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What Do the Trials Say for Catheter Ablation?
Anticoagulation Discontinuation After Successful A ...
Anticoagulation Discontinuation After Successful Ablation: Where Are We and Where Are We Going (Presenter: Atul Verma, MD, FHRS)
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And we will get started with Atul Verma, which is the last presentation on your list, entitled Anticorregulation, Discontinuation After Successful Ablation, Where Are We, and Where Are We Going? And I would like to ask all speakers, please stay in your time. You all have 10 minutes and five minutes for Q&A, because since we moved everything around, we may want to prevent conflict. So thank you very much. It's a pleasure to be here today, and I will promise to stay on time so that everybody can make it to their next presentations. And today I'm gonna be talking about anticoagulation, discontinuation after successful ablation, where are we, and where are we going? These are my disclosures. So I'll just start off by going right to the guidelines. What do the guidelines say about discontinuing oral anticoagulation after a successful ablation? And essentially, by default, they say you shouldn't be affected by the outcome of the ablation. So in other words, calculate your patient's CHADS-VASC risk, and if they're CHADS-VASC-2, for example, you should just continue the oral anticoagulation, because we don't really know if the AF is going to come back. The problem is that even though this is a class one recommendation in the consensus document in 2017, it's based on level C evidence, which means expert opinion. So there's really no trials to guide us on this matter. And we do know that in certain patients, late atrial fibrillation still continues even after an apparently successful ablation. So here we have a meta-analysis from Prash-Sanders Group, and what you can see here is that particularly in patients with non-paroxysmal atrial fibrillation, there is a year-by-year failure rate that's in the order of anywhere from about one to 5%, where patients drop off that Kaplan-Meier curve even after one, two, or three years. We also know from the DECERN-AF study that we published a few years ago now, that there tends to be an increase in the proportion of asymptomatic episodes of atrial fibrillation versus symptomatic episodes. So even in a highly symptomatic patient population, it's interesting that about 50% of the episodes are asymptomatic, but that ratio goes up even after ablation. So if the patients are not as aware of their AFib, it's going to be more difficult to detect and even more of a rationale to continue oral anticoagulation. And then of course, we've all seen this slide in numerous iterations where they talk about the relationship of stroke, which occurs at the red line in the center of this figure, and the black represents atrial fibrillation. And while there are some patients where clearly the AF is related in timing to the stroke, there are other patients where they may not have AF for a period of several days or even weeks before or after the time of their stroke. So if you put all this together, you would argue that it's very clear we should continue oral anticoagulation no matter what, even if the AF ablation is successful. But we have to ask ourselves, can a reduction in AF burden actually impact the risk of stroke? And I think when we look back at some of the evidence that has convinced us that as little as six minutes may be enough to increase the risk of stroke, and this is the ASSERT trial by my colleague, Jeff Healy, sure, it looks like on the Kaplan-Meier curves that the risk of stroke is two and a half times higher if you have six minutes of AF compared to if you don't have six minutes or more of AF. But when you look at the absolute scores, risk of stroke per year, you see that for the CHADS one, two, and greater than two patients, the percentage risk of stroke per year is actually pretty small. And if you compare that to the actual risks of stroke by CHADS score, you'll see that the CHADS score would normally predict a much, much higher annual risk of stroke than what they actually found in ASSERT. So it's not absolutely clear that low burdens of atrial fibrillation actually increase the risk of stroke. Now, both the ROCKIT-AF study and now the ENGAGE study have gone back and looked at their data, and they have compared the risk of stroke of patients in persistent atrial fibrillation versus paroxysmal atrial fibrillation. And as you probably know, when we were in medical school or residency, we were taught it doesn't matter. The risk of persistent or paroxysmal atrial fibrillation is exactly the same. You should treat them exactly the same. But of course, in newer data, we're now learning that in fact, the risk of stroke in the paroxysmal patients who are in the blue may actually be lower than the risk of AF in the patients who are in the red. And then if we go back to this slide, which I already just said we've seen millions of times, so now you've seen it a million and one times, we have to look back at this data a little bit more carefully and ask ourselves, were all of those strokes actually related to atrial fibrillation? And in fact, the underlying mechanism of those strokes were just any ischemic stroke. So they could have been a lacune, which is absolutely not related to AFib. They could have been carotid strokes. And in fact, Jeff and his group have gone back and started to adjudicate the MRIs for the patients that are actually available. And it turns out only 20 to 30% of all these strokes were actually due to cardioembolism. So this has a lot of noise in it with strokes that are probably not related at all to atrial fibrillation. And Mintu Tarakiya took a look at this in a different perspective and said, when is the risk of stroke highest after you've had an episode of atrial fibrillation? And in fact, they found that the risk of stroke was in fact highest within the first five days after a prolonged episode of atrial fibrillation. So there may actually be more of a temporal relationship than those