Bad Nauheim, Germany - The treatment of atrial fibrillation (AF) with an investigational cryoablation balloon device (Arctic Front, Cryocath) is safe and feasible, but success is limited to patients with paroxysmal AF only, according to the results of a new study [1].

Publishing their findings in the July 22, 2008 issue of the Journal of the American College of Cardiology, lead investigator Dr Thomas Neumann (Kerckhoff Heart Center, Bad Nauheim, Germany) and colleagues report no pulmonary vein stenosis or atrioesophageal fistula with the novel cryoballoon technique, although phrenic-nerve injury was observed in 26 patients, mainly when the smaller balloon was used.

The new balloon device is designed to simplify pulmonary vein isolation in AF ablations and to reduce procedure time by using an anatomically based approach, write the authors. With this device, the catheter is designed as a balloon, which allows the surface area of the encircling atrial tissue of the pulmonary vein to be ablated at once, subsequently reducing the number of lesions required. The cryoablation device works on the same premise as a radio-frequency ablation device, with the aim of blocking electrical conduction in myocardial tissue; instead of radio-frequency current, the cryoballoon delivers extreme cold.

With the device, the left atrium is accessed transseptally from the right femoral vein to guide the double-walled cryoballoon over the wire. With the deflated balloon catheter inside the sheath, a guidewire is placed in one of the pulmonary vein branches. The balloon is then advanced toward the pulmonary vein ostium and inflated. Based on previous studies, investigators chose an application time between 240 and 360 seconds per freeze. In this study, investigators enrolled 346 patients with symptomatic, drug-refractory paroxysmal (n=293) or persistent AF (n=53).

After a median follow-up of 12 months and after a three-month blanking period in which all patients were treated with antiarrhythmic agents, circumferential pulmonary vein isolation with the cryoballoon device resulted in the maintenance of sinus rhythm without antiarrhythmic drug therapy in 74% of patients with paroxysmal AF. Maintenance of sinus rhythm without drug therapy was successful in just 42% of patients with persistent AF. Nearly 12% of patients were unable to discontinue to antiarrhythmic drug therapy (amiodarone or other class 1 agents) after the three-month blanking period,

"We speculate that one reason for poor outcome in persistent AF might be that the depth of penetration using the cryoballoon technique is inadequate," write Neumann and colleagues. "Possibly, the strategy of atrial pulmonary vein isolation or the cryoballoon device does not produce sufficient substrate modification as required in persistent AF."

In 26 of the 346 patients, phrenic-nerve palsy was observed during cryoablation of the right superior pulmonary vein. In 24 of these of patients, the phrenic-nerve injury occurred when the smaller 23-mm balloon was used, with just two injuries occurring with the 28-mm balloon. Two of the phrenic-nerve palsy cases were resolved during the procedure, and full recovery of phrenic function was observed in follow-up of less than one year. There were no atrioesophageal fistula, stroke, death, or other periprocedural complications.

The authors write that a conclusive comparison between the cryoballoon technology and radio-frequency ablation strategies will require randomized trials.