Complications of Atrial Fibrillation Ablation

Phrenic Nerve Injury

Phrenic nerve injury is another well-described complication of AF ablation. Sacher et al.^[58] first examined rates of phrenic injury in 3755 consecutive patients who had undergone AF ablation at five different centres between 1997 and 2004. Phrenic nerve injury occurred in 0.48% of cases, with right phrenic nerve affected more frequently then the left. Right phrenic nerve injury usually was associated with the electrical disconnection of the right superior pulmonary vein or of the superior vena cava. Left phrenic nerve injury occurred instead after ablation of the left atrial appendage. Phrenic nerve palsy is usually associated with dyspnea, cough, or hiccups; diagnosis is usually made with evidence of diaphragmatic elevation at the chest X-ray. Prognosis of phrenic nerve injury is usually very good: complete recovery has been described in a report by Bai et al.^[59] after an average follow-up of about 9 months.

Phrenic nerve injury has been described also consequently to AF catheter ablation with different technologies. For example, in the STOP-AF trial, the incidence of right phrenic nerve palsy was 11.2% with a complete resolution noted in >80% of the cases.^[52] Anecdotal case reports have reported phrenic nerve injury during PVI using the Ablation Frontiers pulmonary vein ablation catheter,^[60] during PVI using a novel endoscopic ablation system^[61] or during PVI obtained with a forward directed, high-intensity focused ultrasound balloon catheter.^[62]

Avoiding this complication can be attempted using 'pace-mapping' with a high output in the areas of presumable contact with phrenic nerves (usually right superior pulmonary vein, superior vena cava, and the roof of left atrial appendage) before delivery of any type of energy. Recently, Horton et al.^[63] reported a novel method of localization of the phrenic nerve with cardiac computed tomography and found that a distance between the right pericardionephric artery and the right superior pulmonary vein <10 mm expose patients to higher risks of phrenic nerve palsy using balloon-based ablation systems.