Microvolt T-wave alternans complemented with electrophysiologic study for prediction of ventricular tachyarrhythmias in patients with arrhythmogenic right ventricular cardiomyopathy: a long-term follow-up study

Background: The long-term predicted value of microvolt T-wave alternans (MTWA) for ventricular tachyarrhythmia in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) remains unclear. Our study explored the characteristics of MTWA and its prognostic value when combined with an electrophysiologic study (EPS) in patients with ARVC. Methods: All patients underwent non-invasive MTWA examination with modified moving average (MMA) analysis and an EPS. A positive event was defined as the first occurrence of sudden cardiac death, documented sustained ventricular tachycardia (VT), ventricular fibrillation, or the administration of appropriate implantable cardioverter defibrillator therapy including shock or antitachycardia pacing. Results: Thirty-five patients with ARVC (age 38.6 ± 11.0 years;28 males) with preserved left ventricular (LV) function were recruited. The maximal TWA value (MaxValt) was 17.0 (11.0–27.0)μV. Sustained VT was induced in 22 patients by the EPS. During a median follow-up of 99.9 ± 7.7 months, 15 patients had positive clinical events. When inducible VT was combined with the MaxValt, the area under the curve improved from 0.739 to 0.797. The receiver operating characteristic curve showed that a MaxValt of 23.5 μV was the optimal cutoff value to identify positive events. The multivariate Cox regression model for survival showed that MTWA (MaxValt, hazard ratio [HR], 1.06;95% confidence interval [CI], 1.01–1.11;P = 0.01) and inducible VT (HR, 5.98;95% CI, 1.33–26.8;P = 0.01) independently predicted positive events in patients with ARVC. Conclusions: MTWA assessment with MMA analysis complemented by an EPS might provide improved prognostic ability in patients with ARVC with preserved LV function during long-term follow-up.

The Relationship between T-Wave Alternans and Adverse Cardiac Events in Patients with Congenital Long QT Syndrome:A Systematic Review and Meta-Analysis

Background:T-wave alternans(TWA)is a risk factor of ventricular arrhythmias or sudden cardiac death(SCD)in patients with ischemic cardiomyopathy.Nevertheless,the relationship between TWA and adverse cardiac events(ACE)in patients with congenital long QT syndrome(LQT)remains controversial.Methods:A systematic electronic search of PubMed,Embase and the Cochrane Library was conducted from database inception dates to 28 April 2021 and assessed the relationship between TWA and ACE in patients with LQTS.Sub-group analysis evaluated the association between microvolt TWA(MTWA)and ACE in different monitoring models and ECGlead numbers.Results:A pooled analysis of seven studies of 625 patients with LQTS showed that TWA was significantly associated with ACE(OR 3.16,95%CI 1.86–5.37,P<0.001).Advanced analysis showed that macroscopic TWA was significantly related to ACE(OR 6.01,95%CI 2.96–12.21,P<0.001),while MTWA did not(OR 0.92,95%CI 0.37–2.30,P=0.85).Sub-group analysis showed that MTWA recorded in 24 h continuous ECG(OR 6.79,95%CI 0.80–57.75,P=0.08)might have a stronger association with ACE than recorded in stress ECG(OR 0.28,95%CI 0.07–1.10,P=0.07).No difference was observed between MTWA measured in multi-lead ECG and limited ECG leads(P=0.15).Conclusions:Macroscopic TWA was significantly related to ACE in patients with LQTS.In terms of MTWA,MTWA recorded in 24 h continuous ECG might have a stronger association with ACE than stress ECG,but still deserves further evaluation.

Detection of T-wave Alternans in ECG Signals Using FRFT and Tensor Decomposition

T-wave alternans(TWA)refers to the periodic beat-to-beat variation in the amplitude of T-wave in the electrocardiogram(ECG)signal in an ABAB-pattern.TWA has been proven to be a very important indicator of malignant arrhythmia risk stratification.A new method to detect TWA by combining fractional Fourier transform(FRFT)and tensor decomposition is proposed.First,the T-wave vector is extracted from the ECG of each heartbeat,and its FRFT amplitudes at multiple orders are arranged to form a T-wave matrix.Then,a third-order tensor is composed of T-wave matrices of several consecutive heart beats.After tensor decomposition,projection matrices are obtained in three dimensions.The complexity of the projection matrix is measured by Shannon entropy to obtain feature vector to detect the presence of TWA.Results show that the sensitivity,specificity,and accuracy of the algorithm on the MIT-BIH database are 91.16%,94.25%,and 92.68%,respectively.This method effectively utilizes the fractional domain information of ECG,and shows the promising potential of the FRFT in ECG signal processing.

