title: Scatter in repolarization timing predicts clinical events in post-myocardial infarction patients.
abstract: BACKGROUND
  Increased spatial and temporal dispersion of repolarization contributes to ventricular arrhythmogenesis. Beat-to-beat fluctuations in T-wave timing are thought to represent such dispersion and may predict clinical events.
  
  
  OBJECTIVE
  The purpose of this study was to assess whether a novel noninvasive measure of beat-to-beat instability in T-wave timing would provide additive prognostic information in post-myocardial infarction patients.
  
  
  METHODS
  We studied 678 patients from 12 hospitals with 32-lead 5-minute electrocardiogram recordings 6-8 weeks after myocardial infarction. Custom software identified R wave-to-T wave intervals (RTIs) and diastolic intervals (DIs). Repolarization scatter (RTI:DI(StdErr)) was then calculated as the standard error about the RTI:DI regression line. In addition, left ventricular ejection fraction (LVEF), short-term heart rate variability (HRV) parameters, and QT variability index were measured. Patients were followed for the composite endpoint of death or life-threatening ventricular arrhythmia.
  
  
  RESULTS
  After a mean follow-up of 63 months, 134 patients met the composite endpoint. An RTI:DI(StdErr) >5.50 ms was associated with a 210% increase in arrhythmias or deaths (P <.001). After adjusting for LVEF, RTI:DI(StdErr) remained an independent predictor (P <.001). RTI:DI(StdErr) was also independent of short-term HRV parameters and the QT variability index.
  
  
  CONCLUSIONS
  Increased repolarization scatter, a measure of high-frequency, cycle-length-dependent repolarization instability, predicts poor outcomes in patients after myocardial infarction.
authors.affiliation: University of Utah School of Medicine, Department of Internal Medicine, Division of Cardiology, Salt Lake City, Utah, USA. Nathan.Segerson@hsc.utah.edu
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Segerson
authors.forename: Sheldon E
authors.initials: SE
authors.lastname: Litwin
authors.forename: Marcos
authors.initials: M
authors.lastname: Daccarett
authors.forename: T Scott
authors.initials: TS
authors.lastname: Wall
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Hamdan
authors.forename: Robert L
authors.initials: RL
authors.lastname: Lux
mesh_terms: D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology*; D010414:Pennsylvania; D011446:Prospective Studies; D012189:Retrospective Studies; D018570:Risk Assessment; D013318:Stroke Volume; D013997:Time Factors; D014589:Utah; D016277:Ventricular Function, Left