Is AF Ablation the Fifth Pillar in Heart Failure Care? CASTLE-HTx

John M. Mandrola, MD; Christian Sohns, MD, PhD; Philipp Sommer, MD


September 08, 2023

Recorded August 28,2023. This transcript has been edited for clarity.

John M. Mandrola, MD: Hi, everyone. This is John Mandrola from | Medscape Cardiology. I'm here at the European Society of Cardiology meeting, and I'm very excited to have two colleagues whom I met at the Western Atrial Fibrillation Symposium (Western AFib) and who presented the CASTLE-HTx study, This is Christian Sohns and Philipp Sommer, and the CASTLE-HTx study is very exciting.

Before I get into that, I really want to introduce the concept of atrial fibrillation in heart failure. I like to say that there are two big populations of patients with atrial fibrillation, and the vast majority can be treated slowly with reassurance and education. There is a group of patients who have heart failure who, when they develop atrial fibrillation, can degenerate rapidly. The CASTLE-HTx study looked at catheter ablation vs medical therapy in patients with advanced heart failure.

Christian, why don't you tell us the top-line results and what you found.

CASTLE-HTx Key Findings

Christian Sohns, MD, PhD: Thanks, first of all, for mentioning this special cohort of patients in end-stage heart failure, which is very important. The endpoint of the study was a composite of death from any cause or left ventricular assist device implantation and heart transplantation. These are very hard, strong clinical endpoints, not the rate of rehospitalization or something like that.

Catheter ablation was superior to medical therapy alone in terms of this composite endpoint. That was driven by cardiovascular death and all-cause mortality, which highlights the fact that you should always consider atrial fibrillation ablation in the end-stage heart failure cohort. The findings were driven by the fact that we saw left ventricular reverse remodeling and the reduction of atrial fibrillation in these patients.

Mandrola: Tell me about how it came about. It was conducted at your center. Who were these patients?

Philipp Sommer, MD: As one of the biggest centers for heart transplantations all over Europe, with roughly 100 transplants per year, we had many patients being referred to our center with the questions of whether those patients are eligible for a heart transplantation. Not all of the patients in our study were listed for a transplant, but all of them were admitted in that end-stage heart failure status to evaluate their eligibility for transplant.

If we look at the baseline data of those patients, they had an ejection fraction of 29%. They had a 6-minute walk test as a functional capacity parameter of around 300 m. Approximately two thirds of them were New York Heart Association (NYHA) class III and IV, which is significantly worse than what we saw in the previous studies dealing with heart failure patients.

I think overall, if you also look at NT-proBNP levels, this is a really sick patient population where some people might doubt if they should admit and refer those patients for an ablation procedure. Therefore, it's really interesting and fascinating to see the results.

Mandrola: I did read in the manuscript, and I heard from you, that these were recruited as outpatients. So they were stable outpatients who were referred to the center for consideration of a left ventricular assist device (LVAD) or transplant?

Sohns: The definition of stability is very difficult in these patients because they have hospital stays, they have a history of drug therapy, and they have a history of interventions also behind them — not atrial fibrillation ablation, but others. I think these patients are referred because the referring physicians are done with the case. They can no longer offer any option to the patients other than surgical treatment, assist device, pump implantation, or transplantation.

If you look at the guidelines, they do not comment on atrial fibrillation ablation in this cohort of patients. Also, they have different recommendations between the American societies and the European societies regarding what is end-stage heart failure and how to treat these patients. Therefore, it was a big benefit of CASTLE-HTx that we randomized a cohort of patients with advanced end-stage heart failure.

How Can AF Ablation Have Such Big, Early Effects?

Mandrola: These are very clinically significant findings, with large effect sizes and very early separation of the Kaplan-Meier curves. How do you explain how dramatic an effect that is, and how early of an effect?

Sommer: That's one of the key questions at the end of the day. I think our job basically was to provide the data and to ensure that the data are clean and that it's all perfectly done. The interpretation of these data is really kind of difficult, although we do not have the 100% perfect and obvious explanation why the curves separated so early. Our view on that is that we are talking about a pretty fragile patient population, so little differences like having a tachyarrhythmia of 110 day in, day out or being in sinus rhythm of 60 can make a huge difference. That's obviously pretty early.

The one that remains in tachyarrhythmia will deteriorate and will require an LVAD after a couple of months, and the one that you may keep in sinus rhythm, even with reduced atrial fibrillation burden — not zero, but reduced atrial fibrillation burden — and improved LV function, all of a sudden this patient will still remain on a low level of being stable, but he or she will remain stable and will not require any surgical interventions for the next 1.5 to 2 years. If we can manage to do this, just postponing the natural cause of the disease, I think that is a great benefit for the patient.

Mandrola: One of the things that comes up in our center is that I look at some of these patients and think, there's no way I can put this patient under general anesthetic and do all of this. Your ablation procedure wasn't that extensive, was it?

Sohns: On the one hand, no. On the other hand, yes. You need to take into consideration that it has been performed by experienced physicians with experience in heart failure treatment and atrial fibrillation in heart transplantation centers, though it's not sure that we can transfer these results 1-to-1 to all other centers in the world.

