EP Lab Digest - February 2008 - (Page 32)

CRYOTHERAPY ROUNDTABLE Continued from page 31 UPDATE FEBRUARY often wondered about that. I don’t really know the right answer. PETER J.WELLS, MD:That brings up the point about if all you have are single AV node echos, then if you’re using RF, your only endpoint is junctional tachycardia, which tells you that you’re in the right place.The problem is that not infrequently after you get junctional tachycardia, you still have a single echo. So it’s very difficult to know when you don’t have very clear endpoints how aggressive you can be. Whereas with cryo, you know that you can, as George puts it,“push the envelope” a bit because the likelihood of complete, permanent AV block is very low, although you may see transient AV block. PETER J. WELLS, MD: What happens if you ablate where you think the slow pathway is, and let’s say you can’t get it. Well, with cryo, the very first thing we do here at Baylor — and George, you chime in as well — is we tend to pull back toward the compact AV node. Now, we don’t do that in any sort of cavalier fashion. We’re very careful about it, but as George showed, the higher AV relationship, particularly if you’ve started at more of a traditional RF site with a small A big V, is important. Therefore, the very first thing we do is pull back until that AV relationship is at least 1:1. What if that doesn’t work? This is just our practice, but we tend to then go inside the mouth of the coronary sinus and look for that posterior leftward AV node extension that Anton Becker and Sonny Jackman have so elegantly described. If that doesn’t work, what we typically do as a last resort — or actually,as a second-to-last resort — is to go north up the septum toward the compact His bundle, understanding that it is very difficult to produce complete heart block with cryo, so the technology is reasonably safe. The last thing I would say, which we’ve never actually done with cryo, is to go retrograde.We do this with RF.You can go retrograde across the aortic valve and come down to just below the His bundle, which puts you right across the septum from where you’ve been working for the past hour. Frequently you can get accelerated junctional rhythm there and effective slow pathway ablation there as well. GEORGE F.VAN HARE, MD: I think the issue of the left atrial extensions of the compact AV node is really interesting. Certainly some of our cryo and RF failures for that matter are probably patients who had that problem. Mapping that location is of course a challenge. If you have the advantage of having demonstrated a retrograde jump, you can then map the earliest retrograde atrial activation. If you find that a centimeter into the coronary sinus, that is your hint that that is where you’re going to go. The other possible thing is if you should be fortunate enough to induce an atypical AV node reentry, where you’re actually coming up the slow pathway, you can then go ahead and map that. The very few cases that I have addressed that issue knowingly have been situations like that. PETER J.WELLS, MD: Right. So don’t miss the opportunity with AV node reentry just because it’s a nodal pathway to map earliest retrograde atrial activation. That is somewhat of a lost art, I think. We have another question: “What is the role of cryoablation for accessory pathways?”You know, one of the real benefits of cryoablation is in the area of pathways that are right on the His bundle, the so-called parahisian pathways, which we here would define as at least a 100 microvolt His deflection when the catheter electrode is at a site that is recording the accessory pathway potential.Traditionally those have not fared well with RF, and this is for a couple reasons. One is that efficacy and safety are linked in that procedure. In other words, you can get the pathway with RF, but you’ll probably also produce complete heart block. It’s this balancing act of “Well, how close can I get? How many watts, what’s the temperature?” that leads to low efficacy rates and higher recurrence rates. With cryo, that is a good use of the tool. As far as other accessory pathways, this is a summary of the Atakr Registry database, published in 1999 in Circulation;3 this was a multicenter study mainly of academic centers and very experienced physicians. They looked at different pathway locations and what the success was with RF ablation. With left free-wall pathways, which at least in adults are probably 55% of all the pathways, there was 92% initial success. On a second procedure, they got another 3%, so with one or two procedures, there was 95% success. The recurrence rate was on the order of 3%, and there obviously was no heart block. So do we need cryoablation for left free-wall pathways? Almost certainly not, unless they are in unusual locations, as George alluded to. If they are within the coronary sinus, particularly within 5 millimeters of an epicardial coronary artery, then we know that the risk of coronary artery damage is high with RF. However, for the usual endocardial pathways, we really don’t need cryo for the left free-wall pathways. With septal pathways, it’s a different story, though. If you look at the Atakr Registry database, there was only 84% initial success with RF ablation of septal pathways, and these are right anteroseptal, intermediate septal, and posterior septal pathways