T波电交替的研究进展

通过对近年来国内外对T波电交替的机制及其临床意义的研究总结,认为T波电交替是人类及动物缺血心肌发生室速、室颤的标志,是预测发生恶性室性心律失常及猝死的危险性独立的意义指标.     

T波电交替对复杂性室性心律失常的预测价值

目的探讨T波电交替对预测复杂性室性心律失常的价值。方法对照分析20例T波电交替患者与20例正常人的动态心电图复杂性室性心律失常发生情况。结果T波电交替组15例75%)出现复杂性室性心律失常,2例死亡;对照组3例出现复杂性室性心律失常(15%)无死亡;两组差异有非常显著性意义(P<0.01)。结论T波电交替对预测严重室性心律失常有重要价值。     

T波电交替预测心力衰竭病人心源性猝死价值的新分歧

有半数的心力衰竭病AN致命性室性心律失常事件死于心源性猝死。T波电交替是公认的预测心源性猝死的重要指标。早在许多年前就发现T波电交替与心源性猝死有关,近年来新建了频域和时域测量方法。跨室壁复极离散度异常增大是T波电交替的机制。最近研究发布的用微伏级T波电交替进行心肌梗死后危险性分层的初步结果否定心肌梗死后左室射血分数〈30％的病人发生致死性快速室性心律失常的价值。但体内除颤器置入前T波电交替的对心源性猝死一级预防试验和非缺血性心肌病心力衰竭T波电交替的预测价值试验则强有力地支持T波电交替能预测心律失常。     

长QT综合征伴多种心电现象一例

患者男,5岁,反复晕厥2年。心电图示QT间期、QTc间期明显延长,T波宽大畸形,可见明显电交替,动态心电图可见阵发性2:1房室传导阻滞及短阵多形性室性心动过速。长QT综合征诱发T波电交替是一种少见异常心电现象,是预测发生恶性室性心律失常与心脏性猝死独立的指标之一,合并房室传导阻滞或室内传导阻滞是预后不良的标志。     

T波电交替的研究进展

T波电交替是指在规整的心律时,体表心电图上T波形态、极性和振幅出现逐搏交替变化的现象,其与恶性室性心律失常以及心脏性猝死的发生有着极为密切的联系。T波电交替的检测方法有频域分析和时域分析方法两种。临床试验证实,T波电交替对恶性室性心律失常事件的预测价值与有创的电生理检测价值相似。但微伏级T波电交替检测作为一种无创的检测手段,其对于发生各种致死性心脏病危险分级的作用仍需要临床实验进一步研究证实,现就T波电交替的发生机制、临床意义以及发展现状等进行综述。     

动态心电图检测T波电交替

T波电交替是心室复极不一致的表现，提示心肌电活动不稳定，是患者发生恶性室性心律失常和心脏性猝死的强有力的独立预测指标。在常规心电图上观察到的T波电交替幅度为毫伏级（mV），又称显性T波电交替。而目前T波电交替的检查已发展为肉眼看不见、幅度为微伏级（μV）的电交替，又称微伏级T波电交替（microvolt Twave alternans，MTWA），需借助特殊的诊断系统和专用软件检测。     

T波电交替

Ｔ波电交替 (Ｔｗａｖｅａｌｔｅｒｎａｔｉｏｎ ,ＴＷＡ)是指心电图上Ｔ波幅度、形态的逐搏交替变化。反映心肌复极变化的Ｔ波电交替与反映心肌除极变化的ＱＲＳ波电交替两者均呈频率依赖性 ,但其电生理基础及临床意义却迥然不同。ＴＷＡ阳性者与发生恶性室性心律失常的倾向性呈明显正相关 ,而ＱＲＳ波电交替在快频率的阵发性室上性心动过速时较为常见 ,但它与室性心律失常之间并无相关性。肉眼可见的ＴＷＡ在 1910年即被Ｌｅｗｉｓ发现并确定其为室性心动过速 /心室颤动 (室速 /室颤 )及心性猝死的先兆。此后ＴＷＡ一直受到学者们的关注 ,…     

T波电交替及其对恶性心律失常的预测价值

T波电交替(TWA)是心肌电活动不稳定的标志。TWA发生机制可能与动作电位时程,细胞内钙循环和神经调节有关。研究证明,TWA与恶性室性心律失常[单形/多形室性心动过速、尖端扭转型室性心动过速、心室颤动]、心脏性猝死之间有着极为密切的关系,是当前对心律失常事件最具预测价值的无创电生理检测指标。TWA具有较高的阴性预测价值,因而具有在低危人群中筛选高危患者的作用;还可用于排除高危人群中不需要置入埋藏式心脏转复除颤器的患者。     

