A new stepwise approach to minimize phrenic nerve injury during cryoballoon pulmonary vein isolation.

Background: A phrenic nerve injury (PNI) during cryoballoon (CB) pulmonary vein isolation (PVI) continues to represent a limitation of this technique. The objective of this study was to develop a novel technique with the aim of reducing the incidence of PNI.

Methods: We performed a retrospective analysis of data from two hospitals in patients with symptomatic, drug-resistant atrial fibrillation (AF) over 7 years to evaluate the incidence and clinical characteristics of PNI during cryoballoon PVI. Patients in the intervention group were treated with a new technique consisting of the following consecutive steps: (A) phrenic nerve stimulation near stimulation threshold instead of 10 V stimulation; (B) advanced ablation to the right superior pulmonary vein (PV) using a pre-freezing technique; (C) "pulling away" of the CB after vein isolation and/or after reaching - 40 °C for both right PVs. Two subtypes of PNI were studied: persistent (no recovery to discharge) and transient (recovery to discharge) PNI.

Results: Nine hundred patients with a mean age of 62.3 (± 10.9) years (38% female) were analyzed. Transient PNI occurred in 8/250 patients (3.2%) in the intervention group compared to 39/750 patients (6%) in the control group (p = 0.09). Persistent PNI occurred in one patient (0.4%) in the intervention group compared to 18 (2.8%) in the control group (p = 0.03). Any PNI occurred in 9 patients in the intervention group (3.6%) compared to 57 patients (8.8%) in the control group (p = 0.008).

Conclusion: In this retrospective analysis, a new cryo-PVI technique significantly reduces the incidence of PNI, particularly persistent PNI.