I'm very happy that I'm able to participate in this fellows conference and you know that Nishant has done a great job, you know, collecting fellows all over the country. So most of the stuff that I'm going to talk about today is work I've done as Nishant rightly pointed out with Dr. Scheinman while I was at UCSF, I was there for about 18 years. And I think it's a very, it's interesting work because I think most of the electrophysiology is when you're dealing with the supraventricular tachycardia. I'm going to start off with the, my disclosures and then I'm going to move to the first slide. So the first couple of slides are ECG slides that I wanted to show, share with you guys and I want you guys to look at it and then give me what, you know, give me an answer. You have four choices. So basically what I'm showing you here is a patient, is the same patient who has two kinds of SVT if you can see, the cycle length is the same. So this is within say 10 minutes of each other. It's not at different points in time. And looking at that, you have to tell me what the diagnosis is. And usually it's, you know, one of the four, atrial tachycardia, AVNRT, AVRT or junctional tachycardia. Now this slide is showing you something which is the reverse of what is taught in terms of, you know, RP relationships. So if you just use that, then you will be able to get the. We have a little over, you know, almost 60% of people who have voted, so I'll end it and share the results here. Okay, great. So it looks like most of the people have voted for AV node reentry tachycardia. And then the second most common is atrial tachycardia, followed by AV reentry tachycardia. Nobody voted for junctional tachycardia, which is good because I think junctional tachycardia is rare and most probably most of the people have not seen it. So let me show you what the answer is and it's a little bit of a surprise. The second most common is the right answer. It is atrial tachycardia and I'll show you why that is true. So the common teaching that we have for fellows is if you see a Holter monitor tracing and the RP is always fixed, but the cycle length keeps changing, then it can never be atrial tachycardia, right? Because in atrial tachycardia, if the cycle length changes, the RP will change. So there is no RP relationship that is fixed, but if you see a fixed RP, then you know it is either AV node reentry or AV reentry because both of them required a fixed RP. Here what I'm showing you is the same cycle length. So I'm showing you the opposite of that. Cycle length is not changing, but the RP is changing. When the cycle length is not changing and the RP is changing, for sure it cannot be AV reentry tachycardia because AV reentry usually has the same RP. But even if you were to change the RP, you say if somebody has longitudinal dissociation or something, the cycle length will change because the minute you change the RP, PR is not going to change in the same fashion. Second thing is that the, so that is why it cannot be AV node reentry as well as AV reentry tachycardia. AV node reentry can give you different RP relationships. Some patients have short RP, long RP, but again, in AV NRT also, if you change the RP relationship, you cannot have the same cycle length. So this patient actually had parahysian atrial tachycardia, which you can see over here that the P waves are very narrow, especially in the long RP, you can see they're very narrow and negative in the inferior leads. And they just look like, you know, AV NRT coming from the typical AV NRT. So this is, this, the answer is not AV NRT, it's going to be atrial tachycardia, sorry, the arrow is on the wrong place. This is up. This just makes sense. It's a RP relationship changing, but the cycle length is the same. So the atrial tachycardia has the same cycle length. This patient has dual AV node physiology. This is going over the, the short RP one is going over the fast pathway. The long, the shorter RP is going over the slow pathway. This patient had dual AV node physiology. So the ATAC kept firing and just kept switching from a slow pathway to a fast pathway. In fact, we gave this patient very low dose adenosine and he would switch from one to the other. And then we would give him a little bit more adenosine and then the tachycardia would terminate. And as you guys know, this is work done from Bruce Lerman's group. They have shown that most focal atrial tachycardias are due to CAMP dependent mechanism. And so they would terminate with the adenosine. Okay. So this is another ECG. This is another patient who now looks like has long RP tachycardia. Okay. And so in the long RP tachycardia, you got to figure out whether this is typical AVNRT, PGRT, an atrial tachycardia arising from the coronary sinus ostium, a junctional tachycardia or none of the above. So it looks like we've got about 60% of people who have voted. So I'll end here and share the results. Okay. So most of the people have picked a choice as coronary sinus osteoatrial tachycardia. The second most common choice I think is PGRT followed by I think none of the above, yeah, the third choice is none of the above and then typical AVNRT. So let's look at what the answer should be. So let's look at the tracing. So it's a long RP tachycardia. So you know, long RP tachycardia cannot be typical AV node reentry tachycardia. Typical AV node reentry tachycardia is an A on V tachycardia. At the most, sometimes you can get the P wave right before the QRS if there is some delay going down to the ventricle, but this patient has a normal looking QRS complex. So the one thing that it should not be is a typical AV node reentry tachycardia. And the same for junctional tachycardia. Most of the junctional tachycardia that we have seen, we have described a series of focal junctional tachycardia from UCSF. We had some collaborators at different centers, but junctional tachycardia for most part looks like A on V tachycardia or there's evidence of AV dissociation. Now the most people picked up, so, you know, if you look at it, long RP with a P wave inverted like this, you usually tachycardia and they would both look like the same. There is one key finding in this ECG which actually gives the answer. And that is, if you look over here, I don't know if I have an arrow going over there. Well, it's not, I think. Yeah. So there is a circle. So if you look over here, so look above the circle, look in lead three. If you look in lead three, there's a deep inverted P wave plus P wave. So there you see the P wave. See the P wave. I hope everybody can see the app that I have. Vishak, can you see my app on the PowerPoint? I hope people can. So you can see here, yeah, so you can see where I made the circle, the P wave had disappeared. Look in AVR. P wave, P wave. And there's one place there's no P wave. The tach continues. So you're showing one point in time where the P wave has disappeared. If you take away the P wave from two things, one is an atrial tachycardia, because the in atrial tachycardia, the P wave is driving the QRS. Number two, it cannot be AV reentry. In AV reentry tachycardia, using an accessory pathway, atrium and ventricle are an integral part of the circuit. So those two things are out. The only thing that this can be is AVNRT, junctional tachycardia, or nodal ventricular tachycardia. Now, junctional tachycardia typically does not look like a long RP tachycardia. It looks more like a A on V tachycardia. So typically AVNRT would be our answer, but this is not typical AVNRT. This is atypical AV node reentry tachycardia. And in all of these three, atrium is not part of the circuit. So this is what leads me to the topic that we are going to discuss today. So I hope this is clear to everybody that you really have to look carefully when the P wave disappears, you cannot have CSRs and PGRT as the diagnosis. So the topic is SVT with VA dissociation. So the three main causes of SVT with VA dissociation. The most common finding you will see is actually AV node reentry tachycardia. Why? Because AV node reentry tachycardia is the most common SVT that we see. So most commonly you will get a block, upper