Hi everyone, I'd like to welcome you to our session on how to approach conduction system pacing. My name is Chris Patton. I'm from the University of Washington and I'm here with Gaurav Upadhyay, who's from the University of Chicago. I have some pre-notes for you, in addition to it being my pleasure to welcome you here to San Diego and the Heart Rhythm Society 2025 meeting. If you've not already done so, please download the HRS 2025 mobile app from your preferred app store. This is how you can participate in live Q&A during these sessions. Like this session. We want to know what your questions are. Please scan the QR code on the screen to access this session's Q&A. When using the mobile app, log in with your HRS credentials and please note that visual reproduction of Heart Rhythm 2025, either by video or by still photography, is strictly prohibited. Does that mean we can't post? I think we can take selfies. Huh. All right. Well, okay. It's red now. And now it's my pleasure to introduce Dr. Merrick Yastrzebski to the podium. There has really been a renaissance in pacing over the past decade and that's been driven by key physiologic insights. It's an honor to introduce Dr. Yastrzebski, who has been at the very forefront of making these observations to try to understand what areas are actually being captured. He'll be talking to us about how to implant stylet-driven versus a lumen-less conduction system pacing lead. Dr. Yastrzebski. Thank you very much for the kind introduction, ladies and gentlemen. So my talk is what are the differences between the stylet-driven and lumen-less leads when you pace the conduction system lead bundle branch. Actually I believe that there are much more similarities than differences because the indications are the same, lead bundle branch capture. Success rate actually, if you look at the studies, is more or less the same. Much more depends on the preference and your learning curve. For example, my success rate is much higher with the lumen-less, but we just talked here with the other speakers, and they prefer the stylet-driven leads. Much depends on your experience. Well, many important things like kind of injury during implantation, a curious morphology during implantation, capture criteria during implantation, all the same. So there are much more similarities, in my opinion, than differences. And this should be kept in mind, that this is just a tool that you choose. If you go to the septum like you see on this picture, you will see exactly the same thing regardless if this is lumen-less or stylet-driven lead. You will see how the kind of injury changes. You will see how the cures changes if you use continuous basing and continuous monitoring. So these differences do not overshadow overwhelming similarities. This is just a tool that you use for the same goal. Okay, let's look at the lattice leads. If you see the most popular leads, you will see that the tip to ring spacing is more or less the same. That they all have active helix. You will see that they all have steroid. That the helix length is more or less the same, 1.8 to 2 millimeters was the difference. But what is most important, they all use dedicated delivery sheets. So maybe the shape of the sheet is actually, and the stiffness is more important than the lead. So a lot of similarities, okay. But differences. Differences is the stylet-driven leads have a stylet, while the lumen-less don't have a stylet. So that's the bigger difference, and we'll focus on that in a moment. Then the lead body diameter is important. The fact that the lumen-less lead has a non-fixed helix, while the stylet-driven leads have extendable helix. But is this really a part of the fact that they have a stylet? No, this is just a design of the current leads, and in the future that will change. We all know that all manufacturers are trying to produce now stylet-driven leads that will have a fixed helix. So if you look at the detail differences, that they are very tiny. What is really, seems bigger here is, sorry for this, but I don't know how it operates. I don't see a pointer here. Okay, do you see a pointer? Pointer is only on my screen, sorry for this, but I can't use pointer. So if you look at the differences that really seem important, is that the footprint of the 3830, I have it here, but not anywhere else. Okay, okay, I have it, okay, sorry, there are three screens. So if you look at the footprint, that's a big difference. Why? Because the 3830 footprint is 1.5 square millimeters, like for example for tendril, it's almost two times more. So if you do many repositions, you may have a Swiss cheese effect with the tendril, but not necessarily with the thinner lead. So I think that's part of the design that will play a role in the future, and that is an important thing to consider right now. This is why I prefer the thinner leads, to have less damage. Also the cathode area may play a role to have a more selective capture. It's also a big difference, almost two times bigger cathode area for the tendril lead than compared to 3830. Okay, so what are the problems specific to the current stylet-driven lead design? Well, the helix retraction is the biggest thing that is a difference, in my opinion. And the damage to the helix extension mechanism, especially if there is a retraction and some tissue is caught there. This is something that we absolutely do not see in the luminous leads. And there are some problems that are facilitated by current design. And one of them is that the septal curve straightens when you have a stiff stylet, because it opens the curve in the catheter. My opinion, there are more late micro-dislodgements, because the stiffer lead produce more tension on the tip, and in my opinion, Soria tends to produce more micro-dislodgements. But this again might be much operator-dependent rather than design-dependent. The septal damage that I have mentioned, and also the lead fracture is something that is facilitated by the current stylet-driven lead design, but not necessarily by the stylet per se. It's just that the current leads are not so robust as the 3830. So lead screwing requires extended helix, right? So no risk of helix retraction with luminless, but there is a risk of helix retraction during screwing. Why? You see this on this picture. You screw the lead, and