title: T wave alternans as a predictor of spontaneous ventricular tachycardia in a canine model of sudden cardiac death.
abstract: BACKGROUND
  We recently developed an ambulatory canine model of spontaneous ventricular tachycardia (VT) and sudden cardiac death by creating myocardial infarction, complete AV block, and infusion of nerve growth factor to the left stellate ganglion. Whether or not T wave alternans is associated with the spontaneously occurring episodes of VT in our model was unclear.
  
  
  RESULTS
  Through intracardiac electrograms obtained from an implantable cardioverter defibrillator, we manually measured T wave amplitudes prior to VT and while the dogs were at rest (baseline, no VT). Of the 79 VT episodes analyzed, 28 (35.4%) exhibited repolarization alternans. In contrast, only 3 (4.7%) of 64 baseline data cases displayed alternans (P < 0.0001). The magnitude of T wave alternans for dogs that died of sudden cardiac death, dogs that did not die suddenly, and for the total 28 episodes that exhibited repolarization alternans were 4.8 +/- 2.8 mm, 4.9 +/- 3.5 mm, and 4.9 +/- 3.3 mm, respectively (P = NS). We also found the sensitivity, specificity, positive predictive value, negative predictive value, and relative risk of repolarization alternans in predicting VT to be 35.4%, 95.3%, 90.3%, 54.5%, and 1.98, respectively. The ventricular rate prior to VT (65 +/- 11 beats/min) was significantly higher than that at rest (49 +/- 12 beats/min; P < 0.0001).
  
  
  CONCLUSIONS
  T wave alternans often occurred immediately before the onset of VT in dogs with myocardial infarction, complete AV block, and nerve growth factor infusion to the left stellate ganglion. Increased sympathetic activity might be responsible for the occurrence of the T wave alternans.
authors.affiliation: Department of Medicine, Cedars-Sinai Medical Center, and University of California Los Angeles, 90048-1865, USA.
authors.forename: Jerome
authors.initials: J
authors.lastname: Tsai
authors.forename: Ji-Min
authors.initials: JM
authors.lastname: Cao
authors.forename: Shengmei
authors.initials: S
authors.lastname: Zhou
authors.forename: Moshe
authors.initials: M
authors.lastname: Swissa
authors.forename: Adam W
authors.initials: AW
authors.lastname: Cates
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Kenknight
authors.forename: Lan S
authors.initials: LS
authors.lastname: Chen
authors.forename: Hrayr S
authors.initials: HS
authors.lastname: Karagueuzian
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
mesh_terms: D000818:Animals; D016757:Death, Sudden, Cardiac; D017147:Defibrillators, Implantable; D004285:Dogs; D004562:Electrocardiography; D006352:Heart Ventricles / Q000503:physiopathology; D011237:Predictive Value of Tests; D018570:Risk Assessment; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology