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Following the presentation of new data from the AVANT GUARD pivotal trial at the 2026 Heart Rhythm Society (HRS) annual meeting (23–26 April, Chicago, USA)—and their simultaneous publication in the New England Journal of Medicine—leading investigator Julian Chun (Bethanien Cardioangiological Centre, Frankfurt, Germany) speaks to Cardiac Rhythm News to discuss the study’s potential impact on the management of persistent atrial fibrillation (AF).
“We know that catheter ablation is very powerful in paroxysmal AF, because we have numerous prospective randomised trials comparing membrane-active antiarrhythmic drugs [AADs] versus catheter ablation. And, based on these findings, we know that ablation is much more effective in restoring and maintaining sinus rhythm in those patients,” Chun comments. “We also know that progression to more sustained and persistent forms of AF can be delayed [with catheter ablation]—and, therefore, first-line or early ablation of persistent AF patients represents a very interesting group. However, there had been no prospective randomised trial looking into whether catheter ablation could be the superior or preferred first-line therapy in persistent AF.”
Because of the picture Chun outlines here, catheter ablation for persistent AF—whereby a patient experiences an irregular heart rhythm continuously for more than seven days—is not presently recommended as a first-line treatment by major medical societies around the world. However, the AVANT GUARD trial has gone some way to introducing new evidence indicating that ablation—more specifically, non-thermal pulsed field ablation (PFA) delivered via the FARAPULSE™ PFA System (Boston Scientific)—may be a suitable alternative to AAD therapy alone.
AVANT GUARD enrolled patients with previously untreated persistent AF, randomly assigning them at a 2:1 ratio to undergo PFA or receive AADs. After screening across 68 investigational sites in 14 different countries, a total of 310 patients were randomised; 207 to PFA and 103 to AADs. Furthermore, all patients in both groups received an insertable cardiac monitor (ICM). Here, Chun also highlights the fact that amiodarone—despite being considered the most potent AAD that is currently available—was not permitted in the trial’s control arm, owing to its known side-effects and the potential risks this may have created in a study population with an average age of more than 65 years.
According to Chun, ablation treatments in the trial were performed using a pentaspline catheter, the FARAWAVE™ PFA Catheter (Boston Scientific), which enabled “very predictable and very high-quality” pulmonary vein isolation (PVI), but also allowed for additional empiric ablation at the posterior wall—a location that many believe plays a major role in more progressed forms of AF, including persistent AF.
“Therefore, with AVANT GUARD, we were able to take advantage of the latest developments in catheter designs and energy forms,” Chun adds, also noting that a total of 179 patients ultimately received PFA—both PVI and posterior wall isolation (PWI)—in the treatment arm.
The trial’s primary effectiveness endpoint was based on the short-term and long-term success of treatment through 12 months. Short-term success was defined as procedural success in the PFA group, and the absence of ablation during the 90-day blanking period after treatment initiation in the AAD group, while long-term success was defined as freedom from recurrence of atrial arrhythmias, repeat ablation or need for AADs from 90 days through 12 months in the PFA group, and freedom from amiodarone use at any time. An additional group of 78 patients underwent PFA and were analysed solely for the primary safety endpoint, which pertained to a combination of device- and procedure-related serious adverse events.
Providing a closer look at the trial’s somewhat “novel” primary effectiveness endpoint, Chun highlights the fact that AVANT GUARD—in addition to measuring symptomatic episodes with durations ≥30 seconds—used continuous rhythm monitoring via the LUX-Dx™ ICM (Boston Scientific) to capture asymptomatic arrhythmia episodes lasting one hour or more that would otherwise have gone undetected. Chun points to recent research indicating that overall AF burden may be of even greater clinical relevance compared to AF recurrence alone, with AVANT GUARD therefore providing a more comprehensive assessment of this burden versus many prior AF studies.
“Having those data available on both symptomatic and asymptomatic episodes is a unique strength of this trial in the field of persistent AF ablation,” he continues. “From a scientific and academic perspective, we want to understand what the AF burden is in these patients, whether they are treated with ablation or AADs. The information an ICM gives us is perfect—it not only tells us about the time to recurrence, but also about the arrhythmia burden, which, as we know from phase two of the ADVANTAGE AF study, is related to healthcare utilisation.”
AVANT GUARD results
As per the now-published results from AVANT GUARD, 56% of patients in the PFA group met the trial’s primary effectiveness endpoint at 12 months versus 30.1% in the AAD group, meaning catheter ablation successfully achieved superiority over the control arm. Additionally, a statistically significantly higher rate of patients treated with PFA demonstrated no atrial arrhythmia recurrence compared to patients who received AADs (51.7% vs 32.2%, respectively). And, compared to those receiving AADs, significantly more patients (19.5%) treated via the Farawave catheter had no detected atrial arrhythmia burden at one year, while the mean atrial arrhythmia burden was found to be 6.5% lower in the PFA group versus the AAD group.
“These findings are in line with the notion that catheter ablation is more powerful in reducing or even eliminating AF burden as compared to standard-of-care AADs,” Chun comments. “This is really pointing in a direction that may be relevant for future clinical guidelines; in persistent AF, instead of waiting and trialling different medications, it may be better to go for catheter ablation.”