the helix, instead of going to the tissue, goes back to the lead. And actually, I think I've been the very first guy who observed that. We did this 2019 study of how the lead behave when you rotate it, cadaver model study. We described the screwdriver effect, entanglement effect, dip, and also the drill effect. But that study was only published on 3830. Why? Because we actually did also test the Soria on 10-drill, and I have observed that the screw retracts. My decision was that these leads will never be suitable for lead bundle branch spacing, so there is no point of publishing the data on them. So I've been wrong, of course, but that was my impression, because this helix retraction seems like a bigger problem, a big problem that is not unavoidable. But of course, you know that it is avoidable. All you need to do is to do a little bit of pretension. All companies came up with some kind of locking tool. So you do pretension of the inner coil, and then when you rotate it, the helix, instead of going back to the lead, goes into the tissue. So there was a solution to this problem. And why did we have this problem? Because these leads were not actually designed for lead bundle branch spacing. So now we have to fight with the problems that would not be there if we had a properly designed lead. Another problem is that the stiffer stylet produces opening of the septal curve. And you see this here. And actually, this is a problem if you want to really be directed by the sheath, but it's also a trick. You can use this to direct the tip more anterior or more posterior just using your stylet. So this is something you cannot do without a stylet, so with lumenless leads. And as you can see, if you are not aware of that, you will have an anterior jump all the time. But if you are aware of that, you may avoid that, then catch the lead to the septum, and then introduce the stylet for more stiffness and forward push. Okay, so another problem I mentioned is the lead survival thing. And there's an excellent study by Professor Puter who put together with Professor Gouri several thousands of cases, and they found that there is approximately 1% difference in lead survival, mainly because these leads with stylet are less robust, especially when they are slightly kinked or the penetration of the septum is at a very acute angle. But is it, again, related to the stylet or just to the care and the design of the leads that are on the market? I think the later, because I can easily imagine a lead that is stylet-driven and without these problems that lead to lower survival during observation. But what are the benefits of the stylet? Because I have only mentioned problems. There are benefits. Well, stiffer lead, everyone tells that this is a benefit because you have a better forward push, especially in fibrous septum, and you have a better torque transmission. This is true. But also to a certain degree, maybe large degree, offset by bigger footprint. So you have more resistance to the lead to cross the septum. And also bigger lead means, and stiffer lead means, more resistance and tension inside the sheath. So actually, the stiffer lead have a better forward push, but also more resistance in the tissue and in the sheath. So another benefit is that you have, as you see here, you can connect the alligator clip instead of the distal pin, you can connect it to the stylet and have a beautiful continuous recording of the cure as if you pace, or if injury, if you just monitor. And this is very important. You don't need any rotatable adapter, nothing. Just put the stylet on the stylet and you have it. And that would be number one for me to choose these leads over the lumenless leads, because I very strongly believe that this is the way to go when you implant. We have proposed that technique already in 2018. You constantly pace, you constantly monitor. Fortunately, if you do not have stylet-driven leads, you can have the same beautiful, continuous monitoring when you make a makeshift adapter, as we've been doing for many years, or if you use one of the commercially available adapters like Darius Chapman TorqueView or other adapters. And then you can have the same thing. But with the lumenless leads, you can have it for free. But the biggest difference is actually what you see here. This is the difference when you take the stylet-driven approach really seriously. Because we say stylet-driven leads. Are they really stylet-driven? All leads are sheath-driven. The stylet is there, but they are not driven by the stylet. They are driven by the rail created by the sheath, regardless if this is stylet or lumenless. But you can actually implant stylet-driven leads without a sheath, using just a stylet as a rail to provide support. And this is the study that shows that it results in pretty good results. Actually, this is not just a couple of cases. I know about 1,000 cases implanted in this approach in three centers in Poland. And the beauty of this approach is that you are not just limited to one or two, three sheath shapes. You can model the stylet depending on the anatomy. If the atrium is big, you make the first curve big. If you want to go higher, you make the curve more bent up. So this is a beautiful thing that you can really adjust for echo results and fluorescence to the anatomy of the patient. And then, as you see on this movie, you basically rotate the lead while keeping the stylet as a rail. And OK, let's see. Because this is really a very, very simple thing. So the benefit of that approach is that if the atrium is very big and none of the sheaths really guides you to the target, you can use this approach. And this is really the biggest difference for me between the stylet-driven and lumenless leads, that the stylet-driven leads enable this technique of implantation without a sheath. As you see, the stylet is kept still, and then you just rotate the sheath. But you have to have a pressure against the septum, so-called neck shape. And it produces excellent ECG, excellent echo, excellent everything. So this is the end of my talk. Thank you very much. Thank you so much, and we will have time for questions and answers at the end of the four talks. I'd like to welcome Francisco Zanon to the podium. He will speak with us about how to approach challenges and complications