co-chair from Quebec City, Canada. I'm pleased to introduce Dr. Marczliński, Dr. Francis Marczliński from Philadelphia, who obviously needs no introduction. It is our pleasure to welcome you in San Diego and Heart Rhythm 2025 at the 45th Annual Meeting of the Heart Rhythm Society. If you have not already done so, please download the mobile app from the App Store. You can participate in live Q&A and there will be some polling questions in this session. You can scan the QR code on the screen to access the session Q&A and the poll. Please note that visual reproduction of Heart Rhythm 2025 either by video or still photography is prohibited. Now, we will start, this is a debate. We will start with our first debater. My pleasure to introduce Dr. Roderick Tang from University of Arizona in Phoenix, who will talk to us about epicardial axis mapping and ablation and with the pro side that should, that epicardial should be part of every structural VT ablation. Great. Is there an updated slide deck there by any chance? If not, we can work off of it, but there was an update on. This is amazing to have this much attendance, especially when the late breakers are going on, but you'll be able to walk out of here understanding there's late breaking news that everyone should have epicardial VT ablation and an access and I'm really grateful to be able to take the pro on this because this is very controversial and I think that many people, we talked yesterday about VT management and it's really do I need to be able to do epicardial access to be able to have a VT center? So why do we care about the epicardium? Well, when I was a fellow, I remember reading the multi-center thermocool and this is the who's who of VT and I felt that it was slightly depressing that the success rate was just over 50% with the best of the best, with the new irrigated technology at six months and that is when I said, I'm gonna go into VT because you don't go into a field that's got a 98% success rate. You go to into one that is desperate for help to see if we can improve it. Now, why is the success rate so low? Why is VT success rate so low? Because we actually understand the mechanism of VT contrary to atrial fibrillation where it's been all about energy sources for the last decade to get durable PVI. We've not done anything mechanistically beyond pulmonary vein isolation, but we know that there's a re-entrant circuit from Mark Josephson and Frank Munchlin's getting colleagues because of diastolic activity, what they called localized fibrillation actually back in the 70s and like SVT, I think the goal for VT ablation before I'm long and gone should be 90% success rate and I know that is bold. I think if we know the mechanism, we can map the whole circuit, we have tools and we are there with mapping. It's often that we think about mapping versus ablation, which one do we need? I think that it's time for us to strive for this VT road to 90% and here would just be an example of a case that we just did about a month and a half ago where we were able to map two VTs that are totally polar opposite expressions of the human heart, left summit, which is our wave dominant on your right and then you've got one that's left bundle with almost no transition, but it's beautiful because they have a shared isthmus that comes right across the middle of the heart underneath the LAD and this is a patient with sarcoidosis, a patient of Pete Weiss's that sent us over, but we don't need more mapping, we really understand this so much better and typically even when you think about multiple electrodes, you only have about five or six bipoles that are really representing diastole, even if you have a million points. So we probably are at the limit in terms of where we really need to be with mapping, we need better ablation technologies or we need to be able to get transmural therapies and epicardial ablation is one way to do it. Now, I don't wanna debate pattern B, which is a complete isolated endocardial scar where I would like to frame the debate that we should go up a curl and everyone that has evidence of transmural or epicardial substrate, just like we can't talk about going doing VT ablation to people that don't have VT. So I do think that we need to frame it and say, it's probably not gonna win if, I'm not gonna win a debate by saying purely endocardial and then Frank Marchlinsky and Oscar Cano definitely showed us that there's a lot of epicardial involvement in a distinct proportion of those infralateral non ischemic cardiomyopathy patients and the epicardial mapping is really a two dimensional approach to a 3D complex structure. So the easiest way to describe that to patients is you got a crack in the wall, you keep patching on one side, you know that something's happened on the other side and we're trying to do everything from one side, but sometimes you just think, I'll probably get a better fix if I patch both sides of a crack in the wall. So when do we do this? I think this is antiquated and this is something that Shiv, Noel, Boyle wrote in epicardial interventions in circulation in 2012. Hard to believe that's 13 years ago and we use the exit sites because we worship exit sites and I'm gonna totally try to debunk that and then prior unsuccessful ablation for endocardial and we actually might even start with de novo and we'll talk about why that's the case, but I do think that the value of imaging is really important, but MRI often can fool us. There's a lot of partial volume effects and we're actually finding that sometimes intracardiac ice is better than MRI, but we're typically taught that ischemic cardiomyopathy is an endocardial problem, like Reimer and Jennings described with the wavefront of necrosis and that you need not go to the epicardium because this is an endocardial problem, although when you really think about the figure of eight pattern that Al Sharif described, it was actually the spared epicardial regions that with a figure of eight pattern was first mapped in a preclinical model. When I was at UCLA, we actually looked at our ischemic cardiomyopathy proportion and looked at, and this was non-randomized, small, limited numbers, but those that underwent