Additionally, at 12 months, the trial’s primary safety endpoint had occurred in 13 out of 257 patients (5.1%) across the combined PFA group—which included both those randomised to PFA and those assigned to PFA for the safety analyses specifically. As such, AVANT GUARD was deemed to have achieved a rate that was significantly lower compared to its predefined performance goal of 12%. Among PFA patients, the trial saw no instances of procedure-related death, oesophageal injury, pulmonary vein stenosis, haemolysis or delayed-onset vasospasm, but there were six reports of non-disabling stroke, among small numbers of other adverse events including pulmonary oedema, cardiovascular adverse events, and vascular access complications. Overall, serious adverse events had occurred at statistically similar rates of 25% in the PFA group and 21% in the AAD group at 12 months, indicating that these risks were largely driven by underlying characteristics of the patient population rather than the therapy itself.
This is really pointing in a direction that may be relevant for future clinical guidelines; in persistent AF, instead of waiting and trialling different medications, it may be better to go for catheter ablation
“There has been some discussion around the rate of cerebrovascular events—or strokes—in AVANT GUARD,” Chun outlines. “Due to these stroke rates, there was a pause during the trial as we re-analysed the CHA2DS2-VASc scores, and we found that the average score was 2.7 prior to that pause, meaning this population had a high baseline risk of ischaemic stroke [compared to patients in prior trials studying persistent AF]. This was one of the explanations for those unexpectedly high stroke rates—and that’s why we paused, re-evaluated, and continued, but with a more careful approach to the general stroke risk.
“We undertook this precautionary pause and re-analysis to better understand the stroke rates, which I think shows that we took this very seriously, and that readjustment was just to ensure we were enrolling patients with CHA₂DS₂-VASc scores in a similar range to other persistent AF trials. And, after continuation of the trial, the average CHA2DS2-VASc score came down to 2.1 and there were no more stroke events after that pause.”
Measures taken as part of the more cautious protocol Chun describes here included exclusion of patients with CHA₂DS₂-VASc scores ≥4, as well as left atrial thrombus screening within 24 hours of the procedure using transoesophageal echocardiography (TEE) or computed tomography (CT), uninterrupted anticoagulation for at least four weeks prior to the procedure, and a minimum activated clotting time (ACT) of 350 seconds prior to ablation.
In Chun’s view, another more general explanation beyond patients’ baseline characteristics within the trial may be the inherent and “well-recognised” increase in transient, periprocedural thromboembolic risk that is created by left-sided ablation procedures—but he also notes that this consideration represents a trade-off, as any rise in short-term stroke rates must be balanced alongside the fact that reduced long-term AF burden is associated with lower stroke risks over time.
Following on from these reports of AVANT GUARD’s one-year follow-up results, analyses of three-year follow-up data are also ongoing and expected to be presented further down the line.
Practice-changing impact?
“Overall, this trial shows that first-line catheter ablation—versus AADs—is associated with lower AF burden, higher success rates, and greater freedom from AF and atrial tachycardia, and is therefore beneficial for these patients,” Chun continues. “The potential implications of this include lower risks of hospitalisation and healthcare utilisation in the future, but also, I would assume, a lower long-term stroke risk because of the reduction in arrhythmias.”
Chun acknowledges the fact that, despite the prior paucity of high-level evidence, it would be naïve to suggest that catheter ablation has not already been used to treat persistent AF in clinical practice. In “the real world”, he explains, many operators and centres have been performing these treatments, and many patients have been asking for them as well.
“However, AVANT GUARD supports what our centre and some other centres have been doing,” Chun says. “It is reassuring to have scientific data that really support this pathway, and I think this has the potential to at least impact future clinical recommendations and guidelines by opening the door to first-line catheter ablation in persistent AF.”
Despite the trial’s positive outcomes and potentially significant implications for the electrophysiology (EP) space, Chun feels that multiple areas for improvement remain. For example, he notes that, in AVANT GUARD, while posterior wall ablation was performed with fluoroscopy only in some instances rather than via the FARAVIEW™ Software Module (Boston Scientific) 3D mapping system, centres—particularly lower-volume facilities—should be “well-acquainted” with FARAVIEW owing to its value in better navigating PFA lesions.
Providing advice to his peers in the EP field, Chun avers: “I would select patients carefully, and go for early ablation treatment in younger patients with lower CHA₂DS₂-VASc scores rather than trying different AADs. I would also ensure, of course, that the procedure is done well and that you have passed the learning curve using a pentaspline catheter so that you have a high level of technical expertise.”
Finally, touching on additional indications into which PFA may yet advance, Chun states that repeat procedures in patients presenting with organised arrhythmias like atrial tachycardia—rather than AF—constitute a major emerging space, as does the “big unresolved problem” of delivering deep lesions (>1cm) for ventricular arrhythmias.
“PFA as an energy source has the potential to be attractive in that area, but we need a much better understanding of different waveforms, and their impact and side-effects,” he concludes. “There is a lot of enthusiasm around PFA—and I am very much pro-PFA too—but we still need to make sure we understand these treatments and carefully monitor what we’re doing in order to continue learning during this journey.”
The FARAWAVE catheter is indicated for treatment of paroxysmal and persistent AF for drug-refractory patients.
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