What is the purpose of the STOP AF trial? Describe the trial objectives.

What is important about STOP AF is that it is the first trial designed to obtain FDA approval for a catheter-based treatment for atrial fibrillation. Although the area of AF ablation has grown tremendously over the past 5 or 6 years, all of it has been based on radiofrequency catheter ablation, which has evolved from treatment of many other types of arrhythmias. None of the catheters that we currently use are actually approved for atrial fibrillation ablation by the FDA; they are used off label. This is a pivotal trial in that it is the first time that the FDA has dealt with the issue of defining the success of catheter-based ablation approaches to atrial fibrillation. STOP AF has a rigorous all or none endpoint of any documented AF as a failure in either the medical or balloon treatment arms. The objective of the trial is to prove that cryoablation of the PV ostium is better than medical therapy in patients with idiopathic paroxysmal atrial fibrillation. The endpoint of the study is the elimination of spontaneous AF at one year. The secondary endpoints of the trial are symptomatic improvement, reduction in frequency of the episodes, differences in incidence of hospitalizations or need for cardioversion, etc. Most importantly, the primary goal of the trial is to statistically prove that the catheter cryoablation technique is as safe as medication, but offers improved efficacy.

What is the target patient population for the study? How many sites are participating?

There are a total of 22 North American sites. STOP AF is a randomized controlled trial, with a 2:1 randomization; this means that 2 patients will receive cryoablation and 1 patient will receive medication. This design is predicated on statistical modeling designed to prove or disprove the study hypothesis that ablation is equal to or better than medication for prevention of AF. The medication (or control) group will receive 1 of 3 different antiarrhythmic drugs flecainide, propafenone or sotalol. The study design is for a total of 243 patients, with 12 months of follow up. There is also the opportunity of crossover from the drugs to the cryo treatment arm at 6 months.

The specific target population is patients with idiopathic paroxysmal atrial fibrillation, defined as 2 or more episodes of AF during the 2 months preceding enrollment, at least 1 of which must be documented by EKG. Patients are only allowed mild structural heart disease. The age range is 18-75 years old, and these patients have to have failed at least 1 primary antiarrhythmic drug in the past (see website for details of inclusion/exclusion criteria).

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