Impact of right superior pulmonary vein anatomy and 31-mm cryoballoon use on the risk of phrenic nerve injury during cryoablation for atrial fibrillation

Background: Phrenic nerve injury (PNI) is a common complication of cryoballoon pulmonary vein isolation, especially during right superior pulmonary vein (RSPV) ablation. The impact of a newly introduced size-adjustable 31-mm cryoballoon on PNI and its anatomical predictors remain unclear. Methods and Results: This retrospective study included 249 patients who underwent first-time cryoballoon ablation with successful RSPV isolation: 153 with a conventional 28-mm balloon and 96 with a size-adjustable balloon in the 31-mm configuration. Preprocedural computed tomography assessed RSPV anatomical features, including ostial diameters, cross-sectional area, and the RSPV–left atrium (LA) angle, defined as the angle between the RSPV and anterolateral LA wall on axial slices. The overall incidence of PNI did not differ between groups (28-mm: 10%; 31-mm: 15%; P = 0.330). However, persistent PNI, defined as dysfunction beyond the procedure, occurred only in the 28-mm group (5%). Multivariate analysis showed that the RSPV–LA angle independently predicted PNI in both groups (28-mm: odds ratio 3.819, 95% confidence interval 1.825–7.926, P < 0.001; 31-mm: odds ratio 3.633, 95% confidence interval 1.538–8.594, P = 0.003). No other anatomical parameters showed consistent associations. Conclusion: The RSPV–LA angle is a robust anatomical predictor of PNI during RSPV cryoballoon ablation, regardless of balloon size. Use of the 31-mm cryoballoon may help to reduce the risk of persistent PNI.