Opinions differ on AFib ablation’s role
Despite this expansive assessment of the current status of AFib ablation for patients with heart failure from Dr. Di Biase and shared by others, another camp of cardiologists currently sees ablation as having more limited current utility, as recommended earlier this year by a guideline-update panel representing the American Heart Association, the American College of Cardiology, and the Heart Rhythm Society. The guideline update included this new recommendation for how to use AFib ablation in heart failure patients: “AF catheter ablation may be reasonable in selected patients with symptomatic AFib and heart failure with reduced left ventricular ejection fraction to potentially lower mortality rate and reduce hospitalization for heart failure,” a class IIb recommendation. (J Am Coll Cardiol. 2019 Jul 9;74[1]:104-32). The guideline’s text cited the findings from AATAC and CASTLE-AF, but qualified both studies as “relatively small” and with “highly selected patient populations.” The guideline also incorporated the CABANA results into its considerations (although they may not have had the full analysis in heart failure patients available during their deliberations), but cited the study’s main limitation: CABANA failed to show a statistically significant difference in the primary endpoint in its primary, intention-to-treat analysis, which meant that by the strict statistical criteria that trialists apply to study findings, all other endpoints analyzed using CABANA’s are merely “hypothesis generating” and not definitive.
Questions about the extent of patient selection required to see a clear clinical-endpoint benefit from AFib ablation in heart failure patients, as well as the flawed validity of the CABANA results for making unqualified practice recommendation are the main arguments advanced by experts who caution against broader and more routine ablations.
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Dr. Gregg C. Fonarow
“The findings from the heart failure subgroup of CABANA are hypothesis generating rather than definitive. Even with the recent meta-analysis, uncertainty remains regarding the ability of catheter ablation to improve outcomes beyond reducing AFib-related symptoms,” commented Gregg Fonarow, MD, a heart failure physician and professor of medicine at the University of California, Los Angeles.
“CASTLE-HF had fewer than 100 deaths combined in both arms, which means very unstable results. We don’t know a lot of detail about the heart failure patients in CABANA, and overall we do not have much data from patients with heart failure with preserved ejection fraction [HFpEF],” said Javed Butler, MD, a heart failure physician and professor and chairman of medicine at the University of Mississippi in Jackson. Dr. Butler also voiced his concerns (shared by other heart failure specialists) about the safety of ablation in heart failure patients, noting that “many patients require multiple ablations; many burns result in scarring and can worsen atrial function. In short, ablation of AFib is probably good for selected patients, but to have a class 1 recommendation, we need much larger trials with well-phenotyped heart failure patients,” Dr. Butler said in an interview.
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Dr. Larry A. Allen
“The totality of data still captures a relatively small number of patients. CASTLE-HF took 8 years to enroll fewer than 400 patients, and the results showed some heterogeneity. Study patients were a decade younger than average HFrEF patients in the community, and thus the effectiveness and safety of catheter ablation in people with more comorbidity and frailty remains in question. Certain HFrEF patients may be less likely to benefit, such as those with amyloid cardiomyopathy. And with the increasing availability of other treatments for HFrEF such as sacubitril/valsartan, dapagliflozin, and MitraClip, it is less clear how catheter ablation would [benefit patients] on top of what is now current best therapy,” said Larry Allen, MD, a heart failure physician and professor of medicine at the University of Colorado in Aurora.
“With these limitations and the fact that catheter ablation is not a simple procedure, a large randomized, controlled trial of ablation, compared with no ablation, in a wide range of HFrEF patients on contemporary therapy would be welcome,” Dr. Allen said. “Given the prevalence of heart failure and AFib and the potential positive and negative implications of catheter ablation running such a trial seems critical for patients and for society.”
“For ablation of AFib in heart failure to become a class I recommendation there will need to be results from larger randomized studies,” summed up Dr. Stavrakis. The meta-analysis that he coauthored noted that “the benefits of catheter ablation for AFib in HFrEF patients have been consistently shown for over a decade now; however, the uptake of this procedure by clinicians in practice has been slow.”
Despite this history of reticence and ongoing caution about ablation, some cardiology experts see the indications for AFib ablation in heart failure steadily creeping forward, buoyed by a safety record that has more benign than ablation’s reputation suggests.
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Dr. Peter R. Kowey
The CABANA results showed that “ablation is remarkably safe in the hands of experienced clinicians, with risks comparable to anti-arrhythmic drugs,” said Peter R. Kowey, MD, a specialist in treating AFib and professor of medicine at Thomas Jefferson University in Philadelphia, who made this assessment during a talk at an AFib meeting in early 2019. Dr. Kowey’s take on what the CABANA safety data showed contrasts with the impression of other cardiologists who are wary of perceived dangers from ablation.
“Ablation comes with a lot of morbidity and mortality. It’s not that the idea of ablation is wrong, but the ability to do it without a lot of adverse effects. ... We’re not quite there yet,” said Douglas L. Mann, MD, a heart failure physician and professor of medicine and chief of the cardiovascular division at Washington University in St. Louis.