epi-endoablation with ischemic cardiomyopathy did better than those that did endo alone, which was really contrary to a lot of what the field was showing and Luigi and Andrea have shown this very nicely with epi-endo homogenization as well. And in fact, here's a beautiful case of an epicardial reentry in a patient that was de novo and has complete reentry here up at the apex, of the heart tilting up this way. And we actually found activation gaps on the endocardium. So it really can live in three dimensions. And Jorge Romero did a beautiful combined endo-epi, and I only say beautiful because we love affirmation bias. So anything that's published that you agree with, you think it's just an incredible paper. And this incredible paper showed that there's actually mortality benefit to epi-endo versus epi in structural heart disease. So if we want to walk to that road to 90, wouldn't we want something that's more successful? If Fred wants a road to 60 or 70, he's gonna win. But if I'm asking you the question is, where should VT ablation end? And I think that VT ablation should be more successful than AFib. AFib appears, regardless of energy source, to top out around 80%. And if you put a loop monitor in, it looks like it's about 60. That hasn't changed with all the new technologies. It has not changed. And the story is probably the most clear with the resistance to go epicardial, even in ARVC. And there's many people still fighting that fight where they say, well, we can still get success endo. And we're not saying you can't, but you're not gonna get 90% success with endo. And this was a nice paper by Rong Bai and Natali's group showing epi-endo is better for ARVC. And when you look at the Hopkins ARVC experience, and yes, that is much more of an epicardial predominant problem, they had a 15% freedom from VT, which is 85% recurrence in 2007. We should just marvel about how much progress we've made as a field in VT, which is pretty awesome in our lifetime. And then when they started adopting epicardial strategies, they got to 84% freedom. So they flipped that percentage. And then when they started mapping more epicardially, they found that, oh, almost 70% of circuits are epicardial. So this really explains the ARVC story, which is why we start first line for all ARVC. Now, many people believe, and the most common reason we get an epicardial referral is, well, this looks really wide. Rod, this looks really wide, so go ahead and send it over. Well, here's a wide VT that's actually 300 milliseconds. I remember our fellow walked in and go, ah, epi, and walked away. Like it was a mic drop, and they were so proud of themselves. And then what we did was we did some pace mapping from the epi and the endo in a patient that's got severe cardiomyopathy and amiodarone, all of those slow conduction. And what you see is that the pace map of the QRS width was 290 on the epi and 285 on the endo. So width does not always tell you in a structural heart disease patient on antiarrhythmics that this is endo or epi. And this was an endocardial termination for this VT with a QRS complex of 300 milliseconds wide. We've recently started looking into TR fusion, which is when the prior T wave superimposes and blurs or obscures the onset of the QRS. And you can see that the first pace mapping beat has a very clear inflection. And as you move with burst pacing faster and faster, you can't see where the T ends and where the R begins, hence the superimposition. So these are actually pseudo, pseudo delta waves. So many things will look epicardial. And here, and this was just published in Jack EP, we've got this beautiful pace map with a very clear R wave. And the UPenn group has taught us that if you have a QS and lead one, you should think epicardial, what site specific. And then you also see these straight isoelectric lines with the systemic QRS. The VT is over here at 343. And when we pace a little faster, we actually start getting TR fusion and that little R wave starts going away. When you pace even faster, it's completely gone. So you're gonna interpret that as a QS because of the speed of the VT. And we've done additional analysis that when that exceeds the QT interval, that's when you have the most TR fusion. And that would make sense. And even looking at the entire QRS match and the best pace map is at the rate of VT, which makes sense, but not everyone does that. The first half has the worst match versus the second half, which is why we believe it is related to a TR fusion event. And Martinick and Stevenson, Fred's former group that he trained at, looked at every QRS characteristic that Baruso and Wilbur described, the MDI, the pseudo delta of 34, the RS of 85, and they didn't find a single one to be discriminatory for epi versus endo. So the idea that you can just take a look at an EKG and say, this is epicardial, is completely fraught with limitations in structural heart disease. So what is an epicardial VT? I think this is our greatest challenge as a field. Is it something where the whole circuit is on the epicardium or is it something where you have more on the epi than the endo, if you were able to map both? Is it something where you have to just have the entire isthmus on the epi? Or is it just that you can find any diastolic part? Or is it that the exit site is epicardial? Or is it that we can just terminate it with epicardial ablation? These are six potential definitions for what an epicardial VT is, and there's no consensus on what an epicardial VT is. Most people, and also crazy to think how time flies, because this was almost seven years ago when I put this on Twitter, most people think that if you can terminate it on the epi, that's an epicardial VT to me, which is a very pragmatic definition of an epicardial VT, but it's not biological in terms of does the VT involve the epicardium? And we look at these six definitions. In non-ischemic cardiomyopathy, QRS breakout, which is just prior to the QRS onset, is actually 81% in non-ischemic. Any part of the isthmus you can find in non-ischemic patients in 73%. Epi is greater than endo, and ablation term's about 57. That's in non-ischemic cardiomyopathy. What does ischemic cardiomyopathy look like? Hmm, not very different. They actually look quite similar. 