心电T波电交替检测算法综述

现代临床研究表明,T波电交替(TWA)是一项预测心源性猝死的重要指标。自TWA现象被发现以来,相继出现了很多TWA检测的算法,大体上可以分为频域法和时域法两大类。文中对这两大类典型算法进行系统的分类阐述,讨论它们的优缺点;对其他算法做简要论述;最后探讨了影响TWA检测的因素以及TWA检测算法的发展方向。     

心绞痛患者T波交替的检测与分析

目的 检测与分析心绞痛患者的T波交替(T wave alternans,TWA).方法 先采用谱分析法检测European ST-T数据库中部分不同程度心绞痛患者是否存在TWA现象,再采用相关分析法检测出心动周期中具体发生TWA的时间段的数目和长度等.结果 文中所有被检测的心绞痛患者均有TWA发生.结论 TWA的出现次数基本上与患者心绞痛的严重程度有关,随着心绞痛程度的加强,TWA出现的次数增多;但不能判断TWA幅度和持续拍数是否与心绞痛严重程度有关.     

T波交替散点图法的指标检测评估

目的研究心电信号散点图形态特征与T波交替(T-wave alternans,TWA)的相关程度,评估形态指标检测T波交替存在与否的可靠性,为T波交替的检测提供准确、有效、计算简单的检测方式。方法首先在散点图图形基础上提出向量长度指标(vector length index,VLI),然后用MATLAB7.0软件对美国MIT/BIH标准心律失常数据库和欧洲ST-T心电数据库进行仿真,并将仿真所得散点图法的VLI和谱分析法的Vtwa作阈值分析及相关性分析。结果仿真检测结果显示,在向量长度指数VLI≤10 ms时,心电图中含有TWA,否则不含TWA。根据Kappa一致性检验得出:K=0.6932,即VLI与Vtwa具有很强的相关性。结论 VLI能够用于检测心电信号中是否存在T波交替。     

T波交替的研究进展

T波交替是指在心电图T波的幅度、形态的逐搏交替变化。作为一项新的无创心电检测方法,T波交替已成为预测室性心律失常及心脏性猝死等疾病的有效手段。较全面地阐述了T波交替的产生机理、检测方法及临床研究等方面的内容,并指出了T波交替的研究方向和发展前景。     

基于形态学的T波交替散点图法的研究

本文采用非线性动力学系统中的周期性散点图法来检测T波交替(TWA),即根据散点图的矢量角度指数(VAI)判断TWA是否存在。用美国MIT/BIH标准心律失常数据库和欧洲ST-T心电数据库进行仿真,对由散点图法和谱分析法所得VAI和Vtwa作曲线拟合和相关性分析,得到其相关系数γ=0.860 1,这表明该方法对TWA的检测具有很高的准确性,进而为TWA的检测提供了新方法。     

基于T波最大值的T波电交替分析法

提出了一种基于T波最大值T波电交替(T-wave alternans,TWA)的快速傅氏变换(Fast fouriertransform,FFT)分析法。该方法能在减少抽样频率的条件下,保证计算精度。基于T波最大值的方法还解决了固定T波的取样点随着心率的变化而变化问题。该方法对连续128个正常心跳周期的ST-T结构中的T波最大值进行FFT变换,进而可以得到其功率谱曲线图。该功率谱图可反映TWA。     

心肌炎患者高频心电图T波功率谱的初步分析

本文分析了幼儿心肌炎、学龄儿童心肌炎、成人心肌炎的高频心电图Ⅱ、ａＶＦ、Ｖ＿２、Ｖ＿５导联的Ｔ波功率谱。结果表明：（１）０一１０００Ｈｚ频段的总能量，幼儿心肌炎组，学龄心肌炎组无论哪个导联与其对照组相比，均无显著性差异（Ｐ＞０．０５）。成人心肌炎组ａＶＦ、Ｖ＿５导联显著高于对照组（Ｐ＜０．０５），Ⅱ、Ｖ＿２导联与对照组相比也无显著性差异。（２）１００一１０００Ｈｚ频段的绝对能量，幼儿心肌炎组ａＶＦ导较对照组显著升高；学龄心肌炎组Ｖ＿２、Ｖ＿５导较对照组显著升高；成人心肌炎组与对照组相比，无论哪个导联均无显著性差异。（３）８０一３００Ｈｚ频段的绝对能量，除学龄心肌炎组的Ｖ＿２导比对照组显著升高外，３个年龄段的心肌炎组无论哪个导联与对照组比较均无显著性差异。这些结果提示，３个年龄段心肌炎组的Ｔ波总能量及高频能量在各个导联中的变化规律是不同的。     

基于时频分析的T波交替检测算法的研究

心电的T波交替现象与室性心律失常有关,已成为预测心脏猝死的一个无创的临床指标.当前T波交替分析常用谱分析方法,为弥补其不具备时间分辨率的不足,本研究提出一种鲁棒的基于时频分析的微伏级T波交替检测算法:通过心电信号的短时傅里叶变换,提取时域T波序列,计算其在选定时频区域的能量谱;然后运用Wilcoxon秩和检验统计分析方法,检测微伏级T波交替现象.经仿真实验、欧洲ST-T数据及临床检测实验,本算法对T波交替检测的平均灵敏性达90.4％,正确预测率达92.0％,在30 dB及以上信噪比情况下,实现了100％的正确检测.仿真实验还表明本算法也支持短时心电数据的TWA准确检测.     

