Well, thank you so much for allowing me to participate in this program. There's no way we can cover everything, so I just wanted to highlight a few pearls and then maybe we can elaborate, flesh these out during the discussion. I thought I would begin with the so-called nodal tachycardias, namely avianodal re-entry, functional rhythms, and in this schema, we're showing, does it, let's see, the arrow doesn't point to where I want it to point, okay, okay, so anyway, in this schema, we designate with the dark black arrow the fast pathway and the other arrow, scrunchy arrow, is a slow pathway and normally you're zipping down the fast pathway and you're blocking conduction over the slow pathway, so you have a normal beat. If you have a premature beat, you block in the fast pathway, go down the slow, down the wiggly line, and then you have a return beat, an echo beat, and this can eventuate into a sustained tachycardia. In the uncommon variety seen on panel B, it's the other way around. You have anagrade conduction over a fast pathway, retrograde conduction over the slow pathway, okay, so this I think is very well known to you. Now, what about the EKG, the classic EKG of avianodal re-entry? So we're sailing along in sinus rhythm, you can see the top two, this arrow doesn't want to move over, so anyway, I'll just have to talk my way through it, or if you have a pointer. For this to be successful, there's going to be lots of pointing. Yeah, so anyway, you can see the first two beats, sinus beats, then you see an atrial premature beat, with a marked prolongation of the PR interval, yeah, I can move it here, but it doesn't show up, okay, so that's one clue when you have marked prolongation of the PR interval, in other words, if you have a critical lengthening of the PR interval preceding the onset of the tachycardia, and then the next wide beat is obviously an aberrant beat from the atrial premature beat, and then during the tachycardia, we see path mnemonic changes that you see in typical avianodal re-entry. There's the pseudo R prime, if you look at V1, if you look at my blue arrow, you can see that little blip that was first taught to us by Dr. Hein Wellens, a pseudo R prime, and sometimes you'll see it in leads II, III, and AVF, a little negative deflection. Now, the reason it's a pseudo R prime is because the node is an interatrial structure, so that when you activate the node, you have rapid activation of both right and left atria, and so you get this narrow deflection, the so-called pseudo R prime. So these would be the typical features, oh, thank you very much, these would be the typical features of a patient with AV nodal re-entry. Now, a few points about AV nodal re-entry. AV nodal re-entry, as we pointed out in the schema, the critical circuit is the area around the AV junction, so that the atrium and the ventricles are not dependent on the SVT circuit. So here we have an example of a patient who's sailing along in a supraventricular rhythm. You have an atrial premature beat, you have a critical AH, and then you have initiation of an A on V tachycardia. But lo and behold, you have a P wave, you have an atrial deflection, and no QRS, okay? And this is seen because you're twirling around in the AV node, but there's anagrade block to the ventricle, and these are the his bundle recordings. So when you're looking at the EKG, and you see an EKG, narrow complex tachycardia, and you see a P wave right in the middle of two narrow QRSs, you immediately think of the possibility that this is AV node re-entry with anagrade block to the ventricle, okay? Now what does this signify when you see isolated block to the ventricle? Well obviously it cannot be an AV re-entrant tachycardia. It makes junctional tachycardia very unlikely. It doesn't exclude the possibility that you have an atrial tachycardia, and the atrial tachycardia just happens to fall in between, but it's less likely. This makes you really think of an AV nodal re-entry with anagrade block to the ventricle. Okay, on the other hand, you can have a situation where you have a supraventricular tachycardia, okay, and then suddenly you lose the atrial deflection. There's retrograde block to the atrium, and again, if the loss is midway between two QRSs, think first of AV nodal re-entry with retrograde block to the atrium, because the atrium is not necessary in AV nodal re-entrant tachycardia. So if you see this, if you see a tachycardia, you see an SVT looking at the surface ECG, and you don't need the atrium, you can immediately exclude the possibility of an AV re-entrant tachycardia, accessory pathway, or atrial tachycardia, okay? So this is, I mean, it's seldom that you can look at an ECG tracing and say, this is the precise diagnosis. More likely, what you do is you look at it and you say, what can I exclude and what's left? So for here, for example, I cannot exclude the possibility that this is a junctional tachycardia with retrograde block to the atrium, okay? That's rare, particularly in adults, but you can't exclude that. Okay, now let's look at this. This is another interesting arrhythmia, and very