title: Defibillator electrogram T wave alternans as a predictor of spontaneous ventricular tachyarrhythmias in defibrillator recipients.
abstract: BACKGROUND
  Although T wave alternans (TWA) and the T wave peak-to-end (Tpte) interval are associated with vulnerability to ventricular tachyarrhythmia (VT), no previous reports have demonstrated that TWA immediately precedes spontaneous VT in the human ambulatory setting.
  
  
  RESULTS
  Stored electrograms from the implantable cardioverter defibrillators (ICD) of 74 patients (59 males, 55.3+/-12.2 years) were analyzed. TWA (DeltaT amplitude), Tpte interval, QT interval, and RR intervals were measured from magnified digital images immediately before spontaneous VT (VT(Clinical); n=73), or immediately after ICD shocks during artificially-induced VT (VT(Induced); n=74) or inappropriate shocks (Shock(Inapp); n=6). (1) TWA was significantly greater in VT(Clinical) than VT(Induced) (P<0.01) or Shock(Inapp) (P<0.001), but Tpte was not (P=NS). (2) In the VT(Clinical) group, TWA was significantly greater in patients with ischemic VT than in those with non-ischemic cardiomyopathy or idiopathic VF (P<0.05). (3) In the same patient, the TWA for VT(Clinical) was significantly greater than that for VT(Induced) (P<0.01).
  
  
  CONCLUSIONS
  TWA measured from ICD electrograms is significantly greater immediately before spontaneous VT than immediately after inappropriate shocks or shocks during induced VT. These findings indicate that repolarization alternans plays an important role in the induction of VT in humans.
authors.affiliation: Korea University Cardiovascular Center, Seoul, Republic of Korea.
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Kim
authors.forename: Hui-Nam
authors.initials: HN
authors.lastname: Pak
authors.forename: Jae Hyung
authors.initials: JH
authors.lastname: Park
authors.forename: Gi-Byoung
authors.initials: GB
authors.lastname: Nam
authors.forename: Sook Kyoung
authors.initials: SK
authors.lastname: Kim
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Lee
authors.forename: Jin Kun
authors.initials: JK
authors.lastname: Jang
authors.forename: Jong Il
authors.initials: JI
authors.lastname: Choi
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D053840:Brugada Syndrome / Q000503:physiopathology / Q000628:therapy; D002312:Cardiomyopathy, Hypertrophic / Q000503:physiopathology / Q000628:therapy; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008133:Long QT Syndrome / Q000503:physiopathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology* / Q000628:therapy