Phrenic Nerve Injury during Cryoballoon Isolation with Arctic Front vs Polar X system

Background:
Pulmonary vein isolation (PVI) with cryoballoon to treat symptomatic atrial fibrillation (AF) is well established. The most frequent complication during cryoballoon-based PVI is phrenic nerve injury. Data on PNI with Arctic Front has been described previously. However, data for the balloon system Polar X is scarce. The purpose of this retrospective study was to compare the incidence and characteristics of PNI between the two cryoballoon systems.  

Methods:
The study enrolled patients, who underwent cryoballoon-based PVI between January 2024 and October 2024 in our center. Continuous PN pacing was performed during energy delivery at the right sided pulmonary veins using a multipolar catheter positioned in the vena cava superior. The safety endpoint PNI was diagnosed, if a decrease or loss of diaphragmatic movement either through palpation or fluoroscopic imaging and/or a reduction in compound motor action potential amplitude was observed. The delivery of refrigerant was stopped by using the double-stop technique.

Results:
A total of 654 consecutive patients were enrolled. There were 452 patients in the Arctic Front group and 202 patients in the Polar X group. The safety endpoint occurred in 22 patients (4,9%) in the Arctic Front group, while 18 patients (8,9%) in the Polar X group (p<0,05). The mean temperature measured at the time of PNI was -51,6± 5,7 °C in the Arctic Front group and -52,9± 6,3°C in Polar X group (p =0,5). There was no significant difference in temperature between patients with or without PNI within both groups (-52,3± 6,0°C in Arctic Front group without PNI and -55,7± 6,8°C in Polar X group, respectively). Time to PNI was 142,6 ± 73,1 sec in Arctic Front group and 146,1 ±55,7 sec in Polar X group (p=0,5). The ablation time was significantly shorter compared to the patients without PNI in both systems.

Conclusions:
In our study we found significantly more phrenic nerve palsies in the Polar X group, which is consistent with previous findings in smaller patient populations. Balloon temperature and ablation time were not found to be critical factors for PNI. The potential mechanism may be related to the compliant design of the Polar X system, which results in the positioning of the balloon more distally. The next generation, called PolarX Fit, features pressure-controlled sizing (28 to 31 mm). It is conceivable that the larger size may reduce the risk of PNI, but this hypothesis still needs to be evaluated.