74% of the time you get a QRS breakout. You can find any part of the isthmus in 69% of patients on the epicardium in ischemic cardiomyopathy. And ablation termination was around 39%, but you can probably terminate many VTs on both surfaces because VT, we increasingly recognize, is a three-dimensional animal. And the final debunking of sites of origin and epicardial exits is that we always map our QRS windows at the onset where purple and white, that interface, represents QRS inscription. So what you'll notice here is this is an epicardial map, an endocardial map on the right. You've got complete reentry with all the colors of the rainbow coursing through the central corridor on the epi, and you've got some activation gap here where green loses blue and dark blue, but still breaks out in purple. The most important part about this is that you've got dual breakout during QRS inscription on both endo and epi, and these would be representative electrograms of those on both endo and epi. So the next time someone asks you if this looks like an epi or an endo VT, 67% of the time you will be right if you say both. There needs to be a third category because VT is non-binary. We understand this much more in three dimensions, and as a matter of fact, the majority of circuits have mid-myocardial components, and attacking these from both surfaces makes the most sense to be able to eliminate this until we can get a technology that actually is transmural from the endocardium alone. And when we looked at all of the cycle length on the epicardium in blue and all the cycle length that we can record on the endocardium, you can see the preponderance of both surfaces participating in reentry, and only 17% of the time do you have this restricted to only one surface. So everyone is gonna be well aware that Fred Sasher, who is an expert in our field and is a pioneer, is gonna tell you there's just too much risk. There's too much risk to go epi. And I would say that that is probably true if you're not experienced, and we know that there's risk anteriorly to get a double puncture. There could be a superior epigastric lemma continuation. And if posteriorly, we worry about puncture the diaphragm and puncturing the liver. So those are not ideal. But there are new ways to make this safer. And one of them is CO2 insufflation. We have this group from Montana that would always send us their epicardial VTs, and they read about this, which is the Silberbauer technique. Sant'Angeli's been doing some great work, many great centers across the world, but being able to intentionally have a wire exit with something that's 0.014, insufflating some CO2, finding a little air bubble, and then basically piercing the pericardium into pneumopericardium, which makes it a lot easier. So one group in Montana read about it, they did it, and we haven't heard from them again. And I think that's great. I think that's absolutely great for these patients that really need it. And this is courtesy from Sant'Angeli. So here is intentional wire exit. You get a little bit of localized pneumopericardium, and then you can stick into this region. So if you really had safe epicardial access, would we have so much resistance to it, knowing this is a 3D animal? It's almost like the back in the days when people were right-sided electrophysiologists, and we don't wanna go to the left side because it's too much risk. But if we can make it safer, I don't think that the extinction will really happen. So that's really important. And these are just some tips for epicardial approach, holding anticoagulation, know your complications of regional anatomy, always check that wire and LAO, shoot a pericardiogram. When you get access into a privileged space, maintain it with double wires so you never lose it. That'll pay off in life as well. Never leave a sheath exposed. And prior to RF, think about coronaries and phrenic. I had another slide as an update. Pete Weiss has been working on a pericross technique, which is actually using what used to be called the Rook catheter, which is now able to grab a little bit of the pericardium, pull the pericardium towards the operator, and then introduce a needle into that space. And that just got FDA clearance as well. So I think there are new ways that we can make this a lot safer. So in my last 11 seconds, epicardial mapping and ablation is necessary if we really want a road to 90, which is what I'd like to see. Newer developments are in play to make this safer. And if there was no risk for the epicardium, would you actually be so resistant to it as well? Thank you very much. Thank you. Thank you, Rod. Okay, we have two EP heavyweights, neither of them sweat very much, and we've got the second one heading to the podium, Fred Satcher, who's from Lyric Institute in Bordeaux University in Bordeaux, France, and he's going to take the con in terms of epicardial axis and mapping should not be performed in every scar-related VT ablation. Thank you very much, dear Isabel, dear Frank, dear Rod. It's really a privilege for me to be part of this debate. I must say when I saw I was against Rod, one of the smartest EP of our generation, I think there may be a trap somewhere. So please get your app. I have some questions for you, if you get that. I guess the first question is, did Rod convince you that epicardial axis should be performed in every single scar-related VT? So waiting for your answer, Rod is not only a brilliant, eloquent, elegant EP, he created his own short collection and he's very talented because I learned recently that he even is a singer, and a very good singer. I'm sorry I cannot have the song, but I'm sure you can find it elsewhere. So did you answer this question? So, wait 10 seconds more. So, yeah, I think we can have it, if you can send. So did he convince you that, well, Rod, okay. So I have 25 more percent of people to convince now, so let's start on that. So when you have this kind of debate and this kind of question, of course it's kind of controversial and what you are looking at is science and evidence. Unfortunately for me, there has been a clinical statement, a consensus