So, Dr. Shiv Kumar is going to be talking about the dynamic structural and functional hierarchy of the autonomic nervous system. Can we modulate effectively and safely? Go. Thank you so much, Dr. Day, and truly a distinguished panel. So like much, if they are rock stars, I'm the opening act. So you know what the junior most people do. So for this very brief presentation, I'm going to simplify a very, very, very complex field. And for the experts in the audience, bear with me a little bit, because sometimes there's a saying in electrophysiology, if you cannot convince, confuse. That is, my aim is exactly the opposite of that. So let's talk about physiology and pathophysiology. And the simplest way, and this is, of course, we were never taught this in medical school. Here is an image of the heart, and you see signals going from the heart to various parts of the nervous system, which is on the left side, which is these, you know, where you see these blue lines. And then you actually have the impulses, neural impulses, go to these neural sites. It's processed over there. It's like a computer. And then it comes back to the heart using the two canonical limbs of the nervous system. We call them sympathetic and parasympathetic. What it does is we say, oh, parasympathetic slows down the heart, the vagus. Sympathetic speeds up the heart. But it turns out they do so much more. And very importantly, I want you to focus on the tiniest little circuit. If you just look at the heart over here, the term ICNS stands for Intrinsic Cardiac Nervous System. Then the heart sends signals to the stellate, comes back to the heart. Heart via the dorsal root ganglia to the spinal cord, back to the heart. All the way to the brainstem, back to the heart. That is the vagus. Now what do these layers, you know, many tiered reflexes do? You can take the human body and you can replace the heart with any other organ. And by the way, it can even be circulating blood cells. They still are talking to the nervous system. And they more or less follow a similar pattern. So take this from me. Neural control is central to all of cardiac physiology. Every single thing the heart does is under neural control. It's pretty scary, isn't it? And the simplest example, and of course, welcome to my state, which is California. So right now, if you hear a fire alarm or feel an earthquake, both of which has happened in this state, your heart rate will start going up. We don't wish that upon ourselves for this meeting. But then when that happens, when you hear an alarm, your brain sends signals to various parts of your body and instantly your heart rate starts accelerating. That reflex is there to save your life if you're being chased by a predator. That's why teleologically we have this. It's called the fight or flight response, right? The exact same alarm can be triggered by the heart itself. We don't teach this properly. Think of this as a two-way switch, right? So why the hell would the heart tell the brain the same fear that you have when you feel an earthquake when your brain senses it through your eyes or whatever other sensory system? That signal is what goes to the brain when you have angina. And many a times, even when you don't have angina, when you have post-infarct state, that signal going to the heart tells the brain, oh, it's hypovolemia. This hemorrhagic shock is what the brain is thinking. Of course, it's a heart attack. It's a small region of the heart that has been injured. And that is the reason why you get neuroendocrine activation, which is, by the way, central to all of cardiac disease. Here is an image of a... This is molecular stains, immunostains, showing smooth muscle actin. And what is blue is nerve fibers. You see nerves everywhere in the heart. And those signals going back and forth is communicating to the brain. And this alarm signal that is the same as you getting scared, the heart is now scaring the brain, except it doesn't come to our consciousness. That is what is responsible for heart failure, the entire syndrome of neuroendocrine activation. You have RV apical pacing. That's why a patient develops heart failure. When you look at the David trial, why did patients with BVI pacing get shocks? That's because they had neuroendocrine activation. So this is the central concept to be understood in understanding autonomic nervous system. So it turns out, as I told you in the case of heart, a lot of work over the past three decades by our group and many distinguished groups around the world has shown the nervous system also tends to constantly try to compensate for these things. And there are things, if you have a scar, nerves try to regrow in that area and so forth. And this sets up a cascade where step by step the nervous system is also trying to compensate for this, but then it also induces a syndrome of neural inflammation. So the stellate ganglia, all these sites getting inflamed because there's so much signal coming from the heart. And eventually that's what sets the stage for heart failure and bad outcomes. The good news is when you see such a complex system, you can also hack into the system in many different ways. All the way from the higher centers by meditation as a good life practice or getting a good night's sleep. But things like general anesthesia, vagal nerve stimulation, spinal cord stimulation, thoracic epidural anesthesia, sympathetic denervation, stellectomy. And very interestingly, we're going to talk about cardio neural ablation and modulating the intrinsic neurons of the heart using things like Botox. So all of these things are ways of hacking into the nervous system to treat heart disease. And it turns out we know it works well. The entire field of heart failure is basically dealing with the downstream effects of neuroendocrine activation, right? So think of this as the next stage of therapeutics. So using this as a broad brush stroke, this one slide tells you a variety of conditions that can be treated by neuromodulation, heart failure, ventricular arrhythmias, atrial