important clinically for a number of reasons. Here you have a situation where you have a supraventricular arrhythmia, and it's irregular, but there's a regular irregularity, there's short cycles, little longer, short, long. And then if you look for the P waves, which you should do very avidly in all of these supraventricular tachycardias, you can see that there's one P wave to two QRSs, one for two. And so this one to two response is best explained by going down the fast pathway, down the slow pathway, down fast, down slow. Now the reason this is extremely important is we've had patients referred for cardiac transplantation. They come in with heart failure, because they stay at a rate of 150, 160 all the time, because their sinus rate is 70, and it's a one for two response, so they're running 140, 150 all the time. So they develop a tachycardic myopathy. The cure is not a heart transplant, the cure is just simple slow pathway ablation. So these are the common nodal type of expressions of nodal tachycardias. Now I'm going to switch now to the issue of patients who come in with accessory pathway type tachycardias. Again, we can't cover everything, but I want to focus on a couple of important principles. So here's a patient who actually presented to us with a very bizarre QRS. Look, he's got a little R, a deep S, and lead one. His axis is way off to the right. It's a right bundle branch, and this particular patient was referred to us. He had coronary disease, underwent stenting, but his echo showed normal function, his MR was normal, actually. But he had this wide complex tachycardia, and he was referred for an epicardial ablation, which is not actually a bad idea. But during the study, it was clear that there was a hiss in front of every QRS, so this was just a very bizarre form of aberrancy. And the other thing that I wanted to emphasize is in SVT, bundle branch block is your friend. You don't have many friends, true friends in life. You've discovered that. I don't have to preach on that. For SVT, if you see an arrhythmia where you have a right bundle, left bundle, and normal, that is wonderful. So let's emphasize it. So here, for example, this patient was sailing along with a wide complex tachycardia, and here we have a left bundle aberrancy, and then we have a few beats that are normal, and then it goes off to a right bundle. Okay, now, with the left bundle aberrancy, the VA interval was 115 milliseconds. With the normal, or with the right bundle, it was 100 milliseconds. So the delta, the delta VA, when you lose the left bundle, is 15 milliseconds, okay? Now, we all know that when you have a circuit involving an accessory pathway, and you go down the AV node, if you have a bundle branch block ipsilateral to the site of the accessory pathway, the VA interval will get longer. That's well known. However, what's less well known is the fact that it takes about 35 milliseconds to cross the septum, so the delta VA, say, on the left side of the accessory pathway with left bundle branch block, would be expected to be about 35, 40 milliseconds, because it takes that long to cross the septum. Here it was 15 milliseconds, so what does that tell you? It tells you that the pathway is in the posterior septal region. Left bundle branch block with a delta VA of 15, 20 milliseconds puts the pathway in that left posterior septum. Alternatively, with a right bundle branch block, and the VA coming out 15, 20 milliseconds puts the pathway in the antraceptal region. This is extremely important. All you need is this observation, and you say, I know exactly where this pathway is. I'm going to look very carefully on the post-receptal region. You don't have to worry about AV nodal entry. You don't have to worry about all kinds of things. You have your diagnosis almost straight away. So bundle branch block is your friend. What other friends do you have? OK, so here again is a wide complex tachycardia. It's his spondylosis in front of it, so this is SVT, but this guy always ends with a narrow QRS. So when you lose the left bundle and you have a narrow QRS, tachycardia terminates. Why does it terminate? Because you lose the left bundle, you zip down the AV node, his axis, go up the left bundle, come back up to the atrium, you pull in the atrium, now the A blocks in the AV node. So when you see this pattern on EKG, left bundle, and it always ends with a narrow, it's a left-sided accessory pathway. OK, you can take that, that's money, take that to the bank. OK, now you guys will stop me whenever, OK? So because this, you can talk forever on this topic, but I just wanted to say that one thing that's very, very helpful are the simple rules that we have to try and morphologically distinguish left bundle and right bundle arrhythmias. So left bundle, this is something that Mark Josephson Kinwall taught us many years ago. You have a small R and a rapid descent, OK? When you see that with a left bundle, this is typical left bundle and points to involvement of the normal conducting system. VT is ugly looking, it has a broad R, a notch, and a long delay between R and S, greater than 