T波电交替及其对恶性心律失常的预测价值

T波电交替（TWA）是心肌电活动不稳定的标志。TWA发生机制可能与动作电位时程，细胞内钙循环和神经调节有关。研究证明，TWA与恶性室性心律失常[单形／多形室性心动过速、尖端扭转型室性心动过速、心室颤动]、心脏性猝死之间有着极为密切的关系，是当前对心律失常事件最具预测价值的无创电生理检测指标。TWA具有较高的阴性预测价值，因而具有在低危人群中筛选高危患者的作用；还可用于排除高危人群中不需要置入埋藏式心脏转复除颤器的患者。     

T波电交替计算机检测及其临床研究进展

T波电交替现象可见于长QT综合征、急性心肌缺血、变异型心绞痛、心脏性猝死以及电解质紊乱等。它在预测室性心律失常方面与电生理检查具有高度的一致性,是恶性室性心律失常和心脏性猝死的独立预测指标,是评定恶性心律失常以及心脏性猝死的可信、实用的技术之一。现在,T波电交替已经成为了一种廉价、方便的非侵入式心电检测方法。现综述T波电交替的研究背景、产生机制、检测方法及其临床研究,并简要分析了T波电交替的研究方向和发展前景。     

T波电交替预测扩张性心肌病患者恶性室性心律失常的作用

扩张型心肌病（DCM）是一种以心腔扩大与心肌收缩功能障碍为主要特征的原因不明的心肌疾病,不但易导致心力衰竭及心律紊乱,且易并发复杂或严重的恶性室性心律失常引起猝死（SCD）。研究表明,T波电交替（TWA）与恶性室性心律失常（单形／多形室速、尖端扭转型室速、室颤）、SCD之间有着极为密切的联系,经大量临床试验证实TWA是当前对心律失常事件最具预测价值的无创电生理检测指标。     

T-wave alternans in microwave frequency as a new indicator of disordered ventricular repolarization: pathophysiology, methodology, clinical results

Primary prevention of sudden cardiac death is hampered by the inability to accurately identify high risk patients. Various noninvasive methods such as determination of left ventricular function or heart rate variability as well as invasive electrophysiologic testing are currently used for risk stratification. Noninvasive measurement of microvolt T wave alternans (TWA) is a promising new method to assess repolarization abnormalities; in experimental studies, TWA was associated with an increased incidence of ventricular tachyarrhythmias. Since the occurrence of TWA is heart rate-dependent, it is measured either during atrial pacing or during exercise stress testing. The first clinical validation of the method was performed in patients undergoing invasive EP testing to assess prediction of inducibility of ventricular tachyarrhythmias. A first prospective validation of the noninvasive method was performed in patients surviving out-of-hospital cardiac arrest fitted with an ICD. Further studies have shown a good concordance between invasive and noninvasive TWA determination. The occurrence of TWA in this population was of predictive value with respect to arrhythmia recurrence. Recently published data confirm the value of TWA assessment with respect to identification of patients with congestive heart failure at high risk of malignant ventricular tachyarrhythmias. The use of this method in post myocardial infarction risk stratification is currently under prospective evaluation.     

Ventricular arrhythmia induced by sodium channel blocker in patients with Brugada syndrome

OBJECTIVES: We administered pilsicainide chloride, a class Ic pure sodium channel blocker, to patients with Brugada syndrome (BS) and evaluated the occurrence of ventricular arrhythmia (VA) and T-wave alternans (TWA). BACKGROUND: Ventricular arrhythmia and TWA are sometimes induced by a sodium channel blocker challenge test in BS patients, but the significance of the induced VA and TWA is not known. METHODS: Pilsicainide was administered to 65 patients with BS (10 symptomatic and 55 asymptomatic patients), and the occurrence of VA, TWA, and change of electrocardiogram were evaluated. Electrophysiologic study was performed in 57 patients, and the induction of VA by programmed electrical stimulation (PES) was evaluated. RESULTS: Ventricular arrhythmia was not induced by administration of pilsicainide in 55 patients (no-VA group). Administration of pilsicainide-induced VA in 10 patients (Pil-VA group) and polymorphic ventricular tachycardia in four patients. Pilsicainide-induced VA in 60% of the symptomatic patients but in only 7% of asymptomatic patients (p < 0.01). ST level, QTc, and indexes of cardiac conduction in the Pil-VA group were not different from those in the no-VA group. Ventricular fibrillation was induced by PES in 67% of the patients in the Pil-VA group and in 33% of the patients in the no-VA group. In six cases, macroscopic TWA occurred in association with pilsicainide-induced VA, but TWA occurred in only one patient without pilsicainide-induced arrhythmia. CONCLUSIONS: Administration of a sodium channel blocker results in induction of not only ST-elevation but also VA and TWA in patients with BS.     