statement just published a few weeks ago, just on epicardial ventricular arrhythmia ablation. And looking at it, the answer is clearly no. It should not be performed in every single patient. So having said that, you will see most of the same articles that Rod showed, but with different interpretation, though. And I would like to emphasize not only on complication, I will discuss a little bit on that, but also on patient selection, because I think this is a key point here. And I'm not saying you should not go epicardial, but I think it's always good to balance the advantages and the benefit for the patient and the risk. And I will discuss all these different entities. Concerning brugada syndrome, I give this one to Rod. I think this is probably should be done in every single patient. This is a 2A indication, epicardial substrate ablation in patient with recurrent ICD shocks. This is a patient actually we did a few weeks ago, where on top of the brugada pattern, this artery polarization pattern, and we did the map, epicardial map with the H-degradex, which is pretty good to map epicardium with abnormal potential on the RVOT, but also inferior leads because of that. But anyway, it's probably a good idea to go epicardial straight to this patient when they got arrhythmia, but in our experience, it's pretty rare. I mean, we have quite a lot of brugada patient, but brugada patient with shocks is pretty rare. So it's not a lot of patient. So let's look at myocardial infarction. Because Rob showed you beautiful images, and he's great. He did a lot of mapping, but he mixed a bit on ischemic, ischemic. So the substrate is very important there. And in patient with myocardial infarction, looking at the literature, it varies a lot. So meaning that there is a part of epicardial circuit does not mean that you can't get it from the endocardium. And depending on the studies, it's approximately between 10% or max 20% of patient you have to go epicardial in patient with myocardial infarction. There are clear indication for epicardial mapping and ablation in patient with myocardial infarction. Those with failed endocardial ablation, even though in our experience where patients are referred to our center for failed endocardial ablation in the context of MI, it's often that still endocardial target to chase, and not so often epicardial one. Of course, in the presence of floating LV thrombus, if you cannot postpone the procedure, it's probably a good idea not to maneuver a scatetal within the endocardium. And there are also imagined criteria that have been described by the group of Barcelona and others. Some kind of epicardial scar on MRI larger than the 14 centimeter square. And this wall thinning part there, but I'm less convinced about that. Because when the wall is very thin, you often can have that from the other side and at least identify the area that should be targeted. So let's go to our VC now. And he showed you these two nice example. Should the epicardial access be performed in every single procedure? Well, this is more questionable. Probably not, but I'm OK to discuss further afterwards. It comes from this study showing that endocardial ablation in our VC patient was not, when you go endocardial knee, the outcome was not good. At that time, the answer was not that we were not good. The answer was, oh, there is disease progression. And actually, Frank Marcheson group at UPenn showed that there was not so much disease progression. And eventually, it was on the other side. And this second study, when you go epicardial on top of endocardial, the outcome was much better. So this is why in our VC, we generally go epicardial as a first line. However, maybe we can limit the approach. Because yes, it's not trivial to go epicardial. You have some risk. And it's not me, actually. Roderick Tong showed that localized epicardial reentry may be a manifestation at earlier stage of the disease with a relative paucity of endocardial substrate. So when you don't have an endocardial substrate, epicardial is probably the key there. And the group from Barcelona and others showed also that when you have a large scar endocardially, it's often from the endocardium peritricosphere, inferior or lateral, below the valve for the tricuspid valve that the channel is and should be targeted. And finally, the epicardial is not helping so much in those advanced RVC patients. More than that, in patients without this epicardial scar, they do have a cardiac component that led to death. So it's not, once again, trivial to go epicardial, especially if you are not so trained for that without surgical backup. I would like to address also the non-ischemic cardiomyopathy patient. And all of that of my demonstration is that the substrate is key to know whether you have to go epicardial or not. So Chagas disease, I must admit that I don't have much experience in the literature. You have epicardial substrate in more than 80% of the case, so it may be worse to go straight epicardial. Probably the same for myocarditis thecola or arrhythmogenic left ventricular cardiomyopathy. But for all the others, the substrate may be very different from one patient to the other. And it's absolutely crucial to get more information. And this has been very well shown by the group of Frank Marczynski, especially in non-ischemic cardiomyopathy and basal VT. And when you get the VT morphology, it's not always the case. But when you have it, you have the criteria that has been described by Roy with the advantage and the limitation of these criteria. And others also show criteria in sinus rhythm that could help you to know whether you have epicardial substrate or not. So just with ECG, you can have some piece of information, which is not zero one, but this is some piece of information helping you to decide whether you will have epicardial substrate and you should go epicardial. But you have more than that, once again, by the UPenn group as the endocardial mapping and the unipolar mapping with these thresholds can tell you whether you have intramural or epicardial substrate on top of the endocardial one while you are mapping the endocardium. So it gives you an idea of the transmurality of the