Adaptive Match-Filtering: A Biomedical Application to Identify T-Wave Alternans

T-wave alternans (TWA), consisting in an alternation of the electrocardiographic (ECG) repolarization segment (T-wave), is a promising index of the risk of sudden cardiac death. By definition, it is characterized by a frequency component, termed fTWA, that matches half heart rate. The heart-rate adaptive match filter (AMF) based method is a technique for automatic TWA identification from the digital ECG. Aim of the present study was to provide a complete technical description of the filter able to explain its methodological principles. The AMF is usually realized as a 6th order Butterworth filter with a narrow (0.12 Hz) passing band centered in fTWA. It is applied in a bidirectional fashion, so that final filtering order is 12. While extracting the TWA component, the AMF simultaneously filters out every ECG component including noise and artefacts, and thus results are very robust. Goodness of the technique was tested using 8 synthetic ECG tracings corrupted by typical noisy factors, such as white random noise, baseline wanderings, heart-rate variability, and others. Six ECG tracings were affected by 100 μV TWA, whereas two were not. Results indicate that the AMF-based method is able to prevent false-positive and false-negative detections and, thus, represents a useful tool for a reliable TWA identification.

On the basis of the morphology of the T-wave alternans: A Poincare mapping method research

Presently T-wave alternans (TWA) has become a clinical index of non-invasive diagnosis for heart sudden death prediction, and detecting T-wave alternate accurately is particularly important. This paper introduces an algorithm for detecting TWA using Poincare mapping method which is a technique for nonlinear dynamic systems to display periodic behavior. Sample series of beat to beat cycles were selected to prepare Poincare mapping method. Vector Angle Index (VAI), which is the mean of the difference between θi (the angle between the line connecting the i point to the origin and the X axis) and 45 degrees was used to present the presence or absence of TWA. The value of 0.9 rad ≤ VAI ≤ 1.03 rad is accepted as a level determinative for presence of TWA. VAI via Poincare mapping method (PM) is used for correlation analysis with T-wave alternans voltage (Vtwa) by way of the spectral method (SM). The cross-correlation coefficient between Vtwa and VAI is γ = 0.8601. The algorithm can identify the absence and presence of TWA accurately and provide idea for further study of TWA-PM.

Application of T-Wave Alternans in Evaluation of Prognosis in Patients with Intracerebral Hemorrhage

Objective: To explore the application value of electrocardiograph (ECG) T-wave Alternans (TWA) anomaly in acute stage of intracerebral hemorrhage patients. Methods: We choose 1175 intracerebral hemorrhage patients whose conventional 12-lead ECG has TWA in our hospital from January 2011 to December 2015, 751 patients without TWA in the same period as the control group, compared the volume of intracerebral hemorrhage, bleeding site and mortality between the 2 groups. Results: In TWA group, 247 cases died, 361 cases with massive intracerebral hemorrhage, 298 cases with brain stem hemorrhage;in TWA negative group (control group), 41 cases died, 93 cases with massive brain hemorrhage, 64 cases with brain stem hemorrhage. There are statistical differences between two groups (P Conclusion: The occurrence of TWA is significantly related to the volume of bleeding, the bleeding site and mortality, and can be used as an important parameter in the prognosis of intracerebral hemorrhage.

Improved modified moving average analysis of T-wave alternans using least squares-based curve fitting method

T-wave alternans （TWA） in surface electrocardiograph （ECG） signal is considered a marker of abnormal ventricular function which may be associated with ventricular tachy- cardia. Several methods have been developed in recent years to evaluate the important feature. One such method is known as modified moving average （MMA） analysis, which performs well for different levels of TWA, but it is sensitive to the noise in T-waves. In this paper we propose an improved MMA algorithm, which adds a stage of T-wave curve fitting for the MMA method before intermediate averaging. The curve fitting is performed by means of least square method technique. Our assessment study demon- strates the improved performance.

微伏T波电交替监测对恶性心律失常的预测价值

目的目的观察微伏T波电交替(TWA)监测对缺血性心脏病伴室性心律失常患者发生恶性心律失常的预测价值。方法 80例缺血性心脏病伴室性心律失常患者随机分为观察组和对照组各40例,根据患者临床症状和实验室检查预测恶性心律失常的发生,观察组同时用TWA监测预测恶性心律失常的发生。观察两组预测准确率、从发生心脏猝死到抢救用时、抢救成功率及抢救后并发症发生情况。结果观察组发生恶性心律失常18例,其中预测准确14例,发生而未预测2例,未发生却被预测2例,预测准确率为77.8%(14/18);对照组分别为26、15、6、5例和77.8%(15/26),两组预测准确率比较,P<0.05。结论 TWA监测可有效预测缺血性心脏病伴室性心律失常患者恶性心律失常的发生。

