title: Clinical experience with a novel electromyographic approach to preventing phrenic nerve injury during cryoballoon ablation in atrial fibrillation.
abstract: BACKGROUND
  Phrenic nerve palsy remains the most frequent complication associated with cryoballoon-based pulmonary vein (PV) isolation. We sought to characterize our experience using a novel monitoring technique for the prevention of phrenic nerve palsy.
  
  
  RESULTS
  Two hundred consecutive cryoballoon-based PV isolation procedures between October 2010 and October 2013 were studied. In addition to standard abdominal palpation during right phrenic nerve pacing from the superior vena cava, all patients underwent diaphragmatic electromyographic monitoring using surface electrodes. Cryoablation was terminated on any perceived reduction in diaphragmatic motion or a 30% decrease in the compound motor action potential (CMAP). During right-sided ablation, a ≥30% reduction in CMAP amplitude occurred in 49 patients (24.5%). Diaphragmatic motion decreased in 30 of 49 patients and was preceded by a 30% reduction in CMAP amplitude in all. In 82% of cases, this reduction in CMAP amplitude occurred during right superior PV isolation. The baseline CMAP amplitude was 946.5±609.2 mV and decreased by 13.8±13.8% at the end of application. This decrease was more marked in the 33 PVs with a reduction in diaphragmatic motion than in those without (40.9±15.3% versus 11.3±10.5%; P<0.001). In 3 cases, phrenic nerve palsy persisted beyond the end of the procedure, with all cases recovering within 6 months. Despite the shortened application all veins were isolated. At repeat procedure the right-sided PVs reconnected less frequently than the left-sided PVs in those with phrenic nerve palsy.
  
  
  CONCLUSIONS
  Electromyographic phrenic nerve monitoring using the surface CMAP is reliable, easy to perform, and offers an early warning to impending phrenic nerve injury.
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Blandine
authors.initials: B
authors.lastname: Mondésert
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada. marcdubuc@me.com.
authors.forename: Jason G
authors.initials: JG
authors.lastname: Andrade
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Khairy
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Guerra
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Katia
authors.initials: K
authors.lastname: Dyrda
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Laurent
authors.initials: L
authors.lastname: Macle
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Léna
authors.initials: L
authors.lastname: Rivard
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Thibault
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Mario
authors.initials: M
authors.lastname: Talajic
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada.
authors.forename: Denis
authors.initials: D
authors.lastname: Roy
authors.affiliation: From the Electrophysiology Service, Montreal Heart Institute, and the Department of Medicine, Université de Montréal, Montreal, Canada. marcdubuc@me.com.
authors.forename: Marc
authors.initials: M
authors.lastname: Dubuc
authors.forename: Azadeh
authors.initials: A
authors.lastname: Shohoudi
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000601:surgery*; D003452:Cryosurgery / Q000009:adverse effects*; D003964:Diaphragm / Q000294:innervation*; D004558:Electric Stimulation; D004562:Electrocardiography; D004576:Electromyography; D022062:Electrophysiologic Techniques, Cardiac; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010243:Paralysis / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D059348:Peripheral Nerve Injuries / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D010791:Phrenic Nerve / Q000293:injuries* / Q000503:physiopathology; D011237:Predictive Value of Tests; D013997:Time Factors; D016896:Treatment Outcome
keywords: atrial fibrillation; catheter ablation; cryosurgery