title: Prevalence of a shared isthmus in postinfarction patients with pleiomorphic, hemodynamically tolerated ventricular tachycardias.
abstract: BACKGROUND
  Multiple forms of ventricular tachycardia (VT) after myocardial infarction may result from multiple reentrant circuits that share an isthmus or from separate reentrant circuits. The prevalence of a shared isthmus in patients with multiple hemodynamically tolerated VTs has not been determined.
  
  
  RESULTS
  Criteria for a shared isthmus consisted of (1) concealed entrainment of >1 VT at a single pacing site; (2) concealed entrainment during VT and a perfect pace map of another VT at the same pacing site; or (3) concealed entrainment of VT of a given morphology that had at least two cycle lengths that varied by at least 100 msec. In a series of 19 patients (16 men and 3 women; age 65+/-14 years, ejection fraction 0.25+/-0.09) with 54 VTs (mean cycle length 494+/-98 msec), there was evidence of a shared isthmus in 23 VTs (43%) at 11 sites in 9 patients. Concealed entrainment of two different VTs was observed at 4 of 11 sites. At 5 of 11 sites there was concealed entrainment of one VT and a perfect pace map of another VT. At the remaining 2 of 11 sites, there was concealed entrainment of a VT that had two different cycle lengths. Nineteen of the 23 VTs were ablated successfully with radiofrequency energy applications at 11 sites.
  
  
  CONCLUSIONS
  In postinfarction patients with pleiomorphic, hemodynamically stable VT, a shared isthmus may be present in approximately 40% of VTs.
authors.affiliation: Division of Cardiology, Henry Ford Hospital, Detroit, Michigan 48202-9888, USA. bogun@eudormail.com
authors.forename: Frank
authors.initials: F
authors.lastname: Bogun
authors.forename: Yi-Gang
authors.initials: YG
authors.lastname: Li
authors.forename: Gerian
authors.initials: G
authors.lastname: Groenefeld
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Hohnloser
authors.forename: Claudio
authors.initials: C
authors.lastname: Schuger
authors.forename: Hakan
authors.initials: H
authors.lastname: Oral
authors.forename: Frank
authors.initials: F
authors.lastname: Pelosi
authors.forename: Bradley
authors.initials: B
authors.lastname: Knight
authors.forename: S Adam
authors.initials: SA
authors.lastname: Strickberger
authors.forename: Fred
authors.initials: F
authors.lastname: Morady
mesh_terms: D000368:Aged; D017115:Catheter Ablation; D016009:Chi-Square Distribution; D003971:Diastole / Q000502:physiology; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000150:complications*; D017180:Tachycardia, Ventricular / Q000209:etiology* / Q000503:physiopathology* / Q000601:surgery