Impact of Increased Cryoballoon Size on the Left Atrium, Superior Vena Cava, and Phrenic Nerve

POLARx FIT is a size-adjustable cryoballoon, but its effect on isolation area and phrenic nerve injury (PNI) is not fully understood. This study aimed to compare the effects of 28 and 31 mm cryoballoon on the left atrium (LA), superior vena cava (SVC), and PNI incidence.

Thirty-one cases of paroxysmal atrial fibrillation treated with POLARx FIT were analyzed. SVC voltage mapping and septal sleeve length measurements were performed before pulmonary vein (PV) isolation. A 28 mm balloon was used to isolate four PVs, followed by SVC and LA mapping. Additional ablation of the superior PVs was performed with a 31 mm balloon, and remapping was conducted. The isolation area of the LA, SVC sleeve length, and PNI incidence were compared before treatment, after the 28 mm treatment, and after the 31 mm treatment. The residual LA posterior wall area was significantly smaller with the 31 mm balloon compared to the 28 mm balloon (p < 0.01), with a significant increase in isolation area on the right side of the PVs after 31 mm treatment (p = 0.03). SVC sleeve length progressively shortened with increasing balloon size, showing a significant reduction between pretreatment and after the 31 mm treatment (p = 0.02). No consistent association was observed between balloon size and PNI.

The larger cryoballoon expanded the LA posterior wall isolation area and had a greater effect on the SVC. Balloon size and PNI have shown inconsistent results.