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04-10-2024 | Atrial Fibrillation | Editor's Choice | News

Pulmonary vein isolation benefit in symptomatic AF not due to ‘placebo effect’

Author: Sara Freeman

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medwireNews: Results of the SHAM-PVI study confirm that the beneficial effects of pulmonary vein isolation (PVI) that have been reported in people with symptomatic atrial fibrillation (AF) are not due to a placebo effect.

In the randomized double-blind trial, PVI via cryoballoon ablation “resulted in a clinically important decrease in AF burden,” over a 6-month follow-up period when compared to a sham procedure, researchers report in JAMA.

Moreover, Rick Veasey (East Sussex Hospitals NHS Trust, Eastbourne, UK) and fellow investigators say that patients’ AF symptoms and overall quality of life also showed “substantial improvements.”

PVI is a standard ablation technique for AF that is recommended when antiarrhythmic medication fails or when patients do not tolerate medical therapy, they explain. But, despite multiple trials proving the value of PVI in AF, none had compared PVI to a sham procedure, meaning that a possible placebo effect could not be ruled out.

Between 2020 and 2024, the researchers recruited 126 individuals with symptomatic AF who had been referred for catheter ablation at two tertiary care centers in the UK. Participants had a mean age of 67 years and 71% were men. The majority (80%) had persistent AF despite medical treatment and one fifth had paroxysmal AF.

At enrollment, these participants had an implantable loop recorder inserted if they did not already have one. This was set to record all episodes of AF that lasted for 2 minutes or more, and tachycardic episodes that lasted for more than 16 heart beats.

The participants were then randomly assigned to undergo catheter ablation (n=64) or a sham procedure (n=62), both with direct current cardioversion if they were in AF. PVI was achieved using a 28 mm cryoballoon catheter with phrenic nerve pacing when ablating the right pulmonary veins. For the sham procedure, a 5F pacing catheter was placed in the right subclavian vein to pace the phrenic nerves. At the end of these procedures, and once sheaths had been removed, all patients underwent a three-way stopcock suture to achieve hemostasis.

The primary outcome was AF burden, which is the percentage of time spent in AF. This was measured continuously from the end of month 3 to the end of month 6 after randomization. The researchers note that the first 3 months of follow-up were designated a “blanking period” and any AF episodes and arrhythmia-based outcomes that occurred during this period were discounted.

At baseline, the mean AF burden was around 78.0% in both the PVI and sham procedure groups, falling to a respective 18.2% and 43.2% at 6 months. This represented a significant 60.3% absolute change in the AF burden in the PVI group and 35.0% in the sham procedure group. 

The AF burden reduction with PVI versus sham procedure was significantly greater in those with persistent than paroxysmal AF. Among those in the persistent AF group, the absolute reductions with PVI and the sham procedure were 71.4% versus 44.9%, while for those with paroxysmal AF, there was an absolute reduction of 16.1% with PVI versus an absolute increase of 2.8% with the sham procedure.

AF symptoms assessed at 6 months using the Atrial Fibrillation Effect on Quality-of-Life questionnaire showed a significant 18.4-point difference on the 100-point score, favoring PVI over the sham procedure. Similarly beneficial results were seen using the Mayo AF-Specific Symptom Inventory. Also, the 36-Item Short Form Health Survey general health score improved by a significant 9.27 points more at 6 months with PVI than with the sham procedure, with similar benefits found for the other subscales.

Discussing some of the studies potential limitations, the researchers acknowledge the short follow-up of 6 months, compared with the typical 1 year of previous trials assessing AF ablation. However, they note that the primary objective was to look at the possible placebo effect rather than long-term benefit of PVI versus sham AF ablation.

They conclude: “At 6-month follow up, this study demonstrated no clinically relevant placebo effect with PVI.”

medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2024 Springer Healthcare Ltd, part of the Springer Nature Group

JAMA 2024; doi:10.1001/jama.2024.17921

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