Comparison of manual, robotic and cryo PVI procedures
BRUSSELS, BELGIUM. Pulmonary vein isolation (PVI) is the most common catheter ablation procedure performed in as effort to cure atrial fibrillation (AF). Originally, PVI was performed manually using radiofrequency (RF) energy to create point-by-point lesion sets around the pulmonary vein ostia so as to create a barrier to rogue electrical impulses originating from the veins and thus stop AF in its tracks. More recently, a couple of systems have emerged which use robot mechanisms to guide the ablation catheter based on electroanatomical (CARTO) rather than electrophysiological mapping. Finally, there are now also balloon-shaped catheters available using cryo-energy to create a complete lesion in one go by actually placing the balloon just inside the pulmonary veins or on the edge (antrum) of the vein and left atrium. Using cryo-energy rather than RF energy reduces the risk of post-procedure pulmonary vein stenosis, but increases the risk of phrenic nerve palsy.

Electrophysiologists from Belgium and Italy have compared the efficacy and safety of the three procedures in a group of 94 afibbers (84% male) with an average age of 56 years. The majority (80%) had paroxysmal AF, 17% had the persistent variety, and the remaining 3% had been in AF for more than 6 months and were classified as permanent.

Twenty-nine patients were assigned to the manual RF group (mRF), 35 were assigned to the robotically-guided RF group (rRF), and the remaining 30 underwent cryoablation (cryo). The robotic system used was the Stereotaxis Niobe II system using CARTO mapping and a 3.5 mm irrigated catheter. The cryo group was ablated with an Arctic Front 28 mm double-walled cryoballoon using electrophysiological mapping. The mRF group was ablated with a 3.5 mm irrigated catheter using a combination of electrophysiological (Lasso) and electroanatomical mapping.

There were no significant differences in the characteristics of patients assigned to the three groups except that 2 of the 3 permanent afibbers were assigned to the mRF group and none were assigned to the cryo group. Both total procedure time and fluoroscopy time were significantly shorter in the cryo group. All patients were examined (with 24-hour Holter monitoring) at 1, 3, 6, and 12 months after the procedure and in the case of symptoms of arrhythmia. After an average 12-month follow-up, 65.5% of the patients in the mRF group, 66.7% of those in the rRF group, and 65.7% of those in the cryo group were free of arrhythmia without the use of antiarrhythmics. Complications were minor and reversible, and the researchers conclude that the three procedures are equally effective and safe.

Sorgente, A, et al. Atrial fibrillation ablation: a single center comparison between remote magnetic navigation, cryoballoon and conventional manual pulmonary vein isolation. Indian Pacing and Electrophysiology Journal, Vol. 10, November 2010, pp. 486-95

Editor's comment: A one-year success rate of 65% after a single procedure is indeed encouraging and shows impressive progress since the early days of PVI procedures when success rates as low as 21% were not unheard of. The shortening of procedure time with the cryoablation vs. manual ablation (116 minutes vs. 195 minutes) is, of course, highly significant as is the shortened exposure to radiation (40 minutes vs. 66 minutes). The balloon catheter used in the cryo group was 28 mm which probably means that it did not actually enter the pulmonary veins, but produced its lesion set on the antrum of the vein, thus further minimizing the risk of stenosis.