Hi, this is Eric Prestowski. Welcome to another segment of EP on EP. I'm delighted to have with me today Dr. Michael Gold, who is the professor of medicine at the Medical University of South Carolina. Michael, welcome to the show. Thanks, great to be here. So, what I'd like to talk to you today is about subcutaneous ICDs. You've been a major player in this field, and I wonder if you could take us from where you think the current technology is and current indications, and then we'll go from there. It's an interesting evolution. The original defibrillators as developed by Murawski and Mohr were simple shock boxes, and were very effective for saving lives. In the early studies that we primarily used as a basis for implanting defibrillators were largely shock boxes as well, with minimal pacing. And what we learned over time as patients lived longer and longer is that lead problems, both from systemic infection and lead failures, become quite common over the years, and that became one of the limitations or drawbacks of transvenous ICDs. So, the subcutaneous ICD was developed as a non-vascular system to defibrillate the heart, which had been shown to work very well. Early on, it was a niche device used largely in young patients, patients with no vascular access, channelopathies, hypertrophic cardiomyopathy, and a variety of groups of patients that were very atypical to what we do in our common practice. It got approved by the FDA, and we had to do a post-marketing study, which turned out to really open our eyes as we expanded throughout the country, we started to see more and more general use of this device, so that now it's being used as a substitute for single-chamber ICDs. And it remains effective despite the latest population having mean injection fractions now in the 30s and not in the 40s, ages higher, the same comorbidities as other patients. So, while it's not a replacement for transvenous devices, it's a reasonable substitute for patients we don't want to put on a transvenous device, a dialysis patient, a patient with issues with vascular access, or just patients who we're worried because they're young, they're inactive, or for other reasons we don't want to have transvenous hardware in them. So that's the natural transit, you probably figured that that would probably happen over time. But there are patient populations, and I know that I'm not as bullish on subcutaneous ICDs, although I totally agree it's effective and there's no problem with it. To be honest, one is cost. They are still a lot more costly. If you're in a big system and you put a lot of defibrillators in, if you don't have to put it in, is cost not an issue at your institution? I don't know. No, no, cost is an issue for all of us. What we don't know, and I can't give you hard numbers on the answer, is the upfront costs are high, we understand that. What are the long-term costs of not having leaf failures, of not having extractions for infections and other things? Is it more cost effective as a long-term strategy in patients with life expectancies of 10 to 20 years, which is our typical patient these days, rather than hoping we can keep them alive for a couple of years? We don't have data on that. Actually, that's a really, really good point, because it's the same thing in the early ablation days. We would run into trouble sometimes with insurance companies. They'd say, well, why are you ablating AV node re-entry? You can give them for FML. As time went on, and people did cost analyses of ER visits, doctor visits, the cure became cost effective. I think you raise a great point. As one goes out and you look at the total cost of the care of the patient, it may become a very cost effective thing. That would certainly change some of my personal choices. I understand to other people that's not a major issue. Upfront costs are the big issue for insurance carriers, for hospitals, and other things. They often don't consider or they downplay long-term costs, because that doesn't affect them as much as what they have to outlay to begin with. Certainly, the lead failure rate of the SICD is remarkably low compared to transvenous leads. While devices do get infected, you don't get bacteremia. Extractions are not a big deal. Let me ask you, though, going forward, because you've been involved in this whole process, especially you've written some nice papers on how to make it more specific arrhythmia detections and not the false arrhythmia detections. Where are our next steps with this device? What's the next wave coming out? The next wave will be to tie this to something that's either directly pacing the heart, inside the heart, or closer to being inside the heart. For instance, a leadless pacemaker with a subcutaneous ICD has several advantages. One, you have pacing characteristics, which are obvious for AD or ATP. But I think what gets missed or has not been emphasized enough is that detection will be exquisite, because now you can detect intracardiac electrograms as well as true far-field electrograms from the surface, so that all the inappropriate shocks will largely go away. It's going to be an even bigger cost issue, if we want to talk about cost as well, if we start combining multiple devices. But at least what I've speculated for several years now is that our future devices are going to be all leadless of some sort. It will be a subcutaneous device, which is a lead, but not a lead inside the heart, and we'll be using pellets or leadless pacemakers or whatever on the left side and on the right side, and leads are rate limiting or Achilles' heel of device therapy. That's very interesting. So, size of the generator? I mean, typically these things shrink down over time. Is that happening? Yeah. The newer generation is smaller than the initial generation. While it's bigger than transvenous leads, cosmetically it's much nicer. So, ironically, women are more attracted to this than men, because in women it's sitting in their axilla and not sitting on the anterior side of their chest. So, women actually often prefer this device, even though it's somewhat larger, but there's much more space to be able to bury it. It's not the same sort of bulge you get often with a transvenous lead in a thin person. So, it would be fair to summarize. I understand this is a very simple summarization. As long as you don't need pacing, you don't need CRT, you don't have to need brady pacing, and a primary prevention, certainly, device, this is ready for prime time, assuming all the issues you brought up. And even secondary prevention patients, for sure. It works for both of those. Yes, and again, we have the limitations of the battery longevity is not as good, the upfront costs are higher. We don't have pacing, although it's rare that you need pacing if you pick your patients appropriately. And those are the trade-offs compared to the benefit of you've left the vascular system untouched, and you don't have complications from lead fractures, lead failures, or systemic infection. Michael, great discussion. Thank you so much for all your work you've done in this area. Thanks for inviting me. Thank you.

subcutaneous ICDs

implantable cardioverter defibrillators

lead problems

transvenous ICDs

cost