T-Wave Alternans and the Susceptibility to Ventricular Arrhythmias

Abstract

T-wave alternans (TWA) reflects beat-to-beat fluctuations in the electrocardiographic T-wave, and is associated with dispersion of repolarization and the mechanisms for sudden cardiac arrest (SCA). This review examines the bench-to-bedside literature that, over decades, has linked alternans of repolarization in cellular, whole-heart, and human studies with spatial dispersion of repolarization, alternans of cellular action potential, and fluctuations in ionic currents that may lead to ventricular arrhythmias. Collectively, these studies provide a foundation for the clinical use of TWA to reflect susceptibility to ventricular arrhythmias in several disease states. This review then provides a contemporary evidence-based framework for the use of TWA to enhance risk stratification for SCA, identifying populations for whom TWA is best established, those for whom further studies are required, and areas for additional investigation.

A Multilead Scheme Based on Periodic Component Analysis for T-Wave Alternans Analysis in the ECG

“…19,23 TWA has been shown to reflect the presence of abnormal repolarization and electrophysiologic inhomogeneities that underlie vulnerability to ventricular fibrillation. 19 Measurement of TWA during controlled heart rate elevation is considered as a potentially useful predictor of ventricular arrhythmic events and mortality in patients with ischemic cardiomyopathy, 3 and its role in identification of patients that would benefit ICD implantation is being currently studied. 6 TWA amplitudes are in the range of microvolts, and can be even below the noise level, making the detection of TWA a difficult task.…”

“…12 Two commercially available techniques are the spectral method (SM) 23,26 and the modified moving average method 22 ; alternative techniques are the complex demodulation method 20 and the Laplacian likelihood ratio method (LLR). 11,13 A major limitation of these methods is their poor sensitivity to low-amplitude alternans 12,19 due to a lack of robustness to noise. With SM, for example, a noise level ‡ 2 lV in a predefined spectral band can lead to an indeterminate TWA test.…”

Is T-wave alternans as good or better than programmed ventricular stimulation?

“…The TWA in CHF and Ohio/Michigan studies (14,21) reported higher event rates in patients with QRS widening, but neither reported NPV of TWA based on QRS width. This issue is important for the bedside application of TWA to individual patients, and may be clarified by the formal subgroup analysis of the ABCD and SCD-HefT TWA substudy or other ongoing trials of TWA (13).…”

“…Since patients with wide QRS were more likely to receive ICDs, this may have led to 'over-reporting' of nonfatal arrhythmias compared to patients with narrow QRS. In addition, Morin et al (17) continued beta-blockers during TWA testing, that may theoretically attenuate TWA and impair its NPV (13). On the other hand, recent TWA trials reported high NPV for TWA either with (21) or without (14) continued betablockade during testing.…”

Cardiovascular magnetic resonance imaging and clinical performance of somatostatin receptor positron emission tomography in cardiac sarcoidosis

“…Moreover, we examined heart rate variability as an established predictor of increased mortality and elevated risk of cardiac events in the general population 14. T‐wave alternans that displays heterogeneity in ventricular repolarization and thus predicts ventricular arrhythmias in patients at risk for sudden cardiac death was additionally registered 15. Both 12‐lead ECG and Holter recording were analysed by experienced cardiologists, blinded to the patients' clinical background information.…”