Management of the Patient after Conduction System Implant

Podcast Transcript

Announcer:

Welcome to Cleveland Clinic Cardiac Consult, brought to you by the Sydell and Arnold Miller Family Heart, Vascular and Thoracic Institute at Cleveland Clinic.

Thomas Callahan, MD:

I'm Tom Callahan with Cleveland Clinic and I'm joined by one of my colleagues here at Cleveland Clinic, Dr. Roy Chung. He is one of the leaders in our conduction system pacing space and certainly the operator here who has the most experience in conduction system pacing. So I'm excited to have him for the conversation today. Roy, welcome to the conversation.

Roy Chung, MD:

Morning, Tom. Thank you very much for the kind introduction.

Thomas Callahan, MD:

Yeah, of course. You were one of the very early adopters, not just here at the Clinic, for conduction system pacing. This was sort of something that seemed to excite you very early on.

Roy Chung, MD:

That's correct. I think back in 2017 or '18 or so, His bundle pacing has gotten a lot of traction around the country and it was a very attractive option as a pacing modality to avoid pacing-induced kind of myopathy. So we sort of dived in and embraced it.

Thomas Callahan, MD:

Yeah. And obviously we've seen the evolution since that time with His bundle pacing and all the excitement that surrounded that and then some of the frustrations and now all of the enthusiasm surrounding left bundle branch area pacing. You know, with any new technology and technique, I think there's early on going to be some variance in outcomes and part of how we manage these patients and these leads is not just during the implant, but post-implant. There's a lot of conversation I think on how to do a successful implant for conduction system leads and certainly some conversation how we manage these patients afterward. But I thought that's where we would focus today and how we manage these leads and patients after the implant.

Roy Chung, MD:

That is correct. Post-implant device management for His bundle pacing is very different than left bundle branch area pacing. The major difference really is the use of auto-capture. In patients with His bundle pacing, evoked response does not work because the His bundle signal is so small, therefore that is not an option. Typically the R-wave sensing is quite small as well. So I think in our institution we have largely abandoned the His bundle approach from what I understand. Conversely, in left bundle branch area pacing, everything we have sort of touched upon is the opposite. You have a much larger R-wave sensing. So auto-capture is a lot easier as well. The way I use it certainly is we approach it with a unipolar testing in the lab, but at the outset when they leave the lab, I am almost 100% all patients are programmed in a bipolar fashion.

Thomas Callahan, MD:

So this is interesting. So I want to go back to a couple things that you said. I think you're right, that there was more enthusiasm for His bundle pacing early and we're certainly seeing much less of that in our institution as left bundle branch area pacing has taken off. I think that's a really good conversation that maybe we should have at a separate podcast. Like how do, the patient selection, which patients are more appropriate for left bundle branch area pacing versus His bundle pacing? Because there's still a population of patients that may benefit from His bundle pacing as opposed to left bundle branch pacing, but I think that's a separate conversation.

So because I think the bulk of our implants, both at our institution and nationally, are left bundle branch area pacing, let's focus on that for the management, like the post-implant management. And so you were just kind of diving into that with how you program. I think there's variance there too. I think a lot of patients, the testing is done unipolar and so they're leaving the lab a paced unipolar. You're saying that you like to program them bipolar right out of the lab. So let's talk about how you're programming these patients as they're leaving the lab and why.

Roy Chung, MD:

So in our lab, we typically turn off the acute phase. Typically in patients who are dependent, the RV output or the left bundle pacing output, the lowest output we set at two volts with one and a half safety margin because typically in patients who have a quite successful implant, we find that the capture threshold is usually sub one, around 0.4 or 0.5 volts. So even at two volts, you have a two to three time safety margin.

Thomas Callahan, MD:

Right.

Roy Chung, MD:

We always thought about device infections and battery preservations and longevity and things like that. The use of auto-capture is actually the best approach and the best thing in these patients. I'm not too worried about lead dislodgement in these patients. So in patients who are dependent, we certainly even set up the lowest output really at two volts and then we turn off auto-capture. Obviously there are differences in different vendors. There's a little bit of a higher risk, but I think if one is comfortable with, you can certainly turn an acute face on for 30 days, keep the output at 3.5 volts for about 30 days, and then after that, just tweak it all the way down. I mean, I've never really set it at five volts at implant for 30 days and things like that.

Thomas Callahan, MD:

Which is what we typically have done for just our standard RV pacing lead implant. So our lab, we would typically set minimum of five volts for the first say four to six weeks and then at a post-device check we would turn it down and I think that speaks to some of the differences that we see, the stability of the lead and changes in capture thresholds, but also maybe just an evolution of practice over time where people are feeling more comfortable with lower margins or safety margins. But yeah. I think you bring up a great point that maybe with these, especially with conduction system leads, we can set that early safety margin lower. We don't have to go up to five volts, maybe we just start at two or have that 1.5 safety margin.