微伏级T波电交替和窦性心率震荡在冠心病诊断中的临床应用

目的探讨微伏级T波电交替和窦性心率震荡在冠心病诊断中的应用价值。方法选取2014年8月至2015年8月笔者所在医院心血管内科就诊并经冠状动脉造影及心电图检查证实冠心病患者86例作为研究对象。根据冠状动脉造影正常或冠状动脉狭窄<50%者为对照组(n=35),行冠状动脉造影证实相关冠状动脉狭窄>75%且血流分级≤3级为冠心病组(n=51),其中冠心病组又分为稳定性心绞痛组(n=27)和陈旧性心肌梗死组(n=24)。记录并比较各组患者24 h动态心电图、微伏级T波电交替(MTWA)及窦性心率震荡(HRT)参数的变化以及MTWA、HRT及MTWA+HRT预测恶性室性心律失常的灵敏度和特异度。结果冠心病组患者的MTWA和HRT阳性率分别为41.2%(21/51)和62.7%(32/51),明显高于对照组的5.7%(2/35)和17.1%(6/35),冠心病组的MTWA联合HRT阳性率为23.5%(12/51),也明显高于对照组的5.7%(2/35),组间各项指标比较差异均有统计学意义(P<0.05);心绞痛组患者的MTWA和HRT阳性率分别为74.1%(20/27)和92.6%(25/27),明显高于陈旧性心肌梗死组的4.2%(1/24)和33.3%(8/24),心肌梗死组的MTWA+HRT阳性率为40.7%(11/27),明显高于对照组的4.2%(1/24),组间各项指标比较差异有统计学意义(P<0.05);与单项指标相比,MTWA+HRT的灵敏度及特异度相对较高。MTWA灵敏度和特异度分别为53.3%(8/15)和60.9%(28/46),HRT灵敏度和特异度分别为66.6%(10/15)和39.1%(18/46),MTWA+HRT灵敏度和特异度分别为71.4%(5/7)和68.8%(22/32)。结论 MTWA、HRT均是评估冠心病患者预后的重要指标,并且对评价冠心病患者发生恶性室性心律失常及心脏性猝死方面具有更佳的预测水平,而MTWA联合HRT检测的灵敏度和特异度高于单项指标,可明显提高24 h动态心电图对冠心病的诊断价值。

健康人微伏级T波电交替试验检测分析

微伏级T波电交替 (MTWA)与器质性心脏病恶性室性心律失常的发生密切相关。T波电交替偶见于正常人运动时。本研究的目的是探讨正常人静息和运动时MTWA的发生情况。用CambridgeHeart.HeartwaveTMsys tem心脏诊断系统 ,以频谱法检测 4 5例健康志愿者MTWA。结果 :所有受试者静息时MTWA阴性。运动负荷试验时 ,非持续性MTWA 5例 (11.11% ) ,持续性MTWA 2例 (4.4 4 % ) ,1例阈值心率 <110次 /分 ,另一例发作心率>110次 /分。 4 5例中 ,MTWA阳性 1例 (2 .2 2 % ) ,但持续时间短暂 (1min) ,不确定性 2例 (4.4 4 % ) ,阴性 4 2例(93.33% )。结论 :健康人MTWA阳性发生率低 (2 .2 2 % ) ,短暂的MTWA无恶性室性心律失常的临床意义。

心室复极微小变化的小波域维纳滤波分析

心室复极微小变化与恶性室性心律失常的关系已引起国内外学者的广泛关注,对心脏性猝死预测有重要的临床意义。为达到对心室复极微小变化逐搏观察、分析,用小波域维纳滤波方法去除体表心电图中的肌电干扰,提取心室复极过程的微伏级高频信号。研究结果表明:小波域维纳滤波器可有效抑制人体肌电干扰,满足心室复极微小变化分析的需求;健康人和无室早患者的心室复极微小变化一般由6个可辨识的微伏级高频波构成,而室早患者心室复极微小变化的微伏级高频波则有可能少于6个。这些微伏级高频波的波宽、相互的时间间隔等特征参数与心脏疾病、心脏猝死的关系值得进一步研究。