T wave alternans for ventricular arrhythmia risk stratification

Sudden cardiac death remains one of the leading causes of death in western societies. Accordingly, the ability to identify patients at high risk of sudden cardiac death is important so that appropriate treatments can be used efficiently. Recently, T wave alternans (TWA) has emerged as a promising new test for such risk stratification. TWA is a heart rate-dependent measure of arrhythmia vulnerability, with maximal predictive accuracy at sustained, regular heart rates of 100 to 120 bpm. In the clinical setting, these conditions may be achieved by either exercise or atrial pacing. TWA has been shown to predict inducibility of ventricular tachycardia with programmed stimulation and also spontaneous arrhythmic events. TWA has been successfully applied to diverse populations, including patients with coronary artery disease, nonischemic cardiomyopathy, congestive heart failure, and implantable defibrillators. Despite these encouraging results, the role of TWA to guide clinical therapy still needs to be elucidated better.     

T wave alternans for ventricular arrhythmia risk stratification

Sudden cardiac death remains one of the leading causes of death in Europe and the United States. Accordingly, the ability to identify patients at high risk of sudden cardiac death is important so that appropriate treatments can be used efficiently. Recently, T wave alternans (TWA) has emerged as a promising new test for such risk stratification. TWA is a heart rate dependent measure of arrhythmia vulnerability, with maximal predictive accuracy at sustained, regular heart rates of 100-120 bpm. In the clinical setting these conditions may be achieved by either exercise or atrial pacing. TWA has been shown to predict inducibility of ventricular tachycardia with programmed stimulation and also spontaneous arrhythmic events. TWA has been successfully applied to diverse populations, including patients with coronary artery disease, nonischemic cardiomyopathy, congestive heart failure and those with implantable defibrillators. Despite these encouraging results, the role of TWA to guide clinical therapy still needs to be better elucidated.     

Prediction values of T wave alternans for sudden cardiac death in patients with chronic heart failure: a brief review

More than 50% of patients with heart failure die from sudden cardiac death as a result of malignant arrhythmia. T wave alternans (TWA) is a convenient, noninvasive, and inexpensive testing modality, with a higher sensitivity and specificity for sudden cardiac death. Its prediction value for malignant arrhythmia may even exceed electrophysiologic study. Generally, the algorithms of TWA can be divided into frequency-domain and time-domain methods, and the latter has a stronger anti-interference ability. So far, a unified measuring formula and diagnostic criteria about TWA measurements have been created. Large clinical studies in recent years strongly suggest that TWA can predict sudden cardiac death, which can be used as a guide for the implanting of implantable cardioverter-defibrillator. This article reviews the current literature on recording techniques and clinical implications of TWA.     

The Prevalence and the Prognostic Value of Microvolt T‐Wave Alternans in Patients with Hypertrophic Cardiomyopathy

Background: Nonsustained ventricular tachycardia (nVT) may have ominous implications for patients with hypertrophic cardiomyopathy (HCM). The microvolt T‐wave alternans (TWA) has been proposed as a noninvasive tool‐identifying patients at risk of sudden cardiac death and ventricular tachycardia/fibrillation (VT/VF). The aim of the study was to determine the significance of TWA in predicting nVT episodes and compare how other electrocardiographic parameters can predict the occurrence of nVT. Methods: The study group consisted of 88 patients with HCM. TWA was assessed during exercise test using the CH2000 system. All patients underwent Holter monitoring (HM) within 2–4 weeks before TWA test (preexercise HM1) and immediately after (postexercise HM2). During HM, we analyzed: arrhythmias, QT intervals, the presence of late ventricular potentials (LP), heart rate variability, heart rate turbulence. Results: Depending on TWA results, the patients were divided into two groups: TWA+; 46 patients (52.3%) with positive/indeterminate results, and TWA–; 42 patients (47.7%) with negative results. The nVT episodes were more frequent among TWA(+) both in HM1 and HM2. The presence of TWA increases the risk of postexercise nVT over twenty times (OR = 21.03). Moreover, in HM1, QTc and LP, and in HM2, again QTc and N‐terminal precursor of brain natriuretic peptide proved to be significant predictors of nVT. The addition of TWA to the models did not improve the arrhythmia risk assessment. Conclusions: Repolarization abnormality plays an important role in generating nVT in patients with HCM, but TWA does not specifically predict the risk of arrhythmic end point. Ann Noninvasive Electrocardiol 2011;16(3):276–286