fibrillation. And most recently, a lot of work in this meeting, you're going to hear about sick sinus syndrome, syncope, and POTS. I don't have time to go over this, but those of you who want to just grab the QR code and this reference on the screen, an entire issue of the Journal of Physiology was just released this month. I co-edited this with my colleague, David Patterson, at Oxford University, and many of the people on this podium are co-authors in some of the papers. You can read about all these treatments that are coming down the pike. And what is this central concept? All of these problems are created by increased sympathetic drive and a decrease in parasympathetic drive. Most neuromodulatory interventions try to balance these two issues so that you get better sympathovagal balance. You're going to be hearing a lot in this meeting about these little neurons in the heart, cardioneural ablation, that is a late-breaking trial that is going to be reporting the global outcomes of U.S. multi-center experience with cardioneural ablation, some of which was pioneered by Dr. Pashon and others over here. And you're going to be hearing a lot about why we can target neurons in the heart to treat very tough conditions like bradycardia, AV block, and POTS and syncope. So this is a shout-out for Late Breaker, which is going to be a simultaneous publication in JAK-EP. So I will leave this thought with you, a quick word of thanks to all our sources of funding, and of course to our collaborators, and most importantly, as promised to John, to finish on time. Thank you so much. Thank you. And you can either be online, or do we have any? I don't see any. Or we do have some microphones here in the audience. Maybe to start us off, two weeks ago, we spent the entire weekend talking about pulse field ablation for atrial fibrillation. And the title of your talk is, can we modulate effectively and safely? What are we doing to the autonomic nervous system with pulse field ablation? Is it good, bad, or we just don't know? So that's a good question. So it's very interesting. So the data is on both sides of the fence. There are some procedures which actually, especially, we know this with RF. We are causing a little bit of cardio-neural ablation during the procedure. That is data to say, based on what we know with PFA, that we are not having that much negative impact on the nervous system. Whereas there have been other PFA studies that have shown that, yes, you do have a component of cardio-neural modulation that happens during the procedure. Our gut instinct is still, PFA is so early stage in terms of waveforms and what we do. And the fact that most of these structures are epicardial, I think it's going to be very interesting to see what we find in the long run. And you'll also notice that, in terms of AFib itself, ablating these fat pads, intrinsic neurons of the heart, was used as an approach. But it has been shown to actually fail. The very best study was the AFact study, which is a surgical fat pad cardio-neural ablation study. And it is a negative study. Patients ended up with more pacemakers. So we now think that, perhaps, if you're dealing with AFib, you're better off tackling the atrium itself and not extensively damage the nervous system of the heart. So perhaps we'll learn more about it and learn how to modulate it versus just ablating it. So it's a great question. Yes, we have a question. Want to come to the microphone, please? Dr. Kantaria. Hi, Bharat. Thank you. That's very nice. I have a question related to denervated heart. What's your view with the autonomic neurons? I mean, does it have any effect? And why do we still see arrhythmias in transplanted hearts? Yeah, that's a great question. So we get asked this question very often. So the heart cannot be denervated. Remember, I told you the heart has its own fat pads. And the only reason a transplanted heart works is because it's transplanted with its own little brain on the surface of the heart. So those fat pads are like a sort of, think of it as a computer chip or a little brain. If the heart is an engine, that is the controller and the computer chips that go with it. That is the only reason why a transplanted heart works, when you take it out of the donor and put it into a recipient. And we now think that some cases where the graft dysfunction occurs is because of preservation and damage to the little brain on the surface of the heart. So that is point number one. A transplanted heart is not denervated. It's decentralized. A decentralized heart actually has a little bit of higher protection against arrhythmias because of this danger signal going from the heart to the brain doesn't occur. Therefore, when you actually have something that should have caused B-fib, now the brain doesn't get into it. So we actually say you now have the man-made modulation of an experiment where you made the mind not matter. So if you can prevent the signals from the heart reaching the brain, which is what stelectomy does in a way, it de-links the heart from the higher centers. So when you do that, there is less catecholamine release in the heart. And in that JFIS issue, you can see we've actually done very extensive experiments to prove why that works. A little bit of a shout out because I see my colleagues from Duke University sitting in the audience. 