改进的谱分析法定量估算T波电交替的研究

T波交替现象已成为医生用于评估心脏病人的指标之一。但TWA检测中的定量问题尚未解决。本研究在传统谱分析方法的基础上进行了改进,采用定长积分平均的方式替代原有的单参照点模式,数据结果表明改进后算法的时域抗干扰能力有了显著的提高。采用线性模型人工合成TWA信号进行仿真研究,针对非理想状态下的TWA信号,基于实际情况中生理信号的多变性和不均匀性,修正了David S.Rosenbaum等人的估算式,提出了一种新的TWA定量分析方法,测试结果表明在信噪比大于10 dB时,估算的TWA幅值的绝对误差控制在±5μV以内。     

体表胃电图慢波提取方法的比较研究

体表胃电图(electrogastrogram,EGG)具有幅值小、频率低和窄带宽的特点,并且极易受到心电、呼吸以及运动等干扰.文中对三种常用的EGG慢波的提取方法进行了比较,包括自适应滤波、小波多尺度分解和经验模态分解,并将三种方法分别应用于模拟的含噪EGG信号以及临床EGG慢波的提取.研究结果表明,三种方法各有优缺点,均能有效地提取出EGG信号中的慢波成分.与自适应滤波相比,小波多分辨率分解和经验模态分解获得了更高的信噪比和更低的重构方差.     

Adaptive Match Filter Based Method for Time vs. Amplitude Characterization of Microvolt ECG T-Wave Alternans

To develop a new method for non-invasive identification of patients prone to ventricular tachyarrhythmia and sudden cardiac death, an adaptive match-filter (AMF) was applied to detect and characterize T-wave alternans (TWA) in 200 coronary artery diseased (CAD) patients compared with 176 healthy (H) subjects. TWA was characterized in terms of duration (TWAD), amplitude (TWAA), and magnitude (TWAM, defined as the product of TWAD times TWAA). A criterion derived from these parameters, estimated over the H-population, allowed discrimination between a risk (TWA+) and a normality (NO TWA) zone in the TWAD-TWAA plane. To gain further ability to discriminate among different risk levels, the TWA+ zone was divided into four sub-zones respectively characterized by low duration and low amplitude (LDLA), low duration and high amplitude (LDHA), high duration and low amplitude (HDLA), and high duration and high amplitude (HDHA). With our methodology, 21 CAD-patients (10.5%) were identified as TWA+, 9 falling in the LDLA zone, 4 in the HDLA, 7 in the LDHA, and 1 in the HDHA. These results are in agreement with clinical expectations and pave the way to further clinical follow-up studies finalized to analyze pathophysiological implications and risk factors associated to each TWA+ zone.     

体表心电Mapping系统中心电信号的处理与峰值定位检测

体表心电Mapping是又一个新的心脏疾病诊断技术。作者考虑了体表心电噪声强、各导联之间心电差异性较大的特点,提出了性能较好的心电处理算法。其中包括:50Hz陷波、零相位低通滤波及宽范围抛物线拟合去除基线漂移的算法等。在此基础上,将心电信号的一阶差分、二阶差分及时域幅值相结合以形成阈值,通过在主峰值左、右作反复搜索的方法对Q、R、S及其它子波作精确定位。通过对28名临床病例的检验,定位准确率为97.7％。     

Evaluation of T-wave alternans in high-resolution ECG maps recorded during the stress test in patients after myocardial infarction

Introduction

Recent studies point to analysis of T-wave alternans as a promising indicator of an increased risk of life-threatening ventricular arrhythmias. In this study the occurrence of T-wave alternans in the high-resolution ECGs recorded during the exercise stress test and scintigraphic tests (SPECT) in patients with ischemic heart disease was examined.

Material and methods

The study group consisted of 33 patients after myocardial infarction. In the group of patients after myocardial infarction and with low left ventricular ejection fraction correlations of 70% between the test results of T-wave alternans and SPECT and 60% between the test results of T-wave alternans and stress test were found.

