Atrial fibrillation is the most commonly encountered arrhythmia in clinical medicine. The presence of atrial fibrillation is associated with an increased risk of stroke, and patients may complain of palpitations, shortness of breath, and fatigue. Buoyed by the success of ablation for paroxysmal supraventricular arrhythmias and atrial flutter, over the last 15 years investigators from around the world have focused on developing catheter-based ablation techniques for the treatment of atrial fibrillation. At our medical center, atrial fibrillation now accounts for more than 80% of our ablation volume.

As has been emphasized by the 2007 Heart Rhythm Society Guidelines on ablation for atrial fibrillation, isolation of the pulmonary veins remains the “cornerstone” for all ablation procedures for atrial fibrillation.¹ Isolation of the pulmonary veins has generally been achieved by placing a series of ablation lesions in the left atrium around the pulmonary veins in a point-by-point fashion using radiofrequency (RF) energy. Although this process has been facilitated by the advent of new mapping tools and irrigated tip ablation catheters, the process can be time consuming and requires even the talented operator to perform a number of procedures to become comfortable. In an effort to shorten the procedure and the “learning curve” for isolating the pulmonary veins, multiple manufacturers have developed catheters designed to produce circular lesions. The first such catheter to be commercially approved in the United States uses cryoenergy delivered by a balloon-based system (Arctic Front®, Medtronic, Minneapolis, MN). Since its approval by the Food and Drug Administration one year ago, over 5,000 cases have been performed in the United States, and worldwide, since its introduction in Europe six years ago, over 25,000 cases have been performed.

Cryoablation

Cryoenergy has been used for almost 50 years for the surgical treatment of arrhythmias and for more than a decade with percutaneous endovascular catheters. Lesions formed by cryoenergy are characterized by relatively sharp borders, dense fibrosis within the lesion with preservation of intercellular architecture, and less disruption of the endovascular surface. Cryoablation causes tissue destruction by the freezing/rewarming cycle, injury to the micro circulation, and triggering of apoptosis (cell death). Although decreased platelet activation and a reduced inflammatory response has been noted with cryoenergy point ablation, a recent study suggests that the systemic inflammatory response is similar for RF catheter ablation and balloon cryoablation.²