during conduction system pacing lead implantation. OK, thanks so much to the chair, thanks to the Aritm for this kind invitation. So my topic is how to approach challenges. So, just to start, challenges, which is a success rate, based to this study, to this European study, which more than 2,050 patient, so the success rate in BRAD indication is more than 90%, while in heart failure indication is 82%. And mainly, the reason of unsuccessful is independent predictor of failure are patient with heart failure, with large cure restoration, and with big heart. So if you go through our, we try to examine our population, so in recent year, we implanted more than 1,000 conduction system, of which, as you can see, 70%, two-third about was LB, and one-third, and one-third, I don't know if, here, and one-third are heat spacing. And the ejection fraction, as you can see, is a little depressed, cure restoration is like this. But if we look inside our success implant, is mainly, in which there are also patient with heart failure, we have a success rate of more than 95%. And the reason of this approximately 5% is described here, which are suboptimal electrical parameter, uncorrected bundle, interprocedural lead dislodgement, impossibility to penetrate the septum, mainly because it's stiff, it's fibrous, also severe right artery enlargement, and unavailable venous success. But why, if you compare with Melos, why we have more success, probably the reason is in this slide, because if we analyze, look here, if we analyze successful implant, in more than 30%, we change approach, so we use different lead or different delivery. So we had what we can call hybrid approach. And yeah, that was, so it's this one. And mainly is, there is not one clear rule, so in, we use more than two sheet in more than 150 patient, but you can see here that we change from one to the other. So from luminous to not, to style it, and also inside the same, we can also change from, also changing lead. And that's probably the reason why new, different, because it's not difficult, but it's, it could be, especially in challenging case, could be difficult. So know the materials and all the different tools could help in increase success rate. And so now I want to accompany you through some example. For example, this is a very giant artery. This is one of the most difficult challenging, and in this case, we, our, personally my first approach is always try to look for his, and in this case also look, this is very calcium mitral valve, and I don't know if it's working. So look, look, this is the wire, just to understand how big was this right atrium. And this is about the speed, we look for his, but as you can see here, without correction. So we try to move, and, but difficult anatomy, look, this angiography seems to be coronary sinus instead is the right ventricle. But at the end, we reach with a second different curve, and we could, and we could end up in successful implant low with transition. Another example, this is a LAO projection, we try, we try his first, as you can see also we have a sort of lesion in the his, which is one of the parameter what we look for when we try his, because he has predictable value on long-term result, but as you can see, there is a selective his capture without, and quite high threshold with the maintaining of the right bundle. So we move and try to go for left bundle, but as you can see, when we push here, it's clearly that does not progress. So what we do is change delivery, look here, there is the first one, so we go for the second one, seemed that was easy, easy to go, but also in this case, when we give more turns, the lead went back, so we go for, we go for a new position, but again, nothing, and at the end, when we use like what I explained also Marek before, we use, we change, so no material is important. We use a stylet, a firm stylet, more stiff stylet, and so we could get inside, and this you can see, which is with a small contrast inside, and when we, when screwing, we can observe and also here, you can see that the coil is going down, we have a lot of, we have a lot of, here, this is extra bit with right bundle, and this is the coil, you can see the difference, more bigger compared to, and so at the end, at the end, we have this from 70 to 80, so we look also for transition. But our approach is, and I think that you have to know both technique, I know that now we started this bundle more than 20 years ago, now it's completely abandoned from the majority of AP, but still, it's not because it's the first love, but it's because you have to know, it's a second possibility in case you cannot reach the left bundle, so it's worth to know both procedure, and our procedure is, because it is an AP procedure, once again, we don't use fluoro, just in this case, because we have a difficult, probably, in venous assess, and then it's just looking, just small maneuver, as you can see my hand, and just for looking for the hiss, like in this case, and this is a potential in filtrated and non-filtrated, and then when we try pacing with, apart from the good result, but there is no, here, as you can see before, there is a complete left bundle in this patient, but with no correction, still wide QRS, so what we do is, moving forward, and, so we move forward, sometime we use a little bit of fluoro, in this case, with narrowing, non-selective narrowing, so means capturing of the conduction system, and if you can see here, well, when also in, with the luminales, with the crocodile inside, I could turn, is a little bit different, difficult, sorry, but you can do, as you can see here, I can screw, and without, with the same, with the signals, and here, we do have the, and this is the correction, but we do some more turns, like in this case, and what we observe, look here, there is a potential, there is a cohesion potential on the hiss, very huge, and so, look here, so this is what we look for, and also in the, also in the, here, in the non-filtrated signals, and this one was, so, but due to the fact that this patient was candidate to a Blast and Pace, so we decided the hiss was, apart from the very good lesion, we decided to put also a backup lead, and see which is the best, so we went for, we went like this, with the second lead, and the second lead, we want, we don't