common pathway block. Either this can happen spontaneously, or it can be seen in some patients who've had some ablation done in the perinodal area. So here you will see a block to the atrium, so you'll have SVT with VA block. Focal junctional tachycardia. So focal junctional tachycardia, you've got to think of it like a focal atrial tachycardia, except that it is coming from the junction. So it comes from the junction. Again the atrium and the ventricle are not part of the circuit. So in focal junctional tachycardia, you can have Vs going on, but it can block to the atrium. And sometimes you can even see sinus P waves go through with focal junctional tachycardia. And then the third part is a patient who has what we call concealed nodal ventricular tachycardia. And that I'll explain more in details. And these are the true Mahayam fibers. So Igor Mahayam was actually trying to describe accessory pathways that inserted from the AV node into the conduction system, either into the fascicles or into the ventricles. So they would call nodal ventricular or nodal fascicular. So in here, the circuit goes from the AV node down to the conduction system and comes back through the concealed nodal ventricular or nodal fascicular fiber. So you can see the circuit is right around here. It has nothing to do with the atrium. So in these patients, you can have block to the atrium. So these are the three main kinds of tachycardias, which will cause SVT with VA dissociation. So this is an example of one of the patients in our series from a patient who had junctional tachycardia. So on the top part, you can see sinus rhythm. And the bottom part, you can see patient is in SVT. But if you look carefully in the inferior leads, you can see positive P waves, which are again dissociated from the tachycardia. So this is a patient who had focal junctional tachycardia. Now, our series that we did, we collaborated with Jay Cheng, who is in Houston right now and used to be at UCSF before this. And here we showed about 18 patients, seven of them were male. Predominantly, these patients had one-to-one AV relationship with the A preceding the QRS. It looked more like an A on B tachycardia. But they did have evidence of AV dissociation, either during the tachycardia or the other way they had it was the ECG example that I showed you, where you had a positive sinus P waves. They behave like paroxysmal SVT. And they have similar symptoms to patients who would have any other form of SVT. And then they had symptoms, they were referred to us for catheter ablation. So this is an example. So first, I'll go through the differential diagnosis. How do you make a diagnosis? What kind of diagnostic maneuvers can you do in these patients? And then we can talk a little bit about catheter ablation. So this is a patient with junctional tachycardia. You can see we are doing atrial overdrive pacing from the ablator in the atrium. And then you can see there is A going to B over a fast pathway. And then the patient goes into a junction tachycardia. So this is preceding both V and A. And that's the tachycardia they have. This is another initiation that we saw in these patients. You could do ventricular overdrive pacing and also initiate a junctional tachycardia. We think that the predominant mechanism for junctional tachycardia is again similar to focal atrial tachycardia, which is a CAMP dependent mechanism. So you can trigger them. These are triggered rhythms. And you can pace them, whether atrial overdrive pacing or ventricular overdrive pacing, and they can go into that. So here you're seeing ventricular overdrive pacing. V is going to be A over the fast pathway. And then the A is the first thing that comes on. And then you have A and V on top of each other. So it then slowly settles into a junctional tachycardia. This is a patient who has similar initiation as I showed you earlier, atrial overdrive pacing. And then the patient goes into A on V tachycardia with the HISS preceding both A and V. So the mode of initiation is the same. However, in this case, this patient happened to have AV node reentry tachycardia. So if you initiate the same kind of tachycardia with the same mechanism, same atrial overdrive pacing, how can you differentiate between junctional tachycardia and AVNRT? Why would this be AVNRT? What happened in this case is this patient has double fire. So single A goes down to the fast pathway. It also goes down to the slow pathway and then returns back the fast pathway. And then you are in AVNRT. What is in focal junctional tachycardia is just overdrive pacing, you stop it, the junction is triggered and it just starts firing. So how do you tell whether this is AVNRT or whether this is junctional tachycardia? This is another patient who had initiation of AV node reentry tachycardia, similar to what I showed you with junctional tachycardia. So ventricular overdrive pacing, V is going to the A, V is going to the A and then suddenly you have A on V tachycardia. Here you don't see the HISS on the HISS catheter, but it's an A on the tachycardia, similar to what we initiated on overdrive pacing. So how do we differentiate these things? So that brings me to this slide. So what I want you guys to do is, this is a patient who, this is a Holter monitor strip on a patient. So it goes from the top strip to the bottom strip. So you see the tachycardia, then you see termination, you see sinus rhythm. Based on this, you have to tell me what is the diagnosis. So the diagnosis is either AVNRT, AVRT, AT or junctional tachycardia or don't know. One of my former colleagues used to say that if you are dealing with SVT and you can't figure out the mechanism, then go and modify the slow pathway. But I think our goal today is to try to understand the mechanisms more, so you have some understanding how you can diagnose because ablation for all three of them is different. Ablation for JT is different from AVNRT and that nodal ventricular is different from that. So looks like we have most of the fellows have answered. And the predominant answer is AV node reentry tachycardia. I want to see if somebody can, does somebody want to answer, whoever answered AV node reentry tachycardia, do they want to explain the tracing? Yeah, if anyone wants to unmute themselves and give an explanation, feel free. Do you have a pseudo R wave? I mean pseudo... Yeah, so it's good. You're saying there is pseudo R wave during tachycardia, which is absent in sinus rhythm. Correct. And that can be also seen in atrial tachycardia and junctional tachycardia. You can also have an atrial tachycardia, which has a pseudo R wave, which conducts with a long PR interval. In fact, how does it terminate? How does this tachycardia terminate? Blocking the fast pathway. Pardon? You don't see the pseudo R wave, right? Yeah, blocking the fast pathway. Yeah. So it terminates with a QRS complex. So if you have a spontaneous termination of an SVT with a QRS, what is the number one diagnosis? Is it AVNRT or atrial tachycardia or AV reentry tachycardia? AVRT. No, it should be atrial tachycardia. I'm talking about spontaneous termination. And atrial tachycardia is the only one that is spontaneously terminate with a QRS. Because in atrial tachycardia, the atrium stops firing. So it will go through the AV node and capture the V. Because both the atrium and the AV node stop firing at the same time, doesn't happen. Whereas in AVNRT and AVRT, they terminate because the AV node fatigues. So they always terminate with an A. So even though this looks like typical AVNRT, but it can be atrial tachycardia. It should be. That is the first thing you should think if you see spontaneous termination with a QRS. And you should always give a denosyne because I have been fooled. I saw the pseudo R prime and I said, Oh, this is AVNRT. And I gave a denosyne and next thing you know, there is AV block and the P waves are marching through. So you can have atrial tachycardia with a long PR interval that gives you a pseudo R prime. So now whoever was answering, I do want to take them. I think you are right. Now explain to me why you are right. Even though this is spontaneously