title: Triggers of sustained monomorphic ventricular tachycardia differ among patients with varying etiologies of left ventricular dysfunction.
abstract: BACKGROUND
  The mechanisms underlying the initiation of sustained ventricular tachycardia (VT) have not been fully elucidated. The extent to which reentry, abnormal automaticity, and triggered activity play a role in VT differs depending on the etiology of left ventricular dysfunction. By analyzing electrograms from implantable cardioverter defibrillator (ICD), we sought to determine whether there were differences in VT initiation patterns between patients with ischemic and nonischemic cardiomyopathy.
  
  
  METHODS
  We analyzed ICD electrograms in patients with ejection fractions < 40% who had sustained VT over a 27-month period. The trigger for VT onset was classified as a ventricular premature beat (VPB), supraventricular tachycardia, or of "sudden onset." The baseline cycle length, VT cycle length, coupling interval, and prematurity ratio were recorded for each event. The prematurity ratio was calculated as the coupling interval of the VT initiator divided by the baseline cycle length.
  
  
  RESULTS
  Sixty-three VT events in 14 patients met the inclusion criteria. A VPB initiated the VT in 58 episodes (92%), 1 episode (2%) was initiated by a supraventricular tachycardia, and 4 episodes (6%) were sudden onset. The prematurity ratio was significantly higher (P < 0.05) in patients with ischemic cardiomyopathy (0.751 +/- 0.068) as compared to patients with nonischemic cardiomyopathy (0.604 +/- 0.139).
  
  
  CONCLUSIONS
  VPBs initiated most sustained VT episodes. A significantly higher prematurity ratio was observed in the ischemic heart disease group. This may represent different mechanisms of VT initiation in patients with ischemic versus nonischemic heart disease.
authors.affiliation: Beth Israel Medical Center, University Hospital and Manhattan Campus for the Albert Einstein College of Medicine, New York, New York 10003, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rosman
authors.forename: Sam
authors.initials: S
authors.lastname: Hanon
authors.forename: Michael
authors.initials: M
authors.lastname: Shapiro
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Evans
authors.forename: Paul
authors.initials: P
authors.lastname: Schweitzer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000209:etiology* / Q000503:physiopathology*; D018487:Ventricular Dysfunction, Left / Q000150:complications* / Q000209:etiology / Q000503:physiopathology*