figures may otherwise suggest. Now, a number of studies have looked at whether or not you can safely discontinue oral anticoagulation after AFiblation, and many of them have reported low event rates. But the caution here is that a lot of these were single-center, retrospective cohort designs. And a lot of these patients also had very low CHAD scores. So it wouldn't be surprising that their risk of stroke is very low. This is some interesting data that was just recently published by Frank Marshalinsky's group, where they took a look at their approach of following patients with pulse checks on a daily basis. And if the patient was good by pulse check for more than a year, they would stop the oral anticoagulation. And certainly in this prospective cohort, they didn't see any strokes with many of the patients having discontinued their oral anticoagulation after a successful ablation, but continuing to monitor themselves on a fairly regular basis. But that's where we have a bit of a vacuum, and this is where the OCEAN trial comes in. This is a trial that I'm working on with my colleague David Burney and Gerhard Hendricks. And in this trial, we are actually trying to figure out what is the most appropriate strategy for antithrombotic therapy post-successful atrial fibrillation. Now, we're actually hypothesizing on the other end of this argument. We're actually saying that OAC will be superior to aspirin post-AF ablation, but this will be the first time that this has been looked at in a randomized trial. How were we able to do this? Well, we used a composite of stroke systemic embolism and covert embolic stroke, because as Doug has said many times, if you were to do this properly powered only for stroke, you'd probably need about eight to 10,000 patients, and we just can't do trials like that in AF ablation. So we looked at new lesions greater than 15 millimeters. These are not the asymptomatic cerebral emboli post-ablation that we're talking about here. These are real, true build strokes. We then enroll the patients after they've had their baseline MRI to either aspirin or a NOAC, in this case, rivaroxaban. We'll need about 1,572 patients in order to complete this trial. And I'm proud to say that we're actually not that far away. We've enrolled over a third of the patients, 545 patients enrolled, and we're opening up sites, and momentum is picking up on the trial. So if you just be patient with us and wait for about 40 years, we'll give you an answer. Thank you very much, and I'm happy to take questions. Thank you. Thank you, Dr. Verma. Are there questions from the audience? Well, I may have one. Jim, it seems from the data that you show that the risk of stroke is not necessarily determined by the burden of AF, by the amount of episodes, but particularly by the underlying cardiovascular risk, as assessed by the CHAT-VASc score or other scores. So that's basically what the guidelines say, that you should determine your decision to continue or to discontinue anticoagulation based on the preexisting risk. How would you comment on that? Because you're showing the subclinical AF data, and also there, the risk is highest when the CHAT-VASc is, or the CHATs, in this case, is highest. Yeah, so absolutely. So I think, yes, the CHAT-VASc score is a very important determinant for the risk, but as I showed with the ASSERT trial, a CHATs of one, for example, does not carry the same risk of stroke in every single population. So in the normal risk scoring system, the annual risk of stroke should be about three to 5% with a CHATs of one, but in the subclinical AF population, it's barely 1%. So yes, the CHATs two will have the higher risk, relatively speaking, but the absolute risk may not actually justify initiation of oral anticoagulation. In OSHN, we're only gonna be selecting patients of at least moderate risk, so we're not gonna be enrolling any CHATs zero or CHATs-VASc one females, for example, into the trial. The patients have to be at least CHATs-VASc two. Thank you. So in Frank Machlinsky group, they took the pulse as a denominator for having a recurrence afterwards. Having said that, we probably have some data down the road saying whether we can stop anticoagulation after ablation or not. What do you think would be the best measure to take on a clinical routine basis to sufficiently surely say the patient is a success as an ablation or not? Yeah, so that's a good question. It has no real correct answer. In OSHN, we're gonna be inserting implantable loop recorders in 500 of the 1,500 patients, so that's quite a large number of patients. We'll get a lot of valuable learning from that, and that hopefully may guide us. Right now, I have to say that I'm not comfortable even with a seven-day halter every three months necessarily telling a patient to stop oral anticoagulation on a routine clinical basis if they have a high CHADS score, but if they want to discontinue oral anticoagulation, I tell them to go into OSHN. Good idea. Any more comments from the audience? Thank you very much. All right, thank you. Thank you.
Video Summary
Dr. Atul Verma presented on the topic of anticoagulation discontinuation after successful ablation and the risks associated with it. He discussed the guidelines which recommend continuing oral anticoagulation after ablation, but noted the lack of trials supporting this recommendation. He presented data showing the ongoing risk of atrial fibrillation even after successful ablation, and questioned whether low burdens of AF actually increase the risk of stroke. Dr. Verma also mentioned a trial called OCEAN, which is investigating the most appropriate strategy for antithrombotic therapy post-ablation. He concluded by emphasizing the importance of individual patient risk factors in determining the need for continued anticoagulation.
Meta Tag
Lecture ID
4308
Location
Room 303
Presenter
Atul Verma, MD, FHRS
Role
Invited Speaker
Session Date and Time
May 10, 2019 10:30 AM - 12:00 PM
Session Number
S-058
Keywords
anticoagulation discontinuation
ablation risks
oral anticoagulation
atrial fibrillation
stroke risk
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