terminating with a QRS complex. Because you still could have had block and retrograde fast. You can, but that is rare. But there is something else that terminates this. Does it terminate spontaneously? It does. It's by PAC. I think there is PAC in the last bit. Right. Right. I know him. You are a smarty feet. So does everybody see this? So when I first saw it, I thought the same thing. I said, this is atrial tachycardia is just spontaneously terminating with the QRS complex. This was a holder monitor tracing that Nora Goldschlager, who's one of my former colleagues at SFGH had sent me. And she pointed out, if you look at it carefully, you see the QRS before this, there is a PAC over here. So there is a late PAC that terminates. The reason you don't see the pseudo R prime is because the P wave has been pulled in over here. So the late PAC that terminates an A on V tachycardia without affecting the cycle length, a late PAC terminating an A on V tachycardia without changing the RR interval is absolutely, there are very few things that are diagnostic of AVNRT. That is absolutely diagnostic that this is AVNRT. So that's the next thing we are going to discuss. How do you differentiate JT from AVNRT? So what do you do is you give PACs. Now you can give late PACs or you can give early PACs. I'm going to initially talk about late PACs because that is something that we had proposed. And you can read a review article that I had written with Mel and Mohammed Hamdan. I can send you guys the, you know, the thing for that it was in Cardiac Electrophysiology Review, which we wrote in about, I think 2003, where we proposed this. And we also had a chapter in Zeit's book where he had written about that. So what we said was we give a late, so how do you differentiate early versus late PAC? Basically you divide the RR interval into two halves. If the PAC falls in the second half, it is a late PAC. If the PAC falls in the first half, then it's an early PAC. And the early PAC also has some implications, which I'll show you. That was published by Padanilal with Dr. Przyszkowski's group. And that is used more to make a diagnosis of JT. So if you give a late PAC, these are the three things that can, four things that can happen. Number one is nothing happens. So what you do is you, after the PAC, the first thing to do is to make sure you're not holding the QRS complex right after the PAC. So either you pull it in, what you do is you pull in the next HISS. Either you pull it in, you push it out, you terminate tachycardia, or you can do another interesting thing with the late PAC. You pull in all the A's, but the HISS marches through. And I'll show you examples of all of these that can help you differentiate. In fact, I think nowadays when you do SVT studies, instead of doing ventricular overdrive pacing or atrial overdrive pacing, you should try to give PBCs or PACs. They are more helpful because when you do overdrive pacing, it invariably will terminate the tachycardia. And so then you can't get much information out of it. So this is an example of a patient where a patient had an AONV tachycardia, and we tried to differentiate between JT and AVNRT. So we give a late PAC. Now initially when we said we proposed that the PAC should happen when the HISS is committed, it really doesn't matter. You don't have to be that sophisticated. You just divide the RR interval into two halves, and the PAC should fall in the second half. So you have a PAC which falls in the second half. You know all the A's are captured because you can see the coronary sinus A's have been pulled in. So the first thing to do is to make sure you've not captured the V right after that. So this HISS to HISS interval is fixed. Now what has happened is the next HISS has been pulled in. So if the next HISS is pulled in, does it help us make a diagnosis of AVNRT or JT? Well, you can have a junction that is firing, junction like a focal firing, focal firing. The reason it got pulled in is because you have a patient with dual AV node physiology. The PAC went down the slow pathway and pulled it in. So pulling in doesn't help you make a diagnosis of AVNRT or JT. So that can happen even in JT with dual AV node. But this helps you make a diagnosis. So this is something that I, you know, we only sent an abstract in 2007, but we sent it to heart rhythm. This was a case that I showed you, a patient where the atrial overdrive pacing led to initiation of PAC and it looked like junctional tachycardia, except what we did was we gave a late PAC. So here you can see, you can hardly see the PAC because the stimulation is right here. You see the stem here? If you see a blade approximately here, you can see a stem. So we're giving it, we always try to give it from CS proximal. And the reason is because you want to be very close to the AV node. If you give it from the high right atrial catheter, you can do it, but it's chances of it going into the circuit are much less. So give it from CS proximal. This is given after the HISS is committed. So it's a very late PAC and the tachycardia terminates. So there are two explanations why it terminated. One is that you can say it collided with the retrograde P wave, which was coming up the fast pathway and terminated. But I think most likely what happens is that it goes into the anti-grade slow pathway, which is the, you know, the link that is more, that is the part of the circuit that is more susceptible to be any kind of perturbation. And so this late PAC goes into the slow pathway, which is the critical slow circuit and it blocks and it terminates. So this is absolutely diagnostic of atrial tachycardia, I mean, sorry, AV node reentry tachycardia. Why would it do nothing in junctional tachycardia? The junction is firing here. It's firing here. It fired here. Now it might have collided with the PAC, but the junction is still fired because we know that it captured the V. So what is preventing the next junctional beat from coming? I mean, it's a focal firing. Why would this PAC suppress the next junctional beat, which was supposed to come from here? If it had to suppress, it would have suppressed this beat, but this beat already happened because you saw a V. So there's no way a late PAC can stop a junction, a focal junction from firing, but it can go down the slow pathway and stop it. So that is why this is absolutely diagnostic. Now this is another example, just to prove the point that you don't really have to give the PAC after the His-Ace committee. So here you can see the PAC is there, but it is late because if you divide the RR interval, it's in the second half. And again, it's an A-on-V tachycardia, and you can see that the His-to-His as going on at the tachycycle end, this PAC occurred late. It did not affect this V and it terminated the tachycardia. So this is absolutely diagnostic that this is AV node pre-entry tachycardia. Now, when do you have to deal with this? Some people will say, oh, junctional tachycardia is so rare, you know, I really, if I see A-on-V tachycardia, I don't have to worry about it. The main time this comes into place, like the case I was doing yesterday, a patient sometimes does not have an easily inducible SVT. You have documented SVT, and then you go into the lab, you find dual AV node physiology, and you say, let's say this is AV-NRT and let me do slow pathway modification. And there is enough data that that works. This is a publication from Dr. Moradi's book, but he showed that if you have evidence of dual AV node physiology and you have undocumented SVT, you can modify the slow pathway and that helps the patients. So I did that. After I did the modification, I got some junctional rhythm. Now the patient had very easily inducible A-on-V tachycardia. And I would just do it and it would just keep getting induced. And the second thing I found was no matter how many PACs I did, I even did atrial over type pacing, I could dissociate the A. So I started thinking more and more whether this is junctional tachycardia and not AV node re-entry. Because if it is junctional tachycardia that is happening because I've irritated the junction, I don't need to do any