title: Abnormalities of the repolarization characteristics of patients with heart failure progress with symptom severity.
abstract: BACKGROUND
  Congestive heart failure is a common condition with high mortality. Many of these deaths are sudden and unexpected. Ventricular action potential, surface repolarization (QT interval), and dispersion of repolarization are prolonged in the failing heart, contributing to arrhythmogenesis and sudden death. We studied the relationship between QT and heart rate (RR interval) from ambulatory recordings using a novel method in patients with ischemic heart disease and varying degrees of left-ventricular impairment (IHD) and compared them to healthy subjects (HS). We compare the degree of abnormality with the functional impairment and ejection fraction.
  
  
  METHODS
  Using a previously described automated method for continuous estimation of the QT/RR characteristic that incorporates a correction formula for compensation of QT adaptation lag (VERDA, Del Mar Reynolds Medical Ltd., Hertford, UK), we compared recordings from 41 IHD patients with age-matched HS.
  
  
  RESULTS
  IHD Patients have prolonged 24-hour mean QTo (461 ms vs 426 ms, P < 0.01), and abnormal rate dependence relative to controls (24-hour mean slope: 0.20 vs 0.14, P < 0.001; J: 0.38 vs 0.28, P < 0.001). There is increased temporal variation in J with respect to HS. These abnormalities of repolarization increase with worsening NYHA class, but do not correlate with ejection fraction.
  
  
  CONCLUSIONS
  The use of a universal correction formula to compare dynamic QT data in IHD patients is inappropriate. The observed progressive abnormalities may be responsible for the high incidence of sudden death through promotion of arrhythmias.
authors.affiliation: Department of Cardiology, Royal Infirmary of Edinburgh, Edinburgh, UK.
authors.forename: Christopher C E
authors.initials: CC
authors.lastname: Lang
authors.forename: James M M
authors.initials: JM
authors.lastname: Neilson
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Flapan
mesh_terms: D016022:Case-Control Studies; D018450:Disease Progression; D015716:Electrocardiography, Ambulatory; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index