Lesson Fifty-seven Differences in negative T waves among acute coronary syndrome

●心电学英语

Lesson Fifty-seven Differences in negative T waves among acute coronary syndrome,acute pulmonary embolism,and Takotsubo cardiomyopathy

Negative T waves are common electrocardiographic changes in patients with non-ST-segment elevation acute coronary syndrome(ACS).In particular,negative T waves in the precordial leads suggest severe ischemia of the left ventricular anterior wall due to a critical stenosis of the left anterior descending coronary artery(LAD). However,this electrocardiographic finding is also frequently observed in patients with acute pulmonary embolism(APE),especially in those at risk for adverse outcomes.Furthermore,Takotsubo cardiomyopathy(TC)1is a recently recognized novel cardiac syndrome characterized by new electrocardiographic abnormalities (ST-segment elevation,negative T waves),elevated cardiac enzymes and transient left ventricular apical ballooning without obstructive coronary disease.

APE and TC should thus be included in the differential diagnosis of ACS in patients who have precordial negative T waves at initial presentation.Prompt differentiation among these three diseases is essential to ensure selection of an appropriate management strategy and thus improve outcomes.The 12-lead ECG is a simple,prompt,inexpensive,and most widely available initial clinical diagnostic examination.

300 consecutive patients(198 with ACS,81 with APE and 21 with TC)were admitted to coronary care unit and fulfilled the following criteria:(1)admission within 48 h after the onset of symptoms such as chest pain/discomfort,dyspnea or other ischemic symptoms; (2)no conditions precluding the evaluation of ST-segment changes on ECG(i.e.complete left or right bundle branch block,left ventricular hypertrophy,ventricular pacing or receiving drugs with potential effects on ECG); (3)no obvious past history of cardiopulmonary disease; and(4)fully assessable ECG on admission with negative T waves of at least 1.0 mm in two or more contiguous precordial leads(V1to V4).Patients with new ST-segment elevation of at least 2.0 mm in two contiguous precordial leads on admission ECG were excluded.

Patients with ACS who had an unstable pattern of symptoms,including rest,new-onset,or increasing angina were studied.The culprit lesion was defined as the lesion associated with angiographic findings suggesting local thrombus,the most severe lesion,or both, and it was confirmed to be located in the LAD.The diagnosis of APE was confirmed by pulmonary angiography,lung perfusion scintigraphy or computed tomographic scan.The patients with TC showed the following features:(1)transient hypokinesis,akinesis or dyskinesis2of the left ventricular apical segment(and midventricular segment)with regional wall-motion abnormalities extending beyond a single epicardial vascular distribution;(2)the absence of significant(＞50%)obstructive coronary artery disease or angiographic evidence of acute plaque rupture;(3)new electrocardiographic abnormalities(T wave inversions);and(4)the absence of pheochromocytoma or myocarditis.

In this study,the anatomically contiguous Cabrera sequence3(Ⅲ,aVF,Ⅱ,-aVR,Ⅰand aVL)was used todisplay the limb leads.

Electrocardiographic findings on admission are presented in Table 1.APE was more frequently associated with P pulmonale,S1S2S3pattern and clockwise rotation.Right axis deviation and S1Q3T3pattern were observed in only APE.ACS was more frequently associated with ST-segment depression as well as greater summed ST-segment depression.The number and maximal amplitude of negative T waves were greatest in patients with TC,followed by those with ACS and were lowest in patients with APE.The prevalence of negative T waves in the three groups is shown in Figure 1.In the limb leads,negative T waves were frequently observed in leads I and aVL,particularly in the latter,and were rare in inferior leads and lead-aVR in patients with ACS.In contrast,the prevalence of negative T waves gradually decreased from leadsⅢto-aVR,and negative T waves were not found in leadⅠor aVL in patients with APE,whereas a high prevalence of negative T waves centered around4lead-aVR in patients with TC.In the precordial leads,the distribution of negative T waves centered around lead V3in patients with ACS. In contrast,negative T waves were consistently observed in leads V1and V2,and their prevalence gradually decreased from leads V3to V6in patients with APE, whereas a high prevalence of negative T waves was noted in precordial leads except for lead V1in patients with TC.Negative T waves in both leadsⅢand V1were present in 90%of patients with APE,but only in 3%of patients with ACS or TC.Negative T waves in lead-aVR (i.e.positive T waves in lead aVR)and no negative T waves in lead V1were observed in 95%of patients with TC in contrast to only 3%of patients with ACS or APE. Negative T waves in leadⅢwas highly predictive of APE;furthermore,the diagnostic accuracy of this finding combined with negative T waves in lead V1was very high,representing the highest predictive accuracy.Negative T waves in lead-aVR(i.e.positive T waves in lead aVR)and no negative T waves in lead V1were highly predictive of TC,but the positive predictive values of these findings were low.However,the combination of these two findings resulted in the highest ability to differentiate TC.Figure 2 shows representative ECGs for one patient from each group.