微伏级T波电交替和窦性心率震荡在冠心病患者中的诊断价值

目的探讨微伏级T波电交替(MTWA)及窦性心率震荡(HRT)在冠心病诊断中的应用价值。方法选择2013年10月—2014年12月疑诊冠心病并行冠状动脉造影及24小时动态心电图检查的住院患者共76例。采用Beneware动态心电图分析软件记录24 h动态心电图。经冠状动脉造影正常或者冠状动脉狭窄<50%者为对照组(30例),经冠状动脉造影证实相关冠状动脉狭窄>75%且血流分级≤3级为病变组(46例),其中病变组分心绞痛亚组(24例)及心肌梗死亚组(22例)。同时根据冠状动脉病变累及程度分为单支亚组(10例)、双支亚组(15例)和三支亚组(21例),分析24 h动态心电图,比较MTWA和HRT阳性率的变化。结果(1)病变组MTWA阳性率为41.3%,高于对照组的6.7%(P<0.05);病变组HRT阳性率为63.0%,高于对照组的16.7%(P<0.05);病变组MTWA联合HRT阳性率为23.9%,高于对照组的6.7%(P<0.05)。(2)心绞痛亚组MTWA阳性率为75.0%高于心肌梗死亚组的4.5%(P<0.05);心绞痛亚组HRT阳性率为91.7%,高于心肌梗死亚组的31.8%(P<0.05);心绞痛亚组MTWA联合HRT阳性率为41.7%,高于心肌梗死亚组的4.5%(P<0.05)。(3)单支亚组、双支亚组、三支亚组MTWA阳性率分别为30.0%、40.0%、47.6%,HRT阳性率分别为40.0%、40.0%、90.5%,MTWA联合HRT阳性率分别为10.0%、26.7%、28.6%,3个亚组间比较差异均有统计学意义(P<0.05)。(4)MTWA、HRT以及MTWA联合HRT在冠心病患者中检测恶性室性心律失常的灵敏度分别为50.0%、70.0%、75.0%;特异度分别为61.1%,38.9%,68.0%。结论 MTWA、HRT指标均是评估冠心病危险程度较好的无创电生理指标,二者联合运用可提高24小时动态心电图对冠心病的诊断价值;对于冠心病患者发生恶性室性心律失常的预测,联合指标的敏感度及特异度高于单一指标。

微伏级T波电交替的临床应用价值

T波电交替是指在规则心律时,体表心电图T波振幅、形态逐搏交替变化。用现代仪器监测出的微伏级T波电交替,作为一种无创的心电检测方法,具有广阔的临床应用前景。现结合文献对近些年来微伏级T波电交替最新临床应用进行探讨,为微伏级T波电交替的研究学者提供一个现代化的理论框架。

T波电交替对急性心肌梗死患者恶性心律失常的预测价值

目的探讨时域法微伏级T波电交替（MTWA）对急性心肌梗死（AMI）患者住院期间恶性心律失常的预测价值。方法 105例AMI患者（AMI组）,其中男性77例,女性28例;年龄32~84岁,平均年龄62岁。38例冠状动脉正常者（对照组）,其中男性25例,女性13例;年龄41~79岁,平均年龄59岁。分析2组24h动态心电图检查资料。依据住院期间有无室性心动过速或心室纤颤,将105例AMI患者分为恶性心律失常组（34例）和非恶性心律失常组（71例）。结果 AMI组MTWA高于对照组（P〈0.05）。AMI患者中恶性心律失常组与非恶性心律失常组MTWA差异具有显著统计学意义（P〈0.01）。以MTWA≥25μV为截点,预测AMI患者发生恶性心律失常的灵敏度、特异度、阳性预测值、阴性预测值分别为50.00%、80.28%、54.84%、77.03%。结论时域法测量MTWA对AMI患者住院期间恶性心律失常的发生有预测价值,可用于AMI患者的危险分层。

急性冠状动脉综合征患者PCI术后动态心电图微伏级T波电交替的变化

目的探讨急性冠状动脉综合征治疗(PCI)患者在经皮冠状动脉介入治疗(PCI)手术前后动态心电图微伏级T波电交替(MTWA)的变化及临床价值。方法将31例ACS患者[不稳定性心绞痛(UA)20例、急性ST段抬高型心肌梗死(STEMI)11例]作为观察组;另将冠状动脉造影正常的健康体检者31例设为对照组,对2组进行24h的动态心电图检查,比较2组患者MTWA的变化。结果 PCI术后,观察组STEMI患者2个通道的MTWA指标高于UA患者和对照组(P<0.05)。结论应用动态心电图检测MTWA可对ACS患者进行危险分层,但最大的T波电交替值对进行手术前后的监测结果具有明显的不稳定性。