1961, Dr. Estes at Duke University was the first one to have done sympathectomy for cardiac arrhythmias. And in the same year, a few years later, in the JCI, they've done studies to show why it works. People have measured catecholamines in the myocardium. Thank you for that question. Do we have one last question? All right, we'll let you run to your next session. Thank you. Thank you so much. He's from the Libyan Cardiovascular Institute and he's going to talk to us about what happens in the Vegas does not stay in the Vegas. Thank you very much. When I got that title, I didn't know what I was going to talk about and I still don't know what I'm talking about. So bear with me. Is this thing loading up? Yeah. Can we get this set up to 10 minutes or whatever it is? Okay. Well, yeah, what happens in the Vegas does not stay in the Vegas, whatever that means. So basically the first thing is that, you know, you saw Shiv shows that some very interesting stuff, but we've known that vasovagal syncope and all these things can be triggered by central stimuli. There's actually a very interesting study that this guy, Dr. Keaton published in the British Medical Journal several years ago, where he actually reviewed the 20 canons of Shakespeare and looked at how many people and characters had faints, fits, and died. And he tried to attribute them to these, you know, central things. So as you can see, there's a definitely some of these characters, this demonet and people like that basically had just vasovagal syncope, but some of these actually had sudden cardiac death. So with my buddy, Dr. Angel Moya and myself, we're reviewing all the operas ever done and produced, and we're looking at all of them and we're analyzing if there were vasovagal syncope or sudden cardiac death, and hopefully we'll get a paper in the next year or so. So stay tuned. So the basal gyrus reflex basically was described in 1867, that's 158 years ago. This is from the group in Iowa, Dr. Mark back there, remember visiting him in the early 90s. I'm not 158 years old, but almost. And anyways, you know, that the basal gyrus reflex was initially described in people that had inferior wall infarcts. And you can see here the percentage of patients that had the basal gyrus reflex compared to the anterior myocardial infarction, those that had bradycardial hypotension, tachyonohypotension. And they looked at the discharge frequency of a sympathetic nerve traffic, and then they looked at different other reflexes in the heart. So this is actually very interesting. And this is a really very interesting paper. If you guys want to dig deep into mechanisms of the basal gerous reflex, go to this paper. This is from the neurobiology group at the University of California here in San Diego. This was published in Nature last year and basically what they did is they did optogenetics. If anybody knows what that is, explain it to me. Because what they did is RNA sequencing and then they created this model in this little rat. They looked at the they did some optical fiber stimulation and they triggered all these reflexes and they identified all these different phenotypes. Because we all are propense to having the basal gerous relief reflex, but we have different genetic propensity to do that. So you can see that this study, you can see that you know pupil dilatation, the response to respiration and different things was actually able to be modulated. One of the things that actually also modulated, you know if you remember way back in the late 90s, the Vanderbilt group showed that neuropeptide Y could be a protector for vasovagal syncope. Well these guys actually did an ablation, not like the ablation that Dr. Paschon here has promoted and discovered, but this is ablation in the brain, which probably we're not going to be suggesting anytime soon. But if you do an ablation in the area postrema, you can actually prevent the basal gerous reflex from happening. And these are the three different levels in which they can modulate the vagus. So does the vagus stay in the vagus? Well the answer is no, because there's different levels that are modulated, but they're modulated centrally. Now these are some of the first recordings that I did back in the early 90s when I was with Dr. Ekberg at Medical College of Virginia and with Ken Ellenbogen. We were doing sympathetic nerve traffic during tilt, which is actually very difficult to keep that little needle there recording sympathetic nerve traffic. But if you see here some things here that are marked in black, is one of the things that you see when people start getting this vasovagal reflex when they're tilted up, is that they change a respiratory pattern. Why do they do that? Because the brain is telling you, buddy, you're going to faint, so you're going to do something. And one of the ways of doing that centrally is recruiting respiratory bioreceptors and your bioreceptors to try to prevent this. And you can see here that the blood pressure is dropping, but the sympathetic nerve traffic and respiration changes, so it kind of recruits them again. And then it goes again and again until suddenly just the system can't stand it and says, you know what, we're just going to faint. Because that's the best thing we can do to protect the brain and to protect the heart. And that's what happens here, down there. So just for your information, I've subjected myself to every torture that I've subjected my volunteers, including sympathetic nerve traffic, lower body negative pressure, the carotid thing that Dwayne Egbert designed, and all those things. But the vagus actually is very important because we need to be careful when we start ablating all these neurons, because the vagus is actually a protective mechanism. So I don't like to talk about ablating, but more modulation of the vagus. And you know, obviously chronic orthostatic intolerance, we know that an appropriate sign is tachycardia, chronic fatigue syndromes, and all these different syndromes. And you know, more recently, a few years ago, the Canadian group with Satish Raj and myself and Bob Sheldon, we kind of created this newer kind of classifications of POT+, PSW+, you know, we just created a little bit of a confusion. So you can't convince, confuse. So postural symptoms without tachycardia that you can also see, this is not necessarily vaguely mediated, but it's more sympathetically mediated. And this is some work that we did back in the early 90s, when it was George Klein looking at an appropriate sign of tachycardia, and we looked at the sympathovagal balance that was, we thought, quite important. And back then, we started trying to ablate an appropriate sign of tachycardia, and that didn't go that well, as you probably know. Now, we