正常人QT离散度测量的重复性

目的：观察不同方法测量ＱＴ离散度的重复性和误差大小。方法：用５０ｍｍ／ｓ纸速１２导同步心电图机和２５ｍｍ／ｓ纸速三导同步心电图机同时启示２０例正常人的心电图，采用ＱＴｄ，ＱＴｃｄ，ＱＴａｄ，ＪＴｄ，ＪＴｃｄ，ＪＴａｄ六个指标进行ＱＴ离散度分析。结果：由５０ｍｍ／ｓ纸速１２导联同步心电图测得的ＱＴ离散度，ＪＴ离散度的相对误差在两位测量者之间分别为１２－１３％与１４－１５％，在同一测量者两次之间的分别     

单导联顺序采样测定QT离散度的重复性

在研究QT离散度(QTd)时,国内已有的文献较多的采用单导联顺序采样法描记心电图,这样的方法测出的QTd是否可靠?为此我们作了重复性研究。对象与方法符合WHO(1979年)诊断标准的急性心肌梗死(AMI)119例,男102例,女17例;年龄34～78岁,平均59.6±9.2岁。除外电解质紊乱、房颤、左右束支阻滞、服用胺碘酮、安置起搏器等影响QT测量者。要求心电图描记清晰,基线无飘移,资料完整。取AMI6小时单导联顺序描记的心电图,由两位从事心电图专业10年以上的中级职称的技师同时独立分析测量。心电图为标准12导,按50mm/s和10mV/cm记录,QT间期测量从QR…     

QT间期及其离散度测定的方法学研究和正常值

报告１００例健康成人同步体表１２导联心电图的ＱＴ间期和ＱＴ间期离散度（ＱＴｄ）：（１）各参数测量结果（±ｓ）：ＱＴｄ、ＱＴｃｄ（矫正ＱＴｄ）、ＪＴｄ（ＪＴ离散度）、ＱＴｐｄ（ＱＴ顶点离散度）、ＪＴｐｄ（ＪＴｐ离散度）、Ｔｐ－ＴＥｄ（Ｔ波顶点至Ｔ波终点间期离散度）、ＱＲＳｄ（ＱＲＳ间期离散度）和Ｏ－Ｑｄ（ＱＲＳ起始时间离散度）分别为２５．６±１１．２，２６．８±１２．６，２６．１±１２．５，２４．６±１４．７，３２．０±１５．６，３１．０±１４．６，２０．６±８．８和１２．５±７．３ｍｓ，其范围均在５～５０ｍｓ以内，与国际上研究结果一致。笔者认为ＱＴｄ的正常值可暂定为＜５０ｍｓ；（２）体表１２导联心电图同步记录方法，比常规非同步记录更能反映ＱＴｄ的实际情况，并且可测量同步１２导联ＱＲＳ起始部时间（Ｑ－ＱＴ）及其离散度（Ｑ－ＱＴｄ）；（３）本文资料由国内和国外三组不同人员测量结果相同，表明ＱＴ、ＱＴｄ测定的可重复性好；（４）性别差异，ＱＴ间期女性比男性长，而ＱＲＳ间期男性比女性长，其机理尚待进一步研究探讨。     

QTc离散度测定的重复性

为评价QT间期离散度（QTcd）测定的重复性，研究了同一观测者不同时间及两个观测者同一时间测定的46例急性心肌梗塞者的QTCd测定值的变化。结果发现同一观测者不同时间测定的QTcd的绝对误差为6ms，相对误差为20.1％，二者的相关系数r＝0．71，P＜o.01；两个观测者同一时间测定的QTcd的绝对误差为8ms，相对误差为23．9％，二者的相关系数r＝0．65，P＜0．01。提示，QTcd测定的重复性较差。     

QT离散度的方法学及其正常参考值研究

目的探讨ＱＴ离散度（ＱＴｄ）的正常参考值及在不同心电图记录纸速、不同时间重复测量、不同测量方法之间的可重复性。方法分别以纸速２５ｍｍ／ｓ、５０ｍｍ／ｓ记录５０４例健康成人体表１２导联同步心电图，用手工分规和电脑半自动测量ＱＴｄ，比较不同心电图纸速、不同时间重复测量、不同测量方法之间的可重复性。结果（１）同一或不同测量者不同时间内重复测量的ＱＴｄ、ＱＴｃｄ、ＲＲ间期显著相关，ｒ分别为０．９３、０．９５、０．９９，Ｐ均小于０．０１。（２）计算机半自动测量与手工分规测量的ＱＴ、ＱＴｄ显著相关，ｒ分别为０．８４、０．８８，Ｐ均小于０．０１。（３）在２５ｍｍ／ｓ纸速与５０ｍｍ／ｓ纸速的心电图分别测量ＱＴｄ、ＱＴｃｄ、ＲＲ间期，两次结果相关性好，ｒ分别为０．８６、０．８４、０．９６，Ｐ均＜０．０５。（４）用不同方法测量ＱＴｄ、ＱＴｃｄ的结果差异无显著性，其平均误差小于７ｍｓ。（５）ＱＴｄ、ＱＴｃｄ的正常参考值为４５±１３ｍｓ、４９±１４ｍｓ。结论①ＱＴｄ在不同心电图记录纸速、不同时间重复测量、不同测量方法之间显著相关，可重复性好。②ＱＴｄ的正常参考值为４５±１３ｍｓ，范围为２０～７０ｍｓ。     

QT离散度

QT离散度(QTd)系指体表12导联心电图各导联QT间期存在的差异,这一现象早被人们发现,但未重视。直至1985年,Campbell等发现心电图导联间存在的QT间期差异是有规律性的,遂提出QT离散度这一概念。 概述 体表心电图与心肌细胞单相动作电位有着密切的关系。心电图的QT间期相当于动作电     

QT离散度

ＱＴ离散度陈义汉，龚兰生数十年以前人们就发现ＱＴ间期存在导联间的差异，但一直被视为记录伪差所致，而未予重视。１９８５年Ｃａｍｐｂｅｌｌ等发现不同导联间ＱＴ间期的差异有其规律性，因而提出了ＱＴ离散度（ＱＴｄｉｓｐｅｒｓｉｏｎ）这个概念。然而，直到１９９...     

QT离散度

体表心电图各导联间ＱＴ间期的差异称ＱＴ离散度。它可能反映了心室肌复极的非同步性，对于通过心电图测算ＱＴ离散度评价心脏病发生猝死的危险性，本文作了综述。     

心肌梗死不同部位及阶段QT离散度变化

分析急性心肌梗死存活患者Ｑ一Ｔ离散度（ＱＴｃ）演变及不同梗死部位的差异。方法：分析４９例急性心肌梗死患者一周内（急性期）与三个月（恢复期，１９例）及一年后（陈旧期，１５例）心电图ＱＴｃ变化及其差异。结果：急性期、恢复期及陈旧期，经心率校正的ＱＴｃ（ＱＴｃｄ）分别为５０．７±１８．５ｍｓ、３９．９±２１．２ｍｓ、３３．７±１９．３ｍＳ（Ｐ＜０．０５）。前壁梗死（包括前间壁，广泛前壁，ｎ＝２５）与下壁梗死（包括后壁，ｎ＝２４）相比，ＱＲｃｄ分别为５６．０±２２．７ｍｓ，４５．０±１０．７ｍｓ（Ｐ＜０．０１）。而未经心率校正的ＱＴｃ差异无显著性。结论：急性心肌梗死患者经心率校正的ＱＴ离散度明显增大，恢复期至陈旧期逐渐恢复，急性期前壁梗死增大较下壁显著。     

