STAR AF 2: 'Less Is More' When Using Ablation to Treat Persistent Atrial Fibrillation

Deborah Brauser

May 11, 2015

TORONTO, ON — There may be no need for additional procedures after a patient with persistent atrial fibrillation undergoes pulmonary-vein isolation (PVI), according to researchers from the Substrate and Trigger Ablation for Reduction of Atrial Fibrillation Trial Part II (STAR AF 2)[1].

The randomized study, which was published in the May 7, 2015 issue of the New England Journal of Medicine, compared three strategies for maintaining sinus rhythm: PVI alone vs PVI plus ablation of complex fractionated electrograms vs PVI plus additional linear ablation. Results 18 months later showed no significant between-group differences for the primary outcome of freedom from AF recurrence (defined as an episode lasting longer than 30 seconds) or for any of the secondary outcomes.

"This surprised us," lead author Dr Atul Verma (University of Toronto, ON), told heartwire from Medscape. "We bought into the dogma, so to speak, and thought the added-ablation arms would provide better results. So it was important to see the actual findings," said Verma. "Many people have been arguing about this for many years; it's good to finally have an answer."

The results were first presented at a hot-line session at the European Society of Cardiology 2014 Congress, with Dr Paulus Kirchhof (University of Birmingham, UK) acting as the session's discussant. He recently told heartwire he has given a lot of additional thought to the study since last year's presentation.

"STAR AF 2 had a result that was unexpected to the audience and to the investigators," said Kirchhof. Not only was PVI alone equally as effective as the other ablation strategies, it was "somewhat safer, with shorter procedures and less radiation," he said, adding that the overall results could be practice changing.

"The main take-home message for clinicians is that less may be more, as [PVI] alone is probably a very reasonable first approach for catheter ablation in persistent atrial fibrillation. Also important, at least to me, is that paroxysmal fibrillation and [persistent] atrial fibrillation may not be that different."

Putting Evidence to the Test

Verma noted that catheter ablation has long been known to be an effective therapy in patients with paroxysmal fibrillation, "but the results have never been as good for persistent atrial fibrillation."

"A lot of people have gone back to the old surgical literature and said: maybe we need to do more ablation" in these patients, he said. "Without much evidence, this kind of became the standard of care to the point where even the guidelines were saying you shouldn't perform only [PVI], which is considered the cornerstone of ablation. So we felt it was time to actually put all of this to the test."

Persistent-AF patients from 48 centers in 12 countries were enrolled in STAR AF 2 between November 2010 and July 2012. They were randomized in a 1:4:4 design to receive PV alone (n= 67, 78% men) or with complex electrogram ablation (n=263, 81% men) or "linear ablation across the left atrial roof and mitral valve isthmus" (n=259, 76% men). None of the participants had paroxysmal AF.

When the researchers compared the three ablation strategies across several measures, the only significant differences were in procedure time and fluoroscopy exposure, which were both significantly shorter for PVI only (P<0.001 for both comparisons and procedures).

Freedom from recurrent AF at the 18-month follow-up, with or without antiarrhythmic drugs, was achieved by 59% of those receiving PVI only, 49% of those receiving PVI plus electrograms, and 46% of those receiving PVI plus lines. Freedom from any atrial arrhythmia was achieved by 49%, 41%, and 37%, respectively.

A total of 21%, 26%, and 33% of each group underwent a repeat ablation. After the second procedure, there were still no significant group differences in freedom from AF or any atrial arrhythmia.

In an unplanned post hoc analysis, patients not taking antiarrhythmic agents showed significantly reduced freedom from both AF and atrial arrhythmia in the PVI-plus-lines group vs the PVI-only group (P=0.04 for both end points).

"Represents Maturity for the Field"

The only treatment-related serious adverse events reported included tamponade in two of the PVI-plus-lines patients and one of the PVI-only patients and stroke or transient ischemic attack in one of the PVI-plus-lines patients and two of the PVI-plus-electrograms patients.

One of the PVI-plus-electrograms patients also had an atrioesophageal fistula complicated by a stroke. "This was successfully treated by esophageal stenting, but the patient died three months later of aspiration pneumonia," report the investigators.

They add that their overall findings that performing linear or complex electrogram ablation in addition to PVI did not reduce rate of AF in their patient population "are not in accordance with the current guideline recommendation" that these patients should receive additional substrate ablation.

"Our data suggest that [PVI] alone can achieve a successful outcome in about half of patients, with success rates close to 60% after two procedures," write the researchers.

"I think this is practice changing and represents a growing maturity for our field, that we need to have good clinical evidence backing up what we do," added Verma. "Many people, including myself, are starting to think twice before adding ablation without knowing what that result is really going to be."

Clinical Implications

After the study presentation at last year's ESC Congress, theheart.org on Medscape columnist Dr John Mandrola wrote that STAR AF 2 was compelling, with clear and definitive results.

"This is an important trial. It should, and likely will, change the ablative approach to persistent AF," he wrote. "I also hope these finding force a history lesson onto the electrophysiology community—namely, what is it that makes us hold on so strongly to ideas not based on evidence?"

Kirchhof said that in addition to the "less-is-more" message, the study highlights that safety should come first. "It also brings up important points and raises questions," such as: do clinicians really need to differentiate between persistent AF and paroxysmal AF when deciding on rhythm-control therapies, such as catheter ablation? "We should also reconsider the use of cardioversion and antiarrhythmic drugs," he added.

"In the future, we may be able to treat patients with different types of atrial fibrillation differently, but we need to develop the tools for such precision medicine in AF."

The study was funded by St Jude Medical. Verma reports receiving grant support and fees for serving on advisory boards from Bayer, Boehringer Ingelheim, Medtronic, Biosense Webster, and St Jude Medical. Disclosures for the coauthors are listed in the article. Kirchof has previously reported receiving consultancy fees and honoraria from 3M Medica, AstraZeneca, Bayer, Boehringer Ingelheim, Boston Scientific, Bristol-Myers Squibb, Cardiome, Daiichi Sankyo, MEDA Pharma, Medtronic, Merck, Otsuka, Pfizer, Sanofi, Servier, Siemens, and Takeda and research grants from 3M Medica, Cardiovascular Therapeutics, Daiichi Sankyo, MEDA Pharma, Medtronic, OMRON, and St Jude Medical.

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