Background: Although phrenic nerve injury (PNI) is the most common complication of cryoballoon pulmonary vein isolation (PVI) for atrial fibrillation (AF), long-term follow-up of PNI has not been reported.
Objective: This study aimed to investigate the long-term follow-up of PNI after cryoballoon ablation.
Methods: 512 consecutive AF patients who underwent initial cryoballoon PVI were included. Compound motor action potentials (CMAP) were monitored in all patients. If 30% reduction of CMAP or loss of capture was observed, the freeze application was immediately aborted. Transient and persistent PNI was defined as a progressive weakening of diaphragmatic motility and an elevated hemidiaphragm noted on post-procedural radiography, which persisted after the procedure, respectively. Once the diagnosis of PNI was established, the patient was closely monitored in the clinic with repeated tests at 2 weeks, one month and every 3 months after the procedure.
Results: PNI did not occur during left-side PVI. During right-side PVI, CMAP was reduced in 46 (8.9%) patients (37 in RSPV and 9 in RIPV). After the double stop of the cryo application, PNI presented in 29 (5.6%) patients (18 in RSPV and 8 in RIPV). PNI occurred despite the absence of CMAP reduction in 3 (0.6%) patients. PNI continued until the end of the procedure in 26 (5.1%). Of those, only one patient complained of mild dyspnea. In all patient, PNI recovered until 2 years after the procedure (Figure).
Conclusion: After the cryoballoon ablation, PNI occurred in 5.1% of patients. PNI occurred even during right inferior PVI in 1.6% and despite the absence of CMAP reduction in 0.6%. Two years after the procedure, all patients recovered from PNI.