60 milliseconds, OK? Right bundle branch block, as you all know, is RSR prime or RR prime, whereas if you have monophasic R or QR, this is VT. So these are extremely helpful. OK, I'll give you an example. All right, this is a young man, came in, had two ablations that were unsuccessful, and so here he has a Y complex tachycardia, OK? And we look at V1, and this is odd, because most, about 80% of the Y complex tachycardias will be VT. But look at this guy, it's a sharp, a small R, and a rapid descent. That's interesting. The other thing that's interesting, if you come along here, in V6, I'll show you a blowup in a moment, there is a beat-to-beat alteration on the T wave, OK? That turns out to be, that turns out to be retrograde 2-to-1 block. So we have a Y complex tachycardia that doesn't need the atrium, right? The atrium is recorded on every other beat. So this V goes back to the A, this V blocks, et cetera, et cetera. So here we have a pattern where the arrhythmia looks like it's involving the normal conducting system, OK, it's involving the fascicles, but it doesn't need the atrium. So one of the things, the first things you'll think of is this is a rare nodoventricular pathway. It's not atriofascicular, right? You can look at this and say, oh, this could be an atriofascicular, right? However, however, with an atriofascicular pathway, the atrium is part of the circuit. If you can dissociate the atrium, then this is diagnostic of a nodoventricular pathway. OK, and this is a nice depiction of it. See from the node to the right bundle and back up through the node. OK, this, I'm going to end with this, but this is a beauty. This comes from my friend from Dr. Mario Njim from Lebanon, and he shows me this beauty. So look at this. You have a patient who has a narrow complex tachycardia and then develops a broad complex tachycardia at roughly the same rate. OK, now, if you look at the narrow complex tachycardia, you can see that there appears to be a P wave here, here, and not here. So it looks like it's not associated with the atrium, OK? Let's look at the wide complex tachycardia. Wide complex tachycardia has a typical right bundle branch block pattern with a markedly superior axis. So this has a right bundle, left anterior fascicle block pattern, and this arrhythmia also has A-B dissociation. Here's a P wave here, here it is here, and here. So the sum and substance of it was this patient had a fascicular tachycardia. He had a tachycardia involving the fascicles, and one manifestation was a typical posterior fascicular tachycardia, giving you the right bundle superior axis. The other manifestation was a so-called upper septal ventricular tachycardia. This is very interesting because upper septal, this was taught to us by Mogami, these are instances where you go up the septum and you fire both right and left ventricles, and you can have a normal pattern. So these patients can have fascicular patterns, and if they zip up to the proximal his bundle or the his bundle itself, they can fire both right and left bundles and give you a narrow complex. Let me just show you a schema to better understand it. The fascicular system is much more complicated than Mauricio Rosenbaum taught us. There are really three fascicles, an anterior fascicle, a posterior fascicle, and a mid fascicle. Most people have this configuration. So the fascicles are wonderful, you get all kinds of beautiful arrhythmias. So the ones that we're most used to are the ones arising from the posterior fascicle, and they zip around in this fashion. But remember, you can have an arrhythmia involving the mid-septal fascicle, and if it gets onto the his bundle itself or the very proximal left bundle, it can fire both right and left ventricles and give you a narrow complex. So if you see narrow and wide, and the wide looks like a fascicular tachycardia, and you have AV dissociation, then think of a upper septal ventricular, upper septal tachycardia. Okay, so in conclusion, in conclusion, nodal arrhythmias, we said, can present with absent A or absent B. Bungle branch block is your friend. Morphologic criteria are very helpful for separating the two. Wide complex tachycardias with SVT morphology and AV block, think of nodal ventricular, and fascicular pathways may mimic SVT. Thank you very much. Thank you, Mel. We have time for maybe one question or comment or tidbit that anyone has. While the audience is ruminating about this excessively charming talk, as always, Mel, thank you. I think the important feature of this is that we should really go back to our roots. We're all, to some degree, invasive interventional cardiologists, and the key to this all is the EKG, which dates back to the early 1900s, and it's fascinating, and it's intellectually challenging, and the substance that we see from Mel's talk is it really lends itself to aiding you in doing invasive procedures, so you don't have to search around for things. You can pick up the diagnosis from the EKG.

arrhythmias

AV nodal re-entry tachycardia

EKG features

accessory pathway type tachycardias

bundle branch block

fascicular tachycardias