scar, which is kind of important to know whether you should go further in and go for more aggressive procedure. Because at present time and waiting for more tools, it's still an aggressive procedure going epicardial. But I think the key thing here is imaging, especially non-ischemic cardiomyopathy patient, imaging and high-resolution delayed enhancement MRI will tell you where the substrate is. And if you got, as in this case, inferolateral sub-epicardial scar, like in myocarditis sequelae or mutation of the desmoplakia, for example, then you need to go epicardial for sure as a first-line strategy. But if you are, in this case, with intramural scar, like in laminopathies, for example, then it's not worth going epicardial. You will take more risk for no benefit for the patient. So once again, I truly think that patients with non-ischemic cardiomyopathy should have MRI before ICD implantation. It tells you a lot on the etiology, on the outcome of the patient, and on the strategy if they have VT. So imaging, it has been said a little bit on the risk of the procedure, because it's not without risk. Imaging can help you to know where is the left internal memory artery, for example, choosing between an anterior or inferior access. You see that in this case, the infra-diaphragmatic track and digestive track was pretty superficial. So if you go inferiorly, you will cross it, and you will have complication. So all piece of information is very important. It can help you also, imaging can help you during your epicardial procedure. This was a patient with myocarditis secular, and you can see the coronary artery displayed on the electroanatomic system. And we were mid-diastolic in VT, ready to push on the pedal, because this was it. But you see that we were just pushing on the artery, the merge was too good, and we were already on it, so we had to move forward a little bit. So imaging for epicardial is also something important. From the literature, at present time at least, and waiting for more useful tool or more safe tool to go epicardial, we have 5 to 10% of major complication related to pericardial access. This was a retrospective study showing that inferior access may contain more risk, 10% versus anterior, but this was not randomized, so with all the limitation. There are some patient-specific factors for risk that you need to know, especially if you start with that. Do not start with patient with previous cardiac surgery. Obesity will have adherences, and this increase the risk if you go epicardial. Obesity is clearly something a bit less, I mean, it depends on the degree of obesity, of course. Other things that we may not think before starting, but pictus excavactum may be more problematic to access also. So all these things have to be kept in mind, and once again, waiting between the benefit for the patient and the risk of such a procedure. So to conclude, ladies and gentlemen, it's very important to check carefully your patient before the procedure in terms of anatomy, medical history, because the etiology will tell you where the scar is, anticoagulation also to limit the risk. Use all available tools such as, of course, ECG, information for unipolar mapping or imaging, to plan your ablation and anticipate any potential problem. Choose your access, anterior or inferior, depending on your patient or on your experience. And once again, I think if you start, at present time, at least, there's still some risk with epicardial, so it's good to get surgical backup in case of refractory bleeding. Thank you very much. Thank you very much, Professor Satcher. Okay, time for a rebuttal. Well, I really am appreciative of the 25% that are with me. I will make a concession. I will say that in our own clinical practice now, as one ages, you become less adventurous and more risk-averse. And I would say our approach is probably about 25% on its own, that maybe one out of four will go epicardial. And it used to be that if we were thinking we would go epicardial, we would get it right up front. And now it's more of, let's try what we can do endo, as much as we can. What's the worst case scenario? You come out transeptal, reverse anticoagulation, give some protamine, and then you stick epi. So our practice has totally changed. And I think that a lot of the, what we were doing, and Frank and I have spoken about this, the biology of VT, which does live in three dimensions, it's crazy to think that this could be a monolayer of a circuit. And rarely it is, but it's maybe a couple monolayers. But I think those isolated epicardials, as Fred is saying, where you could see a little, as Fan and Marchlinsky have shown, a little white stripe on the epi, and there's nothing else endo. Those are the ones that are a home run. And in those cases, I would say there's no reason to even map endo. But those are not that common. So I would really say it probably is one out of four. So that would be my concession, and I think it is interesting to see people trying to get into the epicardial space more safely. We are planning a trial, because there actually has never been an epi endo versus endo alone, large randomized trial on ischemic cardiomyopathy. Ablation was tested with epi endo, but there were two variables there. There was the extensiveness of the ablation, and then there was the epi versus endo with Luigi and Andrea. So we are trying to come up with a trial there to look at it. And the last thing I would conclude, which is more of real talk, is I think that there's a physician perspective, which is the last thing I want is to create a complication. And currently, the health care climate de-incentivizes us from doing longer cases, which is probably why doing short plane flights and selling that to a patient, say, I'd rather take a short trip, get up in the air and land, and if it's not enough, we'll come back and do a second time. But it is interesting with patient expectations that if you give them the choice and say we can do them both in the same during your anesthesia, or you're going to have two, there are some patients that are like, I don't want to have two. I want one and done. And that's where shared decision making is important when you offer