微伏级T波电交替对未植入ICD的心力衰竭患者危险度预测的Meta分析

目的：用Meta分析方法系统性评价微伏级T波电交替（MTWA）对未植入体内自动除颤器（ICD）的心衰患者恶性心律失常和死亡的预测价值。方法检索1990年1月~2013年6月关于运动负荷试验时异常的MTWA对未植入ICD的心衰患者预后预测的前瞻性临床研究。通过χ2统计量结合I2统计量进行异质性检验，用倒方差法固定效应模型分析MTWA对恶性心律失常和死亡的风险，得到合并效应指标风险比（hazard ratio，HR）及其95％可信区间（CI）。结果共有7项研究被纳入，总样本量2953人。其中662人MTWA阳性，1705人MTWA阴性，340人MTWA不确定，246人MTWA非阴性（包括阳性和不确定性）。和MTWA阴性的患者相比较，MTWA异常的患者发生恶性心律失常和死亡的危险度增加（HR为4.51，95%CI：2.28～8.89，P＜0.001）。结论 MTWA检测进行危险分层的评估对未植入ICD的心衰患者恶性心律失常事件和死亡有预测价值。

扩张型心肌病患者微伏级T波电交替检测分析

目的研究扩张型心肌病患者微伏级T波电交替(MTWA)的发生情况及与心率的关系。方法对31例扩张型心肌病患者用频谱法检测MTWA,分析扩张型心肌病MTWA的阳性率及不确定结果的原因,静息和运动时MTWA的发生情况,心率与交替压(Valt)的关系。结果①扩张型心肌病患者MTWA的阳性率为35.48%;②扩张型心肌病者,运动时的心率大于静息时,运动时各导联的Valt值大于静息时(P均<0.01)。静息时MTWA阳性2例,运动时MTWA阳性11例,运动时MTWA的阳性率高于静息时(35.48%vs 6.45%,P<0.01);③心率与综合导联Valt呈正相关,随心率的增加,Valt增大(r=0.984,P<0.01)。结论①扩张型心肌病患者MTWA阳性率高于正常人;②MTWA的发生与心率相关,随心率增快,Valt增大,MTWA阳性检出率增加。

T波电交替及心率变异性对恶性心律失常的预测价值

目的：分析急性心肌梗死（AMI）患者微伏级T波电交替（MTWA）以及心率变异性（HRV）指标,探讨其对AMI患者住院期间恶性心律失常的预测价值。方法：117例AMI患者（AMI组）,男性86例,女性31例;年龄32~84岁,平均年龄（61±11）岁。分析其24 h动态心电图检查资料。依据住院期间有无室速或室颤,将117例AMI患者分为恶性心律失常组（37例）和非恶性心律失常组（80例）。结果：恶性心律失常组与非恶性心律失常组MTWA差异具有显著统计学意义（P〈0.01）。以MTWA≥25μV为截点,MTWA预测AMI患者发生恶性心律失常的灵敏度、特异度、阳性预测值、阴性预测值分别为50.00%、80.28%、54.84%、77.03%。MTWA以及SDNN（SDANN）联合预测恶性心律失常的灵敏度、特异度、阳性预测值、阴性预测值分别为20.59%（20.59%）、94.37%（95.77%）、63.64%（70.00%）、71.28%（71.58%）。结论：MTWA及HRV对AMI患者住院期间恶性心律失常的发生有预测价值,可用于AMI患者的危险分层。

高强度训练对武警战士心律失常的影响

目的探讨高强度训练对武警战士心律失常的影响。方法选择128名参加任职强化训练的武警战士为训练组,144名同一部队日常基础训练的战士为对照组,利用动态心电图进行心率、心律失常情况及微伏级T波电交替(microvolt T wave alternans,MTWA)等指标变化的分析。结果训练组平均心率[(77.15±8.85)次/min]、最快心率[(149.10±17.93)次/min]和最慢心率[(59.67±10.50)次/min]均加快(均P<0.05);室性及房性心律失常的发生率和平均数量有升高的趋势且高于对照组(P<0.05);早晨9:00及最快心率时MTWA均高于对照组(均P<0.05)。结论高强度训练应激状态下,武警战士发生心律失常的情况增多,心脏自主神经功能异常导致心肌细胞电活动不稳定,是心律失常的重要原因之一。

基于USB及无线传输的微伏T波电位交替检测系统设计

本文介绍了一个基于无线传输和USB接口相结合的T波电交替检测系统的设计。该系统首先对心电信号进行放大,放大器放大倍数为2000倍,共模抑制比为80db。放大后的信号经过12位AD采样再经过无线传输和USB总线传输到PC处理端。在处理端,利用谱分析方法对T波交替进行检测。实验结果表明,该系统具有高数据传输速率和实时数据处理能力,能够实现微伏T波电交替的测定。