventricle typically very, very late, especially when it's a severe Epstein's. And so they should have a very pronounced complete right bundle branch block pattern. If there's an accessory pathway, however, this area is pre-excited. But it does take a long time to get here through this atrial myocardium and through this diseased RV. So these forces generally cancel themselves out. And you end up with an atypical pattern that is not a complete right bundle branch block, but also does not oftentimes look like a typical WPW with a delta wave. So very important to look for that right bundle branch block in patients with severe Epstein's. If you eliminate the pathway, this is the same patient after catheter ablation, you develop a complete right bundle branch block. So, you know, this EKG here on the left, you should be very suspicious for accessory pathway conduction. This is an example at our center with this same, I mean, this essentially the same finding. This patient came in with recurrent SVT. This is the baseline EKG here. You can see that there is some slurring in some of the leads, but it's not pronounced in some of them and could be easily missed. And obviously doesn't have a right bundle branch block in the initial EKG. We've had a septal accessory pathway that was ablated. And after that, the EKG changed, but it was still not a typical right bundle branch block. And we ended up finding another pathway in the lateral annulus that was ablated. And then at that point, you know, you start to see what looks more like a, at this point this patient had no VA conduction and AV block with venosine. And we couldn't find any more pathways. I think it's important to remember that patients with Epstein's anomaly who have WPW or accessory pathways in general, 50% of them will have a second accessory pathway. So, you know, after you ablate the first one, you know, keep being on the lookout for, you know, I think examination of the EKG is important, but to be on the lookout for other pathways. These pathways can be quite challenging to ablate in an Epstein's anomaly because of various factors that include things like the fractionated electrograms in the diseased, in this HLI's right ventricle can really obscure the correct location of accessory pathways because some of these fractionate electrograms can extend. So, for instance, in tachycardia, orthodromic tachycardia, you may see fractionated ventricular electrograms that are later than some of the earliest atrial electrograms. And it can be difficult to distinguish these without pacing maneuvers sometimes. The AV valve, the true AV valve annulus is where these pathways exist. But the true AV valve annulus can be difficult to appreciate because it's oftentimes very diseased. Again, and the valve is displaced. Patients have distortion of the atrial anatomy and the ventricular anatomy, which can create some difficulty with catheter stability. And finally, they oftentimes have multiple pathways or broad pathways. The pathways themselves tend to align with where the valve is most displaced. So septally and inferiorly is the most common location for pathways in Epstein's anomaly. And that's been reproduced in multiple studies. You can see here in this Boston group, septal and posterior, although you can get them anywhere around the tricuspid valve annulus. You've obviously on the mitral valve annulus. But the vast majority are in this areas where the tricuspid valve is most abnormal. This is a, I think, kind of an interesting case. It's a patient who had Epstein's anomalies in his 30s, came to us with this Y-complex tachycardia, had a history of three ablations in childhood in India, and continued to have palpitations and sort of lived with it for many, many years, but finally came to see us. And this was documented, I think, just in a routine clinic EKG when he came to see us. This is his sinus rhythm, EKG. You see this, what looks like a right bundle branch block pattern here and massive P waves, which is consistent with Epstein's anomaly. So we took him to the lab. And actually, this is where I have the audience response questions if anybody wants to participate in this. But let me move this over. So basically, we're atrial pacing here. And the question is, you know, what happens with atrial, what's the finding with atrial pacing? If anybody wants to take a stab at that. Jeremy, while they're looking at that, maybe I can ask a question that came through here. It's related to patients you take for intra-atrial re-entry, what the endpoints for ablation should be? Should you try to eliminate every tachycardia that you induced or just focus on the clinical? Good question. Our approach is to eliminate all of them. We're pretty thorough. I mean, we found that, you know, if you have an inducible sustained arrhythmia after you're done ablating, even if it's not the clinical one, most likely they're going to show up with that arrhythmia later on. That's been our experience at least. We're actually looking at that in a form of a study right now. But what we do is we'll look at conduction block across all the instances that we ablate and we basically go to non-inducibility if possible. Okay, thanks. Well, it looks like an even split. Okay. I don't know if this is really a fair question to be honest with you, but basically you have this right bundle branch block here at baseline. And then when you pace, this right bundle pattern becomes less prominent. Let's see how to move this out of the way. So essentially what this would suggest is you may be preferentially conducting over the AV node and less so over the pathway versus the AV node with atrial pacing. And this is sort of a clue that