more. But if it is AV node re-entry tachycardia, I do need to do ablation because the patient will keep on having it. And so that is where differentiating JT from AV-NRT is very important. And so giving this late PACs will help you make that diagnosis. So this is the same thing. Now, this is another example of a patient in SVT. And I think there'll be a question that follows this. So look at this very carefully. This is something I wrote up with Dewey who used to be a fellow with us at UCSF and now then he went to Denver and now he's joined us back at Stanford. So this is a patient at baseline. This patient has AV dissociation, as you can see. He doesn't have, you can see the junction is firing and the sinus is firing. This is a high-low activation pattern. So there is no JA conduction. And this was on isopril. Then at other times, this patient would go into an SVT, which was an A on V. So when you see this, you usually think that this is just a junctional firing because there's no association with the A, which is the example I showed you earlier. Now this patient goes into A on V tachycardia. And this same diagnostic maneuver is performed. We give a late PAC and these are the findings. They're giving you the timings after that. Now you have to use this to try to give a diagnosis, whether this is junctional tachycardia, this is parahysian atrial tachycardia, this is atrial tachycardia arising from the crista terminalis or is none of the above. So the choices are again, junctional tachycardia, parahysian atrial tachycardia or atrial tachycardia from crista or none of the above. There was a question about PACs to distinguish junctional from AVNRT. Any utility to early PACs rather than late PACs? There is a utility to early PACs. I'm going to show you that later on. So I started with the late PACs and then I'll show you the work by Dr. Przyszkowski's group how you can use early PACs also. So what I drew is I don't time the PACs to the SVT. I just send the PACs at a slower rate. So like if the tach is going at 400, I'll just start pacing CS proximal at 800. So then the PACs will happen randomly all over the place. It's easy to do. You don't have to sense it and time it. And then you can go back and look at what happened to all of those PACs. But yeah, there is definitely a utility to early and I'll show you that. So it looks like most of the people have answered and most of the people got the answer right. And so that means people are paying attention to what I'm saying. So the answer that they said is none of the above, which means that they're implying this is AVNRT and pre-entry tachycardia, which is what this is. So this is the third response you get to the late PAC. So what happens here is you have an A on V tachycardia. At baseline, I showed you there was junctional prism because there was no conduction between the J to the A. The patient had had a prior ablation done, which is probably why there was JA block because they had done extensive ablation in the slow path area. But then the patient was able to go into an A on V tachycardia. And when you give a late PAC, here what has happened is as you can see by the timing, the next HISS is pushed out. When the next HISS is pushed out by capturing the A, then you know that this slow path is part of the circuit. You know it cannot be junctional tachycardia because the junction would have fired at the same cycle length. A PAC happening over here would not have affected the junction to be firing late. It could only affect the junction here, it could not affect there. So a PAC which pushes out the next HISS, which means that it has gone into the slow pathway. Either it could have terminated or push it out. These are two are absolutely diagnostic. This is just like giving a V on HISS during an AVRT. If it terminates or pushes out the next HISS, it is absolutely diagnostic of AV nodal re-entry tachycardia. Okay. So this is something I want you guys to remember and use it a lot instead of doing atrial overdrive pacing. So now we look at the role of early PACs. So this is a work done by Dr. Pistovsky's group. So now you divide the RR interval again into half and you give a PAC that happens in the first half of the RR interval. If a PAC happens in the first half of the RR interval, you can look at what it does. If it captures the next V, remember in the previous one I told you whenever you give a late PAC, it should not affect the V that happens right after it. This case, when you give a PAC, it actually pulls in the V right next to it. And the way it is pulling in is pulling in through a fast pathway because it's a very short AV interval. And if you propose this was AVNRT, it was going down slow and up fast. So going down slow, up fast. Now you already captured down with a fast. So it cannot go up fast. So technically if it was AVNRT, the tachycardia would have terminated. So if you give an early PAC, it captures the V with a short AV interval and the tach continues, you have proven that this should not be AVNRT. And then by default, this should be junctional tachycardia. So that's the proposal that they have. And I think it's a very sound proposal to make a diagnosis of focal junctional tachycardia. So this is one diagnostic maneuver that would be diagnostic of a junctional tachycardia. If you give an early PAC, it pulls in the next V with a short AV interval and the A on V tachycardia continues. This proves that AVNRT is not the diagnosis. Now the only caveat to this or only exception to this would be, and we have seen some of these cases, is you could have double fire. So even though this terminated the tachycardia. So because you cannot go up fast now, because you've gone down fast, it's possible this did this, and then it restarted tachycardia by at the same time going down the slow pathway and then reinitiating tachycardia. So you could have terminated and reinitiated. That is very rare, but that is an exception to this rule that you should remember. But for all practical purposes, you show this, you can test it all the time. When you have a junctional rhythm, when you do a slow pathway modification, or sometimes you give a little bit of isopril after that, you get a junctional rhythm. Try giving PACs and you will see this. You'll see the capture with a short AV and the A on V tachycardia continues. So this is another example of a patient that we had in our lab. So this patient was sent to us for a redo procedure. And I'm showing you the SVT that the patient has. Spontaneously, the patient has AV venky bar during tachycardia. So do you see that? AV is prolonging and then keeps prolonging and then it blocks at one point. And then it starts doing the same behavior. So usually when you see this, most people will think that I've got blocked to the V, it's most likely going to be an atrial tachycardia. And the person who had done this procedure before, they thought that they had a parahysian atrial tachycardia. They mapped it in the parahysian region and they thought it was parahysian. They tried to do some ablation in the right parahysian region. They did not get an effect. They were worried about AV block. So they sent the patient to our center saying that, you know, if you need to map on the other side or, you know, do other things, you should do that. But that's the finding that we have in this case. So this is the diagnostic maneuver that was done. We did the same thing. We started giving PACs during tachycardia. So we are giving PACs and this is the PAC that is given. And then there are certain things that are measured over here for you. So now I'm going to give you a question about this here. So you have a short RP tachycardia going on. A patient also had AV Wenckebach during this tachycardia earlier. And you give a PAC and these are the findings. So these are your choices, atypical AV NRT, parahysian atrial tachycardia, parahysian AV reentry tachycardia, or we need more data. a close tie between atypical AVNRT and more data needed. Okay, so most of the people think we need more data and then that's followed by the second most common is atypical AV node re-entry tachycardia. And the right answer