Left posterior fascicular block: a new endpoint of ablation for verapamil-sensitive idiopathic ventricular tachycardia.
BACKGROUND
Verapamil-sensitive, idiopathic left ventricular tachycardia (ILVT) with right bundle branch block configuration and left-axis deviation is known to be due to re-entry mechanism but the exact nature of reentrant circuit in ILVT is not fully elucidated. Radiofrequency (RF) ablation was applied during ventricular tachycardia (VT) and termination of the VT or abolishing the inducibility of the tachycardia was used as an endpoint for successful RF. In this study, the left posterior fascicular block in surface electrocardiogram (ECG) was used as a new endpoint of ablation to cure ILVT.


METHODS
Electrophysiological studies and radiofrequency ablation were performed in 39 consecutive patients [30 men, 9 women; age ranging from 10 to 64 years, mean (29 +/- 16) years] with verapamil-sensitive ILVT and structurally normal hearts. VT could be terminated by the intravenous administration of verapamil in all patients. The target site was the midseptum of LV where the earliest Purkinje potentials were recorded during VT. RF current was applied to the target site with or without late diastolic potential (LDP) during sinus rhythm in 37 patients and during VT in 2 patients to meet the ablation endpoint: the left posterior fascicular block in the surface ECG.


RESULTS
Thirty-seven patients with ILVT had been treated by RF ablation during sinus rhythm and two had been treated during VT. All of them met the endpoint of the left posterior fascicular block. Thirty-eight cases were symptom-free without medications during the follow-up period (range from 3 to 95 months, median 17 months). One patient developed a clinical recurrence and the left posterior fascicular block in surface ECG disappeared. The patient received another treatment. The endpoint was met and the procedure was successful.


CONCLUSIONS
The left posterior fascicular block in surface ECG used as an endpoint of RF ablation to treat ILVT is effective. It is important especially in those patients whose VT can not be induced or the inducible condition is unstable. The effective endpoint implied that the left posterior fascicle might be a critical part of the re-entrant circuit.
Center of Arrhythmia Diagnosis and Treatment, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.
Fu-sheng
FS
Ma
Jian
J
Ma
Kai
K
Tang
Hao
H
Han
Yu-he
YH
Jia
Pi-hua
PH
Fang
Jian-min
JM
Chu
Jie-lin
JL
Pu
Shu
S
Zhang
D000293:Adolescent; D000328:Adult; D017115:Catheter Ablation / Q000379:methods*; D002648:Child; D003971:Diastole; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000601:surgery*; D014700:Verapamil / Q000627:therapeutic use*
D014700:Verapamil