there's actually an antigrade conducting pathway here. So the answer I would have chosen would have been progressive pre-excitation, but it's not really probably the easiest question, not the fairest question in the world. All right, this is the next one. I think this is more useful though. So this is during tachycardia. You have this Y complex, this is clinical tachycardia. And then we're delivering a timed atrial extra stimulus here. This is in the atrium here. So we're going to deliver a timed atrial extra stimulus. And the question is, what does this maneuver show essentially? All right. While they're looking at that, another question here. Any hemodynamic consequences to either trans baffle or extracardiac puncture particularly with cryosheath? Yeah, I think the concern would be, you know, if you're potentially leaving the vascular space and outside the heart and could you have bleeding. So we, you know, obviously worry about that. It just hasn't become, it hasn't turned out to be much of an issue like we initially would have thought. I think it has to do with just, these are all postoperative patients. So there's a lot of, after surgery, there's a lot of bleeding in that space and then that becomes adhesions over time. And it can kind of contains any kind of bleeding concern you might have with the puncture as long as you're doing it, you know, in that true space between the, when there's overlap between the structures. So we have not seen any bleeding issues so far with that approach. And then the other issue obviously would be, is there going to be a residual shunt, especially with the large, like the flex cath sheath for the cryo balloon. And I think there's been some concern that, you know, maybe we should be closing this off with an occlusion device at the end of the case. I think that's what we did on that one case. But typically with the smaller sheaths, we have not seen residual shunts after the puncture. So like with the, typically we use an agilis, we have not seen any residual shunting on fall surface echoes or any right to left shunting with hypoxemia afterwards. So it doesn't seem like we've seen, we've had a big, we've had any problems with either one of those things. Okay. So I think it looks like most people said resetting of an atrioventricular fiber. That's actually the right answer, which is great. I don't, I'm not sure this is even a fair question either. But basically there is a, there is a histoflexion here. It's, you know, you have to look at the previous strips to see this. But there's a long VH time here. This is a long VH tachycardia. And then this is an atrial extra stimulus time to a navy junction or for factory. And what happens is you advance the next beat of tachycardia. The next QRS is advanced with the same QRS morphology, which basically essentially proves the presence of participation of a, of a basically an anadromic pathway. Whether it's MHIME or accessory pathway is hard to say, except that the VH time is very long. So you might be favoring an atrioventricular connection here. So very nice. That's, that's the right answer. And that's actually what we found. So when we, when we did the mapping, we actually mapped this retrograde. It was a, it was surprisingly, it was actually a short AV connection, but with decremental conduction properties and very weak conduction properties, we suspected this is probably a damaged pathway from prior ablation. But we were able to ablate this and, and, and eliminate this guy's tachycardia. The last thing I wanted to talk about with Epstein's anomaly is this, this finding that just was published last month in Heart Rhythm. A lot of these patients have this very prominent muscular ridge along the true annulus. And the Boston group looked at a series of, of patients, autopsy actually, Epstein's patients, and found this was very, very common. And it was actually associated clinically with SVT during life. So they, they went, they went and histologically assessed and found that these patients, a lot of these ridges contained accessory connections, at least grossly. And some of them histologically. And they commented that, you know, a lot of the times the coronary arteries actually ran inside, inside these ridges. And so they pointed out this is an under-recognized structure for Epstein's anomaly that may make a big difference when you're going after these and ablating them. Turns out this was not the first description of this. It was actually described in 1955. But there is a prominent ridge in these patients with a lot of, a lot of times it harbors this muscular connections with accessory pathway fibers. And so I think it's important to realize these can be very broad. This is a case we had actually with, with one of these ridges here. This is looking from the right ventricle in towards the right atrium here. And you can see that there's this, the true annulus has this very thick ridge. The leaflets were attached much further down. And this patient also had a very broad connection here. We actually had to ablate several locations along this area to eliminate the tachycardia. So I think this is a, probably is an underappreciated finding for Epstein's anomaly. And it probably explains the higher recurrence rates in these patients, among the other things we mentioned earlier. This is just an example of a, just a massively enlarged right atrium. This is an Epstein's patient who had a CTI dependent flutter. He was going to have an, he was going to have a valve placed. And so we wanted to make sure there's no pathways. We ablated the CTI flutter. The flutter slowed, I can't remember the exact cycle lengths, but I think it was to around the cycling of the 