The study was supported by a Canada Research Chair in Electrophysiology and Adult Congenital Heart Disease (PK) and an investigator-initiated research grant from Medtronic CryoCath LP.
Histopathology of Cryoballoon Ablation-Induced Phrenic Nerve Injury
Article first published online: 11 OCT 2013
© 2013 Wiley Periodicals, Inc.
Journal of Cardiovascular Electrophysiology
Volume 25, Issue 2, pages 187–194, February 2014
How to Cite
ANDRADE, J. G., DUBUC, M., FERREIRA, J., GUERRA, P. G., LANDRY, E., COULOMBE, N., RIVARD, L., MACLE, L., THIBAULT, B., TALAJIC, M., ROY, D. and KHAIRY, P. (2014), Histopathology of Cryoballoon Ablation-Induced Phrenic Nerve Injury. Journal of Cardiovascular Electrophysiology, 25: 187–194. doi: 10.1111/jce.12296
Drs. Marc Dubuc, Peter Guerra, and Jason Andrade are consultants for Medtronic CryoCath LP. Dr. Paul Khairy received research funding from Medtronic CryoCath LP. Dr. Denis Roy was chairman of a clinical adjudicating events committee for a trial sponsored by Medtronic CryoCath LP (STOP-AF). Dr. Talajic serves on a Medtronic advisory board. Mr. Coulombe is an employee of Medtronic, owns stock in the company, and holds patents related to this topic. Other authors: No disclosures.
- Issue published online: 12 FEB 2014
- Article first published online: 11 OCT 2013
- Accepted manuscript online: 19 SEP 2013 07:30AM EST
- Manuscript Accepted: 21 AUG 2013
- Manuscript Revised: 19 AUG 2013
- Manuscript Received: 4 JUN 2013
- Medtronic CryoCath LP
- atrial fibrillation;
- catheter ablation;
- cryoballoon; pulmonary vein isolation;
- phrenic nerve
Cryoballoon-Induced Phrenic Nerve Injury
Hemi-diaphragmatic paralysis is the most common complication associated with cryoballoon ablation for atrial fibrillation, yet the histopathology of phrenic nerve injury has not been well described.
Methods and Results
A preclinical randomized study was conducted to characterize the histopathology of phrenic nerve injury induced by cryoballoon ablation and assess the potential for electromyographic (EMG) monitoring to limit phrenic nerve damage. Thirty-two dogs underwent cryoballoon ablation of the right superior pulmonary vein with the objective of inducing phrenic nerve injury. Animals were randomized 1:1 to standard monitoring (i.e., interruption of ablation upon reduction in diaphragmatic motion) versus EMG guidance (i.e., cessation of ablation upon a 30% reduction in the diaphragmatic compound motor action potential [CMAP] amplitude). The acute procedural endpoint was achieved in all dogs. Phrenic nerve injury was characterized by Wallerian degeneration, with subperineural injury to large myelinated axons and evidence of axonal regeneration. The degree of phrenic nerve injury paralleled the reduction in CMAP amplitude (P = 0.007). Animals randomized to EMG guidance had a lower incidence of acute hemi-diaphragmatic paralysis (50% vs 100%; P = 0.001), persistent paralysis at 30 days (21% vs 75%; multivariate odds ratio 0.12, 95% confidence interval [0.02, 0.69], P = 0.017), and a lesser severity of histologic injury (P = 0.001). Mature pulmonary vein ablation lesion characteristics, including circumferentiality and transmurality, were similar in both groups.
Phrenic nerve injury induced by cryoballoon ablation is axonal in nature and characterized by Wallerian degeneration, with potential for recovery. An EMG-guided approach is superior to standard monitoring in limiting phrenic nerve damage.