Chapters Transcript Video What's New in Conduction System Pacing It's been very exciting for us to talk about conduction system pacing because it has been almost half a century that we were so used to the classic RV apical pacing. So when conduction system pacing came about, then it's become more and more data and it's become fast paced. So for this afternoon, we'll delve on these different topics and conduction system pacing, we'll talk about the conduct the con confirmation of conduction system pacing because it's not just we drill a lead in and that's it because there are certain criteria that we have to fulfill before we say it is conduction system pacing, we'll talk about guidelines and um they, they're the guideline that came about uh last year and um the conduction system pacing that has been used for um cardiac resynchronization. So over the years, we have noted that there is uh the synchrony caused by the traditional RV apical pacing. And I would include left bundle branch block with that physiology because here looking at the right upper portion, you can see um the activation of, of the of the heart that goes from the right and the earliest in being the left lateral wall um in blue, which becomes the latest. And as we know if that early activation occurs, it contracts early and the late activating segments of the um of, of the left ventricle. Um Over time, the, the synchrony will cause a lot of impact to the heart like LV, the impaired relaxation, there's ad adverse remodeling um long term. So this has been recognized over the past several years and that's why in the most recent guidelines, they have indicated that if we have substantial RV pacing, that we cannot minimize by our programming, whether we, you know, prolong our A V delays, make it a different setting. Then we should always look after these pacing induced cardiomyopathies in patients with chronic left bundle. We always have to have periodic assessment of the LV function. And how did they define the substantial pacing which I'll, I'll talk about later. Historically, they've mentioned 40% but there are more data showing that as low as 20% RV pacing can actually cause this. Um the synchron uh substantial um pacing causing the synchrony. So what is cardiac physiologic pacing? Basically, the goal of that is to restore um or preserve synchrony of the ventricular contraction. Um There are two ways to do the physiologic pacing. The first one is the conduction system pacing wherein we use the patient's intrinsic conduction system. So we can do it via the hiss or the left bundle um branch area in its fascicles. The other one is the card, the C RT for this purpose, the C RT will be used as the traditional biventricular pacing. This is when we put a lead in the in the Coronary sinus. The differences between the two is that there is already a lot of randomized control data supporting the traditional bi ventricular pacing where whereas the conduction system pacing, we we just have a lot of observational data this year, the past two years. However, there there is a lot of randomized control trials but um there are ongoing. So conduction system pacing basically delves on the recruitment of our own intrinsic conduction. Whether it's in the higher part of the conduction system, it's in the HS bundle area or in the the lower which is the left uh bundle branch area. So it really depends for the his bundle. What output you give, whether you go selective or non selective. When you go high output, you recruit the the, you know, the myocardium around your conduction system versus your left bundle branch area pacing. And all part of the area of the left bundle branch is involved. So it could either be a septal pacing LV, septal pacing or a nonselective left bundle branch area pacing, which we will, I'll show you earlier uh later, what is the difference between, you know these? So his bundle uh pacing has a lot of data already showing its superiority over RV pacing. However, it's, there's a lot of challenges with the his bundle pacing. So if, if you look at it histologically, the his bundle area is very challenging. It's very small area and it's encapsulated by a fibrous tissue. So it's really hard to penetrate and you have a very small area to work with. Um and there is a problem with the threshold with the sensing. And because of that, now we've switched gears to the left bundle branch area pacing. So when we look into our fluoroscopy, we kind of see where the his bundle area and then we approximate around one cm from that area to the apex. And that's where we will target for our left bundle branch. Um uh where we would put our lead technically is less challenging because as you can see here in the picture, you see a lot, you have a big area to work with, you can start from the basal septum, mid and apical. So versus the hiss, you just have that small area and um it's a higher, um it's in case in dense muscle rather than the fibrous tissue. And because of that, you have lower thresholds. And here is just an example of how an EKG would look like if you had um either of the two. So here is uh the general term for the left bundle branch area pacing. So uh in the magnified view on the right, you would see the different aspects of the septum. So the first three being the LV septum, if you're just in the middle, just beyond the RV septum, and then you have the actual bundle branch and then the non selective is when you capture the bundle branch, it's hard to see the number three there and the surrounding myocardium and those um three are the area pa the lbbap and anything that is more superficial is the RV septal pacing. And that is why in our lab staff will witness here. We are very oc. Every time we see the depth, we always stop, we just, you know, turn our leads just because there is AAA big discrepancy later with the data if um depending on the depth of um our lead. So here it's um showing that, you know, deeper into the interventricular septum, there will be different levels of uh the synchrony on the first panel, you, you can see here in the RV septal pa um pacing. So um up to down in the legend there, you will see V one on the top and then V six you would see on the X axis will be your QR S duration. All right, for the RV septal pacing, you will see you have a wide QR S and the main dis synchrony happens when you go to the left side to the LV, right. So that's where your um EKG of V four to V six. So you have a good septal V one