is atypical AV node re-entry tachycardia. We don't need any more data and I'll show you why that is the case. So initially when you saw AV Wenkebach, you would think more of atrial tachycardia. So that's right. You can also have AV node re-entry tachycardia because in AV node re-entry tachycardia, the AV node, A and V are not part of the circuit. Remember, AV node re-entry is just happening in the AV node. Both the atrium and ventricular are not obligatory parts of the circuit. So you can have block to that. In fact, it's very common in typical AV node re-entry tachycardia, sometimes you get two to one conduction. This is more of an atypical, this is a short RP. So what happens? The HISS is marching through. You give a PAC, you see all the A's have been captured. Gave a PAC from the CS proximal, but you can even see in the high right atrium, you captured all the A's. So you captured all the A's, but the HISS is marching through at the tachycardia cycle. So when you do that, you have dissociated the HISS from the tachy, the HISS is going at the tach cycle length. You basically dissociated the A. Okay. So you've dissociated the A from the circuit. You cannot have atrial tachycardia as a diagnosis because A has been pulled in and the tach continues at the tach cycle length. If it was atrial tachycardia, this HISS would have been pulled in. This tells you that the HISS is driving the tach. So it's an SVT where the HISS is driving the tach. The only SVT where the HISS is driving in the tach is going to be AV node re-entry tachycardia. It cannot be parahysian AVRT. It cannot be in both. Both ATAC and AVRT require the atrium to be part of the circuit. So this was a case which was, and this is a real case we had. This was referred to us as parahysian atrial tachycardia, but because of this diagnostic maneuver, we proved it. And we were actually on the left side mapping this, and then we did these maneuvers and this happened. So we said, this is an AV node re-entry. So we just went back to the right side, did a slow pathway modification and got rid of this atypical AVRT. Nitish, a couple of people asking, what ruled out junctional tach for you in this? So junctional tachycardia, one thing is that it usually is an A on V tachycardia. And so that is one thing, but otherwise, yeah, you're right. This doesn't, this diagnostic maneuver does not rule out junctional tachycardia. This only rules out atrial tachycardia and AV re-entry, but JT would also be part of the circuit. Usually it doesn't happen with a long JA, but it can. Okay. So let's go to the next one. Any other questions about this? Okay. Let's go to the next one. So this is again a cartoon from Dr. Przyszkowski's paper in Jack, where he's showing you that the role of early PAC in diagnosing a junctional tachycardia. So if you give an early PAC and it conducts with a short PR, short AV interval and the tach continues, it's JT. If you give an early PAC and it terminates, then it is AV node re-entry tachycardia, because the junctional tachycardia has nothing to do with that. It should not have terminated. The early PAC would not have terminated the junction firing over here. And this is an example that I showed you earlier, which is the same thing. You give an early PAC, it happened and the tach continues. Okay. So there is another diagnostic maneuver that you can use to differentiate junctional tachycardia from AV node re-entry tachycardia. And this was published by Sai Ewai when he was in Stony Brook. And now I think he's in Westchester County. And he showed that you can do atrial overdrive pacing during tachycardia. And then look at the end of that, try to tell you what the tachycardia is. So if you have a junctional tachycardia where the junction is just firing, you start doing atrial overdrive pacing, A goes to B, A goes to B, A goes to B, you stop and the junction has to take over because it's like a focal tachycardia. So you stop this, the junction takes over. So what you will get is A, H, H, A, right? Because this A went to this H then and caused a V and then the junction has to fire and cause tach. So there will be another H. On the other hand, if you have AV-NRT going on, so in AV-NRT you're going down slow, up fast, down slow, up fast. So you start pacing, the atrium will start overdrive, will capture the circuit and overdrive pace in the same way that the tachycardia is going down, which is it will go down slow, up fast, down slow, up fast. So when you stop, you will have an A, H, A because you are just doing the same thing that the tach is doing, A, H, A. You will not have a A, H, H, A. So this is a very good, this is another diagnostic maneuver you can do. The only problems with this maneuver is many times when we start doing atrial overdrive pacing, it terminates the tachycardia. So if it terminates, it doesn't help you. The second issue with this is, which I've noticed sometimes is that you can have termination while you were doing atrial overdrive pacing. And when you stopped, you could start AV-NRT with an A, H, H, A response, which is a double fire. So you went down slow, fast and slow. So it will give you an A, H, H, A response, which can look like JT, but it is actually AV-NRT. So those are the caveats you have to look at. And that is why I personally favor doing PACs rather than doing overdrive pacing. And the same reason I do PVCs rather than ventricular overdrive pacing, when you're trying to differentiate A-tach versus AV-NRT or AV-RT. So this is an example from their series. So what you're doing is you have an A on V-tachycardia, which you can see on the right side. You're pacing the A which goes to the V, A which goes to the V. And then when you stop, you can see that there is an A, H, H, A response. So that is a junctional tachycardia. This is another patient who has an A on V-tachycardia. So now you have to know which A is going to which V. So that is very important. And the way to tell that is you start somewhere down, when you stop pacing, you take the Hiss to Hiss interval, like more than a beat away. So you take the Hiss to Hiss interval somewhere here, you start going back. When you start going back, then you will know where the cycle length changed. So if this was marching at this cycle length, then I would have said, this A is going to this Hiss, this A is going to this Hiss. So that is very important. And that is a very important thing to remember when you look back at these things. So I always go two beats out, start from a Hiss to Hiss interval here, go back. So I know that till here, this was tach. And so the overdrive pacing only captured up to here. So that is important over here. Here what is happening is this A is going to this V. Because if you just look at it, it looks like A, H, H, A, but that's not true. This A is going to this Hiss, then you get A, H, A. And the proof is the cycle length. The Hiss to Hiss is 300, whereas cycle length of the tach is 320. So it's a good maneuver to remember and do, that you do A, H, A versus A, H, H, A. Just remember the caveat that sometimes you can terminate and restart with a double fire. The last thing that I want you to remember, sometimes this can happen to you. So I wrote it up with one of my fellows, Marwan Rifat. This was how we could initiate tach in this patient. This diagnostic maneuver is how to differentiate the mechanism of tachycardias. So junctional tachycardia is a triggered mechanism, whereas AV node re-entry is re-entry. And this you can use in PVCs also. If you have a PVC or a VT, which is triggered versus re-entrant, same kind of phenomena will happen that I'm going to show you here. So what is happening is you're pacing the A and A is going to be, you pace the A here and that goes to this V and then you have A on V tachycardia that is starting. Normally you would think this is atrial overdrive pacing and the junction started firing and you got a junctional tachycardia. But I showed you, you could also have a double fire where A is going to this V for a fast pathway. A goes to this V through a slow pathway and you have an AVNRT. So how do you tell this is JT or AVNRT apart from doing the PAC