土家族正常人群QT离散度正常值的研究

为了调查土家族正常人群QT离散度正常值范围 ,采集 94 7例土家族健康体格检查者为研究对象 ,其中男5 16例、女 4 31例 ,年龄 4 4 .9± 16 .1(11～ 78)岁。整体年龄近似正态分布。同步记录标准 12导心电图 ,按常规标准方法测量并计算QT离散度 (QTd)及校正QTd(QTcd)。用正态分布法 ( x± 1.96s)和百分位数法 (P2 .5～P97.5)确定其95 %正常值范围。结果 :QTd及QTcd均近似正态分布。方差分析表明QTd、QTcd的性别、按年龄分组 (A组 ,<35岁 ;B组 ,35～ 6 5岁 ;C组 ,>6 5岁 )之间均无显著性差异 (P >0 .0 5 ) ,QTcd的性别间无显著性差异 (P >0 .0 5 ) ,年龄间有显著性差异 (P <0 .0 0 1) ,QTd与QTcd未见性别与年龄间存在交互效应 (P >0 .0 5 )。用正态分布法确定的QTd、QTcd 95 %的正常值范围A、B、C三组分别为 10～ 5 6 ,10～ 5 6 ,11～ 5 4ms ;2～ 4 6 ,5～ 5 0 ,2～ 5 3ms。结论 :从临床应用看 ,土家族 95 %的正常值范围 ,QTd可采用同一值 ,建议为 10～ 5ms;QTcd ,<35岁者为 5～ 4 5ms,35岁及以上者为 5～ 5 5ms。     

Seasonal Variability of QT Dispersion in Healthy Young Males

Background: There are few data related to the seasonal influences on the QT dispersion. Methods: We analyzed the effects of seasons on QT dispersion in a large group of healthy young males. We studied the seasonal variability of QT dispersion in 523 healthy male subjects aged 22 ± 4 years (ranging from 20 to 26). Four seasonal 12‐lead resting electrocardiograms (ECGs) recorded at double amplitude were performed at 25 mm/s at intervals of 3 months. Subsequent ECGs were recorded within 1 hour of the reference winter recording. QT dispersion was defined as the difference between the longest and the shortest mean QT intervals. Results: There was a significant seasonal variation in QT dispersion (P = 0.001) , with the largest QT dispersion in winter (71 ± 18 ms) and the smallest one in spring (43 ± 19) . Conclusion: There exists a significant seasonal variation in QT dispersion of healthy subjects and such variability should be taken into consideration in the evaluation process of QT dispersion.     

QT Dynamics and Variability

Repolarization dynamics and variability are of increasing interest as Holter‐derived parameters reflecting changes in myocardial vulnerability and contributing to increased risk of arrhythmic events and sudden death. Repolarization dynamics is usually defined as phenomenon describing and quantifying QT adaptation to changing heart rate. The analysis of QT–R‐R slopes in long ECG recordings is one of the ways to evaluate repolarization dynamics. Increased QT–R‐R slopes are frequently observed in patients at risk for cardiac death and arrhythmic events: postinfarction patients, long QT syndrome patients, patients with nonischemic cardiomyopathy as well as in patients taking drugs affecting repolarization. QT variability reflects beat‐to‐beat changes in repolarization duration and morphology and such changes can be quantified using a number of algorithms currently in various phases of development and validation. Increased QT variability is observed in several conditions with increased risk of arrhythmias. Recent data from MADIT II indicate that increased QT variability is a powerful predictor of arrhythmic events in postinfarction patients with left ventricular dysfunction. More studies are needed to determine further the potential clinical usefulness for diagnosing patients and for risk stratification purposes using both QT dynamics and QT variability methods, and compare these methods with exercise‐induced T wave alternans.     

The Association of QT Dispersion and QT Dispersion Ratio with Extent and Severity of Coronary Artery Disease