Results

In the group of patients after myocardial infarction but with high left ventricular ejection fraction correlations were respectively 39% and 48%. The analysis of the electrocardiographic maps showed a strong dependence of this correlation on the T-wave alternans amplitude and location of the ECG measuring electrode on the chest. The results might suggest that in patients after myocardial infarction and at increased risk for sudden cardiac death T-wave alternans may also provide information about cardiac electrical instability associated with ischemia.

Conclusions

It can also be assumed that the position of the electrode where the highest level of the T-wave alternans was detected can indicate the location of the ischemic region of the heart.     

Usefulness of microvolt T-wave alternans testing in the assessment of all-cause mortality and life-threatening ventricular arrhythmia risk in patients with left ventricular dysfunction

Introduction

Patients with left ventricular ejection fraction (LVEF) ≤ 35% are eligible for implantable cardioverter-defibrillator (ICD) placement in the primary prevention of sudden cardiac death. Nevertheless, other risk factors facilitating the selection of individuals with highest mortality are still sought. The aim of the study was to verify the usefulness of microvolt T-wave alternans (MTWA) testing in the assessment of all-cause mortality and life-threatening ventricular arrhythmias (EVENTs) in these patients. Previous data from the literature are inconclusive.

Material and methods

Patients with LVEF ≤ 35% were eligible if they did not have a history of sustained ventricular arrhythmias, and were treated with β-blockers. Participants underwent MTWA testing and were subsequently followed.

Results

The group consisted of 139 patients. MTWA results were classified as non-negative (MTWA_non-neg) in 93 and negative (MTWA_neg) in 46 patients. During the 14.3 ±8.6 months of follow-up, EVENTs were observed in 21 patients. The 1-year EVENT rate was 16.4% among MTWA_non-neg patients, and 2.6% among MTWA_neg patients (p = 0.006). The sensitivity of the MTWA test was 95.24%, the specificity – 38.14%, the positive predictive value – 21.51% and the negative predictive value – 97.83%.

Conclusions

In the group of patients with left ventricular systolic dysfunction, with the exclusion of patients with the history of life-threatening ventricular arrhythmia and individuals not being on chronic β-adrenolytic therapy, the abnormal result of MTWA testing is associated with significantly increased risk of all-cause mortality and life-threatening ventricular arrhythmia during 1 year of follow-up, thus identifying the individuals at the highest risk.     

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。     

缺血性心脏病患者运动引发T波交替作为危险因素价值的探讨

目的:探讨微伏T波交替(TWA)可否作为一项缺血性心脏病患者伴室性心律失常危险因素的预测指标。方法:选择经Holter心电图监测检出阵发性室速及/或有室速病史的23例缺血性心脏病患者、30例无室速的缺血性心脏病患者和39例正常人进行运动中TWA检测。TWA采用微机化6353心电图检测系统,在受检者运动至心率95~110bpm时,波间T波变异差超过1.9微伏并在心率阈值内持续出现即为阳性。结果:23例缺血性心脏病室速组中,TWA阳性14例,占60.7%,非室速缺血组阳性出现率为10%(3/30),正常对照组0%(0/39);TWA电压三组分别是2.3±1.1uV、1.1±0.6uV和0.8±0.3uV,组间差异非常显著(P<0.05或P<0.01)。结论:运动微伏TWA测定可作为缺血性心脏病室性心律失常危险因素的参考指标之一。     

基于动态心脏模型的体表心电图仿真研究

以往的电生理心脏模型大多是静态的,而非动态模型.这样在用准静电场理论求解体表电位时,整个心动周期中等效心电偶极子（源点）与体表（场点）之间的距离假设为恒定不变,从而会引入较大的系统误差.因此,为了更准确仿真心电图,有必要采用动态或跳动的心脏模型.基于原来静态心脏模型,构造了一个动态心脏模型,并对体表12导联心电图进行仿真比较研究.在动态心脏模型中考虑了心肌电兴奋引起的心脏机械力学收缩,通过计算心动周期中心室壁的位移,从而将心脏与体表之间的相对距离变化考虑进体表电位计算过程.仿真结果表明,对于正常心电图,基于动态心脏模型的仿真结果比基于静态心脏模型的仿真结果更符合临床记录心电图,特别是V1-V6胸导联的ST段和T波.对于前壁轻微缺血情况,在动态心脏模型的仿真心电图中能明显看出ST段和T波的变化,而在静态心脏模型的仿真心电图中与正常心电图相比看不出什么变化.本研究的仿真研究证实了动态心脏模型的确能更准确地仿真体表心电图.     

体表心电峰值等电位图的描绘及临床应用研究

作者首先讨论了体表心电峰值等电位图的描绘方法，其中包括将２－Ｄ展开平面网格化、建立边表、等位线上点的插值、建立等位值序列表及最后生成峰值等电位图等，利用该方法作者以３２例临床病例对五种异常心电信号进行了研究，得到了一些启发性结果。