know that the baroreflex is also quite integrated within the management of an appropriate sign of tachycardia, and it also depends on a phenotype in which some people respond different to orthostatic stress, and we can actually identify those phenotypes. And you can see here, you know, the patients have resting heart rate before and after propranolol. It's also a very nice study published in Jaha a few years ago, in which they looked at the sinus node automaticity, which I think is quite important to try to identify the differences between an appropriate sign of tachycardia and POTS. And this is also mediated by vagal response. Now, the other thing that's, this is James Stewart, that has done some interesting studies, and this is a little bit complicated. I don't have the time to go all over this, but you can see that there's some overlap when sign of tachycardia becomes too much. So when sign of tachycardia goes too far, the vagus responds, and responds in a moderate way to try to reduce that orthostatic stress and control the heart rate again. But remember that the other very important thing that the vagus does is control inflammation. Other studies that we've done, and others have done several years ago, have shown that when you do vagal simulation, you change the cytokines and you change the inflammatory response. So there's a huge amount of data that is using low-level vagal simulation to control inflammation as part of the modulation of the vagus. So that's the probably the spectrum that you can see here between the healthy POTS IST and those that have high sympathetic traffic. So this has also been seen in long COVID. In long COVID, you know that increases inflammation, there's a significant dysautonomia, and this is from the Canadian group that has an interesting name, the CanLocan, and we published this a couple years ago in the Canadian Journal of Cardiology, where we looked at the initial orthostatic hypotension in patients with what we call post-acute sequelae of COVID-19, and about 61% had initial orthostatic hypotension, 30% had POTS, inappropriate sinus tachycardia was not that frequent, and again this was mostly modulated by increased sympathetic tone. Now we're doing some studies in which we're trying to modulate this, and I'm sure Dr. Starvers is going to give us a little bit of some information on that, that we are using some vagal stimulation to try to both prevent POTS, and also we're looking at inflammatory markers, because these inflammatory markers are the part of the vagus that we, as cardiologists, never look at, but we think that are quite important there. And obviously the innervation or stimulation is a tricky part, and this is also important in people with HF-PEF, and again I won't have the time, but there's some studies that I'm sure Starvers is going to show us from looking at this stimulation of the vagus, trying to improve both RV function and other issues. So just to wrap up, we know that low-level vagal stimulation again has been used quite frequently, and there's some clinical trials coming around, and I'm sure again Starvers is going to talk about that, and these are vagal targets in cardiovascular disease. So the point that I wanted to make is the vagus is very important. Sure, we can modulate it as much as we want, but we don't want to get rid of all the vagus. We want the vagus to stay in the vagus, and to help us modulate that yin-yang response that is not only important from the point of view of cardiac autonomic reflexes, but also is very important for inflammation control and other control systems. Thank you very much. Questions from the audience? I had one quick question. In terms of post-acute sequelae of COVID, why are the presentations so varied, and why some patients get hypotension versus others get tachycardia? Yeah, that's a good question. I think that it has probably to do with the phenotype that you have at baseline for the patient, and you know, it's interesting because we saw that in the patients that had, for example, an appropriate sinus tachycardia, we've reported always an appropriate sinus tachycardia way much more frequent in women, and this in the past population, it was only 1.4 percent, but it was 80 percent men. So we don't understand exactly what was going on there, but it's probable that the virus has created some different type of stimulation on autonomic reflexes, which is actually mediated by inflammation. Hello, my name is Xiao Zongchen from GE Healthcare. So I have to admit that maybe I just get a few percentage of what you talked about, but I still have a question, so forgive me if that question is already answered in your presentation. So basically, when we say the vagus and the heart, they are forming a loop, signal loop, right, transportation. So it's kind of like a feedback system. So if it's a feedback system, then we think about stability, right? If it's a positive feedback, become unstable, maybe proarrhythmia. So when we talk about this vagus modulation, do we know this interaction to the vagus system has a positive or negative feedback to heart? Well, if I understood the question, I think that basically the vagus has a positive interaction. You know, way back then, there was a lot of intentions to try to stimulate the vagus to prevent sudden cardiac death. And initial trials like, you know, you probably remember the ATRIMI trial from Peter Schwartz and the group that looked at baroreflex sensitivity, and those that had reduced baroreflex sensitivity under certain thresholds were at a higher risk of sudden cardiac death. But we're never able to really show that by increasing that vagal tone, we would definitely reduce sudden cardiac death. Some interventions like ACE inhibitors, beta blockers, all these, at a certain extent, increase vagal tone, but they haven't been that successful in reducing sudden cardiac death. So I think that there's a part of the link that we have it, we don't understand yet, but what we need to find to be able to crack that nut. Thank you. All