want to put in the apex, but we look for, for a better result, so we went for LB, like in this case, so usually, I, in LAO projection, I always do some contrast, like in this case, and this is pacing from, from the right side, just to understand what, what we look is on the frontal axis, the D2 and D3, just to have some positive in D2, just to, to be in the middle, and then, and then we screw, sorry. Back, here is advanced, and here you can see an extra bit, okay, and then we pace, and we have a nice correction of the QRS, and this is an extra bit, this, usually we look for LB, when you start screwing in the, in the right septum, so the morphology is of right, of left bundle, and then you have, when you reach, you have a left bundle, and then you stop, and then, and then start pacing, and here you can see, when, when doing the maneuver, here there is a change, so here there is a transition, and the transition, as you can see here, so we have more than 10 milliseconds, and this is the final. So, just final consideration, how to approach challenges, so challenges are mainly due to anatomy, so the next consideration is improve your knowledge in anatomy, but not only in anatomy, but also in electrophysiology, and our suggestion is be familiar with different tools and technology, change all the tools, but also change from LB to east bundle, or the vice-versa, from east bundle to LB. Thank you for your attention. It's now my pleasure to introduce Dr. Amir Shrikar, who will be talking to us about how to achieve true conduction system pacing, which can sometimes be not so clear during cases, so looking forward to this presentation. Great, very good. Thank you for the kind introduction. I'm honored to be here to talk to you guys today about how to achieve true conduction system pacing. All right, just in brief, very high-level view, what is conduction system pacing, or CSP? It implies direct activation of the heart's conduction system by the pacing stimulus. Now, for the sake of this talk, to reflect the practice patterns in the field, I'll be focusing on his bundle pacing and left bundle area pacing. These are my twin girls, Emmy and Ella. They remind me a lot of his bundle pacing and left bundle branch area pacing. Because, like my twins, at first glance, there's a lot of similarities between these two modalities. But also, like my twins, there's a lot of significant differences that's important to know about. So let's get to it. I've broken out my talk into the following sections. I'll review his bundle pacing briefly. Very here, I'll spend the majority of my talk on left bundle branch area pacing and walk you through an implantation. And finally, touch on some differences between his bundle and left bundle branch area pacing. Let's start with the his pacing. So the concept of pacing the bundle of his is not new. It was actually shown back in the 70s they could pace that on a temporary basis. Now, fast forward a couple decades, and here you see in 2000, it was described where you could actually use a permanent pacemaker lead to pace the his bundle. You can see the, there's no pointer here, but you can see the permanent pacer lead coming in from above, and then from the groin, you have two mapping catheters. Fast forward another decade or two, this method has been superseded by direct mapping approaches using the lead itself and the sheath. But as some of you know, this approach may actually be useful for some very unusual anatomies. Integral to this are specialized leads and sheaths. The one that's probably the most well-known and prominent is the Medtronic 3830 SelectSure lead. This is a lumenless lead. And then the following three are the other manufacturers, FDA-approved leads for CSP. These are all stylet-driven leads. Hand-in-hand with them are the sheaths. All of them feature a fixed curve that has this out-of-curve, out-of-plane design to point you to the septum. Now, the degree of selectivity of capture of the his actually depends on the pacing output. So moving from left to right on the screen, you have higher output dropping down to lower output. Here in red, we see non-selective his capture. And you can tell that based on fusion of the QRS. So it's a hybrid between a paced, or sorry, RV septal endocardial paced QRS as well as a native QRS. And then also, the QRS itself starts immediately after the pacing spike. Now drop the output even more and then you see pure his capture in green. You can identify that by the paced QRS being the same as the native QRS. And there's a small, a short isoelectric segment after the pacing spike, which is equivalent to the HV interval. That's all I'm gonna talk about his bundle pacing. Let's focus on left bundle branch area pacing now. So what are we even trying to pace? So the left bundle branch area pacing is defined as capture of the left bundle branch. So we're aiming the lead for the proximal fascicle, or the proximal trunk rather, or some of its proximal fascicles. The left bundle, recall, ramifies very early into different fascicles and then to distal Purkinje fibers. But the proximal part is very much like a trunk or a ribbon that we're trying to stimulate. It actually sets up some challenges in terms of trying to get to it, very different than RV apical pacing or even his bundle pacing. Now collectively, if you stimulate the left bundle branch itself, the left side of the interventricular septum, or one of the fascicles, anterior-posterior, this collectively is known as left bundle branch area pacing. So I've broken down the implantation into a series of these discrete steps. Identification of the target area, transeptal penetration of the lead, confirmation of left bundle capture, which is very important, and then finally a few brief troubleshooting pearls, or troubleshooting and pearls. So first step is identify the area that you wanna be in. I work in the REO 30. Most of the time, you need to locate the hiss, either do that anatomically, based on the tricuspid valve, or an artificial, sorry, the tricuspid valve itself, or an artificial valve, or if you have your electroanatomic EP recording system, which I highly recommend, you can note the hiss bundle signal itself. Identify the apex, draw a line between the two, and clockwise rotate your sheath to get it through the valve, and