It is very clear that we have almost no major complications in these patients. We were able to do these ablation procedures without general anesthesia. We have 60% of patients who had pulmonary vein isolation (PVI) only and 40% of patients who have PVI and additional therapy. We have a procedure duration of almost 90 minutes during radiofrequency (RF) ablation.

We have different categories. When you talk about the different patient cohorts, we also see different stages of myocardial tissue damage, which will be part of another publication for sure. It is, in part, surprising how normal some of the atria were despite having a volume of 180 mL, but they had no fibrosis. That was very interesting.

Mandrola: How did the persistent vs paroxysmal atrial fibrillation sort out? Were these mostly patients with persistent atrial fibrillation?

Sommer: Two thirds were persistent. It would be expected in this patient population that you would not find so many paroxysmal cases. I think it's very important what Christian was just mentioning that when we discussed the trial design, we were anticipating problems with the sedation, for example. With the follow-up of those procedures, would they decompensate because of the fluid that you have to deliver during such a procedure.

We were quite surprised at the end of the day that the procedures were quite straightforward. Fortunately, we had no major complications. I think there were four complications in the 100 ablated patients. I think we were really positive about how the procedures turned out.

I should mention that one of the exclusion criteria was a left atrial (LA) diameter of about 60 mm. The huge ones may be very diseased, and maybe the hopeless ones were excluded from the study. Below 60 mm, we did the ablation.

Rhythm Control

Mandrola: One of my colleagues, who is even more skeptical than me, wanted me to ask you, why wouldn't you take a patient with persistent atrial fibrillation who had heart failure and just cardiovert and use amiodarone and try and maintain sinus rhythm that way?

Sohns: It is important to mention that 50% of the patients have already had amiodarone before they were randomized and enrolled for the trial. It might bring you a couple of minutes or a couple of hours [of relief], but the patients would get recurrence.

It was very interesting also, and this is in line with the data from Jason Andrade, who demonstrated that we were able to reduce the percentage of patients with persistent atrial fibrillation to paroxysmal. We did a downstaging of the underlying disease. This is not possible with cardioversion or drugs, for example.

Sommer: What I really like about that question and that comment is the idea that rhythm control in this subset of patients obviously has a role and an importance. It may be a cardioversion initially, giving amiodarone if they didn't have that before, and you can keep the patient in sinus rhythm with this therapy, I think we're reaching the same goal.

I think the critical point to get into the mind of physicians who treat heart failure is that sinus rhythm is beneficial, however you get there. Ablation, of course, as in other studies, is the most powerful tool to get there. Cardioversion can be a really good thing to do; you just have to think about it and consider it.

Mandrola: I do want to say to everybody that there is a tension sometimes between the heart failure community and the electrophysiology community. I think the ideal situation is that we work together, because I think that we can help with the maintenance of sinus rhythm. The control group mortality at 1 year was 20%, and I've heard people say that that's not advanced heart failure. Advanced heart failure patients have much higher mortality than that. My colleague who is a heart failure specialist was criticizing a selection bias in picking the best patients. How would you answer that?

Sohns: There are data available from Eurotransplant, for example, that the waiting list mortality is 18%, so I think we are almost in line with this 20% mortality in this conservative group. You cannot generalize it. All these patients have different histories. We have 60% dilated cardiomyopathy (DCM) and 40% ischemic cardiomyopathy (ICM). I think it is a very representative group in contrast to your friend who suggests that it is not.

Sommer: What I like about the discussion is that some approach us to say that the mortality in the control group is much too high — like, what are you doing with those patients that you create so many endpoints? Then others say that it's not high enough because that is not end-stage heart failure. Come on! We have a patient cohort that is very well described and very well characterized.

If the label is end-stage heart failure, advanced heart failure, or whatever, they are sicker than the patients that we had in earlier trials. The patients that we treated were mostly excluded from all other trials. We opened the door. We found a clear result. I think everyone can see whatever you like to see.

Mandrola: What would your take-home message be after having done this trial design, the trial was conducted in your single center, and you come up with these amazing results? What would your message be to the whole community?

Sohns: Taking into consideration how severely sick these patients are, I can just repeat it: They are one step away from death, more or less, or from surgical intervention that can prolong their life. You should also consider that there are options like atrial fibrillation ablation that can buy time, postpone the natural course, or even in some patients replace the destination therapy. Therefore, in my opinion the next guidelines should recommend that every patient should carefully be checked for sinus rhythm before bringing these patients into the environment of transplantation.

Sommer: My interpretation is that we have to try to bring into physicians' minds that besides a well-established and well-documented effect of drug therapy with the fabulous four, we may now have the fabulous five, including an ablation option for patients with atrial fibrillation.

Mandrola: Excellent. I also want to just say before we close, congratulations to Christian Sohns and Philipp Sommer for doing a randomized, controlled trial to answer a question. This is the way forward, I think, to answer uncertainties in medicine. I'm really excited to have you here. Thank you very much.

Sohns: Thank you.

Sommer: Thank you.

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