this. And I think Frank Marsalinski says it best. Shared decision making used to be just called good doctoring, right? Just being able to communicate with the patients. But it's interesting because the last thing we want, and once you've had an epicardial complication, you almost never want to do it again. And we just had one two months ago, but that one was no chance from the endo. We tried and tried and tried. We ablated 15 times from a broad breakout and didn't see a piece of diastole. And we went to the epicardium in the first application. The whole circuit was there because it was layered. And that was a beautiful case, but that patient was complicated by an RV puncture that had to go to surgery and had to have a slight larger window than we wanted. And that's not what they expect. But overall, we still say the risk of surgical conversion is less than 1%. And that is true. You know, in 17 years, and I keep a list of all my complications, and there's a great session about my worst complication, I think, at 3 o'clock. But I keep a list of them, and I've had five surgical conversions. So that's less than 1% of all the ones we've done. But it's not insignificant for those five humans. And that's really important as we think about safety as we move on. So I will concede, and Fred gave a great argument, but it was a tough one for me to win. Now, Dr. Satcher's rebuttal. Yeah, so I have nothing else to say. I mean, he said it all. And he did great because it was not easy. I mean, they gave me the easy part, actually. But I guess this is the point. I mean, the true epicardial, purely epicardial are not so frequent. Epicardial is OK, and conversion is minimal in experienced centers. And that should be taken into account also. I think, depending on your experience, it's probably better to refer to more experienced centers than going epicardial, especially if you don't have surgical backup. Because even though most of the time it goes well, sometimes it can be a problem. And then you don't want that for your patient. So once again, in some patients, very well-selected, epicardial as a first-line therapy is important and should be performed. Brigada, some IRVC patient, of course. And when you've got purely epicardial scars, there's no question about that. And Roddy is right on that. But really, patient selection is key. And knowing very well the anatomy is also important to limit complication. Thank you very much. Great. Thank you. Thanks to both Fred and Rod for great presentations. We have a few questions from the audience. But I would like to start with one question to, in fact, two questions to both of you. When you go EPI, because we know we go EPI for burning, but we go EPI for mapping also. And sometimes the mapping is useful and the burning is not necessary. So when you go EPI and then you achieve non-inducibility or you achieve VT ablation from the endo, do you go apply bonuses ablations, bonuses lesion on the epicardial side because you already have access or you limit yourself to endo applications? And the second part of my question is with maybe newer, more powerful tools that maybe we could, with whom we could achieve transmurality. Well, how would you rely on your endo mapping and your imaging tools in order to be confident that your endo ablation will be sufficient and you would not require the need for EPI ablation? First of all, yeah. Sometimes epicardial mapping gives you more information. Rod did a great job with endo mapping and make us understand better the circuits that he showed are really beautiful and very inspiring and led us to understand better. The question is, once again, when to go to compete with the risk? And at least in our point of view, it's worth going when you think you may do something epicardial, when you are a part of substrate. I don't know if the substrate will be involved in the VT, but at least there is a substrate to map on the side. One thing is, especially on the right side with IRVC, we go almost all the time epicardial. It can tell you the effect and transmurality effect of your application. So in that, it's good to get a map. Even if you do not ablate on the epicardial side, it gives you an idea of your efficacy by transmurality. I mean, there is something very elegant about an epicardial-only procedure. And that is that if we do look at asymptomatic cerebral emboli, et cetera, that, and Greg Marcus has shown that that might be more than a quarter of it. But if you do a lot of ablation endo, that's probably going to increase the risk of that. Whereas epicardial, sometimes you get those LV thrombus cases and you go epi-only, and you're like, oh, I see a lot of stuff there. You think it's thin, it's really clean. There's no anticoagulation through the whole case. And then the risk of any sort of brain events, which I think we underestimate, is none. But to answer your question is, how often do we actually go to the epi, get non-induced from the endo, and not do anything epi? But I think if you're already there, you don't want to waste that opportunity. You'd rather still finish off the corresponding across that way. There is a counter to that argument, which is that even Hemel Nayak showed, with a sinus node modification, three lesions around the sinus node in the epicardium created a constricted pericarditis. So when we do ablate, we often will ablate the pericardium when you look at ice, and not just the myocardium, by definition. And then I think that that might be a reason to withhold. But typically, when we're there, we do it. But Komatsu et al. from Bordeaux showed beautifully that when you ablate endo, even with RF, 33% of the time, you can completely eliminate an epicardial channel and all that. And I think Vivek showed a field medical case where they mapped the epi during endo, and all the epi went away, which is really promising. But 33% of the time, that can happen with RF as well. So we need to see more. But I think the thing that we should agree on is that if you have a purely layered scar in the epicardium, I don't think it's advisable to try to go through all of the normal tissue to do that. And that's why I don't think epicardial procedures will be gone, even