advance it about one to two centimeters towards the apex. All right? Now once you're there, or sorry, this is if you use a TAVR valve, which is actually quite common, it's great, because in this view, well, in any view, actually, but in this view in particular, the left, this side of the, the most inferior portion of the TAVR valve itself is next to the non-coronary cusp, which, as you know, is right next to the bundle of hiss. Pardon me. All right. So once you're here, once you're in the target region, pace unipolar and assess that you're in the correct area by looking for the following morphology. These are all stylized diagrams, but the most well-known one is looking in V1, lead V1. You want to see a QS pattern with a notch in the nadir of that QS. This is known as the W sign. Also in lead two and three, you want to see lead two more positive than lead three, and AVR and AVL should be discordant. Now lead two and lead three can each be a little bit positive. They can each be a little bit negative. Each of those corresponds to the anterior or posterior fascicles. What you'd like to avoid is both of them being very positive, because that suggests you're probably in the RVOT. Now, in case you're wondering the reasoning behind this, this just reflects the anatomic location of the hiss. It's a little bit more posterior, inferior, and rightward. One way to think about it is a pair of hissy and PVC has similar deflections. Those are stylized diagrams. Here's an actual implantation on a recording system. You see this notched, the W sign in V1. You see two is more positive than three, and AVR and AVL are discordant. Moving on to the transeptal penetration of the lead, you can work in REO, you can work in LAO. In REO, you want to shoot for the trajectory of about one to two o'clock. In LAO, you want to be very perpendicular to the septum, which is typically right around two to three o'clock. Split the difference, and if you use about two to 230 o'clock in either view, that's sufficient. So if all the prefixation criteria from the previous slide are met, you want to position your lead like this, record baseline impedance, and then reconfirm the ECG characteristics and start spinning the lead. You want to break through that septum with some quick turns. Two different videos here demonstrating just how quickly to turn. The reason for this, I'll dwell on this a little bit more later, is to break through that septum, that sheen of the right side of the endocardial septum. On the left side, you see if you're doing this as a solo operator. With one hand, you hold both the sheath and the lead. On your right hand, you spin the lead. If you have the luxury of another set of hands and attending a fellow at tech, have them hold the sheath while you use both hands on the lead. This is a great video put up by Rod Tong a few years ago on Twitter, which shows the precise moment, as he's injecting contrast, the precise moment as the lead breaks through the septum on the right side. All right, sorry about that. Anyways, rotate the lead two to four turns at a time. These are whole body turns of the lead until this paced QRS goes from this W sign to resembling a right bundle branch block or a right bundle branch conduction delay, namely as manifest by that terminal R wave in lead V1. So that terminal R wave in V1 is what indicates that you've activated the right bundle branch with a delay, of course. Monitor the impedances the entire time. As you're driving the lead further into the septum, you want to see, or you will see the impedance rise, and then at some point it's going to back off and drop a little bit. Up to about 100 ohms is okay. That indicates you're approaching the left side of the septum. Beyond that, if you're getting towards 200 ohms, that's either impending or already perforated lead, so beware of that. Finally, optional is a septogram. You can inject contrast through your sheath in the LAO projection to see just how far your lead tip is driven into the septum. In this septogram I did here, this is the 3830 lead. The squiggly line demonstrates where the septum is based on where the most opacified part of the contrast is, and I know for this lead that's a 10.8 millimeter distance from the tip of the helix to the distal part of this ring, so keep that in mind. Also keep in mind the interventricular septal width of your patient to make sure you can try to avoid perforation. All right, probably the most important part of all this is now how do you confirm you have left bundle branch area capture? The most important criterion is this transition in the QRS morphology. So as you pace from a high output and drop it down towards a lower output, initially, if you're in the correct area, you should see a non-selective left bundle branch area morphology, a non-selective left bundle morphology. As you drop it, you should see one of two different morphologies, either LV septal pacing or selective left bundle pacing. Now just in the interest of time, I won't go into the details of those, but it's important to see this transition from non-selective left bundle pacing to either septal pacing or selective left bundle pacing. What else to look at? You can look at the LV activation time. This is defined as the time from the LV, I'm sorry, from V6, the stem spike, to the peak of the R wave in V6. Remember, in V6, that demonstrates your LV activation time. You want that to be short, and by short, we mean 75 to 80 milliseconds. You can also use this novel technique, this novel criterion, this V6 to V1 interpeak difference. This is the measurement of the time from the peak in V6, which is your LV, to the peak in V1, which is your RV. You want to see a separation here. You want to see the LV being activated much earlier than the RV. This is nice because the patient sort of acts as their own control, and you're looking for something long here, so 33 milliseconds is very good for very good sensitivity and specificity. If you raise it up to 44, you have 100% specificity. Now, if you don't have any of those, and all you have is that QR, you likely just have LV deep septal pacing, just right in the middle of the septum. Now, it may satisfy the needs of you and your patient, but just know that it's unlikely that it'll provide much resynchronization. And again, going back