Roy Chung, MD:

Correct. I think that if the leads are pretty deep in the septum, at higher voltage you're going to have a nodal capture or septal capture at times that you just don't see the good QRS that you want. And then people start playing around with unipolar output. And I'm never a huge fan of unipolar configurations because I really don't think it matters. If you have conduction system capture, lower output at two volts with bipolar configuration works as well.

Thomas Callahan, MD:

Yeah. So you're not a great fan of unipolar programming to get that optimal QRS. Is that because of battery longevity with unipolar?

Roy Chung, MD:

No. It's just because it makes no difference.

Thomas Callahan, MD:

Okay. All right. Fair enough.

Roy Chung, MD:

In terms of, I mean you can have a very beautiful QRS, but physiology standpoint, I know they have proven that we don't really need selective left bundle branch pacing to preserve synchrony. Even in a patient with non-selective left bundle branch pacing, they do as well to prevent pacing myopathy. But the key is to have conduction system capture.

Thomas Callahan, MD:

Yeah. So you need to do that work upfront during implant and make sure that you've got a lead in good position during implant. But then once you do, maybe the programming, unipolar versus bipolar, as long as you have done the work to get a lead in good position, that's not going to matter as much as they're leaving the lab.

Roy Chung, MD:

That's correct.

Thomas Callahan, MD:

Yeah. And so you're typically programming people bipolar as they leave the lab. Anything different that you're doing at that post-implant check? Usually that evening before they leave or maybe the next morning before they leave the hospital, they'll get a post-implant check. Anything different that you're doing at those post-implant checks acutely that you maybe wouldn't do with a standard right ventricular pacing lead?

Roy Chung, MD:

No. I mean once we are pretty confident with the lead parameters at implant, we leave it at two volts. Bipolar configuration, auto-captures on the outset. Now in patients with CRT indications, those patients are a little bit more different in terms of approaches. How do you set up the AV delay and get the best optimal AV delay? So in patients with left bundle branch block, if we have just a dual chamber can, meaning we put a left bundle lead in the RV port, we set up the AV delay at a very, very short interval, as short as 40 to 60 milliseconds.

Thomas Callahan, MD:

Really? Okay.

Roy Chung, MD:

Correct, because you want to engage the left bundle system very early on to have optimal RV or right bundle fusion because otherwise if you set up too late, the left bundle activates right after the right bundle activation, your QRS is going to be not very optimal. The alternative actually is perhaps better to have a CRT can because you have much more options in terms of AV delay.

Thomas Callahan, MD:

And so with that sort of configuration, are you talking about having an RV lead in addition to the bundle branch area lead or are you talking about a lot CRT where you have a CS lead?

Roy Chung, MD:

So if you have a typical just an RV lead and you have an additional left bundle lead where the left bundle lead go to the CS port, that options allow you to have much more of a play in the AV delay settings.

Thomas Callahan, MD:

I see. Yeah. More flexibility there.

Roy Chung, MD:

Right. Correct. Now actually more and more so now for the past six months I've been sort of considering a LOT-CRT approach because then at the get-go, you have two really great options. If there’s left [bundle lead] micro-dislodgement where it's just septal pacing and these are such with CRT indications, I think it's best to just put up a CS lead up front. So then if one left bundle lead doesn't perform as well as you want it to be, let's say two months, three months down the road, the QRS is not great, then at follow up you just basically turn on biventricular pacing.

Thomas Callahan, MD:

Right.

Roy Chung, MD:

And that gives you a much better sort of an option. It prevents you from bringing patient back for let's say an upgrade per se.

Thomas Callahan, MD:

Right. Yeah. You're sort of beating me to the punch on one of my questions I wanted to ask, which is, for these patients that have CRT indications, you've placed a dual chamber system with left bundle branch area pacing, and they're not responding the way that you want say at eight weeks, 12 weeks, whatever, they're not responding. So what is your next move in terms of reprogramming or when do you start to think about a new lead position and would you go with just repositioning a left bundle or we put in CS lead. All of these questions are coming up so you're beating me to the punch, but your point is, if you just put in both leads out of the gates, you've got all of your options available.

Roy Chung, MD:

Yeah. It's sort of interesting back, and maybe you've asked me this question a year ago, I would really try my best to avoid bringing them back for a CS upgrade.

Thomas Callahan, MD:

Yeah.

Roy Chung, MD:

Just try to optimize the AV delay or the output and try everything possible. But more so actually in the last six months or so, I think we should avoid adjusting the programming because it's just not going to work. If we think it was a left bundle capture initially and somehow it has micro dislodgement, it's just septal pacing and they have CRT patients, I think it's just best to say, "Hey look, just bring them back for traditional CS lead upgrade," instead of trying a left bundle lead. I think it's not fair to just try another left bundle lead and just leave it at that. I think it's the best to bring them back for a CS.

Thomas Callahan, MD:

So they've proven failure for their first attempt at left bundle branch area lead so maybe go with something different for round two.