Background: Although prolongation of the QT intervals in acute ischemic conditions, such as acute myocardial infarction, intracoronary balloon inflation, and exercise induced ischemia, has been shown, association of rest QT intervals with extent and severity of stable coronary artery disease (CAD) has not been assessed so far. The effects of extent and severity of stable CAD on rest QT interval were analyzed in this study. Methods: Rest 12‐lead electrocardiograms (ECG) were recorded in 162 clinically stable subjects undergoing coronary angiography before the angiography for measurement of corrected QT dispersion (cQTd) and the QT dispersion ratio (QTdR) defined as QT dispersion divided by cycle length and expressed as a percentage. Angiographic “vessel score,”“diffuse score,” and “Gensini score” were used to evaluate the extent and severity of coronary atherosclerosis. Subjects were grouped as follows: those with normal angiogram (Group 1), those with insignificant (<50%) coronary stenosis (Group 2), and those with 1‐ (Group 3), 2‐ (Group 4), or 3‐vessel disease (Group 5). Results: cQTd and QTdR were higher in Group 3 compared with Group 1 (P < 0.001 and P = 0.001, respectively), in Group 4 compared with Group 1 (P < 0.001 for both) and Group 2 (P = 0.001 and P = 0.003, respectively), and in Group 5 compared with Group 1 (P < 0.001 for both) and Group 2 (P < 0.001 and P = 0.003, respectively). cQTd and QTdR were positively correlated with the vessel score (r = 0.422, P < 0.001; r = 0.358, P < 0.001, respectively), diffuse score (r = 0.401, P < 0.001; r = 0.357, P < 0.001, respectively) and Gensini score (r = 0.378, P < 0.001; r = 0.373, P < 0.001, respectively). In multiple linear regression analyses, cQTd was found to be independently associated only with diffuse score (β= 0.325, P = 0.038). Also, QTdR was independently associated with diffuse score (β= 0.416, P = 0.006) and Gensini score (β= 0.374, P = 0.011). Conclusions: Rest cQTd and QTdR are increased, and related to the extent and severity of coronary atherosclerosis in patients with stable CAD.     

胺碘酮与索他洛尔对QT离散度的影响及QT离散度改变对治疗室性心律失常的疗效预测价值

目的通过观察室性早搏(室早)患者治疗前后同步12导联心电图中QT离散度(QTd)及24小时动态心电图变化,分析胺碘酮和索他洛尔作用机制以及QTd应用的临床意义。方法室早患者60例包括Ⅰ组(胺碘酮静脉+口服),Ⅱ组(胺碘酮单纯口服)和Ⅲ组(索他洛尔口服),每组20例。所有患者均在用药前、用药后5天分别检测QT离散度(包括正常波QTd、室早波QTd及室早波随后正常波QTd),以及用药前、用药后两周分别做24小时动态心电图。结果所有患者用药前和用药后正常波QTd有明显的统计学差别(P<0.001),但用药前和用药后5天室早波QTd及室早随后正常波QTd无明显的统计学差别(P>0.05)。Ⅰ组患者总有效13例(65%),Ⅱ组患者总有效13例(65%),Ⅲ组患者总有效11例(55%)。Ⅰ组与Ⅱ组疗效较Ⅲ组为高,但经统计学检验无明显差别(P>0.05)。将所有患者按治疗后有效和无效分为两部分,有效部分和无效部分用药前和用药后5天QTd测定值均有明显的统计学差别(P<0.001),但两部分用药前后QTd差值无明显统计学差别(P>0.05)。结论胺碘酮和索他洛尔治疗效果相似,两者均可降低室早患者的QTd。QTd对于抗心律失常药物疗效无预测价值。     

心肌缺血对QT间期离散度的影响

目的：探讨冠心病患者心肌缺血对ＱＴ间期离散度（ＱＴｄ）及校正后ＱＴ间期离散度（ＱＴｃｄ）的影响。方法：选取３０例冠心病患者，测定每例患者心肌缺血期、缺血缓解期及稳定期的ＱＴｄ及ＱＴｃｄ。结果：ＱＴｄ与ＱＴｃｄ在心肌缺血期为０．０９１３±０．０３２４秒、０．０１０６±０．０３７８秒；在缺血缓解期为０．０５２３±０．０３２８秒、０．０６１１±０．０３７３秒；在稳定期为０．０４９７±０．０２３０秒、０．０５６６±０．０２７１秒。心肌缺血期与缺血缓解期及稳定期相比，有显著性差异（Ｐ均＜０．０１）。而稳定期与缺血缓解期相比无显著性差异（Ｐ＞０．０５）。结论：心肌缺血可引起ＱＴｄ及ＱＴｃｄ的增大；心肌缺血期ＱＴｄ及ＱＴｃｄ增大，且显著高于缺血缓解期及稳定期。     