thing? Just by initiation you can tell. So the answer is if you keep bringing in the S2, if the S2 keeps coming in and that prolongs the timing from the stem to the hiss, that means it's a re-entrant circuit. That means to go down, it is causing delay as you're bringing the A2 inside. So that would argue for re-entry. Whereas if this was a triggered rhythm, the more you would bring the S2, the closer this hiss will come to you. So in a triggered mechanism, if you did A1, A2, the tachycardia that started, if it was triggered, would have come close to you rather than going away from you as you brought in the A2. And so this is how we diagnose that this was AVNRT and not JT, even though we are doing atrial overdrive pacing to start it. Because the more we came tighter, the longer the AH is coming. So just remember, this is something you can use for VT diagnosis when you're doing ventricular overdrive pacing to trigger or to initiate a re-entrant VT. So how do we ablate these patients? We basically ablated them using mapping the earliest A. So at some point they would always have earliest A during tachycardia. And so we would associate the A from the V by giving PVCs and look at the earliest A, which could either be in the CSOS area or the hiss area. And then we would go and map over there and try to ablate. You always have to use a mapping system. So this is one mechanism where we gave a PVC to dissociate the A from the V. If you don't have AV association, then we just use ablating in a stepwise fashion, which is we start off at the slow pathway region and then we go to the fast pathway. This is an example of a 3D map where you have the hiss points marked here. And this was ablated, junction was ablated in the CSOS area. This is an example where the junction was ablated in the area very close to the fast pathway. These are all the hiss points that are marked. In our series, we had most of them coming from the posterior septal area, two of them in the mid-septal and two in the anterior septal. I think if you use a good mapping system, you can get away. And we didn't have, we had one patient who had transient AV block, but did not have permanent AV block in these patients. Okay now we go to another kind of SVT and this is a patient who again has A on V tachycardia as you can see over here. Okay. So the first thing people see this, they say, okay, this is probably either it's an AV atrial tachycardia with a long A to V or it's AV node re-entry. You know, it's not a pathway because the A and V are too short, AV relationship, VA relationship is too short. So this is what happens. Give VOD and it terminates the tachycardia. Okay. So look at that carefully and I'll give you choices based on this, what do you think is the diagnosis is. Whether it's A to V tachycardia, AV node re-entry tachycardia or a pathway or a junctional tachycardia. So based on the response, you have to tell me. Nitish, maybe I'll ask you a few questions while they're looking at that. What do you quote as your incidence of heart block if you go after the junctional tachycardia? What do you tell the patient? The same as what we tell them for parahysian atrial tachycardia. In fact, there is less incidence of AV block with junctional tachycardia than parahysian atrial tachycardia. Usually, you know, say two to 5%. Two to 5%. Okay. And then do you ablate it during the tachycardia or during sinus? No, during tachycardia. We mapped the earliest day and then we just ablate either, you know, most of the junctional tachycardias are incessant or with isopryl, you can get them to sustain. Yeah. That was another question, whether isopryl makes a difference with these tachycardias. Yeah. For junctional tachycardia, we've noticed it does sustain it. And then there was a question about the early PAC maneuver. Is there any chance that you put in an early PAC, it depolarizes the junction and then that terminates the tachycardia, even though it's junctional tachycardia? The answer, it would not. And I'll go back and show you the slide because if you see the junction has already fired, then you give a PAC and that PAC has gone and captured the V with a short AV interval. Okay. So how can it affect the junction? The junction already fired and you gave it within the first half. If you gave it in the latter half, you can say you did something to the junction, but you could not be affecting a junction that was going to fire say at, because you say gave the PAC, the cycle length of the junction is 400. You gave the PAC at 200 millisecond cycle length. You know, that is how you would be early PAC or less than that. So say 150 coupling interval, how can that go and affect a junction that is going to fire 350 milliseconds later? It's not likely to do that, especially one that has just fired right before that. Whereas in AVNRT, you can, you know, especially you've captured the V. So, you know, you did go down the FAST pathway. Yeah. I put up the poll here for you. Okay, that's good. So everybody knows what my third topic is. So they got this answer right, that this is a concealed nodal ventricular tachycardia. And you should know why this is not AVNRT and that's very important to know. So usually when we see an A on V tachycardia, we do ventricular overdrive pacing. The reason we were doing ventricular overdrive pacing is we were trying to see whether we have a VAV response or a VAAV response. Because if you have a VAV, you rule out A-tilt tachycardia, and then you can modify the slow pathway, but it terminates. So when it terminates, you always go back and see. It could have terminated by pulling in the A, which would not have helped you because that can happen to both A-tach and AVNRT. What happened was it terminated by blocking to the A. So whenever you have a PVC that terminates an A on V tachycardia by blocking to the A, by VA block, it's not A-tilt tachycardia. So you've proven that this is not an A-tilt tachycardia. So we were very happy. This is not A-tilt tachycardia and this should be AVNRT. We can go and do a slow pathway modification. However, pretty soon our happiness was not long lived because when we looked up at the surface, we know that this V that terminated is a fused V as you can see. This is a pure V and this is sinus. So this is a fused V between this and that. A fused V terminating an AVNRT is not possible because it cannot go into the junction. Because the AV node has fired, the hiss has already fired, right? If the hiss has fired, there is no way for a V to go down, go up the right bundle into the junction. The hiss is already fired. It's going to meet refractedness and not be able to go. The only way this V can ever go and affect the tachycardia is if it is going up an accessory pathway. Right? This is just like giving V on hiss during AVRT. Absolutely diagnostic that a pathway is present, except we know that there is no extra nodal pathway. Extra nodal pathway will not give you a VA timing less than 60 milliseconds. So you should, you all know that, you know, we rely on that 60 millisecond VA timing published by Bendit. And then I think septal VA, 70 milliseconds were published by Fred Moradi. And the pediatric people have published saying that, you know, 50 is the new 70, which means in PD patients, you can get a pathway with a VA timing of about 50 milliseconds, a septal pathway. But we know that this VA timing is very short. It cannot be an accessory pathway. So you have proof that an accessory pathway is present and it is integral part of the circuit. But how can that be? It's not an extra nodal pathway. So the only answer is it's a nodal ventricular pathway. And that is the circuit that I drew earlier to show you, and we'll show you an example of that. So this should be absolute. This is what got our interest into this field. And we then collected more of these cases and prove that. So this is a cartoon showing you a concealed nodal ventricular fiber or nodal fascicular fiber on the right side. So you have the AV node goes down into the right bundle and the left bundle. So in this case, the tachycardia circuit is going down from the node into the conduction system over