The COR Trial: A Randomized Study With Continuous Rhythm Monitoring to Compare the Efficacy of Cryoenergy and Radiofrequency for Pulmonary Vein Isolation
What is the efficacy of cryoablation of the pulmonary veins (PV) as compared to radiofrequency (RF) energy in patients with paroxysmal atrial fibrillation (AF)?
Fifty patients with paroxysmal AF and four independent PVs were randomized to cryoballoon versus RF ablation. All patients received an implantable loop recorder prior to the procedure. In the cryoablation group, PV isolation was performed using a single balloon (23 or 28 mm), and two 300-second applications per PV. If a gap was present, no “touch-up” lesions were performed. In the RF group, PV isolation was achieved by point-by-point ablation using an irrigated-tip catheter and a 3-D mapping system. The primary endpoint was freedom from AF in the absence of antiarrhythmic medications at 12 months.
All targeted PVs were isolated in the RF group as compared to 83% in the cryoablation group (p < 0.0001). No patient in the RF group required repeat ablation as compared to six patients (24%) in the cryoablation group (p < 0.01). Patients in the RF group (68%) were more likely to remain free of AF as compared to those in the cryoablation group (48%) (p = 0.05). In patients in whom all four PVs were isolated, there was no difference in outcomes between the two groups.
A simplified cryoablation strategy is less effective in eliminating paroxysmal AF as compared to a standard RF technique. The findings of this study also confirm the importance of complete PV isolation in patients with paroxysmal AF.
At first glance, it appears that the cryoablation strategy was destined to be inferior to RF since all PV connections were not eliminated. However, the exclusion of patients with variant PV anatomy probably helped level the playing field. Use of multiple balloons or touch-up lesions may have improved the effectiveness of cryoablation, but at the expense of increased procedural complexity and cost. Large-scale trials powered to answer the question of relative efficacy are ongoing. An issue that was not addressed by this excellent study is the importance of local expertise, which is likely to be critical in determining outcome.
Keywords: Pulmonary Veins, Cryosurgery, Catheter Ablation
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