Author + information
- Received October 29, 1993
- Revision received December 17, 1993
- Accepted December 22, 1993
- Published online June 1, 1994.
- ↵∗Address for correspondence: Dr. Wojciech Zareba, Heart Research Follow-up Program, University of Rochester, Medical Center, Box 653, Rochester, New York 14642.
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 39 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-s1/2unit 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.
↵1 Dr. le Cessie is supported by a NATO Science Fellowship provided by The Netherlands Organization for Scientific Research (NWO), The Hague, The Netherlands.
☆ This research work was supported in part by Grant HL33843 from the National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.
- Received October 29, 1993.
- Revision received December 17, 1993.
- Accepted December 22, 1993.