to the stylized diagram here, LV septal pacing would be this, septal pacing would be this, the one demarcated in red. This is nicely shown in 80 patients in last year's Heart Rhythm Journal, which showed that, again, that transition during threshold testing portended the best improvement in ejection fraction, along with the paced QR morphology. You want a little Q and a big R, as opposed to a large Q and a small R. So again, this stresses the importance of that transition of the QRS during threshold testing. If the implant goes well, you can get a nice, wide QRS left bundle morphology to a paced morphology that looks like the following. I'm running out of time, so I'll briefly go through this. Troubleshooting and pearls. Spin quickly, and you saw those videos, to impale the septum. As Marek and his study elegantly showed, there's several ways that the LV, sorry, that the lead can get into the septum. The majority of them won't get you to where you want to go. Only one of them, this screwdriver approach, really gets you to burrow deep inside the septum. Beware of perforating the septum. This occurs in about 2% to 5% of cases. Now, obviously, if you've perforated the septum, you're just going into the LV, so it's not going to cause tamponade, obviously, but there are some potential clinical consequences. As you're going from a shallow to a deep to a perforated implantation, you'll see the R wave abruptly drop. You'll see your capture thresholds abruptly increase, and you'll see the impedances drop, again, by about 200 ohms. You'll also see the current of injury decrease, and you'll start to see a negative component on that local electrogram. I encourage you to know the details of whatever lead you'd use, just so you know the distance from the tip of the helix to the ring, and keep in mind the separation, the distance of your own patient's interventricular septum. This patient in this implant, for example, this is the 3830, this is 14.5 millimeters from the tip of the helix to the back of the lead, but I knew in this patient his septum was 1.8 centimeters, so it was still okay. Finally, if the sheath doesn't get you to where you want immediately at the start of the case, I like to use a wire to either bring me to the RV apex or into the RV outflow track. I slide the sheath over it, and then pull it back slowly to end me up where I want to be, because usually when you push forward from the atrium, sometimes you'll get stuck in the trabeculations of the septum. Finally, this is sort of fun, but expect some calls, maybe from your imagers or radiologists, saying that your lead's perforated. Oftentimes you'll have this appearance, but in my experience, and it seems the same goes true for the field, if the electrical parameters test fine, then your lead is likely fine as well. It also sort of brings up that existential concept where if it is perforated, but the electricals turn out okay, does it really matter? Who knows? Very, very briefly, I'll touch upon this. In an ideal world, by virtue of the fact that can preserve and or restore biventricular synchrony, his bundle pacing would be the winner, hands down. But given a lot of these real-world constraints and some other realities of life, in terms of a learning curve, in terms of a target zone, in terms of stability of the lead afterwards, left bundle branch area pacing really has overtaken his bundle pacing as a predominant factor. Thanks. Thank you so much. I'd like to welcome Dr. Haran Buri to talk with us a little bit of a shift to how to troubleshoot programming in conduction system pacing. Thank you very much, Chris. Gaurav, ladies and gentlemen. So I'll be finishing off the session with programming. And my first question is, how do you do that? How do you do that? And my first disclosure here is that, for those of you who don't like technical talks about programming, sorry about that. But for those of you who like it or have to do it, well then, buckle up. So these are my other disclosures. And just a few general principles about CSP programming. There are different ports you can place your CSP lead in. It can be the atrial port, the right ventricular port, and the left ventricular port. And obviously, this is going to change the way that you're going to be programming your device. And there are quite a few permutations and combinations that you can see, and this is taken from our CSP consensus document. This figure was great fun to put together and even more fun to decipher. But it just shows you the complexity because it depends very much what the purpose of the CSP is, if it's antibody cardio pacing or if it's CSPCRT or hot lot CRT. It depends if the patient's in sinus rhythm or in AFib, where you won't need the atrial port other than for maybe connecting the CSP lead in. And it'll depend if it's a pacemaker or an ICD. Now the easiest configuration is if your CSP lead is connected to the RV port. And in this situation, it's pretty much the same as with standard RV pacing. The only difference is, well, that's for the VVIR, if it's a single chamber. If it's a dual chamber, also the same thing. And if you're using a CRT device, then you have to program a VV offset by pre-exciting the CSP lead. So you're gonna be programming RV pre-excitation with a VV offset, with RV first. The main issue that we face in this configuration are sensing issues if you've got his bundle pacing, because in this situation, very often, your R-wave amplitude can be quite low, say around two millivolts or even lower. And you may also be getting over-sensing of atrial or even his potentials. This is an example of a patient who had his bundle pacing. You see the non-selective capture, this is intrinsic rhythm, and dropped P waves. Now they're dropped because the his bundle lead had a significant atrial potential that was being over-sensed in the right ventricular channel. So you have AS, VS, and this withholds right ventricular pacing, that's to say his bundle pacing, that could potentially lead to a systole. Note that there's no ventricular safety pacing here because the atrial channel is being sensed. So you don't get ventricular safety pacing with atrial sensing, only with atrial pacing. So the way to get around this is then to lower the sensitivity of the RV channel. The CSP lead in the LV port, there are