Characterization of the phrenic nerve course within the epicardial substrate of patients with nonischemic cardiomyopathy and ventricular tachycardia.
BACKGROUND
Patients with nonischemic cardiomyopathy and ventricular tachycardia (VT) often have low-voltage areas in the lateral left ventricular (LV) epicardium that serve as the VT substrate. The course of the left phrenic nerve in this region may pose a challenge to successful and safe ablation.


OBJECTIVE
The purpose of this study was to delineate the left phrenic nerve course in patients with nonischemic cardiomyopathy and suspected epicardial VT and to characterize its relationship with the VT substrate.


METHODS
In 10 patients with nonischemic cardiomyopathy undergoing epicardial VT mapping and ablation, the course of the phrenic nerve was defined by pacing. The extent of epicardial LV low-voltage areas (<1.0 mV) was characterized by electroanatomic voltage mapping.


RESULTS
Eight of 10 patients had low-voltage areas involving the lateral epicardial LV, and 7 of these 8 patients had sites of phrenic capture within these areas. Ablation was limited due to location of the phrenic nerve in two patients. In one of these patients, a balloon catheter was successfully used to mechanically protect the phrenic nerve during ablation. In the other five patients, adjacent ablation sites were targeted at which no phrenic capture with high-output pacing was demonstrated prior to ablation. In all patients undergoing ablation, the targeted VT became noninducible, and no patient demonstrated phrenic nerve injury.


CONCLUSIONS
In most patients with nonischemic cardiomyopathy undergoing epicardial VT ablation, the phrenic nerve courses through a lateral LV low-voltage area in proximity to potential sites for ablation. Strategies to identify and protect the phrenic nerve are important.
Fan
Roger
R
Department of Medicine, Cardiovascular Division, Electrophysiology Section, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
Cano
Oscar
O
Ho
Siew Yen
SY
Bala
Rupa
R
Callans
David J
DJ
Dixit
Sanjay
S
Garcia
Fermin
F
Gerstenfeld
Edward P
EP
Hutchinson
Mathew
M
Lin
David
D
Riley
Michael
M
Marchlinski
Francis E
FE
D000328:Adult; D000368:Aged; D018780:Body Surface Potential Mapping / Q000379:methods*; D009202:Cardiomyopathies / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D017115:Catheter Ablation / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007431:Intraoperative Complications / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010496:Pericardium / Q000294:innervation* / Q000601:surgery; D010523:Peripheral Nervous System Diseases / Q000517:prevention & control; D010791:Phrenic Nerve / Q000503:physiopathology*; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000150:complications / Q000503:physiopathology* / Q000601:surgery