Electromyographic Monitoring for Prevention of Phrenic Nerve Palsy in Second-Generation Cryoballoon Procedures

Background-Electromyography-guided phrenic nerve (PN) monitoring using a catheter positioned in a hepatic vein can aid in preventing phrenic nerve palsy (PNP) during cryoballoon ablation for atrial fibrillation. We wanted to evaluate the feasibility and efficacy of PN monitoring during procedures using second-generation cryoballoons. Methods and Results-This study included 140 patients (43 women) in whom pulmonary vein isolation was performed using a second-generation cryoballoon. Electromyography-guided PN monitoring was performed by pacing the right PN at 60 per minute and recording diaphragmatic compound motor action potential (CMAP) via a quadripolar catheter positioned in a hepatic vein. If a 30% decrease in CMAP amplitude was observed, cryoapplication was discontinued with forced deflation to avoid a PNP. Monitoring was unfeasible in 8 of 140 patients (5.7%), PNP occurred in 1. Stable CMAP amplitudes were achieved before ablation in 132 of 140 patients (94.3%). In 18 of 132 patients (13.6%), a 30% decrease in CMAP amplitude occurred and cryoablation was discontinued. Each time, recovery of CMAP amplitude took <60 s. In 9 of 18 cases, a second cryoapplication in the same pulmonary vein was safely performed. We observed no PNP or complication related to electromyography-guided PN monitoring. Conclusions-Electromyography-guided PN monitoring using a catheter positioned in a hepatic vein seems feasible and effective to prevent PNP during cryoballoon ablation using second-generation cryoballoon.