Background: In symptomatic atrial fibrillation (AF) patients, cryoballoon pulmonary vein isolation (PVI) is a well-established and highly effective treatment option. Recently, a novel cryoballoon ablation system (POLARx™) was introduced which offers enhancements including a stable balloon diameter (28mm) throughout inflation and ablation as well as a distal sheath deflection point of up to 155°.

Methods: In a prospective single-center study, comprising symptomatic atrial fibrillation patients undergoing PVI, the new cryoballoon ablation system was evaluated regarding its efficacy, safety and short-term outcome. All procedures were conducted using a uniform TTI-based ablation protocol with a standard cycle length of 180s, a TTI cut-off for a bonus application set at ≥45 seconds, and a bonus freeze if no TTI was recorded. The primary endpoint was defined as freedom from atrial arrhythmias.

Results: Overall, fifty-six AF patients (96.4% paroxysmal AF) with a mean age of 67.2±14.1 years and a median AF history of 14.5 [IQR 35] months were included. Study population consisted of 34 (60.7%) male and 22 (39.3%) female patients. Mean procedural time, mean fluoroscopy time and median dose area product were 97.8±25.1 minutes, 15.7±6.3 minutes and 843.5 [IQR 930] cGy x cm², respectively. Acute PVI could be achieved in 224 (98.7%) veins with a median time to isolation (TTI) of 34 [IQR 23] seconds. Overall, TTI was obtained in 190 (83.7%) pulmonary veins (PV). A total of 416 (100%) freeze applications were performed with a median number of 2 [IQR 1] per vein to achieve PVI. Of all 227 veins, 184 (81.1%) were isolated with a single-shot application. Mean balloon temperature was −55.1±6.3 °C and median esophageal temperature was 35 [IQR 6.6] °C. Thirteen (5.7%) freeze attempts were ineffective and nine PV (4.0%) showed intraprocedural reconnection, which required repositioning and additional cryoapplications. There was no major adverse cardiac or cerebrovascular event until hospital discharge. Relevant complications included one premature termination of a procedure because of aspiration from nosebleed, which was not device related. One transient phrenic nerve palsy occurred during ablation of the right superior pulmonary vein with a recovery time of 36 hours. After a mean follow-up of 6.5±4.6 months, AF recurrence was documented in eight (14.3%) patients. At follow-up, four patients (7.1%) received class I or class III antiarrhythmic medication.

Conclusion: In conclusion, the novel cryoballoon system showed favorable results in terms of efficacy, safety and outcome. The main procedural characteristics include a high single shot success rate, a low balloon temperature and a high rate of achieving TTI. Although short-term outcome is promising, larger studies with longer follow-up are needed.

Figure 1: Kaplan-Meier survival curve regarding single procedure short-term outcome for the primary endpoint.