right, last question. BTA reflects, it seems from the left posterior wall, there are some pressure sensors, kind of, which sensor the pressure, they will conduct some synchronous to the neck. So originally from a posterior wall, left posterior wall, when we do the ablation to treat the neuromedian syncope, why would choose this target rather than others? So you're asking me why did we choose the target for coronary ablation instead of other targets? Well, I'll leave that to Dr. Pachon, but you know, remember that these are C-fibers that are mechanoreceptors, so those are much more complicated. We have also mechanoreceptors in the pulmonary bed that actually have very similar responses, but those are very difficult to reach from ablation. But I'm gonna let Dr. Pachon answer that question for you. My another question is that vasovagal syncope is a kind of ill, is a kind of ill BGA refraction. Is, sorry, kind of BGA refraction is too sensitive? Is that, is that what you mentioned, BGA refracts? Yeah, well, let me put it this way. Everybody is susceptible to a vasovagal response if you stimulate them enough. You know, one of the things that we did way back then was that, you know, we tried to see, if you put someone on a tilt table test down 10 minutes every day for 10 days, they're gonna start having orthostatic hypertension and vasovagal response. That's one of the ways they train astronauts, and, and, and that's just because you desensitize the baroreflex. So everybody is susceptible to that. It's just that we also know that there's some genetic propensity to vasovagal syncope also, and it's familiar, and I don't have the time to go over all the different genes that have been identified, but I'm not sure what the question was. This is, it's two response. So when we think about the vasovagal syncope, originally, where is originally from? I think that the first response is from left ventricular posterior wall or other? Yeah, I don't think we know that. That's a good question, but I don't think we know that, because sometimes the the vasovagal response, again, what we see is a different thing, different moments within the response, and the first thing that happens is that you start changing your respiratory pattern. Actually, it happens way before patients start feeling lightheaded and dizzy when you do a tilt. Then you see these major waves that are 0.1 Hertz waves that are baroreflex sensitivity. The baroreflex gain is going off. Then what you see is sympathetic nerve traffic shutting down, and then you see the bradycardia. You know, if you, if you keep people long enough on the tilt table test, everybody's gonna end with bradycardia, and 90% are gonna end with the systole. It all depends on what's your threshold on putting people down from the table when they start having that response. So, if you look at that in the during time, that's basically what you see. Is this originated from the mechanoreceptors down there? I don't think we know that. Thank you. All right, well, thank you very much. Our next speaker, Dr. Pashan from Sao Paulo, is going to talk with us about the role of the vagus nerve in atrial fibrillation. Good afternoon, greetings to all. We are talking about the Vagus Nerve, new insights on its role in atrial fibrillation pathophysiology and management. And there is nothing to be disclosed. And the first of all is this talk about this article. It is very important for us because this author, Jangan Kohls, found that the reconnection of the pulmonary veins was similar in patients cured and in patients with recurrence. So in this trial, it was clear that the PVI alone is not enough to treat atrial fibrillation. There is a crucial background player, in our opinion, is the vagal innervation. So for us, treating the vagus, treating the innervation is extremely important to solve the problem, to do the ablation of the atrial fibrillation. In this study, Sharifov and Kohls showed that acetylcholine is a potent inducer of atrial fibrillation. Adrenaline does not trigger atrial fibrillation if the vagus nerve is previously blocked by atropine. In the 90s, we described the atrial fibrillation as that are the vagal innervation sites, the input of the innervation in the atrial wall. They are the substratum of the atrial fibrillation in normal heart, due to their high frequency and electrical resonance during the atrial fibrillation. We observed that the ablation of the atrial fibrillation has had two consequences. The first one, it causes a notable atrial stability, allowing the atrial fibrillation treatment, and in addition, led to a significant vagal innervation. Based on this, we proposed the cardioneuroablation in the 90s, that is a method for vagal innervation by endocardial atrial RF ablation. Beyond treating atrial fibrillation, the cardioneuroablation has also very good results in managing all types of functional bradyarrhythmias. In 2017, Stavrakis and Sunny Poe published an article corroborating the idea that vagal innervation improves atrial fibrillation ablation outcomes. To study better the vagal effect, we developed the extracardiac vagal stimulation, which enables non-contact vagus nerve stimulation during any electrophysiological study. And for example, in the upper panel, these patients presented a spontaneous atrial fibrillation induction after the vagus stimulation. It is very important to see that the vagus is extremely arrhythmogenic for atrial wall. And after the cardioneuroablation, eliminating the vagus effect, there is again another vagal stimulation. There is no more induction of the atrial fibrillation. And the cellular arrhythmogenic effect of acetylcholine is based on the calcium transient phenomenon, which causes trigger activity, typically initiating atrial fibrillation. A further striking arrhythmogenic effect of acetylcholine is the plateau-cutting property, which blunts the axial potential plateau, making the myocardium highly susceptible to atrial fibrillation. Yet an issue arrhythmogenic effect of the vagus nerve is the open