400 and became one to one. And we kept ablating thinking, okay, we just haven't interrupted the CTI. Turns out that he had converted to, or actually she had converted to a one, to an accessory pathway tachycardia with almost the same kind of atrial activation, as far as we could tell from the catheters that were in place at the time. So we actually, we did, finally did a few diagnostic maneuvers, realized this was a pathway and went after that. So just important to keep in mind multiple mechanisms in these patients and should always be thinking about what's common too, I suppose. Just dual lubri, I just kind of, I just want to emphasize dual lubrientary. This is an under-operated Epstein's patient. This dual lubrientary was going around the tricuspid valve and the IVC. No prior surgery, but the IVC circuit actually seemed to be the driver here, rather than the tricuspid valve circuit, I guess you could argue at that point. After surgery, especially tricuspid valve replacement, these patients can have very difficult to ablate annular substrates that include the CTI. We've been looking at this pretty extensively at UCLA. This is an example of a patient who had multiple outside flutter ablations, and I think even a prior ablation at our own center. We couldn't get to the CTI from either the atrial aspect or the ventricular aspect. And we finally, just from symptoms and nothing to do, we eventually decided to just get the catheter below the bioprosthetic valve. So we did a puncture to get there. And we're able to, this is just showing us puncturing below the valve. You can see we're staining the struts of the valve here. And eventually, though, we actually got the catheter through that, into that little spot right there. And we're able to terminate the tachycardia, and fortunately no recurrence. So, but I think the point of this is just it highlights how difficult it can be to ablate the low valves, and actually even annular rings in patients with Epstein's anomaly. We just completed a multicenter study looking at this just earlier this year. These patients have, with either a ring or replacement of the valve, have longer procedures, a greater number of procedures, and longer fluoroscopy times in general. And if you look at the success rate, and this is all sites combined, ring and replacements had a lower success rate than either repair, just valve repairs, or no peritracosmal valve surgeries controls. And it was due almost exclusively to, these are all annular targets, by the way. So there's, it was worse for annular targets. But the CTI was the culprit in a lot of cases, and focal atrial tachycardias along the annulus was the culprit in these cases. So we're sort of, you know, promoting, I think a lot of people do this already, but we're promoting preoperative EP studies, and kind of a low threshold to just ablate the CTI for these patients that are going to, and expected to undergo tracheous valve rings or replacement, just because it can be extremely difficult to control those arrhythmias postoperatively. Mayo Clinic actually published something kind of similar a few years back showing that even after a maze operation, CTI-dependent flutter is common in Epstein's anomaly. So, you know, it just goes to, I guess, support the notion that you might want to go after these even preoperatively in some cases. So we're, I think there's not any consensus on this yet, though. If we have time, you know, it looks like we're actually out of time. I was going to talk about VT, but it's kind of a long topic. I don't know if we should just stop at this point. Sure. Okay. So basically, that's it. Hope you guys enjoyed this. Sorry I didn't get through all the slides. That was fantastic. Thank you. Interestingly, there's a device-related question. Maybe you want to just touch on it. That's probably a whole other topic. But the use of physiologic pacing in adult congenital heart disease, is that something you consider? Absolutely. I think that's underutilized. We have been, there's some issues, I think, though, one of the problems I think is going to be that a lot of these patients have VSD closures, which are going to be very close to the conduction system in most cases. And then when you're going to go, if you're going to go after his pacing, after VSD closure, I worry about a lot of scar in that area, and then long-term durability of the leads and the characteristics of the leads. But we've looked at it certainly with CCTGA, which we know those patients get worse with single-site pacing, they develop heart failure pretty rapidly. So we've looked at his bundle pacing for those patients. And they actually seem to do quite, the leads actually seem to be pretty durable, and those patients do pretty well after his bundle pacing. So, you know, I don't know. I mean, maybe we can, I mean, the left bundle area pacing, branch area pacing, I don't think, I don't know of any case reports. There may be some actually now in congenital heart disease. But there's probably going to be new ways that we can get to the conduction system and better preserve ventricular function, because, you know, heart failure is also a very big problem for congenital heart disease patients. And a lot of it's pacing-related. So I think there's definitely a role for that. But it's, we're just at the, sort of just learning about it right now. All right, great. And I think you do talk about pacing in that review article that I mentioned. I'll try and put up online.

catheter ablation

adult congenital heart disease

atrial arrhythmias

morbidity

mortality

supraventricular cava-inferior cava isthmus

AV valve annulus

Transposition of the Great Arteries

physiologic pacing