When It Comes to Defining the Outcomes of Catheter Ablation of Atrial Fibrillation, an Implantable Monitor Is a Great Place to Start.

Catheter ablation of atrial fibrillation (AF) is a widely accepted and commonly performed procedure throughout the world.1 Although the techniques, as well as the safety and efficacy of the procedure, have improved dramatically since they were first introduced 2 decades ago, unanswered questions remain. One question concerns the relative safety and efficacy of radiofrequency versus cryoballoon AF ablation. All physicians want the best for their patients and a definitive determination of which ablation tool is best is important. A second question concerns how best to deliver cryoablation energy. In particular, do two 2-minute freezes achieve the same result as two 4-minute freezes? A final question concerns the efficacy of AF ablation. Those in the field are aware that some physicians inform patients that the success rate is 85% or higher. But published results from clinical trials performed to obtain US Food and Drug Administration approval show much lower success rates.2,3 This difference likely relates to the increased intensity of ECG monitoring required in trials for US Food and Drug Administration approval as compared with the limited monitoring used by most physicians as part of routine clinical practice. It is with this background that we consider the results of the CIRCA-DOSE study (Cryoballoon vs Irrigated Radiofrequency Catheter Ablation: Double Short vs Standard Exposure Duration) published in this issue of Circulation.4 This was a multicenter, prospective, parallel-group, single-blinded randomized clinical trial with blinded end point ascertainment. Conducted at 8 clinical centers in Canada, the study randomized 346 patients with paroxysmal drug-refractory AF to radiofrequency catheter ablation with a contact force–sensing catheter or cryoballoon ablation with two 2-minute freezes or two 4-minute freezes. Patients were followed for 12 months. The primary outcome was time to first documented symptomatic or asymptomatic recurrence of AF, atrial tachycardia (AT), and atrial flutter (AFL) after a 3-month blanking period. Secondary end points included freedom from symptomatic recurrence of AF/AT/AFL and AF burden. All patients in this study had an implantable cardiac monitor (ICM) inserted at least 30 days before ablation. Recurrences of AF/AT/AFL were evaluated with the ICM as well as at clinic visits, and with ECGs and 24-hour Holter monitors at 3-, 6-, and 12-month follow-up. Antiarrhythmic medications were discontinued at least 5 half-lives before the end of the 3-month blanking period. One year of freedom from atrial arrhythmias as detected by the ICM was 53.9%, 52.2%, and 51.7% with radiofrequency, 4-minute cryoballoon ablation, and 2-minute cryoballoon ablation, respectively (P=0.98). One year of freedom from symptomatic atrial arrhythmias was 79.1%, 79.1%, and 73% with radiofrequency, 4-minute cryoballoon ablation, and 2-minute cryoballoon ablation, respectively (P=0.26). The AF burden was reduced by a median of 99.3%, 99.9%, and 98.4% with radiofrequency, 4-minute cryoballoon ablation, and 2-minute cryoballoon ablation, respectively (P=0.98). Serious adverse © 2019 American Heart Association, Inc.