Roy Chung, MD:

Correct. Which BiV has been proven to do well. So I think BiV is going away. I think it's really a compliment to conduction system pacing.

Thomas Callahan, MD:

Right. I want to step back for a moment and talk about that patient again, a CRT indication, they have a left bundle branch area pacing lead that you were happy with the position when they left the lab, they're not responding. How are you teasing out whether there's a micro-dislodgement? What are the steps that you're taking to see, "Is this lead still where I want it to be or is it maybe a micro-dislodgement?"

Roy Chung, MD:

So that's a great question. In patients that you think they have perhaps adequate left bundle capture, but you're not so sure, we'll just do a 12 lead, do a unipolar testing if you will, and change from a high output to a low output.

Thomas Callahan, MD:

So kind of like what we're doing in the lab at the time of implant? Yeah.

Roy Chung, MD:

If things have changed, I'll do the interpeak levels, the right bundle pacing configurations, the LVAT, and just see if there's a change in LVAT time. Are they long? Are they short? If there's not much changes and the interpeak levels are quite short, then all you have is perhaps left septal pacing. There are times that the EF is quite low with CRT indications. It does take a while to get better, but if you have all those markers with left bundle captures criteria, then I would just hold off and bringing them back and see how they perform. But I think you can tease out the difference between left septal capture versus left bundle capture pretty easily on a 12 lead EKG.

Thomas Callahan, MD:

So if you do that testing, you've got this patient, they're not responding, you do that testing and they no longer have evidence of good left bundle branch capture, well then you certainly don't want to do anything with the programming, the timing. That's just not going to help. So then you're probably thinking about a new lead and most likely a CS lead. But how about those patients where you do the testing and it still looks like they've got good selective left bundle branch capture, is that a patient that you might have more enthusiasm about trying some of the programming, whether it's AV timing or other programming techniques, to see if you can hopefully get a response?

Roy Chung, MD:

Yeah. If, again, during follow-up testing and you're pretty confident that they do exhibit left bundle capture then I will give them some time. Even if it's just six months out, I will give them another six months to see how they do with follow up echo. There are times you can do a limited echo strain pattern or dyssynchrony pattern just to see how much dyssynchrony they have. Those are certainly challenging.

Thomas Callahan, MD:

Right. And I guess, as we start to wrap up, we'll think about the patients that were doing well for a while and now, maybe a year or two years out, now they're not responding. Basically the same thing? You're going to check for appropriate left bundle capture and then make your decisions from there?

Roy Chung, MD:

Correct. So some patients are a little different. So we have patients with let's say cardiac amyloidosis who initially did well and over five or six years time the EF starts deteriorating. Those patients, we again just look for strain patterns to see if there's some degree of dyssynchrony. We had actually a patient similar like this and we thought the CS upgrade will help, but eventually it really didn't help because it was the primary pathology deteriorating from that. So again, not all things appears simple per se. A lot of times we think it's a pacing-induced issue, but it may not be.

I mean we sort of have to, especially infiltrative cardiomyopathy, you're going to have to look at the whole picture and sometimes just the heart is failing. we had another patient that initially had good left bundle capture, but over time, over the years, he's developed worsening LVH and the lead just somewhat sat in the mid-septum and he didn't do well. And so those patients we just say, "Hey, you know what? Just come back. We'll upgrade you to a CRT system."

Thomas Callahan, MD:

Yeah.

Roy Chung, MD:

But I think as physicians, we have to recognize our limitations in these patients and say, "Hey, look. We thought we did a pretty good job in the beginning, but I think this is not going the way we want it to be," and just recognize that limitation and have an open mind and say, "Look, I think it's best that we bring them back early on,” rather to have that cardiomyopathy progress further down.

Thomas Callahan, MD:

Right. Yeah. I mean that's an area that we certainly need to improve. Trying to decide which patients with cardiomyopathy and conduction system disease will truly benefit from conduction system pacing. And it's the same thing with CRT where the response rates were around 66% or something like two-thirds, but there's still a third of patients that we're probably not selecting appropriately. And I think that's going to be an issue with conduction system pacing as well, that we just need to continue to study and try and get better at selecting which patients will truly respond because right now a lot of it is just you put in the lead and you wait and see.

Roy Chung, MD:

Correct. Yeah. I think bringing them back, I think for a LOT-CRT considerations are the best. I mean, you can take out the prior left bundle lead and put another left if you're going to do a CRT anyway. I think it's not a bad idea to, if you can give it a shot at getting a better left bundle.

Thomas Callahan, MD:

Sure.

Roy Chung, MD:

But at that same time, just put in a CS. There's nothing really wrong with that because then you have so much more options down the road.

Thomas Callahan, MD:

Right. Yeah. I think that's a great point. That's a great point. Well, Roy, this is a great conversation. I think there's so much more in this space that I'm excited to talk about. So thank you very much for joining the conversation and I'll look forward to talking to you more.

Roy Chung, MD:

Yeah. Thanks very much.

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