Hi, this is Eric Prostowski. Welcome to another segment of EP on EP. Dr. Wilber is back. We had a wonderful discussion on Part 1, which I hope you will look at, where we were talking about idiopathic VT. The first segment, David, we talked about was ECG and mapping criteria to try to figure out where it is. So, the logical next step is getting rid of it. So, David, tell us, let's talk about a couple areas you found that people have struggled with. I know you've talked to me about the papillary muscle area, and then there's maybe some other areas. Do you want to give us your approach and tricks to getting those areas? Yeah, I think we talked about the papillary muscles, which I think is always a challenge. And I think as you noted, and it's certainly true, acute success is not always followed by long-term success. And I actually urge, particularly as people learn, you need to do some long-term follow-up, because you'll be surprised in two ways. One, when you use a lot of power, you can have an initial success, a recurrence, but then occasionally they go away again. You have to let enough time go by to re-evaluate. So how much time do you think is fair to wait? I think sometimes you have to wait as long as six months to know the outcome. Six months. It's really when you start to apply high power for long periods of time, which get these deep intramural ones, which can happen even in patients without structural heart disease. And so one can be, and you can see the other way around, that it's often that you don't see any acute success, but even a week later, you'll see that the ectopy has disappeared. So there are some caveats to that, hopefully as we get better in mapping. And so it's less brute force and more elegance. And I think that's possible when they're endocardial or sub-endocardial, but the trick is to identify those that are deeper in the muscle. So the papillary muscle is really one of those. So can I stop you one moment on that and ask you a question? I know some people advocate cryo for better contact. We've personally not done that, but your thoughts on that? Yeah. Well, there's certainly data, and that would suggest that that's true. The problem is that all the series are small, it's eight or 10 patients. I think it's kind of like a surgeon, when if they have a certain way that they do their graphs and how they sew them in and it works for them, it's better. And so I think that it's hard to generalize from that, though. And I think there's a little bit of that truth in cryo versus RF. It's all about your expertise with the arrhythmia and your use of a particular technique and technology, because it's not just about... Mapping is important, and I do think high-density mapping is very important, and you can learn some things that when we only gathered a few points in that area, we really didn't understand. And occasionally, you'll find that critical information in the density of the map and where the breakouts are. So before you go on to another area, I don't do the VT ablations anymore, but my team, they tell me it's not uncommon that they'll get what they look like was the best site for the papillary area, only shortly thereafter to see it exiting somewhere else. So do you think it's coming deep down and you just took out an exit point, or it's multiple sites? Yeah, I think some of them can be intramural and multiple exits, and in fact, you can identify some of those exits with high-density mapping. So in other words, one of the things that's interesting, if you collect that thousands of points that you can get now with some of the very high-density mapping systems, when you look in the areas of the papillary muscle, you see complex patterns of activation that you might not see otherwise. So it's probably deep down there. Yeah, and you get a clue then that it's very complex. Fiber orientation is complex as well. Certainly, we still go for the earliest site. We still go for the best unipolar electrogram, although occasionally, these do have very discrete pre-potentials that can precede the QRS, and so in those cases, we target those first. And do you manage power differently when you're in a pap? We do. Contact force is very important. I think that obviously, irrigation is important. But in addition to that, occasionally, when we get a late termination or disappearance of ectopy, then you may need to do RF for a long period of time. In addition, there are clearly some patients where it is deep enough that we've actually only been successful with an epicardial approach, and that's very uncommon. It's more common in patients with structural heart disease, but we've had a couple of patients where even in a structurally normal heart, the epicardium was the only way to get rid of one. So with the time we have remaining, is there another area that you find is often a struggle and maybe you can tell us about that? The LV summit is the challenge, because it can be endocardial about maybe 50% of the time. It can be intramural about a third of the time, and then it's epicardial the other. And the trick is to understand before you start ablating what it's most likely to be. If the time, and you need to map in the sinus of Valsalva, you need to map in the coronary veins, and you need to map in the endocardium, all before you start burning. You don't necessarily do an epicardial map, you do the others first. The important thing about going and doing a traditional epicardial map is that there's so much fat in that area around the vessels, and because the vessels are so close, you can only give a limited amount of power, then it's almost never an effective approach. If it's epicardial, you can ablate in the coronary veins very successfully. The veins are usually beneath the fat, so it's not a problem, and you can usually safely give up to 30 watts without, if you're within at least 5 millimeters or so away from the coronary artery, which is the vast majority of times. If it's truly epicardial, but many of these, and I think what people don't realize is that the majority of these are still endocardial or they're intramural, and so it's easy to identify the ones that are superficial, and if that time beats the epicardial time by more than 20 milliseconds, usually you get it from the endocardium. If it's intramural, do you use a two-catheter approach, or do you think you can usually get it with a single? Yeah. What we normally do is we give high-power, long-duration lesions from underneath the ... Now, I know because you've actually done a patient of mine, define for the audience what you mean by high-power, long-duration, what's long? You can use 50 watts, and you can use it in up to a couple of minutes. Couple of minutes, okay. Yeah, and I think you obviously have to monitor the usual parameters for temperature and impedance and those sorts of things, but very oftentimes you can give long lesions, which are required to be successful, and then occasionally, if that doesn't work or if it goes away and comes back within a 30-minute waiting period, then we give an additional epicardial lesion, assuming that we can't. The thing that will surprise you is that even in normal hearts, you can be as thick as one and a half or two centimeters without meeting the traditional criteria for LVH or other sort of structural heart disease. In fact, mapping to start with, and be sure before you burn, you're where you want to be, sometimes you just have to suck it up and make a long lesion, but it all starts with making sure you're in the right spot. You got it. David, fantastic. Thank you so much for helping us out. My pleasure. Take care. Thank you.

idiopathic VT

long-term follow-up

cryo ablation

high-density mapping

epicardial approach