synapses. The vagus presents unpassed synapses that are related to the origin of the atrial fibrillation. Unlike skeletal muscle, neuromyocardial junctions lack synaptic clefts, allowing heterogeneous acetylcholine diffusion, enhancing the electrical instability. By vagal stimulation in our patients, we have found that the vagus causes remarkable atrial refractory dispersion. In this example, from 18 to 70 milliseconds, followed by significant refractory shortening. All of these effects are highly arrhythmogenic and completely eliminated by cardio-neuroablation. In this study, patients who underwent PVI combined with cardio-neuroablation had nearly five times less atrial fibrillation recurrency, highlighting the significant value of the vagal denervation in AF ablation. The vagal stimulation uncovered the three relatively independent vagal domains, the sinus node, the AV node, and the atrial wall domain. The sinus and AV node domains are easily identified by sinus arrest and AV block during vagal stimulation, whereas the atrial wall domain requires the VEFTI protocol, that is the Vagal Atrial Fibrillation Induction Test for its detection. In the VEFTI protocol, atrial programmed stimulation alone usually induces no arrhythmia. However, under vagal stimulation, it triggers immediate atrial fibrillation in practically all patients, revealing the strong arrhythmogenic effect of the vagus on the atrial wall. After cardio-neuroablation, the same VEFTI, Vagal Atrial Fibrillation Induction Test, no longer induces atrial fibrillation, making it an important key endpoint for confirming successful atrial fibrillation ablation. This study shows that if denervation gets a negative VEFTI, there is 4.5 times fewer atrial fibrillation recurrence, suggesting that VEFTI negativity is a valuable endpoint to be achieved during atrial fibrillation ablation. Obviously, it is based on the denervation of the atrial wall. It's relatively easy to denervate the sinus node and AV node, but denervation of the atrial wall is more difficult. So the VEFTI protocol is very important to study the denervation of the atrial wall. And for treating atrial fibrillation, it's necessary to get the denervation of the atrial wall. And at the end, I would like to say some take-home messages. The first one, acetylcholine is highly arrhythmogenic for atrial walls. The vagal denervation stabilizes the atrial myocardium and is very important for atrial fibrillation ablation. Cardioneuroablation enables vagal denervation through ROF catheter endocardial ablation. Vagal re-nervation is typically observed in atrial fibrillation ablation recurrences. Our studies have shown that successful atrial fibrillation ablation requires both venous atrial and neuroatrial isolation. I think for treatment of the atrial fibrillation is very important to get the isolation of the veins and isolation of the vagus of the neurons. At the end, cardioneuroablation significantly increases the success rate of any atrial fibrillation ablation technique, so all techniques that treat atrial fibrillation are based in some degree of the vagal denervation. Thank you very much. Thank you. We're going to keep with our format and Dr. Pachon, a couple of questions if you want to come up. Anyone wants to come up to the mic? While they're coming back, what are you doing at your heart hospital in Sao Paulo since you started off your talk saying pulmonary vein isolation for atrial fibrillation is not enough? So what is your typical approach there at your hospital? How are you targeting the vagus nerve? It is very interesting question. We began to treat atrial fibrillation in the 90s. In that time, we observed that the isolation of pulmonary veins is not enough to get vagal denervation. By using the extracardiac vagal stimulation after isolating the pulmonary veins, it's possible to get important response, important vagal response. In some patients, after isolation of the pulmonary veins, there is no more vagal response. It is a good patient. It is a patient, surely, that will have good results only with pulmonary vein isolation. But if the patient presents a very important vagal response after PVI, it is necessary to do cardioneurobation to get the best result. In our studies, it is possible to increase, to reduce it five times the recurrence of the atrial fibrillation by adding the cardioneurobation to the pulmonary vein isolation, to eliminating completely the vagal response. Okay. Question. So this is Dr. Noheria from University of Kansas. So my question is with PFA, though. So when you're doing RF ablation, you get some neural modulation irrespective of your intent to do that or not. But now that we are doing more PFA, and that is more selective for the myocardium and spares the nerves and the autonomic nervous system, would you expect, I guess, what are your thoughts on that? Yes. I think PFA is a very interesting tool for isolation of the pulmonary veins. But probably it is not the best one to isolate the neuromyocardial interface. I have to study, obviously, more. But the first study that was performed in Prague with Dr. Kausner showed that PFA was not enough to get a very good vagal denervation. The question is, at the acute moment, it's possible to see pseudo-denervation because there is a stunning of the vagal endings. But after this, there is a recovery because the PFA is featured by avoid lesion of the neural system. So in our opinion, it is necessary to get more lesion of the vagus in order to get the treatment of the, obviously, the good results by long time in the atrial fibrillation ablation. All right. Well, thank you. We'll move on to our final speaker. Our last speaker is Dr. Stavros Stavrakis from University of Oklahoma Health Science Center. He's going to talk to us about cardiac autonomic modulation, the treatment of arrhythmias and autonomic dysfunction, what's the current evidence, and what are the knowledge gaps. Thank you so much. Thank you for inviting me. Thank you all for staying this late. So cardiac autonomic modulation is