Large cryoballoon catheter shows promise
HAMBURG, GERMANY. Paroxysmal (intermittent) atrial fibrillation (PAF) is the most common form of AF affecting about 80% of the afib population. The triggers for PAF are almost exclusively located within the pulmonary veins (PVs) so achieving electrical isolation of the PVs from the left atrium can often result in a complete cure of afib. A pulmonary vein isolation (PVI) is most frequently performed by using a radiofrequency (RF)-powered catheter to create a ring of lesions around each PV. Since these rings are created point-by-point it is not uncommon for conduction gaps to occur following the initial procedure, thus necessitating a second ablation. Not surprisingly, a fair bit of research has gone into developing a ring-shaped catheter that would do the whole PV isolation with one or two applications. This would save time and may also result in better results for relatively inexperienced electrophysiologists.

A team of EPs from the Asklepios Clinic in Hamburg now report on their trial of a 28-mm diameter cryoballoon catheter (Arctic Front, Cryocath). This catheter is powered by cryoenergy and creates a ring-shaped lesion through the application of a balloon-shaped structure cooled to –80oC with liquid nitrogen oxide. The Hamburg trial involved 27 afibbers (70% male) with paroxysmal AF of about 6 years standing (1 – 12 years). The average age of the patients was 56 years (47 – 65 years), average left atrial diameter was 4.2 mm (maximum 5.1 cm or 51 mm); all had highly symptomatic episodes with an average of 10 episodes a month and had not been helped by an average of 3 different antiarrhythmics. Eighty percent of the group were lone afibbers (no underlying heart disease), but 33% had hypertension.

All trial participants underwent a PVI procedure using the 28-mm cryoballoon and a Lasso catheter for mapping and checking of electrical potentials. No anatomical or other mapping was performed prior to the procedure. Overall, average procedure time was 3 hours and 40 minutes during which the balloon was present in the left atrium for 130 minutes and fluoroscopy was used for 50 minutes. Each PV was isolated with an average of two cryoballoon applications of 5 minutes duration each. Complete electrical isolation was achieved in 97 of 99 veins (98%). Recurrence rate (after a 3-month blanking period) was 30% one year following the procedure. However, when including the blanking period, only 52% of the 27 patients were still in sinus rhythm at the one-year end-point.

Unfortunately, it is not entirely clear how many of the afib-free patients were still on antiarrhythmics at the end of the trial. No pulmonary vein stenosis was observed, but 3 patients did experience phrenic nerve palsy, which eventually resolved on its own. It is noteworthy that the two electrophysiologists who performed the procedures had no prior experience with cryoballoon technology. NOTE: The two EPs did receive educational honoraria from Cryocath; however, the other 10 authors of the paper declared no conflict of interest.

Chun, KRJ, et al. The 'single big cryoballoon' technique for acute pulmonary vein isolation in patients with paroxysmal atrial fibrillation: a prospective observational single centre study. European Heart Journal, Vol. 30, No. 6, March 2009, pp. 699-709

Editor's comment: An overall single procedure success rate of 52% (with or without antiarrhythmics) is comparable to the 56% rate obtained at top-ranked RF ablation institutions and twice as good as the 26% average success rate observed for other than top-ranked RF institutions (2008 Ablation/Maze Survey). Thus, it would seem that the cryoballoon technique holds considerable promise for the treatment of PAF by less experienced EPs. It is quite possible that the success rate would improve substantially as operators gain more experience. Nevertheless, 12 months is a relatively short follow-up period and there are indicators that cryo-lesions may not be as durable as RF-lesions – so the jury is still out on this new, but highly promising technique.