title: Alternation of QRS morphology and effect of radiofrequency ablation in idiopathic ventricular tachycardia.
abstract: We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them.
  
  
  RESULTS
  VT was induced by programmed stimulation in all patients and the mean cycle length was 363 +/- 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20-40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re-mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow-up period for a mean of 9.3 +/- 5.2 months.
  
  
  CONCLUSIONS
  RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exists may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS.
authors.affiliation: First Department of Internal Medicine, Niigata University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Washizuka
authors.forename: Y
authors.initials: Y
authors.lastname: Aizawa
authors.forename: M
authors.initials: M
authors.lastname: Chinushi
authors.forename: N
authors.initials: N
authors.lastname: Naitoh
authors.forename: T
authors.initials: T
authors.lastname: Miyajima
authors.forename: Y
authors.initials: Y
authors.lastname: Kusano
authors.forename: H
authors.initials: H
authors.lastname: Kitazawa
authors.forename: H
authors.initials: H
authors.lastname: Uchiyama
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: A
authors.initials: A
authors.lastname: Shibata
mesh_terms: D000293:Adolescent; D000328:Adult; D017115:Catheter Ablation; D004562:Electrocardiography / Q000187:drug effects; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000601:surgery*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D014700:Verapamil