Table 1 Electrocardiographic findings

Negative T waves in ACS

In patients with ACS caused by LAD disease in this study,negative T waves were distributed primarily around leads V2to V4in the precordial leads,facing the anterior region of the left ventricle,and in lead aVL in the limb leads,facing the lateral region of the left ventricle.Negative T waves in lead V1were observed in 63%of these patients.Lead V1is considered to reflect the right paraseptal region,often supplied by the septal branch of the LAD.Negative T waves in this lead may suggest severe ischemia in the interventricular septum caused by more proximal LAD disease.In this study,the majority(75%)of patients with ACS had proximal LAD disease.Conversely,the prevalence of negative T waves in lead-aVR and inferior leads was very low.Lead -aVR(+30°)bridges the gap between5leadⅠ(0°)and leadⅡ(60°);in other words,lead-aVR faces the apical region of the left ventricle.The perfusion territory of the LAD might not extend to the inferior as well as the

Figure 1 Prevalence of negative T waves in patients with ACS,APE and TC.apical regions of the left ventricle,resulting in less negative T waves in leads facing these regions.

Figure2 Representative ECGs of ACS,APE and TC.A.ACS:Negative T waves were observed in leads aVL and V1to V4.When the limb leads were displayed according to the anatomically contiguous Cabrera sequence,negative T waves were seen in only lead aVL,which faces the upper lateral region of the left ventricle. Coronary angiography revealed 90%stenosis of the proximal lesion of the LAD.B.APE:Negative T waves were observed in leadsⅢ,aVF and V1to V4.When the limb leads were displayed according to the Cabrera sequence,the amplitude of negative T waves was greatest in leadⅢ,which faces the inferior region of the right ventricle,and smaller in lead aVF.T wave was slightly inverted in leadⅡ.A computed tomographic scan of the chest showed multiple filling defects in the main right and left pulmonary arteries.Lung perfusion scintigraphy revealed filling defects in the right upper,right middle and left upper lung fields.C.TC:Negative T waves were observed in leadsⅠ,Ⅱ,Ⅲ,aVF and V2to V6.In lead aVR,positive T waves were observed.When the limb leads were displayed

Negative T waves in APE

In the present study,electrocardiographic findings associated with APE,such as P pulmonale,right and left axis deviation,S1S2S3and S1Q3T3patterns,low voltage and clockwise rotation were specific,but not sensitive for APE.In the present study,negative T waves in leadsⅢ,V1and V2were very common in patients with APE. LeadⅢfaces the inferior region of the right ventricle, and leads V1and V2face the anterior region of the right ventricle.With increasing severity of right heart failure and dilation of the right ventricle towards the left owing to limited pericardial expansion,negative T waves are thought to move towards the left,i.e.from leadsⅢto aVF toⅡin the limb leads and from leads V1to V6in the precordial leads.

Negative T waves in both leadsⅢand V1could differentiate APE from ACS in patients who had precordial negative T waves.

