FreezeAF: Cryoballoon Noninferior to Radiofrequency Ablation for Paroxysmal Atrial Fibrillation

heart chambers atrial fibrillation
heart chambers atrial fibrillation
Recent trials have shown that cryoballoon catheter ablation has demonstrated success in treating atrial fibrillation among 74% of patients, presenting an alternative to traditional radiofrequency ablation.

Cryoballoon (CB) catheter ablation was noninferior to traditional radiofrequency (RF) ablation for pulmonary vein isolation in patients with paroxysmal atrial fibrillation (AF), according to study findings published in Circulation.

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia, associated with a high risk of stroke and heart failure, among other complications. Catheter ablation is a well-established treatment for paroxysmal AF, most commonly RF ablation.

In recent clinical trials, the use of a CB catheter has produced encouraging results: approximately 74% of patients maintain sinus rhythm at 12-month follow-up.

In an effort to combat the absence of randomization in most trials comparing the 2 ablation techniques, Armin Luik, MD, of the Academic Teaching Hospital of the University of Freiburg in Karlsruhe, Germany, and colleagues developed the FreezeAF trial to directly compare RF with CB for treating atrial fibrillation.

The randomized, controlled, prospective, noninferiority clinical trial included 315 patients to determine the comparative efficacy and safety of pulmonary vein isolation via either an irrigated radiofrequency or cryoballoon catheter. Patients were randomly assigned to either the RF (n=159) or CB (n=156) procedure group. Overall, the study skewed male (60.6% of participants); there were no significant differences in regard to prescribed medication.

Eligible patients were aged 18 to 75 years, had experienced at least 2 AF episodes 3 months prior to enrollment, had experienced at least one AF episode confirmed by an ECG, and had at least one instance of ineffective antiarrythmia drug (AAD) treatment.

Prior to undergoing either procedure, patients in both groups received 4 weeks of anticoagulation therapy, and had all AAD’s discontinued for 4 to 5 half-life periods. They were monitored at baseline, as well as via clinic visits at 3, 6, 9, and 12 months. Computed tomography (CT) or magnetic resonance imaging (MRI) scans were performed at the 3 month clinic visit, and at least one 24-hour Holter ECG was performed at the 3 or 9 month clinical visit.

The primary endpoint of the study was defined as the absence of both atrial arrhythmias and persistent complications — defined as new pulmonary vein stenosis, phrenic nerve palsy, cerebrovascular accident, bleeding, or vascular complications — at the 6 and 12 month follow-up visits. Analysis of these endpoints took place in both intention-to-treat (ITT) and per-protocol (PP) populations.

In the ITT population, 63.1% of patients in the RF group and 64.1% of patients in the CB group met the defined primary endpoints at 6 months. At 12 months, the proportion increased to 70.7% for RF and 73.6% for CB. Thirty-one patients in each group (62 total, P = .933) underwent redo procedures.

Few adverse events occurred during the index procedure in either treatment group. Overall, 14 patients (4.4%) experienced major events, and 13 (4.1%) experienced minor events. The perioprocedural complication rate was 12.2% in the CB group, compared with 5% in the RF group (P = .022). Overall there were 13 (4.1%) vascular complications reported with no differences in the two groups; 9 of these events were classified as major. Five (1.6%) pericardial effusions took place, with 2 major events occurring in the CB group and requiring pericardial drainage.

 “A number of studies have demonstrated the efficacy and safety of CB ablation for treatment of AF,” the researchers wrote. “At both 12 and 6 month follow-ups, CB was demonstrated to be non-inferior to RF in terms of freedom from AF in combination with an absence of persistent complications.”


  1. Luik A, Radzewitz A, Kieser M, Walter M et al. Cryoballoon versus Open Irrigated Radiofrequency Ablation in Patients With Paroxysmal Atrial Fibrillation: The Prospective, Randomised, Controlled, Noninferiority FreezeAF Study. Circulation. 2015; doi:10.1161/CIRCULATIONAHA.115.016871