with an 11% arrhythmia recurrence rate. Arrhythmia recurrence was only defined in the group that initially had a successful RF ablation. So you’re looking at a nearly 3% incidence of heart block. So that is nearly a 30% incidence of suboptimal outcome that I think we would say we need a different tool for that. Lastly, as far as right-sided pathways, as many of you know that when you read echo, you can see how the tricuspid annulus is really yanked during right ventricular systole, so catheter stability is a real issue on the right side. Initial success was only 83% with right free-wall pathways with a 14% incidence of recurrent arrhythmias, and of course, no heart block. So I think for septal and right-sided pathways, which make up at least in the adult population about 45% of the cases, cryo can have some advantages. GEORGE F. VAN HARE, MD: We’ll do two more questions and then we’ll be done. RAJJIT ABROL, MD: Some of the questions that we’re getting in deal with other arrhythmias, so I’ll just do a summary. Here are two questions: “Please compare cryoablation with RF ablation, and then perhaps you can address the issue of cryotherapy with esophageal injury.” I know that we have been talking for some time about arrhythmias that we can treat with cryo, and the bulk of it that we’ve been talking about is AV node reentry because that happens to be what we use on almost a daily basis. In terms of other arrhythmias and the use of cryo — I’ll just briefly mention ventricular tachycardia. You can potentially safely ablate areas of the outflow tract.As we all know, the coronary arteries run near the right and left ventricular outflow track, and I’ve heard of cases with RF, you’ve had either spasm or coronary artery injury. So the use of cryo in the outflow tract is something that should not be underestimated. Regarding atrial tachycardias, we have done live cases that we were going to show you; there were two young patients with tachycardia that both terminated with vagals and adenosine, and one ended up being an atrial tachycardia. One was a left-lateral pathway, so we spent the majority of our time talking about AV node reentry, but we don’t have examples to show you. In general, I would suspect that with atrial tachycardias, as easy as it is to RF-ablate, it’s hard to find the spot, but when you get to the spot, it’s easy to get rid of it. It is a kind of endocardial tissue that is causing the arrhythmia, and cryo would be effective if you can find the spot. However, a big advantage to cryo is when working near the right phrenic nerve. We did this case where we paced the phrenic nerve and then froze below the place that we were pacing from, to make sure that we could freeze the tachycardia site, which we were effectively able to do. Unfortunately, the patient had four or five different tachycardias, but we were effectively able to in at least three of them eliminate her tachycardia without damaging the phrenic nerve. I think that is an important tool for cryotherapy. As far as atrial fibrillation, we would probably have to have a separate webcast. The cryoballoon is right now under an FDA study, which our hospital is involved with. My personal feeling with the balloon — again, this is biased by the limited experience I’ve had with cryo — is that it potentially gives you good lesions that will dissociate the pulmonary veins from the atrium without having the risks of pulmonary vein stenosis. There is preservation of the endothelium with the cryoballoon. The structural integrity is similar to all the things we talked about — non-arrhythmogenic with cryo, less risk of esophageal injury, the data for all that. If you want to find a treatment or a therapy that is going to provide patients with a safe way of treating their tachycardia in the left atrium, I think cryo is potentially a therapy that we are going to be able to use with the balloon system.We have had very good results here at our institution so far, but the data is not available yet. We haven’t done enough patients to be able to say that this is definitively one way or the other. However, I think in terms of covering the arrhythmias, you probably have to have a webcast covering each different arrhythmia, because we have spent a lot of time talking primarily about AV node reentry today. PETER J. WELLS, MD: George, thank you very much. Raj, I appreciate your help. We’re glad that you joined us. We hope that this has given you some initial information for how cryoablation might fit into your current practice.Thank you very much. References 1. Friedman PL, Dubuc M, Green MS, et al. Catheter cryoablation of suprave http://www.cryocath.com http://www.or-live.com

Table of Contents Feed for the Digital Edition of EP Lab Digest - February 2008

EP Lab Digest - February 2008 Creating the U-M Center for Arrhythmia Research: Interview with José Jalife, MD Texas Cardiac Arrhythmia Institute and St. David’s Medical Center Launch State-of-the-Art Training Center Contents Letter from the Editor Spotlight Interview: Caritas St. Elizabeth’s Medical Center 10-Minute Interview: Sue Deck, BS, RN, RCES Keeping Pace With a Blog Roundtable Discussion on Cryoablation Procedures Email Discussion Group: February 2008 Events Calendar Industry News and Products Classifieds Advertisers Index

EP Lab Digest - February 2008

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