title: QT dynamics in risk stratification after myocardial infarction.
abstract: OBJECTIVE
  The purpose of this study was to compare measures of repolarization dynamics (QT dynamics) with other Holter risk predictors, left ventricular systolic function, and demographic characteristics to establish whether QT dynamics add independent information on risk stratification after myocardial infarction (MI). A novel QT dynamics parameter, the QT/RR variability ratio (VR), was introduced in this study.
  
  
  BACKGROUND
  Abnormal repolarization contributes to arrhythmogenesis, and quantification of QT dynamics may have prognostic value after MI.
  
  
  METHODS
  A 24-hour Holter recording was performed in 481 consecutive MI patients. Recordings from 311 patients were included in the analysis. QT/RR slope and intercept, mean and standard deviation of all QT, QTc, and RR intervals, and VR (defined as the ratio between the standard deviation of all QT intervals and the standard deviation of all RR interval) were calculated. Ventricular premature beats and ventricular tachycardia were counted.
  
  
  RESULTS
  During 3-year follow-up, 70 deaths from all causes occurred. All parameters except mean of all QT intervals and standard deviation of all QTc intervals univariately predicted all-cause mortality. In multivariate Cox analysis, only VR per 0.1 (hazard ratio [HR]: 1.9 [1.5-2.4]), left ventricular ejection fraction per 5% (HR: 1.2 [1.1-1.3]), ventricular premature beats per 10 beats/hour (HR: 1.03 [1.002-1.06]), and age per 10 years (HR: 1.6 [1.3-2.0]) independently predicted all-cause mortality.
  
  
  CONCLUSIONS
  Measures of QT dynamics univariately predicted total mortality. VR, left ventricular ejection fraction, ventricular premature beats, and age made up the optimal Cox model for risk stratification after MI. VR seems to be a promising risk factor for identifying sudden arrhythmic death.
authors.affiliation: Laboratory of Experimental Cardiology, Department of Medical Physiology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Berit T
authors.initials: BT
authors.lastname: Jensen
authors.forename: Steen Z
authors.initials: SZ
authors.lastname: Abildstrom
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Larroude
authors.forename: Erik
authors.initials: E
authors.lastname: Agner
authors.forename: Christian
authors.initials: C
authors.lastname: Torp-Pedersen
authors.forename: Ole
authors.initials: O
authors.lastname: Nyvad
authors.forename: Michael
authors.initials: M
authors.lastname: Ottesen
authors.forename: Kristian
authors.initials: K
authors.lastname: Wachtell
authors.forename: Jørgen K
authors.initials: JK
authors.lastname: Kanters
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000401:mortality* / Q000503:physiopathology; D016757:Death, Sudden, Cardiac / Q000453:epidemiology*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology*; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D018570:Risk Assessment; D016277:Ventricular Function, Left