to where the fiber is, which in this case is attached. We are saying it is attached to the fascicles and then it comes up through that. So the circuit is like this. So you gave a V on HISS. So when you give a V on HISS, you know it cannot go up the conduction system because the HISS is already fired. So the only way it goes up is it goes from here and it causes you to have block into the A and terminates the tachycardia. So AV, it behaves just like AV node reentry, except you show the presence of accessory pathway, integral presence of an accessory pathway. That is how you diagnose concealed nodal ventricular or concealed nodal fascicular fibers. It doesn't matter which one it is because you always burn at the proximal end. So the diagnostic maneuvers for this is you exclude an extra nodal accessory pathway. So the way we did it most of the time is you have to show block to the A. That's how you exclude an extra nodal accessory pathway because in extra nodal accessory pathway, atrium is always integral part of the circuit. And so if you have spontaneous VA dissociation or you give A's and you dissociate them from the V, that is proof enough to show that you have AV. So you don't have an extra nodal. Then you show all diagnostic maneuvers that prove that AV node is an integral part of the circuit. So whatever you do in AV and RT, all those things are positive. And on top of that, you show that an accessory pathway is integral. And there are different ways of showing this. One is by looking at a V on his that terminates or a V on his that pulls in or pushes out the next his or you see you get bundle branch block where the HV changes and that leads to change in the tachycardia circuit. So this is an example of the other one. So this was a patient who has again an SVT because we know the HV, you know, his is driving the circuit. There is a his before every V even though it's a wide complex tachycardia. And there is VA dissociation. A is just marching through. In this patient, when the HV prolonged by about 20 milliseconds, the tachycardia cycle length went up by 20 milliseconds. So the patient goes from right bundle to left bundle branch block aberrancy. The HV goes out by 20 milliseconds and the SVT cycle length goes out by 20 milliseconds. So HV prolongation leading to either HA prolongation or tachycardia cycle and prolongation is absolutely diagnostic that a fiber, ventricular fiber is part of the circuit or an excessive pathways part of the circuit, except in this case, the excessive pathways attached to the node. That is why you have AV dissociation because an extra nodal would always require AV dissociation. This is another example. This was one of the patient in our series given to us by Mark Josephson. He had a very interesting case where the patient had AV dissociation for sure and had sometimes had right bundle aberrancy, sometimes had left bundle aberrancy. And he showed that there is a fused V over here that then pulls in the next V and that proves that the V is part of the circuit. So it's just like a fused V during aberrant SVT that pulls in the next HISS or the next V. This is another diagnostic maneuver that you can do that is a little bit easier to do than sometimes doing ventricular overdrive pacing. And this is called HISS overdrive pacing. This was published by David Singh and Mohan Viswanathan, our fellows, and Mel was the senior author on this. What you do in this is you can do it in any SVT. You just do overdrive pacing from a catheter at the HISS position. So just like you do parahissian pacing in sinus rhythm, you can bring an RV catheter very close to the HISS and do high output pacing from there. And what you do is what we've shown is in this paper that if you capture within two beats of showing HISS capture, if you capture the A, that means that the HISS and V are integral part of the circuit and it is not AV and RT. Whereas in AV and RT, you will need more than two beats of HISS capture to bring in the A. And this is something to prove or absence of presence of the fiber. So we did this in many... So many times you can do this in AV and RT patients and in patients who have A on V tachycardia. If you do this and you pull in within two beats, then you are proving that a concealed node of ventricular fiber is present. The last thing that we do to prove the presence of an accessory pathway in concealed node of ventricular fiber is looking at the HISS activation when you give a ventricular extra stimuli. So when you give ventricular extra stimuli, the HISS should be activated retrogradually. So the HISS activation will be distal to proximal. But if you give an extra stimulus and the HISS activation is proximal to distal, you have proven the presence of an accessory pathway. Now, this thing doesn't prove that it is an extra nodal accessory pathway. It just proves an accessory pathway is present. You will see this fighting even in a extra nodal or a node of ventricular accessory pathway. But if on top of this, you have an A on V tachycardia, then you prove, or you have tachycardia where the VA is blocked, then you prove that it is a concealed node of ventricular fiber. So in our series of concealed node of ventricular tachycardias, we had AV dissociation in all of them, because that was the only way to prove that an extra nodal pathway is not present. We use a V on HISS. In some patients, it delayed the next HISS. Some patients, it advanced it. But in most patients, it terminated. And then we had all other parameters that favored the fact that when you do the RV pace in SVT minus S, the pacing, it was more than 85 milliseconds. And this is something I think Dr. Knight and when he was with Dr. Murady, they had shown this as a way to differentiate atypical AVNRT from AVRT. All of those parameters were favoring AVNRT, except we proved the presence of a concealed fiber. Again, AOD during tachycardia. If you did AOD, AH during AOD minus AH during SVT, and the difference is more than 40 milliseconds, that favors AVNRT over an accessory pathway, AVRT. This is published, a stuff done by again, Dr. Murady's group, Mann was the first author. And in our series, this favored AVNRT. So we had all the parameters that favored AVNRT, except we showed the presence of an accessory pathway. Bundle branch re-entry, a bundle branch block leading to increase in cycle length, parahysian pacing showing the presence of AV nodal conduction. So the diagnostic maneuvers that we used were diagnostic maneuvers that prove the presence of AV node, the tachycardia being AVNRT, except on top of that, we showed the presence of an accessory pathway, which is integral to the circuit, which is parahysian pacing, HISS overdrive pacing, which I think is an easier thing to do, a ventricular fusion with a ventricular overdrive during SVT, which terminates, which is the example I showed you, or programmed RV stimuli that shows anti-grade activation of the HISS. So finally, this is my summary slide. The three forms of SVT that cause VA dissociation or VA block are focal junctional tachycardia, AVNRT, or nodal ventricular slash nodal fascicular. Initiation dependent on critical AV delay is not required for focal junctional tachycardia. So yesterday, the case that I had, every time I initiated that, even after ablation, it would always require a critical AV delay. So that's why I felt that it was not a focal junctional tachycardia. Late PACs help you make a diagnosis of both AVNRT and nodal ventricular, will not do anything to focal junctional. Early PACs will pull in the V with a continuation of tachycardia that is absolutely diagnostic of focal junctional tachycardia, but should not happen in either of these. Atrial overdrive pacing during SVT, in junctional, it'll be AHA, whereas both of these will give you AHA response. And then all diagnostic maneuvers for the presence of pathway, which is V on His, cycle length change with bundle branch block aberrancy, or anti-grade activation of the His, are only seen in concealed nodal ventricular or nodal fascicular tachycardia. So that's my last slide. I'm open to- Thanks so much. So there were a few questions that came