to V four, you have synchrony. But when you go to the left side, that's the the synchrony and that's what causes your QR S duration to be long. Now you go deep, even with just five millimeters, you see that the the synchrony is improved, the the depth of around, of obviously, this is a person to person, right? We have different like um septum uh thickness, but at around a few more millimeters, you already go to the deep septum and that's in the sea. You have the best um interventricular synchrony with that and you have the narrowest QR S duration and then as you go deeper, then you go to a a deep, deeper part of the LV septum, which could also be the nonselective, really depends on the output of, of um testing that you do as you can see in the deep septum that there is a little bit the synchrony in the, you know, the RV side. But the the majority of the LV activation, as you can see in both lower pa well, coming from C to E from V four V five to V six, it's very good um uh left lateral wall kind of activation. So um this is the reason why we are very strict now and later guidelines have even put it um there that there are certain criteria that um that if we have really captured conduction in in the left bundle branch area. So this is the uh criteria we will go. Um I'll talk about some of the more common ones that we use in the lab. So the LV subtle pacing is when you're just deep and you can confirm it once you see that R prime. So seeing that R prime in V one, it's not automatically a left bundle branch capture. And you would maybe like hear us when we go turn our leads, you're like, oh there's an R prime. So that's not necessarily left left bundle area uh pacing. So there are different um other criteria that we have to um satisfy before we say that we are capturing the conduction system. So the most common part is what we call the L VA. Basically, it's just the R wave of the V six. So we measure from our pacing spike to the R wave of our V six. So here in the uh in the picture here, you can see that pacing spike, we're measuring it to V six. Why? Because the LV is our measurement to know the local activation of your LV wall, right? The V six being in the lateral part of the chest. So we use that um as that's one of the most common um you know, g uh criteria that we use. So less than 75 is nearly specific for a non specific left bundle capture. The best balance will be about 80 to 85. However, there is a limitation, right? If you have a dilated heart or if you have a very sick conduction system, the time that takes from your pacing to the left of the lateral wall will take time. It does not mean that you haven't captured your left bundle. It just means that it's so dilated that for it to travel or your conduction system is just so sick that it just really took time to go to the um left lateral wall. So um what did they uh say would be maybe a good kind of um correction is that if we have a wide bundle branch, like a left bundle branch or a right bundle is to change it to maybe about 90 to 100 to take into consideration that myocardial or that, you know, conduction system, disease delay. And as um you can see here in the lower um graph there that once we have that bundle branch blocks in our uh patient, there is really a big difference between the LV Septin and the bundle branch uh area pasting. So we have to look at other criteria here. Um On the right, upper part, you would see the difference between the LV septum and the non uh the uh left bundle branch area with non selective capture, you would see that the L VA right, that pacing spike up until the peak of V six is much shorter when you capture the bund, the left bundle, the second criteria which we don't always use, but looking at this art of all the guidelines and the article, it, it really makes sense that this one makes it more specific is the V six to V one inter peak interval. So V one, as we know as its place on the chest is at that area that is by the septum where you have kind of a great like where the RV conduction, the septum is right. So if you subtract the lateral, the V six to the more uh the, the seal area, then you would more or less know if you're capturing it um at a specific delay. So for example, if you're in the septum, if your lead is not into the bundle branch, just in the septum, you're obviously activating, activating the right septum, the RV. And um the uh the left lateral at the same time, but once you hit a left bundle branch um area, then your LV would be much, you know, farther than your RV. So you would basic this would basically correct the problem that I mentioned before. If you have a very deceased conduction system, right? Because your RV and LVS, they're gonna be affected at the same time. So even if that there's a picture here, the lower uh you would see that the L VA was 85 and you're now concerned, I'm like, am I capturing my left bundle? But what if this is just really a deceased heart, a dilated heart or you just have a bad conduction system. So you, you, the one thing that will make you more sure about it is you do this, the V six minus V one and it should be more than 44 another one that we look at and um that what's been straightforward before is looking at the morphology um when we decrease our output, right? So if we change from a nonselective to a L va seal one, you would see that it would prolong the um the measurement of your um L VA, lot of them are just very subtle uh things that we don't always see to be honest. So there are a lot of um you know, try registry mentioning and, and showing that the conduction system pacing compared to the RV septal uh pacing is much uh better and in terms of heart failure, hospitalizations, um you know, um all cause mortality, heart failure, I'm just going to go by that. Um However, a lot of our, our data are just really um non randomized right now. But again, there are more, a lot of studies that are ongoing. Um The next one is the RVP because we have a lot for the his bundle pacing. Recently. There has been more and more data about the left bundle branch area pacing, but basically a lot of of the improvements or the good outcomes for left bundle branch area pacing are for those patients who have been paced like more than 20% or the substantial RV pacing. And I know this is a busy slide, but I just wanted to show the difference between the 2018 and the 2023 guidelines. Whereas here in the e in the 2018, you see that there's not really much