if field is transmural. But we do need many more cases in which we're mapping the epicardium with these purported transmural sources. In fact, we want to discourage people from going transmural when you just have a layered epicardial scar by imaging, at least for the moment. I mean, again, I guess we'll see how that all shakes out. And maybe there's a role for it. Because as you pointed out, if you're not blading epicardially, you're less damaged to the risk of damaging phrenic, maybe less risk of damaging coronaries. It's still worthwhile from the end of it. Live on the question. Thank you. Hello. Becker, Helsinki, Finland. Nice presentations. I have a question for both of you. Sometimes you see in the imaging that there's a thick layer of fat in the epical space. What are your tips for us to do in those cases? Because it's an insulation. And it's really difficult to ablate the obese patient, for example. This is not so rare. That's a great question. And obviously, fat can mimic low voltage. And it's obviously an impediment to effective ablation. That's where I think going through the venous system is a great way to do it. Because when you think about it, when you're in the coronary vein, you're a little closer to the epimyocardium than you are when you're right over in the pericardial space. So that's why when you're actually recording within the veins, which is what Miguel Valderrano has done, you often see very near-field, high-frequency components to it because you're eliminating that. Now, these veins have variable courses. So sometimes there could be intervening fat. But typically, they're closer to the epimyocardium than not. So that's something I would think about or just try to use high power from the endo to try to get those areas. I don't think we have ways of lipolysis yet. And I know that people have thought about freezing the fat first and then RF-ing later. And people are looking at sequential types of energy sources. But I don't think we're there yet. Any role for a hybrid that surgery is opening it a little bit and taking the fat away? Have you considered that or done that? Yeah, this would be a last step. I mean, if you fail with all the other tools because it's not insignificant either. One more maybe thing is now with contact force, you've got arrows to know where your catheter is pointing to. So it's very important when you're on the epicardium to point towards the tissue. And sometimes it depends on the level of fat. But you can remove a little bit of fat sometimes and get more contact directly to where the tissue and with less fat in between. So it's very important to get the arrow really pointing towards the tissue and not toward the external part of the arm. The other public service announcement that we never got to was that for a while, every non ischemic, we went epicardial. But as we all are aware, there's the infralateral subtype and the antriceptal, as Zeppenfeld and Della Bella have shown very nicely. The anticeptals have very low yield to go epicardial because you're going to be right around the left main, a lot of fat. These typically are intraceptal substrates that are periaortic as well. In those areas, those cases, we never go epicardial anymore. That yield is less than 10% to go there. So that's really changed the game. Whereas before, we used to think non ischemic, epicardial. But you really have to think about the anticeptal subtypes that really don't benefit much from epicardial. We have a few questions that come from the audience online. And so I'll try to group them. And have Rod and Frederic address them. So one is epicardial ablation. Do you perform coronary angiogram all the time before burning? And another one that also says, how do you localize the coronary arteries angiogram or image fusion? Yeah, so we are using image fusion. And CT scan before the procedure help us for that. And we always integrated these images. So basically, when we are away from the coronary artery displayed on 3D system based on these images, we go without shooting the arteries. If we come close and we think we should burn that, we shoot the coronary arteries just to make sure the merge is good and there's not too much discrepancy. But most of the time, if we are more than five millimeters away, we do not even shoot the arteries because we do have the one from the CT scan. And you have also to pay attention to phrenic nerve, especially when you are under general anesthesia. If your anesthesiologist give paralytics, then you will not capture phrenic nerve. And you can burn it. And that's a major complication. I would say that a comment on image integration, and they've done incredible work on it. The reason that we've been more slightly positive than very positive is the best registration error that you could really register in these typical image integrations is about maybe three to five millimeters. That's typically what's reported. And that does make a difference. Of course, it gives you a general sense of where it is, where the branches are. And we're starting to see image integration in conduction system pacing as well. But if that's four or five millimeters, that's probably enough still to make a difference. And you don't know which direction that always is. Coronaries, if you're in a really dense scar and the more distal you are in the system, if you're in the apex and you have an apical aneurysm, that would be the most extreme. We typically don't shoot that. Of course, you can still get ventricular fibrillation if you close one of the vessels as well. But in terms of myocardial salvage and trying to spare damage distal to where you're ablating, we think it's less relevant when you have a really dense scar as well. And obviously, if you have minimal scar, very basal, that's when you have to shoot. So a few questions about access approach that you're currently using. Have you abandoned the posterior approach and now use an anterior approach as many others who do this have altered their technique? And how often now do you use CO2 insufflation in your practice? Okay. So yeah, we are using anterior approach before a long time and very rarely inferior approach except when we got anterior