through for the nodal ventriculars. One was, what happens with parahysian pacing during nodal ventricular, if you have a nodal ventricular pathway? With a nodal ventricular pathway, when you do parahysian pacing, it'll give you an activation pattern just like AVNRT. Because from the node to the atrium, it's the same way as the node goes to the atrium. And then- The only way to prove it is to do maneuvers during tachycardia. Because in tachycardia, then that fiber will not be able to, because the fiber is going to that AV node. And going up from the node to the atrium is dependent on just the node. But when you do it during tachycardia, if you give PVCs and it's a V on His, you know it cannot go to the A. Or you do a His overdrive pacing, which is like parahysian pacing during tachycardia, then it'll capture it within two beats. And then there was a question, if you have a bystander, nodal ventricular or nodal fascicular, and it's connecting to the fast pathway, and you have typical AVNRT, could you terminate with a fused V? I don't think you can terminate. So this is a difference between our group and Reggie Ho. Reggie Ho has published some of these cases in, I think, Sarkaridney and E.P. And he's a good friend of mine, he's in Philadelphia. He says that you can pull it in. I don't think you can terminate. I think you can make a case, if you pull in the next day with a V on His, that it could be a bystander. But I think termination is very, you have to be very, very lucky to be able to terminate that. In all our series, we have proved to show that you can't go and ablate at a normal area. We have shown some potentials that are required that we have to see to ablate in these patients who have concealed notoventricular tachycardias. Yeah, and I guess that was another question. If you have a concealed notoventricular, and you do an empiric slow pathway, and it's still inducible, then how do you map and ablate in that situation? So if you, that is why it's important to do that. So in fact, you know, PD, E.Ps are a little bit smarter, or maybe they do more SVTs than we do. But they always give V on His during A on V tachycardia. Most of us don't. In fact, in adult, we say, Oh, it's an A on V, do VOD, VIV response. It's not A tach, let's go and do. But you should make a habit of giving PVCs or doing, if you don't want to give PVCs and look at that, you can do His overdrive. To me, it's more useful because a His overdrive pacing, if it captures always more than two beats, you've proven that the excessive pathway is not participating. But if you give V on His, it didn't come in, that doesn't prove anything. Only if it is positive. So you have to, you should do that to prove it is not concealed. If it is concealed nodal ventricular, I would look for potentials. We have shown that we have recorded those potentials of the concealed nodal ventricular that can help you target the site of ablation. Especially some of them were left-sided where we, you know, where the circuit was left-sided. So we actually had to go into the mid part of the CS to record those potentials. And we just got that paper accepted in Sarkarithmi and EP. So you can look up that paper for left-sided concealed nodal vesicular. How do we ablate them? What kind of, it looks like a potential, like a His potential in the coronary sinus, except you're like three, four centimeters within the coronary sinus. So that is what you have to map. The tricky ones are where the nodal ventricular fiber is attached to the fast pathway. In those patients, you know, you really have to go and ablate over there. You will never be successful in the slow pathway. So if you do a good slow pathway, you know, you do a slow pathway, you get junctional rhythm and you're still getting tachycardia, you should stop burning over there. Because you could have an AVNRT with a left-sided circuit where you don't want to really destroy the right-sided slow pathway, or you could have concealed nodal ventricular, nodal vesicular, where again, or you could have junctional tachycardia. So you really then need to do these diagnostic maneuvers, make a diagnosis. If it is concealed nodal ventricular or nodal vesicular, look for potentials. And those potentials in sinus rhythm look like, you know, basically a His, as if you're recording a His, but underneath the CS or within the CS. Okay, thanks. So I think Ahmed had a couple of questions. Do you want to unmute yourself and ask them? Thank you very much. This is very helpful for me. Very quick questions. If you have anteroceptal area, junctional tachycardia, the other side of the anteroceptal area, how to avoid risk of AV block, especially if the junctional tachycardia is incessant? Do you do overdrive placing and a plate and any tools to avoid this risk? No, I think that's a good point. It's just like doing a parahysian atrial tachycardia ablation, where you really have to densely map that area. Now we have a lot of good, you know, density. You have a PentaRay with Carto, or you have a HD grid catheter with the Abbott, where you can use, I would use those because they would give you really the earliest activation point. And you can see where the His points are, so you want to be away from that. So one of the slides I showed you where we do that, you can ablate over there in sinus rhythm or in tachycardia. We prefer to do it in tachycardia and that's what we do. You could do, you know, atrial overdrive pacing a little bit faster to show that your thing is, you know, if you don't feel comfortable with that, but if you mark the His bundle area in sinus rhythm or even in tachycardia, then you know where you can be. So you map it very carefully. Usually the exit of the junction is not exactly where the His is. It is a little bit away from it. Thank you. The second question is, do you have a stepwise approach to map the nodal ventricular or nodal vascular? Dr. Shaman sometimes say you ablate the slow pathway and it's usually, sometimes it is conceived nodal vascular, but we didn't know it. Do you have a stepwise approach how to search for this? I think what I would recommend, one thing is, you know, we are all in a rush. Sometimes people just put two catheters and they see an A1V tachycardia and then we should spend a little bit more time. I would say whenever you have an SVT, give PACs and PVCs. You will get a lot of answers to that. One of my former fellows at UCSF, Adam Lee is writing something with me on looking at PACs and looking just at a response to PAC and making the diagnosis of all forms of SVT. I would say just spend a little bit more time because I would think that the 10% of the AVNRTs that people are not successful are most likely either they are left-sided AVNRT or junctional tachycardia or concealed nodal ventricular. So you should spend a little bit of time to make that. If you make a diagnosis of concealed nodal vesicular, then I would look for some potentials. If you don't find, then I would start with the slow pathway region. I would definitely go into the CS to look for potentials over there. The case that I showed you where the V on his terminated the A on V tachycardia. In that case, we found in the mid-CS a his-like potential. And then we have two or three other cases from Dr. Pak Chu in Cleveland, but they also had that. And that is why we wrote up that series describing the left-sided concealed. I think you're looking for potentials is very important. The fast, the ones which are inserted in the fast pathway region, usually they present with a very fast, almost aberrant, like the case I showed you from Dr. Josephson, where it is very fast tachycardia and there's usually AV dissociation. And those are the ones that are attached right next to the fast pathway region. Thank you very much. Much appreciated. Variably that leads to prolonged PR interval because you do do some damage to the fast pathway.

supraventricular tachycardia

SVT

differentiation

diagnostic maneuvers

AV nodal reentry tachycardia

AVNRT

junctional tachycardia

premature atrial contractions

ventriculoatrial dissociation

concealed nodal ventricular tachycardia

ablation techniques