T wave alternans in idiopathic long QT syndrome

J Am Coll Cardiol. 1994 Jun;23(7):1541-6. doi: 10.1016/0735-1097(94)90653-x.


Objectives: 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Death, Sudden, Cardiac
  • Electrocardiography*
  • Female
  • Heart Arrest / etiology
  • Humans
  • Long QT Syndrome / complications
  • Long QT Syndrome / physiopathology*
  • Male
  • Regression Analysis
  • Syncope / etiology