AT ACC 16
CHICAGO (FRONTLINE MEDICAL NEWS) – The largest-ever randomized trial of catheter ablation of atrial fibrillation has ended in a draw between radiofrequency and cryoballoon ablation in safety and efficacy – and that actually represents a win for cryoablation, a simpler and far more easily mastered procedure, Dr. Karl-Heinz Kuck said at the annual meeting of the American College of Cardiology.
“We can teach physicians how to do cryoablation much more easily. That will allow more patients with atrial fibrillation to get access to catheter ablation, which is what we really need,” according to Dr. Kuck, principal investigator in the poetically named FIRE AND ICE trial and head of cardiology at St. Georg Hospital in Hamburg (Germany).
FIRE AND ICE included 769 patients in eight European countries. The participants, all of whom had antiarrhythmic drug–refractory paroxysmal atrial fibrillation (AF), were randomized to radiofrequency ablation – the long-time standard – or to cryoablation, a newer technology. Radiofrequency ablation was guided by three-dimensional electroanatomic mapping, while cryoablation utilized fluoroscopic guidance.
The primary efficacy endpoint was the 1-year rate of clinical failure, defined as an occurrence of AF, atrial flutter, or atrial tachycardia lasting for at least 30 seconds, or repeat ablation or the use of antiarrhythmic drugs following a 90-day postprocedural blanking period. The clinical failure rate was 34.6% in the cryoballoon group and similar at 35.9% in the radiofrequency group.
Serious treatment-related adverse events occurred in 10.2% of the cryoballoon group and 12.8% of the radiofrequency group, a nonsignificant difference. No procedural deaths occurred in the study.
There were, however, several significant procedural differences. Procedure time averaged 124 minutes in the cryoablation group, nearly 20 minutes less than the 142 minutes for radiofrequency ablation. However, the 17-minute fluoroscopy time in the radiofrequency group was 5 minutes shorter than for cryoablation.
Dr. Kuck said the study underestimates the true procedural differences because FIRE AND ICE was carried out by extremely experienced operators. In routine clinical practice involving non-elite operators, it’s not unusual for radiofrequency ablation fluoroscopy times to be two or even three times longer than the 17 minutes seen in the study. Plus, FIRE AND ICE was conducted when the procedure entailed two applications of the cryoballoon. Now only one application is recommended, cutting an additional 12 minutes off the total procedure time, he added.
Radiofrequency ablation takes longer because it entails creating a series of point-to-point lesions in a circle to isolate the pulmonary veins. With cryoablation, the balloon is moved into position, inflated, and a 3-minute-freeze is administered to create a circle of necrotic tissue in a single-step procedure.
Discussant Dr. Hugh G. Calkins praised the FIRE AND ICE investigators’ use of a rigorous definition of recurrence that required as little as a 30-second episode of atrial arrhythmia.
“That’s a very high bar, so I think the results are very impressive,” said Dr. Calkins, professor of medicine and of pediatrics and director of the cardiac arrhythmia service at Johns Hopkins University, Baltimore.
He commented that “this study is a clear reminder that 90% success rates just don’t happen in this field,” despite what some practitioners have claimed.
Asked how he predicts the study results will influence the field of AF ablation, Dr. Kuck replied that he foresees much wider adoption of cryoablation and a stronger endorsement of the technology in updated guideline recommendations.
“I personally believe this will be the most important development in our field in the next several years,” he added.
The electrophysiologist noted that even though current guidelines give a class Ia recommendation to catheter ablation of paroxysmal AF that’s refractory to at least one antiarrhythmic drug, at present only 4% of such patients actually undergo the procedure.
“Having just 4% of patients with AF undergo catheter ablation cannot be what we are looking for as physicians,” Dr. Kuck said. “I believe if we want to roll out catheter ablation for AF, we need simple and safe tools. This trial elegantly shows that with a simpler device that allows single-shot isolation of the pulmonary veins, we can get the same safety and efficacy as with radiofrequency ablation. I often tell people that radiofrequency ablation of atrial fibrillation is the most challenging procedure in all cardiology. We do this procedure from the groin in a moving heart. It’s a very complex technology.”
His dream, he continued, is that cryoablation will eventually enable patients with atrial fibrillation to be managed the same way electrophysiologists treat patients with Wolff-Parkinson-White syndrome; with the first episode, the patient goes to the electrophysiology catheterization lab for an ablation procedure.
“I think there’s a great message here: The cryoballoon will move catheter ablation from a niche procedure performed in specialized centers by the few guys in the world who can do it really well out into the broader world. To do that you need a tool that is safe, simple, and can be handled by the average doctor,” Dr. Kuck said.
Discussant Dr. Anthony DeMaria commented that it would be premature at this point to start thinking about cryoablation as a first approach to new-onset AF, given the roughly 35% clinical failure rate at 1 year seen in FIRE AND ICE. That rate doubtless would have been even higher had patients been equipped with implantable loop recorders, added Dr. DeMaria, professor of medicine at the University of California, San Diego.
Dr. Kuck conceded that the high recurrence rate is one of the great unsolved limitations of catheter ablation of AF.
“We don’t know how to get the pulmonary veins permanently isolated,” he said. “We can create acute lesions, but over time what we’ve seen is recovery of tissue and then reconduction by the pulmonary veins. I believe that 20% of the 40% recurrence rate is due to reconduction from the pulmonary veins, and the rest is probably due to triggers coming from other sites.”
The FIRE AND ICE trial was funded in part by Medtronic, which markets the Arctic Front Advance cryoablation catheter used in the study. Dr. Kuck reported serving on a speakers’ bureau for Medtronic and acting as a consultant to Biosense Webster, Edwards, and St. Jude.
Simultaneous with Dr. Kuck’s presentation at ACC 16, the results of FIRE AND ICE were published online (N Engl J Med. 2016 Apr 4. doi: 10.1056/NEJMoa1602014 ).
