STOP AF First Trial: Cryoballoon Ablation Is Superior to Antiarrhythmic Drug Therapy for the Prevention of Atrial Arrhythmia Recurrence in Patients With Paroxysmal Atrial Fibrillation

Sahar Memar Montazerin, MD
By Sahar Memar Montazerin, MD on

A recent trial by Dr. Oussama M. Wazni, published in the New England Journal of Medicine, indicated that in patients with paroxysmal atrial fibrillation, cryoballoon ablation therapy is superior as compared with antiarrhythmic drug therapy, in the prevention of atrial fibrillation recurrence. The study also showed the non-inferiority of this procedure over the drug therapy approach in terms of safety.

Catheter ablation is the treatment of choice in patients with symptomatic paroxysmal atrial fibrillation who failed to respond to antiarrhythmic medications. Previous studies showed that the early ablation approach was associated with a reduction in arrhythmia recurrence. In addition, in the Early Treatment of Atrial Fibrillation for Stroke Prevention Trial (EAST-AFNET 4), early rhythm control of atrial fibrillation resulted in a lower risk of adverse cardiovascular outcomes as compared to usual care. The STOP AF First trial assessed whether cryoballoon ablation therapy is superior to antiarrhythmic agents, in terms of safety and efficacy, as the first choice of treatment in patients with symptomatic paroxysmal atrial fibrillation.

The STOP AF First trial recruited patients with paroxysmal atrial fibrillation who had not previously received antiarrhythmic agents. Participants were randomized in a 1:1 ratio to receive either pulmonary vein isolation with a cryoballoon or treatment with class I or III antiarrhythmic drugs. Arrhythmia was monitored at various visits with in-person and patient-activated telephone monitoring. Two sessions of 24-hour ambulatory monitoring were conducted every 6 months. The primary efficacy endpoint was evaluated in a Kaplan–Meier analysis and defined as the absence of initial failure of the procedure or atrial arrhythmia recurrence after a 90-day blanking period to allow recovery from the procedure or drug dose adjustment. The primary safety endpoint included serious adverse events associated with the cryoballoon ablation procedure and was only assessed in the procedure group.

A total of 203 patients were assigned to antiarrhythmic therapy (n=99) or cryoballoon ablation therapy (n=104). The procedure success rate was 97%. At 12 months, a total of 78 patients in the cryoballoon group (75%; 95% confidence interval [CI]: 65.0 to 82.0) and 48 patients in the drug-therapy group (45%; 95% CI: 34.6 to 54.7) experienced treatment success (P<0.001 by log-rank test). In the ablation group, the primary safety end-point event occurred in 2 patients.

The trial had some limitations: first, the time of the follow-up was 12 months, which limits the evaluation of potential adverse effects of first-line cryoballoon ablation therapy and efficacy after 12 months. Second, the trial included the use of various agents from class I and III antiarrhythmic medications, which causes variability. Overestimation of treatment success is another limitation that should be taken into account given the periodical use of rhythm monitoring instead of continuous monitoring.

Finally, future studies with a larger population and longer follow-up duration are warranted to support the results of this trial.

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