Dr. Douglas L. Mann
“If I had a patient with HFrEF and AFib who was really sick, I’m not so sure I’d send them for ablation, which is not a simple procedure. The patients we tend to send for ablation are selected. Ablation is a big undertaking in patients who are already sick, and it’s expensive. I don’t think the data we have now will change the consensus view, but every heart failure physician is sending some patients for AFib ablation. People are turning to AFib ablation earlier than before. I think the consensus is that ablation is for symptoms or poor rate control, not for better outcomes,” said Mariell Jessup, MD, a heart failure specialist and chief science and medical officer of the American Heart Association in Dallas.
Dr. Mariell Jessup
However, this caution about safety and skepticism over efficacy may be dissipating as experience with ablation accumulates.
“CASTLE-AF and other data, including evidence for the apparent isolation of beta-blocker benefit to patients in sinus rhythm, have made me much more proactive about considering catheter ablation in my HFrEF patients. I think many other cardiologists have a similar view,” said Dr. Allen in an interview.
“A lot [of heart failure] patients are [being] referred for ablation, depending on the practice, setting, the local availability of electrophysiologists, and patient interest in ablation,” said Dr. Butler.
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Dr. A. John Camm
“We have no absolutely compelling data, but the data we have all point in the same direction. Like most, I am becoming convinced that AFib ablation in heart failure patients is a very valuable method for managing patients, but I can’t point to one study that was conclusive. Results from lots of studies show that it is likely, and when you add them all together it looks indisputable,” commented A. John Camm, MD, an atrial fibrillation specialist and professor of clinical cardiology at St. George’s University in London. “The findings put a responsibility on cardiologists to assess patients with heart failure for AFib. But there are nothing like enough resources to deal with all the patients who have heart failure who also have AFib.”
A rough estimate of just the U.S. volume of patients with heart failure and AFib is likely in the ball park of 2 million people (a third of the estimated 6 million American currently living with heart failure), and with the prevalence of each of these disorders rising precipitously (more than 5 million Americans have AFib) the confluence of the two should also show a steady increase. “It will take a major change in our concept of heart failure management to really address this. Potentially it would mean a large increase in the number of RF ablations of AFib, but the resources for that are not now present,” Dr. Camm said in an interview.
The attractions of catheter ablation also stand in contrast to the limitations of alternative treatments. Ablation is effective in a majority of patients for reducing AFib burden, both the frequency and duration of AFib episodes, and safety issues are mostly limited to the procedural and immediate postprocedural periods. The drugs available for trying to control AFib are beta-blockers, which provide rate control and can help prevent AFib onset, and rhythm-controlling anti-arrhythmic drugs like amiodarone, which have substantial limitations in both their ability to prevent arrhythmia recurrences as well as for safety.
“Most of the conventional antiarrhythmic drugs are contraindicated, frequently ineffective, or not well tolerated in patients with HFrEF. Catheter ablation of AFib provides an increasingly important option for rhythm control in these patients without using antiarrhythmic drugs,” Dr. Di Biase and his associates wrote in a recent review of AFib ablation in heart failure patients (Eur Heart J. 2019 Feb 21;40[8]:663-71).
“The guidelines that are controversial still make amiodarone a class I drug even though it’s been associated with serious side effects and has been shown in several heart failure trials to increase mortality. I can’t believe that ablation is a class IIb recommendation while a drug like amiodarone is a class I recommendation,” Dr. Di Biase said.
And although beta-blockers are a mainstay of heart failure treatment, once AFib becomes established they are less useful for maintaining sinus rhythm. “Beta-blockers provide effective rate control, but they can’t convert patients to sinus rhythm [once AFib begins], and there is no convincing evidence that patients on beta-blockers stay in sinus rhythm longer. You can’t just say: the patient is on a beta-blocker so I’ve done my best,” noted Dr. Jessup.
CABANA received funding from Biosense Webster, Boston Scientific, Medtronic, and St. Jude. Dr. Stavrakis, Dr, Jessup, and Dr. Di Biase. Dr. Hunter has received research funding, educational grants, and speakers fees from Biosense Webster and Medtronic. Dr. Packer had received honoraria from Biotronik and MediaSphere Medical and research support from several companies. Dr. Piccini has been a consultant to Allergan, Biotronik, Medtronic, Phillips, and Sanofi Aventis, he has received research funding from Abbott, ARCA biopharma, Boston Scientific, Gilead, and Johnson & Johnson, and he had a financial relationship with GlaxoSmithKline. Dr. Fonarow has been a consultant to Abbott, Amgen, Bayer, Janssen, and Novartis. Dr. Butler has been a consultant to several companies. Dr. Allen has been a consultant to Boston Scientific, Janssen, and Novartis. Dr. Kowey has been a consultant to several companies. Dr. Mann has been a consultant to Bristol-Myers Squibb, Corvia, and Novartis, and an adviser to miRagen. Dr. Camm has been a consultant to several companies.
This is part one of a two-part article.