Bias of QT Dispersion

Background: Prolonged QT dispersion (QID) is associated with an increased risk of arrhythmic death but its accuracy varies substantially between otherwise similar studies. This study describes a new type of bias that can explain some of these differences. Material: One dataset (DiaSet) consisted of 356 subjects: 169 with diabetes, 187 nondiabetic control persons. Another dataset (ArrSet) consisted of 110 subjects with remote myocardial infarction: 55 with no history of arrhythmia and 55 with a recent history of ventricular tachycardia or fibrillation. Methods: 12‐lead surface ECGs were recorded with an amplification of 10 mm/mV at a paper speed of 50 mm/s. The QT interval was measured manually by the tangent‐method. The bias depends on the magnitude of the measurement errors and the measurable part of the bias increases with the number of the repeated measurements of QT. Results: The measurable bias was significant for both datasets and decreased for increasing QTD in the DiaSet (P < 0.001) and in the ArrSet (P = 0.11). The bias was 2.5 ms and 1.9 ms at QTD = 38 ms and 68 ms, respectively, in the ArrSet, and 7.5 ms and 2.8 ms at QTD = 19 ms and 55 ms, respectively, in the DiaSet. Conclusions: This study shows that random measurement errors of QT introduces a type of bias in QTD that decreases as the dispersion increases, thus reducing the separation between patients with low versus high dispersion. The bias can also explain some of the differences in the mean QTD between studies of healthy populations. Averaging QT over three successive beats reduces the bias efficiently. A.N.E. 2001;6(1):38–42     

对QT离散度实质的探讨

为探讨ＱＴ离散度（ＱＴｄ）的真实意义，观察１３９例急性心肌梗死（ＡＭＩ，ＡＭＩ组）及１０９例正常人（对照组）的最长ＱＴ间期（ＱＴｍａｘ）、校正ＱＴｍａｘ（ＱＴｃｍａｘ）及ＱＴｄ的变化。结果：①ＡＭＩ组的ＱＴｍａｘ、ＱＴｃｍａｘ和ＱＴｄ均显著高于对照组（分别为４２２．６０±３０．５１ｍｓｖｓ３８２．４６±２３．４０ｍｓ、４６０．２１±２８．９６ｍｓｖｓ３８８．５１±２０．１５ｍｓ、５９．８０±２８．４０ｍｓｖｓ３９．４３±１２．２１ｍｓ，Ｐ均＜０．００１）。②ＡＭＩ组中发生严重室性心律失常（ＶＡ）患者（１１４例）的ＱＴｍａｘ、ＱＴｃｍａｘ、ＱＴｄ与无ＶＡ的患者（２５例）相比，均有显著差异（分别为４４８．５８±３３．４０ｍｓｖｓ４１６．１０±３５．３０ｍｓ、４８１．４３±３５．１７ｍｓｖｓ４３９．６０±２７．１０ｍｓ、６６．９０±２０．７２ｍｓｖｓ４８．３２±２３．６１ｍｓ，Ｐ均＜０．００１）。认为ＡＭＩ时ＱＴｄ系Ｔ向量环在不同导联上的“投影”差异所引起的，其异常的本质是ＱＴ间期延长     

健康人不同导联QT变异及QT变异指数

探讨健康人不同导联的QT变异(QTV)及QT变异指数(QTVI)。55例健康人在保持日常工作和生活起居的情况下佩戴12导联动态心电图监测仪,计算机辅助下自动测量12导联QT间期,计算每个导联每小时、24h、白天(6:00～22:00)和夜间(22:00～6:00)QT间期均值及其标准差、HR间期均值及其标准差,它们分别代表相应时间段的QT间期均值(QTm)、QTV、HR间期均值(HRm)和HR间期变异(HRV)。计算QTVI。同时运用心率变异时域指标SDNN观察自主神经活性。结果:不同导联间的QTV、QTVI比较具有显著性差异,P<0.05。不同导联24hQTV、QTVI与SDNN均存在负相关,P<0.05。结论:在使用QTV、QTVI来评价不同人群的心室复极离散时,要考虑到不同导联之间的可比性和一致性。QTVI是一种能更直接地反映心室复极逐波变化的新指标。