HRS: Use of cryoablation has the potential to STOP-AF
DENVER—Use of cryoablation to treat paroxysmal atrial fibrillation (PAF) rather than anti-arrhythmic drug therapy adds quality of life, reduces AF events and has high success rate, according to a late-breaking clinical trial presented at the 31st annual Heart Rhythm Society scientific sessions this morning.

Lead author of the North American STOP-AF trial Jeremy N. Ruskin, MD, of the Massachusetts General Hospital in Boston, said results showed that cryoablation was “significantly more effective than additional trials of anti-arrhythmic drug therapy.”

The multi-center, 26-site randomized trial evaluated 245 patients with documented PAF who had at least two prior incidences of AF and who failed drug therapy. Researchers compare the outcomes of cryo-balloon ablation to anti-arrhythmic drug therapy. Forty-five percent of patients presented with atrial flutter.

Researchers at a 2:1 ratio randomized patients into either the cryoablation arm, which used the Medtronic Arctic Front Cardiac CryoAblation Catheter System (163 patients) or the anti-arrhythmic drug therapy arm (82 patients).

The researchers performed patient follow-up at one, three, six and 12 months, which included clinical ECG and imaging, as well as an evaluation of patient quality of life at 12 months.

Primary endpoint was freedom from chronic treatment failure—the absence of AF after a nine-month follow-up.

Results showed that 69.9 percent of patients who underwent pulmonary vein isolation via cryoablation were free of AF after 12 months compared to only 7.3 percent of the patients in the drug arm.

“These differences were quite dramatic,” noted Ruskin.

There was an 80 percent reduction in the rate of self-reported AF episodes in the cryoablation arm compared to only 25 percent reduction of self-reported episodes in the drug arm.

“The change in AF symptoms which were observed at six months were durable; they were present at the same degree at the 12 month follow-up. This was a sustained effect,” said Ruskin.

During the trial, the researchers found that the cross-over rate of patients in the drug arm to the ablation arm was very high—79 percent. This prevented a statistical analysis of the two arms to be performed.

Additionally, during the study the researchers evaluated quality of life scores between baseline and 12 months, drug-use in the two arms and procedural experience and its effect on safety.

“Quality of life scores were significantly improved between baseline and 12 months,” said Ruskin.

Regarding drug-use, after 12 months, use of anti-arrhythmic drugs in the cryoablation patient group dropped from 100 percent at baseline to almost 25 percent, explained Ruskin.

For the evaluation of procedural experience, the researchers used four quartiles: The lowest was operators who performed one to two ablation procedures and the highest, 12-23 procedures. For these aforementioned groups, treatment success ranged from 56 percent to 90 percent, respectively.

“There is a clear learning curve here with a powerful effect of procedural experience on success rate,” said Ruskin. However, he said that procedural experience was an independent predictor of adverse events.

According to Ruskin, the goal of the study was to “achieve a cryo-procedure adverse event rate of less than 10 percent.” Study results showed that the actual rate of these events for this patient arm was 3.1 percent, compared to 8.5 percent in the drug arm.

Only five strokes occurred during the entirety of the study and only one was ablation related, said Ruskin.

He pointed out that patients who underwent a single ablation procedure saw success rates of 74 percent, while those who required two ablation procedures saw rates of 52 percent.

“Subjects who require two procedures are more resistant. Whether the difference in long-term success rates are as prominent as they are in this particular study, I simply don’t have the data to provide the answer to that,” he said.

Ruskin noted that the device is still investigational, but “the hope is that the new technology will offer some efficiencies and advantages over point-by-point radiofrequency ablation.”

“Cryoablation is a highly effective technique for the prevention of PAF in symptomatic patients who are resistant to at least one anti-arrhythmic drug,” said Ruskin. “Cryoablation is associated with substantial improvements in quality of life and very impressive and sustained production in AF symptoms that travel in parallel in the prevention of PAF.”

Medtronic sponsored the STOP AF trial.