Afib Ablation Delivers in First Sham-Controlled Study

LONDON — Pulmonary vein isolation (PVI) produced real short-term improvements for people with atrial fibrillation (Afib or AF), according to the first sham-controlled trial on the subject.

Continuous monitoring by implantable loop recorders showed that absolute mean Afib burden change from the end of month 3 to the end of month 6 postrandomization was significantly larger with cryoballoon PVI versus sham (60.31% vs 35.0%, P<0.001), reported Rajdip Dulai, MBBS, of Eastbourne District General Hospital and University College London.

This clinical benefit was accompanied by other improvements in symptoms and quality of life by 6 months. For example, overall AF Effect on Quality of Life scores significantly favored PVI over sham (difference from baseline to 6 months +24.1 vs +7.0 points on a scale from 0 to 100), as did Mayo AF-Specific Symptom Inventory frequency and severity scores and the 36-Item Short Form Health Survey general health score.

“At 6 months follow-up, the SHAM-PVI study has demonstrated no clinically relevant placebo effect with PVI … This study provides reassurance that PVI works,” Dulai said at a press conference at the European Society of Cardiology meeting. Results were simultaneously published in JAMA.

PVI has already been the standard ablation technique used in Afib for years. This treatment is guideline-recommended for quality of life improvement in symptomatic individuals for whom antiarrhythmics have failed or are not tolerated, despite holes in the evidence generated thus far.

“Previous studies of catheter ablation for AF have not shown consistent benefits in end points such as death, stroke, and cardiac arrest. Given these results, there is concern that PVI exhibits a substantial placebo effect,” Dulai’s group explained.

SHAM-PVI was designed to provide more definitive answers. The trial was conducted at two tertiary centers in the U.K. and randomized participants to PVI with cryoablation (n=64) or sham with phrenic nerve pacing (n=62). The authors included 126 patients with symptomatic paroxysmal (20.6%) or persistent Afib (79.4%).

Electrophysiologist Peter Kistler, MBBS, PhD, of The Alfred Hospital in Melbourne, Australia, remarked on the trial results showing “unsurprising clear benefit in favour of ablation with reduction in AF burden and improvements in quality of life.” He told MedPage Today that despite the relatively short follow-up, “the findings strongly support the established role of ablation in the management of atrial fibrillation.”

Among the cardiologists who first voiced their concerns about a placebo effect in catheter ablation was Özcan Özeke, MD, of Ankara Bilkent City Hospital, Turkey, who told MedPage Today that he now welcomes the present results. However, he still took issue with the larger trend of cardiovascular interventions being pushed onto patients without sufficient scientific backing.

“The problem today is that physicians’ enthusiasm for performing procedures is more important than the outcomes of these procedures. Since 1992, AF ablation has been performed, and [only] 3 decades later, a well-designed study that follows scientific rules shows its effectiveness,” he commented in an email.

“Many coronary stenting in stable patients or percutaneous LAA [left atrial appendage] closure procedures continue beyond guideline recommendations all around the world, contrary to their conflicted data … Even if it leads to treatment delays, the approach of ‘learn the procedures first, then the data will come’ needs to shift to ‘first the correct scientific data, then training,’ particularly in elective procedures,” he urged.

SHAM-PVI participants averaged age 66.8 and 70.63% were men.

Dulai explained that phrenic nerve stimulation was chosen for sham because this is already done normally to mitigate the risk of phrenic nerve loss during cryoablation, and this is what is felt by patients during the procedure.

While PVI and sham groups shared the same likelihood of needing repeat cardioversions during follow-up, PVI was associated with numerically less need for re-starting a class I or III antiarrhythmic medication (32.3% v s 54.1%).

The authors acknowledged that they had studied just one technology used for Afib ablation, however.

“Despite advances in technology, PVI remains the cornerstone ablation strategy for treatment of symptomatic AF. It would not be expected that PVI with radiofrequency or pulsed-field ablation would have a differing result than that of cryoablation,” they reasoned.

As for safety, PVI was associated with one case of pericarditis, one aortic pressure tracing on transseptal puncture without further adverse consequence, and one patient having transient leg weakness/numbness due to lidocaine.

Major exclusion criteria of SHAM-PVI included long-standing persistent Afib, prior left atrium ablation, other arrhythmias requiring ablative therapy, a large left atrium, and reduced ejection fraction.

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