A randomised controlled trial comparing three methods of pulmonary vein isolation for paroxysmal atrial fibrillation has revealed that procedures were faster with Medtronic’s Arctic Front cryoballoon than wide encirclement using conventional point-by-point radiofrequency ablation. Procedures using the cryoballoon also resulted in a higher single procedure success rate.
Ross J Hunter, St Bartholomew’s Hospital, Bart Health NHS Trust & QMUL, London, United Kingdom, presented the results of the trial at a Late-breaking trial session at the 35th Heart Rhythm Society Annual Scientific Sessions (7–10 May, San Francisco, USA).
“Radiofrequency ablation for pulmonary vein isolation is technically challenging, time consuming and the first time success rate is variable. The cryoballoon is arguably easier to use, but there is a lack of head-to-head data [comparing cryoballoon with radiofrequency ablation] both in terms of procedural parameters but also in terms of efficacy. Pilot data from our institution suggested a higher success rate with a combined approach than with either modality alone. We compared the success rates obtained with these three strategies in a randomised controlled trial with the hypothesis being that the combined approach is superior to either treatment alone for paroxysmal atrial fibrillation,” Hunter said.
The investigators randomised patients undergoing first time ablation for paroxysmal atrial fibrillation using radiofrequency energy, the cryoballoon, or a combined treatment. They defined pulmonary vein electrical isolation (as confirmed by using a circular mapping catheter) as the procedural endpoint for all cases.
In the study, the radiofrequency group underwent wide encirclement of the pulmonary vein using an irrigated radiofrequency ablation catheter guided by a 3D mapping system. Contact force sensing catheters were not used, Hunter clarified. The cryoenergy group underwent ostial pulmonary vein ablation using the Arctic Front cryoballoon. Hunter noted that if pulmonary vein isolation could not be achieved using the cryoballoon alone, then further focal lesions were added. The combined group underwent wide encirclement of the pulmonary veins to achieve isolation, followed by two empirical applications of the cryoballoon to each pulmonary vein ostia.
Patients were followed up at three, six and 12 months with a clinic review and seven days of ambulatory ECG monitoring. The primary endpoint was the one year success rate, defined as freedom from arrhythmia following the three month blanking period, off antiarrhythmic drugs after a single procedure.
A total of 237 paroxysmal atrial fibrillation patients were randomised in a 1:1:1 fashion so that there were 79 patients in each group. In the radiofrequency ablation group, 77 were ablated with two patients being withdrawn (one due to persistent left atrial thrombus and the other was diagnosed with cancer). In the cryoballoon group, 78 patients were ablated and one was withdrawn after being rendered asymptomatic following a change of antiarrhythmic drugs. All 79 patients randomised to the combined group were ablated. All patients were followed up to one year.
Baseline demographics were similar in all groups. Approximately two thirds of the patients in each group were male. Patients were around 60 years of age and had had atrial fibrillation for around five years. Patients in all groups had a left atrial diameter of around 4.3cm and had failed drug therapy with more than two anti-arrhythmics.
Success at one year was achieved in 47% in the radiofrequency group, 67% in the cryo group, and 76% in the combined group (p=0.015 for radiofrequency vs. cryo, p<0.001 for radiofrequency vs. combined, and p=0.166 for cryo vs. combined). Procedure time was 211 minutes for radiofrequency compared to 167 minutes for cryo and 278 minutes for combined (p<0.001 for radiofrequency vs. combined, radiofrequency vs. cryo, and cryo vs. combined groups). In the cryo group, 69% of patients had all pulmonary veins isolated with the cryoballoon alone and the rest needed additional point by point ablation to achieve pulmonary vein isolation.
Complications
Hunter told delegates that there were four complications with radiofrequency ablation: one tamponade; one haematoma; one pulmonary vein stenosis and one case of Dressler’s syndrome. With cryoenergy, there were four cases of phrenic nerve palsy. In the combined method, there were three complications: one pseudoaneurysm and two phrenic nerve palsies.
Conclusion
“The cryoballoon was faster than radiofrequency ablation and had a higher success rate. The combined group also had a higher success rate than radiofrequency, but was not superior to cryoenergy alone. However, there is a learning curve with cryoablation. Point-by-point ablation is still needed to achieve pulmonary vein isolation for some patients,” Hunter explained.
He stated that the implications of the trial results are that the cryoballoon is an appealing option for paroxysmal atrial fibrillation ablation. “The combined approach is less attractive. The impact of Arctic Front Advance and contact force sensing is still to be assessed. Multicentre trials are needed to confirm the superiority of cryoenergy,” Hunter noted.
