SHAM-PVI Study Finds Mainstay Ablation Procedure for Atrial Fibrillation is Substantially More Effective than Placebo

Pulmonary vein isolation (PVI) results in clinically important improvements in both symptom burden and quality of life compared with a placebo in patients with atrial fibrillation (AF), according to a study presented at ESC Congress 2024.

PVI stands as the cornerstone of catheter ablation for both symptomatic intermittent and persistent AF. In this procedure, catheters are inserted into the heart to deliver radiofrequency energy or cryoballoon ablation to destroy harmful tissue on the veins that cause disruptive electrical signals and lead to arrhythmia.

Despite numerous studies advocating for the efficacy of PVI to treat symptomatic AF, there are concerns that PVI has a substantial placebo effect, and thus far, there have been no trials comparing PVI with a sham procedure.

The SHAM-PVI trial sought to fill this data gap. To conduct this analysis, researchers enrolled 126 patients with symptomatic paroxysmal or persistent AF, all of whom were previously treated with at least one antiarrhythmic drug who had been referred for catheter ablation at two NHS trusts in the UK.  The population of interest were randomized in a 1:1 fashion to undergo either PVI using cryoablation, or a placebo procedure involving phrenic nerve pacing to simulate an ablation procedure.

The primary end point of interest was defined as AF burden (% time in AF) at 6-months (excluding an initial 3-month blanking period), which the researchers assessed using a tiny implantable heart monitor placed under the skin. Secondary end points included important quality of life measures reported by patients, such as physical and social functioning, AF symptoms such as palpitations and breathlessness, and time to arrhythmia events.

PVI Beats Out Sham

The results showed that at 6 month follow-up, the average change in AF burden from the start of the trial was 60% in the ablation group and 35% in the sham intervention group. In patients with persistent AF, the investigators observed an average reduction in AF burden of 71% in the ablation group and 45% in the sham intervention group. Moreover, in patients with intermittent AF, the average reduction in AF burden was 16% in the ablation group compared with an average increase of only 3% in the placebo group.

Overall, the study demonstrated that quality of life scores were appreciably better in catheter ablation patients at 6 months. Similarly, the researchers noted, scores based on symptoms, daily activities, and treatment concern were also in favor of ablation. Furthermore, measures of health-related quality of life (e.g., physical functioning, vitality, emotional well-being, social functioning) also improved much more in the ablation group compared with the sham intervention group at 6 months.

“We expected that PVI would be more effective than a placebo procedure in patients with symptomatic AF, and indeed, the results proved our hypothesis was correct,” said lead author Dr Rajdip Dulai via a press release. “Going forward we would expect that patients with symptomatic AF be referred for ablation treatment without hesitation.”