Cryoballoon ablation is a faster procedure and is as effective as radiofrequency ablation for pulmonary vein isolation in patients with paroxysmal atrial fibrillation, but has a greater complication rate and requires higher X-ray dosages. Armin Luik (Staedtisches Klinkum Karlsruhe, Karlsruhe, Germany) presented the findings at a late- breaking clinical trial session at HRS 2015.
The investigator-initiated FREEZEAF study was aimed to prove whether the cryoballoon ablation technique is non-inferior to open irrigated radiofrequency pulmonary vein isolation in paroxysmal atrial fibrillation.
There are only a few studies comparing pulmonary vein isolation using open irrigated radiofrequency ablation and cryoballoon ablation for patients with paroxysmal atrial fibrillation. Luik stated that this is the first large, prospective, randomised controlled, non-inferiority study comparing the effectiveness and safety with those techniques.
The primary endpoint of the study was a combined endpoint, defined as absence of atrial arrhythmias without antiarrhythmic drugs, and without persistent complications at six-and 12-month follow-up. Secondary endpoints were safety endpoints and included peri-procedural complications, total procedure duration, and total X-ray exposure. The study protocol also required that there be no re-do procedures until after six-month follow-up, and that any re-do be performed with the same energy source as the index procedure. However, an additional ablation of cavotricupsidal isthmus was allowed for both groups.
A total of 315 patients aged between 18 and 75 years with paroxysmal atrial fibrillation were analysed. Participants receiving pulmonary vein isolation were randomised to cryoballoon ablation (n=156) or radiofrequency ablation (n=159). Baseline characteristics were similar in both groups, with a mean age of 60 years. Clinical follow-up was at three, six, nine, and 12 months.
In all, 92.4% patients remained at 12-month follow-up.
An intention-to-treat analysis of freedom from atrial arrhythmias without persistent complications found that the single pulmonary vein isolation success rate was 62% in the radiofrequency group and 63% in the cryoballoon group at six-month follow-up (p=0.006). At 12-month follow-up the findings for multiple pulmonary vein isolation were 65% and 68% respectively (p<0.001). Luik said: “Both were statistically significant, which means that this proves that the cryoballoon is non-inferior to the radiofrequency technique. The protocol analysis showed similar results: 64% in the radiofrequency group and 65% in the cryoballoon group for the single procedure success at six months. And 72-74% for multiple procedures after 12-month follow-up.”
Isthmus ablation was performed more often in the radiofrequency group. Luik explained: “The indication for isthmus ablation was a documented ECG with typical atrial flutter before the procedure, or the occurrence of typical atrial flutter during the procedure. We did not perform an isthmus ablation if there was no documentation of typical atrial flutter. But it was more common in the radiofrequency group.”
However, complications were significantly higher in the cryoballoon group than the radiofrequency group: 12.2% versus 5%. “The complication endpoint is driven by the complication of phrenic nerve palsies. We had nine phrenic nerve palsies (5.8%) in the cryoballoon group, which is significantly different. This is pretty in line with all the published data. We had no phrenic nerve palsy, which lasted longer than 12 months, and six of the nine phrenic nerve palsies recovered before the six-month follow-up.”
He concluded: “Pulmonary vein isolation with the cryoballoon in patients with paroxysmal atrial fibrillation is as effective as open irrigated radiofrequency in combination with a 3D mapping system. It is faster regarding to procedure time but it needs higher X-ray dosages to prove the balloon’s occlusion and has a higher complication rate due to a higher rate of phrenic nerve palsies.”
John D Day, (Intermountain Medical Centre, Salt Lake City, UT, USA), chair of the late-breaking session, commented: “I think this study answered intuitively what we already knew from previous studies. Except in the previous studies we were kind of comparing apples to oranges. Now we are able to compare apples to apples. From an efficacy standpoint I think it is equivalent to what we are using now. The one lingering issue is on the safety side, particularly the phrenic nerve issue. Fortunately, all nine patients got better by one year but still that is a lingering concern.
He also commented: “One definite advantage is the procedure [cryoballoon] was 22 minutes faster. The other advantage is, radiofrequency point-by-point is technically far more challenging. And it requires many, many, many more cases until you have achieved a mastery of that technique as opposed to the cryoballoon where you can obtain mastery in much fewer cases. So for people that are starting out it is a much quicker road to learning how to do a procedure.”But he pointed to a drawback of the trial design. “Multicentre would have been better, because then hopefully it would have factored out any potential biases from operator experience or familiarity.”