title: T wave alternans in idiopathic long QT syndrome.
abstract: OBJECTIVE
  The study evaluates the association between T wave alternans and the risk of cardiac events (syncope, aborted cardiac arrest or cardiac death) in a large population of patients with idiopathic long QT syndrome.
  
  
  BACKGROUND
  T wave alternans is an infrequently recorded electrocardiographic (ECG) finding in patients with delayed repolarization, and its clinical significance is not clear.
  
  
  METHODS
  A total of 4,656 ECG recordings in 2,442 patients enrolled in the International Long QT Syndrome Registry were reviewed for episodes of T wave alternans. To determine the risk associated with T wave alternans, independent of corrected QT interval (QTc) duration, patients with T wave alternans were matched for QTc value (every 0.025 s1/2) to patients with long QT syndrome without T wave alternans.
  
  
  RESULTS
  T wave alternans was identified in 30 patients (25 of whom had a QTc interval > 0.50 s1/2). A strong association between QTc prolongation and T wave alternans was observed (odds ratio 1.23 per 0.01-s1/2 unit increase in QTc, p < 0.0001). Conditional logistic regression analyses with adjustment for age, gender, status and QTc value revealed that T wave alternans did not make a significant independent contribution to the risk of cardiac events. The risk of experiencing a major cardiac event was primarily related to length of QTc.
  
  
  CONCLUSIONS
  T wave alternans, a marker of electrical instability and regional heterogeneity of repolarization, identifies a high risk subset of patients with prolonged repolarization. Patients with T wave alternans have an increased risk of cardiac events, but this risk is primarily related to the magnitude of repolarization delay (QTc prolongation). T wave alternans does not make an independent contribution to the risk of cardiac events after adjustment for QTc length.
authors.affiliation: Department of Preventive and Community Medicine, University of Rochester School of Medicine and Dentistry, New York.
authors.forename: W
authors.initials: W
authors.lastname: Zareba
authors.forename: A J
authors.initials: AJ
authors.lastname: Moss
authors.forename: S
authors.initials: S
authors.lastname: le Cessie
authors.forename: W J
authors.initials: WJ
authors.lastname: Hall
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D016757:Death, Sudden, Cardiac; D004562:Electrocardiography; D005260:Female; D006323:Heart Arrest / Q000209:etiology; D006801:Humans; D008133:Long QT Syndrome / Q000150:complications / Q000503:physiopathology*; D008297:Male; D012044:Regression Analysis; D013575:Syncope / Q000209:etiology