different possibilities to program. The easiest way is to program a VV delay, so you're going to be pre-exciting the LV port, that's to say your CSP lead. And if you want full CSP capture, you're going to be programming the largest VV delay that's available, usually 80 to 100 milliseconds. If you want to fuse that with the RV pacing, say in a patient with uncorrected right bundle branch block with his bundle pacing, you may wish to also have RV pacing and then you'll be narrowing your QRS, then you program the VV delay to get the narrowest possible QRS. This configuration is, the only downside with this is that you'll be automatically pacing the right ventricle because even if you're capturing from the conduction system pacing lead, the LV port, there will always be RV pacing afterwards because of the interventricular refractory period. And that's basically wasted energy unless you consider this as being backup pacing, say with his bundle pacing. What's very important is to inactivate these automatic CRT algorithms for AV delays because they're not designed for conduction system pacing. You have to inactivate also the ventricular sense response because whenever you get sensing, you will get automatically pacing. That's just going to lead to pseudo fusion, so it's a waste of energy. There's no point in that and it's better to turn it off. Finally, this is the most complex one if you have the CSP lead in the right atrial port. Now, you may have this if you're using the RV lead as a backup or if you're doing his bundle pacing or left bundle branch error pacing with by V pacing, say lot CRT, or if you're having an ICD in a patient with AFib. And in that instance, your ICD lead is, the purpose of that lead is to provide ICD therapy. And the CSP lead, which is connected to the atrial port in that patient because that patient has chronic AFib, will be the one that will be delivering the pacing. So this is one of the configurations. And you see if it's, you're going to be pacing through the CSP lead. You program an AV interval that's long, that's longer than the CSP to RV sensed interval. And then you'll just be getting CSP pacing and RV sensing, which is basically as a backup. It's important you can inactivate ventricular safety pacing because otherwise you will be constantly pacing from the RV channel and wasting energy. You can also inactivate the ventricular sense response because that also is wasted energy. And basically, your CSP lead is not there to sense the right ventricle because you've got a ventricular lead for that. Okay, so usually we run into over-sensing issues if the lead is placed in the atrial channel. And in that instance, it's best to program the lowest possible sensitivity. Usually it's set to four millivolts. And that usually gets around issues with his bundle pacing, but not so much with left bundle branch error pacing because very often the R-wave amplitude is bigger than four millivolts and you will automatically always sense that signal. So you always get a sensed VS and you can't get around avoiding sensing from the atrial channel. Very important, probably the most important message on this slide is that if you have a CSP lead plugged into the atrial channel in an ICD patient, you need to inactivate the dual-chamber discriminators because it's going to think that this is SVT, right, because it's gonna be ASVS for true VT. And you have to rely on the single-chamber discriminators for that. This is just an example here of a patient with his lead in the atrial port and we have flutter potentials here which are over-sensed by the device. And that's basically going to lead to withholding of his bundle pacing and delivery of conduction system pacing. So there, the way to troubleshoot that is to reduce the sensitivity to the minimum, say four millivolts. This is another instance in a patient with an ICD where the left bundle branch error pacing lead was plugged into the atrial port. This patient was in chronic AFib and if you program to AAI, what happens is you may get T-wave over-sensing. Now, this by itself is not dangerous, but the problem with T-wave over-sensing, it's going to reset your timing interval and you will be pacing at a rate that's actually lower than the lower rate interval and that could be an issue. So the way to get around this is then to program in DDD or DDI and you're relying on the ventricular sensed event to set a PVARP. So the T-wave will be over-sensed in the PVARP and is shown here by an atrial refractory event. So that's still inadequate, but will not reset the lower rate interval because any event that's sensed in a refractory period will not reset the timer. So here at least, you're pacing at truly the lower rate interval. There's no issue there of having inappropriate mode switch either because the counters simply won't be fulfilled for that. This is ventricular safety pacing, showing that to inactivate it, but you need to check for crosstalk before doing that. And finally, if you want to dig a little bit deeper because this was really very fast and I can realize that not all this information is registered well, if you want to dig deeper, you can look up these articles. And with that, I'd like to thank you for attention. Thank you. Thank you so much at a very rare early finish. So we're happy for that because we have more time for questions. I would encourage all of you to use the Q&A app so you can scan the QR code to submit questions. You can also come to the mic. I'm just gonna kick things off by asking a question here, open to the panel as all of you are experts in the field. I was surprised to see actually in the United States appropriate use guidelines that came out in 2025. So within the past couple of months, that in patients with sinus node dysfunction receiving dual chamber devices, that they actually suggested the conduction system pacing was only rarely indicated. It was a rare use of the R, the red box. Now, understandably, this is because the rationale of the guideline statement here is it's sinus node dysfunction. However, we know that some of those patients will end up needing pacing. So they're receiving a dual chamber device. So the question is for all of you here, how many times do you try when you're pursuing a dual chamber pacemaker and someone who you do not expect