The trial, conducted in eight European countries, enrolled 769 patients needing ablation for intermittent atrial fibrillation. Patients were randomly assigned to receive either the radiofrequency or cryoballoon technique; both patients and physicians were aware of which technique was being used. The two groups were similar in terms of demographic factors, such as age and gender, as well as health status, based on parameters such as body mass index, blood pressure and various measures of heart function.

In addition to using different methods for disabling the target heart tissue, the two techniques involved different procedures to help the physician locate the target tissue. For radiofrequency procedures, physicians were guided by 3-D electroanatomical mapping to create tissue lesions in a point-by-point ablation approach. For cryoballoon procedures, physicians used a type of X-ray imaging known as fluoroscopy to create tissue lesions in a single-step ablation approach.


Outcomes were assessed through in-person patient visits conducted three months after the procedure, six months after the procedure and every six months thereafter. Each visit included an electrocardiogram test to assess heart rhythm and function, as well as the use of a Holter monitor, in which the patient wears a monitor for 24 hours to check for any abnormal heart rhythm. Patients were tracked for just over 18 months, on average.

The results revealed no significant difference in the rates of recurrence of an irregular heart rhythm or the need for medication or subsequent procedures to address atrial fibrillation, outcomes that collectively occurred in 64.1 percent of patients receiving radiofrequency ablation and 65.4 percent of cryoballoon patients within 12 months after the procedure.

The results revealed no significant difference in the rates of recurrence of an irregular heart rhythm or the need for medication or subsequent procedures to address atrial fibrillation, outcomes that collectively occurred in 35.9 percent of patients receiving radiofrequency ablation and 34.6 percent of cryoballoon patients within 12 months after the procedure.

In both groups, there was generally a low rate of procedure-related complications such as infection, dangerous heart rhythms or accumulation of fluid in the heart. However, patients receiving cryoballoon ablation were significantly more likely to experience injury to the phrenic nerve, which can affect the functioning of the diaphragm and require patients to use an artificial ventilator. Such injuries occurred in 2.7 percent of cryoballoon patients and zero patients receiving radiofrequency ablation. In all but one of these cases, functioning was restored by 12 months post-operation.

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