adherences. This is where we could go inferior. But otherwise, we always go anterior. The only thing, if you go anterior, do not go towards the left shoulder as you would do for an inferior access because you have a left internal mammary artery. So you can get it if you go towards the left shoulder on an anterior approach and it bleeds a lot. So you should not do that. So you have to go very vertical when you go anterior approach. And for CO2, that's funny in the lab, depends on the operators. There was one people in our lab doing only CO2 and I'm never doing CO2. It's more kind of practice and when we have been trained, I guess. Yeah, we haven't done CO2, but it's kind of like the old dog learning new tricks. I mean, we were resistant with vascular ultrasound, but then we gave in eventually there. I think as far as posterior inferior approach, it depends on the patient. There's some patients you almost can't get inferior on when they have a really wide AP diameter and the real hallmark of thinking that you're gonna be inferior, because obviously the entry point to get very practical is you wanna go as shallow as you can in the initial entry to try to avoid the diaphragm and the liver and then steepen. But then when you kind of go too steep, sometimes you're already right over the heart and you actually can't get behind it. And those are the ones that when you look at the shadow, your needle is already past the most inferior portion of the pericardial silhouette. And that tells you by definition that you are anterior to that heart. And that's when it's really strange because your needle is like almost inside the heart shadow that by definition is anterior. And there's some people you just can't get to that. I would say the most dreaded complication is the through and through puncture, which is when you get into the heart, you don't know it, you keep going and then you come out of it. So essentially you're skewering the heart. That can only happen or most typically happens on an anterior puncture because what happens is you come right over kind of the tip, the top of it, you go through and through, but when you come inferior, it's hard to go into it and then exit it as well. So those dreaded through and throughs that have been published are all with anterior approaches. So there's a trade-off for all of it. Do you wanna just comment on how you manage that? But if you notice it or identify it. Oh, through and through? Well, yeah, and the way to suspect that is if everything's fine, there's no bleeding because you're in, but then the minute you take your sheath out, there's a rapid bleed. That's why we double wire and we always leave a wire in even after we've removed the sheath. So the joke that I always say, that's actually not a joke, they say, well, when should we remove that wire? I said, hold onto the wire and push the patient out of the room. That's how you remove the wire. You wanna maintain access as long as you possibly can. And then obviously call the surgeons if you suspect something like that. Yeah, yeah, we do the same. We let the wire in for five minutes, making sure nothing happens because it will go very fast. If there's double puncture, it will bleed a lot. So we know it very quickly. And then if it starts bleeding and you push back the sheath in and then you call the surgeon. And the superior epigastric and the Lima stick, if you happen to hit that, it often will go through and through it as well, tamponade it, and then you pull out and then the track will start bleeding really rapidly. And that's when you know you've got a problem as well. We actually coil embolized the Lima for one of them that we knew we did so we didn't have to go to surgery, but you can also just cut down and see. Just one more time, Rob, because a few people did ask it. The reversal of anticoagulation. So for people that go endo, can't succeed, then go epi, anticoagulation management. Yeah, we just reverse with 30 or 40 protamine, check the ACT, make sure it's less than 180 and then we'll stick. I do think that the biggest problems are Plavix, Parazigril. All those are the ones that you touch there. Everyone that does pacemakers, which is everyone, you know exactly what that bleed's like. It's crazy that Coumadin doesn't bleed. I don't even know how it prevents strokes when it doesn't bleed, but then all of these new PGY inhibitors, those are the ones that bleed like stink. So we try to withdraw those as far in advance as possible. Those are the ones that are really the challenge. Yeah, I think it's a key point there to avoid complication in bleeding. One last question, I think for Rod. Do you use ice to help guide the epicardial puncture and access? Yeah, we wish that we could. We just haven't had reliable success, but an ultrasound guided would probably be the best, but we just haven't been able to see it. I don't know, Frank, if you guys have any luck. Well, my colleagues can do it, so I swear that it does work. So with confidence, I don't do it as well. So we just use typical fluoro guidance, but I have had echocardiographers help me with the sub-xiphoid imaging just to identify some of the landmarks very nicely. That sometimes works as an alternative. And definitely helpful to see if the wire's in the RV, so you go into a home view and you see there. But the most important thing is if you wire the RV, which Fred showed, is around, I think, 10 or 12% in your 2010 series, the key is that you do not wanna just come out and say, that means you're in. Just like the initial approaches where you do a through and through arterial stick. That means you're in, pull back, try to wire, pull back, try to wire. Don't try to do another stick. You're already in, get access on the way out. And that's really key. And if it's just a wire, that's fine. That would be fine. You don't have to push the sheets, though. Yeah, but a laceration, even if it's small, will bleed. So a lot of caution. Well, terrific. Guys, thank you for a beautiful debate. Perfect. Thank you.

epicardial access

ventricular tachycardia

VT ablation

Heart Rhythm Society

epicardial mapping

CO2 insufflation

patient selection

heart perforation

advanced mapping technologies