that talks about, you know, the definition of the substantial RV pacing. Whereas in the, you know, in 2023 here, you would immediately think about the consequences of substantial RV pacing. And here you would see that, you know, the conduction system pacing of the hiss and the left bundle branch pacing now have a two A or a two B indication. So again, just to reiterate um if you anticipate or know that the patient is gonna have an RV pacing more than 20 to 40% then it's worthwhile considering or not considering. But guidelines say that it is actually better to proceed with the conduction system pacing. So now we go to the traditional cardiac resynchronization therapy because that has been, there's a lot of data RCTS that support C RT. Um What um studies show is that the conduction system pacing is actually comparable. And later I will show you that's actually better in some patients. Um they cause narrower pace QR S duration, there's actually more physiologic because right, when you're using the actual conduction system versus A CS lead, you're pacing something that's epicardial, which we know is not the natural conduction of our, of our hearts. And um there are studies that show that there are better um response rate and clinical response um in the conduction system pacing. So here um in the new guidelines, it also shows that, you know, now it shows that if your C RT effective is not or cannot be accomplished. Now, you go to your conduction system pacing. So we have to always be, you know, um very conscious when we're putting a CS lead that putting in a lead there doesn't mean that you did your job, putting a lead, you have to think eventually is putting a lead there really gonna be effective. And what is it gonna be if it's non apical if you produce smaller QR S and that you have that target, which the best would be the poster lateral area. But if you cannot achieve those criteria, the best for the patient is not to just leave that serious lead. The best thing to do is to cross over and do the conduction system pacing. So once we put in our um conduction system pacing, that it's also always mandatory that aside from the 12 lead, of course, is to prove that you really have a capture. Just putting in something at the septum doesn't necessarily mean you are doing a conduction system pacing as what I've mentioned earlier. So this, this is a good study that's just um we talked about this in one of our uh you know, meetings about the importance of why it's important to know that this is not just LV septal pacing that this you're actually capturing the bundle branch. It's because here, um you can see that the L septum uh every septal pacing which is in the green has a higher risk for mortality, heart failure in patient if you do it for C RT purposes. So if you just put in, it just narrowed, it doesn't mean again that you're in the bundle branch area because it could be septal pacing. When you do that, then you can actually do more harm to the patient. So um same thing there and and here is just an all cause mortality, heart failure, hospitalizations when you clump up all the left bundle area pacing compared to biventricular pacing. And here you clearly have um a better outcome for the left uh bundle branch pacing. But we need more data for of course, the longer term outcomes because all of these data are still fresh and this is just um a few cases. This is back to back. Add on cases when I was a care place. I have a nine year old came in with a, you know, shortness of breath. It's very subtle but you see it's a complete heart block with a junctional escape and the QR S is just very narrow. It's 87. So imagine the injustice that you do. I know she's old but then if you just put in an R VA pacing and you might say, you know what, she's not gonna develop it pacing do cardiomyopathy. But just imagine how narrow her QR S is, how good synchrony there is. And then if you just do injustice and just pace her away when you can actually do a conduction system pacing. So this patient like we, I was able to get a, a narrower QR S and it, and, and it, it was not um it didn't luckily take too much time. And the thing for me, for older patients is to give me more solis that you're by the septum versus the apex where in patients have higher risk of perforation. Um And the second lady 87 syncope and as you can see here, she has a baseline by fascicular block and with bundle branch pacing. Um One of the things that makes me proud is if a colleague of mine reads this as a sinus rhythm without invention of pacing, I'm like, oh, that's a bragging, right? No one even noticed that I was facing this patient. And there are some, you know, cool papers telling us about, you know, EKG predictors when we have a good outcome. Um you know, that QR that we always looked at at the EKG, you know, the small R um versus the tall R and then the axis. And basically this um study shows that the morphology um or the transition during threshold test, uh testing, which is again a point where, you know, you're capturing your bundle branch and the morphology can actually predict in the improvement of your ef it did not show that there is an improvement of ef if just based on your L VA. But what it, one thing is for sure, if you see them for follow up and you lose that our prime or that L VA gets prolonged, then it's a, a predictor that you won't have a good response and that the pace cr Sis doesn't really matter. And finally, this is a patient of mine who had uh a complete heart block, had an E uh Pacer done in 2018, came in for heart failure. You see that the synchrony of the septum, the EF has gone down to around 25%. It's not actually even apical, it's RV septum as you can see by the, by the X ray and the EKG. But the QR S delay was around 160 milliseconds. And now we have him with the left bundle branch area pacing with narrow QR s and this is its ef now, which is um normalized and I don't know if you can see by the septum or that um left bundle pacing lead is as it like really pierces through the septum. All right. But definitely because this is still relatively new. There is a lot of studies ongoing. We have to know the long term risks with using this lead. We have to, um, compare them more RCTS and, um, there are some studies about CS P, preventing, uh, preventing, um, a FB, that's it. Published Created by Related Presenters Constancia Macatangay-Geronilla, M.D. Cardiology, Internal Medicine View full profile
BROADCASTMED