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T wave alternans in idiopathic long QT syndrome
W Zareba1, A J Moss, S le Cessie
1Department of Preventive and Community Medicine, University of Rochester School of Medicine and Dentistry, New York.
Insights
T wave alternans in long QT syndrome patients indicates high risk, but cardiac event risk is mainly due to prolonged repolarization (QTc). T wave alternans itself does not independently increase cardiac event risk when QTc length is considered.
Area of Science:
- Cardiology
- Electrophysiology
- Genetics
Background:
- T wave alternans is an uncommon ECG finding in patients with delayed repolarization.
- Its clinical significance in long QT syndrome (LQTS) is not well-established.
Purpose of the Study:
- To evaluate the association between T wave alternans and cardiac events in a large LQTS population.
- To determine if T wave alternans independently predicts cardiac events beyond QTc duration.
Main Methods:
- Reviewed 4,656 ECGs from 2,442 LQTS patients in the International LQTS Registry.
- Matched patients with T wave alternans to those without, controlling for corrected QT interval (QTc) duration.
Main Results:
- T wave alternans was found in 30 patients, strongly associated with QTc prolongation (OR 1.23 per 0.01-s1/2 increase).
- After adjusting for QTc, age, and gender, T wave alternans did not independently predict cardiac events.
- Cardiac event risk was primarily driven by the magnitude of QTc prolongation.
Conclusions:
- T wave alternans identifies a high-risk LQTS subset with electrical instability.
- While associated with increased cardiac events, the risk is predominantly explained by QTc length.
- T wave alternans lacks independent prognostic value for cardiac events when QTc is accounted for.
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.