to have a very high pacing requirement, we'll say less than 20%, what do you think is an acceptable number of attempts to achieve conduction system pacing? Is intraceptal pacing ever allowable? And where do you draw the line in a procedure? I will start. I think that we try 100% because also the young doctors have to familiarize with. And so it's better that every implant is dedicated to, just to the first attempt. I think that if you implant the ventricular lead, there is a reason for it. So it should be a good lead. So I implant it without any difference between sinus node or AV block. Everyone receives conduction system pacing. Maybe I'm slightly less aggressive. So one, two, three attempts are definitely okay, but I wouldn't fight so long as for CRT case, for example. So there is a difference, but the difference is minor because if you do not think that this lead should be good, then do not implant it. Implant AI pacemaker. Yeah. I agree with what both of you have said. One thing I used to try to help guide me in terms of how aggressive I should be for trying CSP in someone who just has sinus node dysfunction is what I do is I, during the case, I pace in the atrium rapidly and try to see when they start to wanky balk. If it looks like they have a nice, very healthy AV node, I'm usually much less aggressive about trying to put something in the conduction system. If it does look like they wanky balk early on, like around 100 beats a minute, maybe even 120, then I try for some CSP. So it's actually not a rare indication because there was a publication by Pugel from the Medicare data and 37% of the CSP implants that you have in this country were for six sinus syndrome as the first indication. And I think for the reasons that we've already discussed, this is the reason why. So there's a rationale for doing it for sure. You start pacing the atrium, then some of the PR interval prolongs. You can, of course, wanky balk and test that, but how do you know in five years, how do you know about seven years, how's that AV conduction going to be? Some of these patients go into AFib. If they're very elderly, you have an option there if you have a CSP lead in just to ablate the AV node, which is excellent therapy, I think. Simple, effective, economical as well. And if you have a CSP lead in there, then of course you're able to do that. Initially, I think that was the last barrier for me. I was not so much implanting it in six sinus syndrome patients, but just like the other panelists, now I'm really doing it in all of these patients. And in our consensus document that you may have read, it just came out in Europace where HRS was also part of that document. We did not actually give a formal recommendation for CSP in six sinus syndrome simply because we don't have any data, we're not even talking about randomized data, but there's nothing about how these patients fare, how many of them will actually need pacing, how many of them are gonna need AV inablation. So we just did not feel comfortable with giving a formal advice on whether you should do it or not. But we actually included that in the text. And that's one of the things which is different compared to the HRS document where that was not at all, I think, spoken of. Thank you. And there's a question in the chat about left bundle branch area pacing for heart failure therapy, essentially. And if you have a patient with a failed CS lead, conventional CRT, do you use left bundle branch area pacing instead? Do you send to a surgeon for backup? And what do you think of the state of the evidence for CSP as a heart failure therapy while we're awaiting some of the randomized control trials? It's a very broad subject. So many sub-questions, like for a whole session. So I guess we have a simple approach. We use conduction system pacing for all CRT candidates, so not only for failed coronary sinus lead, but for everyone. Of course, if you do not follow that route, then the failed CS lead is definitely a very good candidate because what else you can offer him? Well, surgical approach is much more invasive and never producing such a nice result. So yes, you can do it. At the state of evidence, we have small trials and we have large observational studies, multi-center studies that show that CSP provides very good resynchronization in terms of QRS and in terms of clinical outcomes, but these are observational studies mainly. This is a quick question, and I realize that the session is actually ending, but I think this is an important one. So this is a beginning question, but really critical for the experts. So the question is, in patients where during unipolar stimulation, do you measure the stimulus to the R-wave interval in V6 from the beginning or the end of the stimulus spike? And if all of you can just tell us really quickly what you do, I actually do think this is an important question. It's really important. It's a really important question that's never covered. I think we do things different. I measure it from the beginning, and you can definitely, you know, you add 10 milliseconds to your R-wave peak time, and that can make the difference whether it's 75 milliseconds or 85, but from the beginning. Yeah, yeah, yeah, from the beginning in our lab. Beginning. From the leading edge, yeah, as well, because I don't think that it adds that much. 10 milliseconds? Oh, it does. Oh, yeah. Yes, I can tell you easily, depending how, what kind of system you use and how big is the, but beginning of the, on the EP system of the line is where the stimulus actually started. We know that there is a latency post-stimulus and latency in the myocardium, but this is a very clean moment to measure. So just taking away the stimulus doesn't make much sense. You can take away all of the latency if you want. That makes more sense, probably. It definitely, but the only sense it makes is you get shorter R-wave peak times. That's right, you feel better, yeah. Well, you heard it here first, everybody. You gotta measure from the beginning of the stimulation artifact. Thank you so much for this really very helpful session. I hope all of you have a wonderful day.

conduction system pacing

implantation

programming

stylet-driven leads

lumenless leads

septal penetration

oversensing issues

device settings

heart failure therapy