Microvolt T-Wave Alternans

Abstract

This consensus guideline was prepared on behalf of the International Society for Holter and Noninvasive Electrocardiology and is cosponsored by the Japanese Circulation Society, the Computers in Cardiology Working Group on e-Cardiology of the European Society of Cardiology, and the European Cardiac Arrhythmia Society. It discusses the electrocardiographic phenomenon of T-wave alternans (TWA) (i.e., a beat-to-beat alternation in the morphology and amplitude of the ST- segment or T-wave). This statement focuses on its physiological basis and measurement technologies and its clinical utility in stratifying risk for life-threatening ventricular arrhythmias. Signal processing techniques including the frequency-domain Spectral Method and the time-domain Modified Moving Average method have demonstrated the utility of TWA in arrhythmia risk stratification in prospective studies in >12,000 patients. The majority of exercise-based studies using both methods have reported high relative risks for cardiovascular mortality and for sudden cardiac death in patients with preserved as well as depressed left ventricular ejection fraction. Studies with ambulatory electrocardiogram-based TWA analysis with Modified Moving Average method have yielded significant predictive capacity. However, negative studies with the Spectral Method have also appeared, including 2 interventional studies in patients with implantable defibrillators. Meta-analyses have been performed to gain insights into this issue. Frontiers of TWA research include use in arrhythmia risk stratification of individuals with preserved ejection fraction, improvements in predictivity with quantitative analysis, and utility in guiding medical as well as device-based therapy. Overall, although TWA appears to be a useful marker of risk for arrhythmic and cardiovascular death, there is as yet no definitive evidence that it can guide therapy.

Long-term Non-Invasive ECG-based Risk Stratification of Sudden Cardiac Death: Extended 5-year Results

“…Threshold values obtained in our study differed from findings in other studies [8,14] that may be explained by differences in measurement and in characteristics of study populations, but cut-offs for mTWA at 05.00 AM (CV mortality) and mTWA at 100 bpm (SCD) at 12 and 60 months of follow-up were similar suggesting the good reproducibility of mTWA measurement during short-term and long-term monitoring; it is consistent with the results of Chan et al [15] who showed that the predictive value of the baseline mTWA evaluation persists during 2-3 years, and therefore re-measurement mTWA is reasonable only every 2 years. In this study, duration of follow-up was 18 ± 11 months; our results for the follow-up period of 60 months confirm the conclusions of the authors [15] as repeated measurements at 3, 6 and 12 months were not significantly different.…”

“…In prospective clinical studies of >10,000 patients, mTWA identified patients at risk for fatal arrhythmia and cardiovascular and total mortality [8] and met American Heart Association, American College of Cardiology, European Society of Cardiology, and/or Heart Rhythm Society requirements for class I (level of evidence A) and class IIa (level of evidence A) indications for arrhythmia risk assessment. [4] Goldberger et al [1] stated that mTWA provides valuable information regarding the risk of cardiovascular mortality and SCD among patients with ischemic, dilated, and hypertrophic cardiomyopathies.…”

“…[4] Goldberger et al [1] stated that mTWA provides valuable information regarding the risk of cardiovascular mortality and SCD among patients with ischemic, dilated, and hypertrophic cardiomyopathies. Thus, a recent consensus guideline recommended mTWA monitoring in any suspected risk for fatal arrhythmia [8] but it has not been included in the ESC 2015 Guidelines for management of patients with ventricular arrhythmias and the prevention of SCD [11] due to the lack of evidence-based information.…”

“…[1,7,[8][9][10]] Microvolt TWA has been described as a useful predictor of cardiac events in patients with various ischemic and nonischemic pathologies with or without low ejection fraction including acute coronary syndrome. [8,9] However, there is lack of evidence concerning the use of these methods for SCD risk stratification in the post-MI patients, and they have not been included in the ESC 2015 Guidelines for management of patients with ventricular arrhythmias and the prevention of SCD, [11] despite the inclusion into ACC/AHA/ESC 2006 Guidelines for patients with severe LV dysfunction (classes of recommendations: mTWA -IIA, HRT -IIB). In recent years, deceleration capacity (DC) -parameter reflecting the ability of sinus rhythm to slow down -has also being investigated.…”

Analysis of the Q-T Dispersion and T Wave Alternans in Patients with Epilepsy

“…If effective predictions of the likelihood of ventricular fibrillation can be made, advance prevention will reduce the mortality of patients with epilepsy. Ventricular fibrillation is more often induced by cardiac electrical repolarization abnormalities [8], and heart rate variability, Q-T dispersion, T wave alternans [9] in 12 lead ECG can be used to directly observe the cardiac electrical repolarization abnormalities. While heart rate variability needs dynamic ECG monitoring which takes longer, Q-T dispersion and T wave alternating, conventional ECG is able to interpret; so we choose two parameters on RECG, T wave electric alternating and Q-T dispersion, as the observation index.…”