Pulsed Field Ablation Challenges Conventional Devices in AF

Ted Bosworth

August 27, 2023

Pulsed field ablation (PFA), a technology now approved in Europe but not yet licensed in the United States, achieved noninferiority to conventional thermal ablation for the treatment of atrial fibrillation (AF) in a head-to-head trial, an outcome that might favor PFA in the context of other considerations.

"The take-home message is that this is a new technology that has important safety benefits. Patients do not have to worry about the possibility — albeit rare — of esophageal fistulae and other problems. It is faster with at least the same efficacy," reported Vivek Y. Reddy MD, director of Cardiac Arrhythmia Services, Mount Sinai Hospital, New York, New York.

As opposed to conventional catheter-based thermal ablation, which isolates pulmonary veins harboring AF triggers by heating or freezing the tissue, PFA uses microsecond high-voltage electrical fields to produce cellular necrosis. It is largely nonthermal, Reddy said.

New Device Might Spare Adjacent Tissue

In experimental studies, PFA has demonstrated a high degree of ablative specificity, limiting effects on adjacent tissues, such as the esophagus and phrenic nerve, he explained.

Several previous clinical studies support the specificity of the PFA ablative effect, but the ADVENT trial, which Reddy presented August 27 at the European Society of Cardiology (ESC) 2023 Congress, is the first trial in which patients have been randomly assigned to PFA or catheter-based ablation.

The study was published online in the New England Journal of Medicine simultaneously with the ESC presentation.

The primary efficacy endpoint was the absence of a composite of endpoints indicating incomplete ablation. These included an initial procedural failure, atrial tachyarrhythmias arising after a 3-month blanking period, subsequent use of antiarrhythmic drugs, cardioversion, or repeat ablation. The primary safety endpoint involved a composite of procedure-related adverse events.

The 607 patients enrolled in this trial had AF refractory to at least one antiarrhythmic drug class. They were randomly assigned in a 1:1 ratio to PFA with a catheter system (Farapulse–Boston Scientific) or to thermal ablation.

Of the thermal approaches, radiofrequency or cryoablation was permitted, but each center was required to use just one for the control arm. For the comparison to PFA, outcomes for the two thermal techniques, which were used in similar proportions of patients, were combined based on previous evidence that these approaches perform similarly.

At 1 year, 73.3% of patients in the  PFA group and 71.3% of those in the control group met the primary outcome, meaning none of the events signaling ablation failure occurred. The numeric advantage of PFA confirmed noninferiority, although an evaluation of superiority for efficacy, which was triggered by the advantage of PFA, was not significant.

As predicted by previous studies, stratification of thermal ablation approaches showed that outcomes were similar, although the proportion of patients who  remained free of events at 1 year was numerically higher in the cryoablation group relative to the radiofrequency group (73.6% vs 69.2%).

An adverse safety event occurred in 2.1% of those who underwent PFA and in 1.5% of those who underwent thermal ablation. This 0.6–percentage point difference placed PFA well within the boundary of noninferiority for safety.

Of notable events, the only death in this study occurred in the PFA group, and the only stroke occurred in the control group. Phrenic nerve palsies occurred only in the control group (2 vs 0) while pericarditis was seen only in the PFA group (2 vs 0). One case of pulmonary edema occurred in each group.

"Catheter ablation is quite safe and effective," said Reddy, explaining why this comparison was conducted on the basis of noninferiority.

Reddy emphasized that noninferiority for PFA was achieved by operators with little or no experience with this technology, whereas the catheter ablations were delivered by operators who typically had previously performed hundreds of interventions.

"With experience, one would expect even better rates of success. This is the floor," Reddy said.

Procedure Time Faster With PFA

Despite working with a new technology, the mean procedure performance time with PFA was faster (105 vs 123 minutes) even though mean fluoroscopy time was longer (21.1 vs 13.9 minutes). Reddy considers the difference in procedure time a meaningful demonstration of the efficiency of PFA.

"When you look at procedure performance, it is remarkable that the procedure times were statistically significantly shorter for a first-use technology in the hands of multiple operators," Reddy said.

There was also a statistically significant advantage for PFA regarding change in the mean pulmonary vein cross-sectional area following the procedures (0.9% vs 12%). Reddy acknowledged that small changes in pulmonary vein dimension are not clinically meaningful, but this result "gets at the question of whether we can achieve ablation without tissue proliferation that we see with conventional ablation."

Overall, Reddy believes that the data from ADVENT provide several reasons "to get excited about PFA," including the efficiency of this technique in the context of at least similar efficacy but a potential for fewer adverse events.

The ESC-invited discussant, Samuel Kiil Sørensen, MD, Gentofte University Hospital, Copenhagen, Denmark, agreed that the ADVENT data support PFA as an alternative to thermal ablation. He suggested that the shorter procedure times are clinically meaningful given comparable safety and efficacy.

"Which property of PFA justifies noninferiority?" he asked. "Many of the complications of AF ablation are not specific to the energy modality. The devastating complications from damage to the esophagus, pulmonary veins, and phrenic nerve that the PFA technology may eliminate are rare, so they would not be expected to change the overall complication rate in a [randomized controlled trial] of realistic size."

However, he suggested PFA might still prove to be an incremental advance for AF. He cited previous evidence that supports the specificity of its ablative activity and emphasized that ADVENT tested a first-generation device that might not capture the full advantages of the PFA technology.

The trial was supported by FarapulseBoston Scientific. Reddy reports financial relationships with more than 30 pharmaceutical or device manufacturers, including FarapulseBoston Scientific. Sørensen reports financial relationships with Medtronic and Biosense Webster.

European Society of Cardiology (ESC) 2023 Congress. Presented August 27, 2023.

N Engl J Med. Published online August 27, 2023. Abstract

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