a promising approach. I don't know why it doesn't show up. I could see it here. Anyway, so this concept is not new. The first VNS device, which stimulated bilateral carotid arteries, not my preference, but was reported in 1884 by the American neurologist James Corning for the treatment of epilepsy. And by the way, cervical VNS was approved for the treatment of direct refractory epilepsy in 1997. Now, fast forward 100 years. Xian Chen's group made the astute observation that in patients with paroxysmal atrial fibrillation originating from the pulmonary veins, infusion of phenylephrine, which increased the blood pressure and slightly slowed the heart rate, as you see here, resulted in decrease in pulmonary vein firing, as you cannot see here, suggesting that changes in autonomic tone induced by phenylephrine injection suppressed focal AF originating from the pulmonary veins. And that's where the idea of vagus nerve stimulation to suppress AF came from. Now, you could tell me vagus nerve stimulation for AF, are you joking? This is a paradox, because for 100 years, and as you saw from Dr. Pachon's presentation, vagus stimulation is a powerful inducer of atrial fibrillation. It increases refractoriness. But again, note that in order to induce atrial fibrillation, there is sinus rate slowing at least 2 thirds of baseline. And in fact, slowing the heart rate slightly does not increase AF inducibility. So low-level vagus stimulation, defined as vagus stimulation that doesn't cause bradycardia, is not arrhythmogenic. And in fact, it's the opposite. It could suppress, this is from our group, a canine model of atrial fibrillation. During six hours, three hours of rapid atrial pacing, you could see the increase in AF inducibility. And then with VNS, there is a decrease, and when VNS is applied at the same time as rabid atrial pacing, there is no increase of AF inducibility. And this effect comes from suppression of the neural activity of the epicardial autonomic ganglia. Now, we can stimulate the vagus nerve noninvasively by accessing the auricular branch of the vagus nerve. Stimulation of this area resulted in evoked potentials in the brainstem in humans, as well as stimulation or activation of vagal projections in the brainstem by functional MRI. One important property of VNS and noninvasive VNS is that it exhibits memory, meaning that the effect lasts much longer than the stimulus application, and that's important. Now, we did trigger stimulation, same canine model of rabid atrial pacing, and as you can see, the results are very similar to cervical VNS. And then we translated these results in humans that came to the EP lab for AF ablation. We did one hour of trigger stimulation and induced AF with rabid atrial pacing before and after, and you can see that there was a significant decrease in AF duration, significant increase in AF cycle length, and an increase in atrial ERP. And then we went on to design the TREAT-AF randomized clinical trial. This was a six-month study. Primary endpoint was the AF burden, measured at baseline three months and six months. And note that the six-month endpoint was done without any stimulation, and that highlights the memory effect that I alluded to earlier. Patients were randomized to active versus sham, trigger stimulation for one hour, and at six months, there was a significant decrease in AF burden, in the median AF burden compared to sham stimulation. But if we analyze the individual patients, half of the patients responded very nicely. Half of them did not. Why is that? We don't know. We could not decipher that based on clinical characteristics. We analyzed a lot. So the question is how to optimize the cardiac autonomic modulation for atrial fibrillation. That's kind of how to move the needle forward. Patient selection appears to be key. And we tried to find biomarkers. Biomarkers in the blood, such as neuropeptide Y. And you could see that changes in neuropeptide Y mirror the AF burden changes. But importantly, those who had high NPY level at baseline were those that had the largest decrease in their AF burden. We also analyzed an ECG marker, P-wave alternans, at the microvolt level using signal processing. This is not visible with your eyes. And again, there was a decrease with trigger stimulation, but those that had an acute change in P-wave alternans were those that benefited the most with a significant decrease in their AF burden. What else can we do? The individual dosing of neuromodulation matters. And we hypothesized that the optimal stimulation parameters depend on baseline autonomic tone. Obviously, our autonomic tones differ, so maybe we could dose it differently. We did hierarchical cluster analysis and found that there are two clusters in our patient population based on autonomic heart rate variability parameters. And you can see that in cluster two, these patients have lower low frequency, higher high frequency, and a different low frequency to high frequency ratio, suggesting higher parasympathetic and lower sympathetic tone. And in fact, those people in cluster two respond better to five hertz compared to cluster one, in which people respond to 10 or 20 hertz better. Just a word, because my talk also mentions autonomic dysfunction, and you heard about this from Dr. Shivkumar. We used trigger stimulation in patients with POTS, and we saw a significant decrease in orthostatic tachycardia, autoantibodies, inflammatory cytokines, and heart rate variability. So what's my vision for the future? I think we're gonna see a wireless device which can monitor physiological signals and apply a deep neural network model to predict disease and provide patient-specific autonomic modulation in a closed-loop system. We're not there yet, but stay tuned. We're working on it. So in conclusion, the autonomic nervous system plays a significant role in atrial fibrillation and autonomic dysfunction, and autonomic modulation is a promising therapy for atrial fibrillation and autonomic dysfunction. But one size does not fit all. We need more research to identify responders from non-responders in order to maximize the efficacy of this novel therapy. I would like to acknowledge members of my lab, collaborators, funding sources, and thank you for your attention. Question. Yeah, quick question. Thank you very much. Very clear presentation. Just, I mean, obviously the problem is titration, right, and understanding the response. And I just want to, I mean, Peng Cheng's work using neuro ECG recording for sympathetic cutaneous sympathetic nerve activity. Tricky to do, but what's your experience of using that or other biomarkers? I have not used that. We have not used that in my lab. It is a potential, it is of potential use, I believe, because, you know, it's measuring sympathetic, it correlates with sympathetic tone. Yeah. So on the same token that I said earlier, the baseline autonomic tone dictates the individualization of the dosing. Yeah. So that's something we could do. And also, do you find that when you actually give stimulation, you then get a dynamic change in their responsiveness? So this is a, you get a potentiation effect or you get a resistance to therapy. Have you looked at some different windows of therapy which are effective? We did not look that. We saw that there is, over time, a buildup of the effect. Right. Using continuous monitoring. Right. You find a decline or an increase? No, an increase of the effect. Okay. Thank you. Peter Kistler from Melbourne, Australia. Congratulations on your work. I also wanted to draw you out a little bit around where Pierre was coming from and some of your final slides there about how do you think you should personalize or the amount of tragus stimulation that you deliver? I gather from your work that it was a standard one hour for each patient? Like what are the, I think that was one of the true disasters of renal denervation is that there was no acute endpoint for that treatment. What do you think should be the acute endpoint? Exactly. Heart rate variability is what we did, the cluster analysis here that I showed. Is it perfect? Probably not. We're also looking at PPG signal analysis, which can also correlate with sympathetic tone. I think if we could get it with PPG, then that would be the easiest thing because you don't want to do, biomarkers in the blood are good, but you cannot do it at point of care. You see a patient, you tell them, okay, I'm going to collect 30 patients and run my kit. It doesn't work like that. Something simple like PPG would be great. Short of that, heart rate variability would be something else. Would you still say that the gold standard for assessment of autonomic tone for any treatment is heart rate variability? That's the best we have. It's not perfect, but there is a lot of evidence behind that. Thank you. Any other questions? When we use radio frequency to update the atrial fibrillation, more or less, we will injure the GP, more or less. But now we have PFA, head-to-head comparison, radio frequency and the PFA, PFA is not inferior to RFA. So if, in your opinion, GP is one of the most important factors, how to explain this? Thank you for this question. Again, we're looking at, you know, one size does not fit all, okay? So in some people, GP are important, in some people are not as important. So on average, perhaps it doesn't matter. But at the individual patient, like Dr. Pachon alluded to, there are some patients, you do PVI and it's enough. There are some other patients that, you know, you need to do more. And I think that's where we need to focus, just a little bit more individualization of therapy rather than the one size fits all concept. Do you mean we should choose some special patient like vasosensitive atrial fibrillation? Correct. There are some patients where the GP are more, play a more important role. Yeah. We have two different atrial fibrillation, right? One is vasovagal sensitive, another one is a sympathetic sensitive. When we do the GP, it seems that we don't match the selection, but the result seems the same. I mean... You mean PFA versus RF? Radio frequency, yeah. It's not exactly true. If you look, there's a paper from Vivek Reddy's group that they showed that if you do extracranial vagal stimulation in patients after RF, there is 100% elimination of this effect. If you do the same thing post PFA, that is in 33%, you still have this effect. So it's not exactly myocardial specific. I think we're still learning about PFA. Last question. We know paroxysmal AV block usually will induce a syncope, very severe syncope, repeat. Some of these paroxysmal AV block is neutral-mediated, I mean, it's a vasovagal-mediated one. I read some articles from Japan or other countries, they just focus on the GP or some neuros, then would implant a pacemaker for them. So what's your opinion to this kind of management? I apologize, I think there is a language barrier and I don't understand the question. Can you repeat it again? I mean, paroxysmal AV block, atrial ventricular block, some of them is because of vasovagal induced, neuro-mediated induced. Some experts, they do the GP ablation for treatment, this kind of AV block. Yeah, cardio-neuro ablation, yeah. Do you think that this patient should combination implant pacemaker as well as do the neural ablation put together or just a single neural ablation, that's all? I think you can try, I don't think you can do, it's wise to do both. You just start with one, I think it's a shared decision, you talk to the patients, you do one, and if it doesn't work, then you put a pacemaker, but I think cardio-neuro ablation would be first. But again, patient preference and clinical characteristics would dictate that. I think we're running out of time. Yeah, we're running out of time, we have to close the session. Thank you everyone for attending. Thank you. Appreciate it.

autonomic nervous system

cardiac modulation

sympathetic system

parasympathetic system

intrinsic cardiac nervous system

neural activity

neuromodulation

vagus nerve stimulation

cardiac diseases

personalized treatment