Negative T waves in TC

Electrocardiographic changes in TC have been shown to be similar to those in anterior acute myocardialaccording to the Cabrera sequence,negative T waves were broadly distributed in all leads except for lead aVL,which faces the upper lateral region of the left ventricle. Echocardiography showed transient akinesis of the left ventricular apical and mid-ventricular segments,and coronary angiography revealed no significant coronary stenosis.

infarction.TC was associated with a greater amplitude and higher prevalence of negative T waves,as compared with ACS and APE.In addition,negative T waves were more broadly distributed around lead-aVR in the limb leads and the precordial leads except lead V1.These findings are probably ascribed to the fact that wall motion abnormalities in TC are centered around the apical region of the left ventricle faced by lead-aVR and less frequently extend to the regions faced by lead V1,i.e.the right ventricular anterior region as well as the right paraseptal region.Moreover,less negative T waves in lead V1may be attributed to another reason:TC,but not ACS caused by LAD disease or APE,is usually associated with wall motion abnormalities in the posterolateral region,resulting in negative T waves in this region.

词汇

balloon n.&v.&adj.气球；使鼓起，使激增，鼓起，激增；像气球般鼓起的

preclude v.阻止，妨碍，排除

assessable adj.可评价的，可征税的

contiguous adj.连续的，相邻的，接触的

scintigraphy n.闪烁扫描术

pheochromocytoma n.嗜铬细胞瘤

注释

1.Takotsubo cardiomyopathy指应激性心肌病、左心室心尖球囊综合征，其主要特征为可逆的左心室室壁运动异常而无冠状动脉的异常。

2.hypokinesis，akinesis，dyskinesis分别指运动低下，运动丧失，反向或异常运动。这三个词均由kinesis（运动）加不同的前缀构成，类似构成的词有hypotonic（低张力的）,atonic（无张力的），dystonic（张力异常的）。

3.Cabrera sequence又称Cabrera format。我们目前所用心电图额面六轴系统中，没有-aVR，只有aVR（210°），而其镜像虚构导联即为-aVR（30°），位于Ⅰ（0°）与Ⅱ（60°）正中间，使得Ⅲ、aVF、Ⅱ、-aVR、Ⅰ和aVL之间的夹角均为30°，这种顺序关系即称为Cabrera sequence或Cabrera format。-aVR的心电图可由aVR的心电图作一个上下翻转获得。-aVR作为标准导联最早见于瑞典的相关文献中。

4.center around指以…为中心，如center around human being以人为本。

5.bridges the gap between指消除…之间的隔阂，弥合…之间的差异。

参考译文

第57课急性冠状动脉综合征、肺栓塞和应激性心肌病T波倒置的差异

T波倒置是非ST段抬高急性冠状动脉综合征（ACS）常见的心电图表现。特别是胸导联T波倒置，提示左前降支（LAD）明显狭窄导致的左心室前壁严重缺血。然而，这种心电图变化也常见于急性肺栓塞（APE）患者，特别是那些有不良后果危险的患者。此外，应激性心肌病（TC）是新近发现的新型心脏综合征，特征表现为新发的心电图异常（ST段抬高，T波倒置），心肌酶增高，一过性左心室心尖球样扩张而无冠状动脉阻塞。

对于初始胸导联T波倒置的ACS患者，APE和TC应包含在鉴别诊断之列。对于这三种疾病，为保证选择合适的治疗方案和改善预后，快速鉴别至关重要。12导联心电图是一种简便、快速、廉价和极为广泛应用的初始临床诊断检查。

300例（ACS198例、APE81例、TC 21例）连续入住ICU的患者，并符合以下标准：（1）胸痛、不适、呼吸困难或其他缺血症状发作48h内入院；（2）没有影响心电图ST段变化的情况如完全性左或右束支传导阻滞、左心室肥大、心室起搏或使用影响心电图的药物；（3）无明显的心肺疾病史；（4）入院心电图符合全面分析，倒置的T波在两个或以上相邻的胸导联上（V1～V4）至少达1mm。入院时两个相邻胸导联上ST段抬高至少2mm以上者剔除。

ACS患者不稳定症状包括静息、新发和加剧的心绞痛。罪犯病变定义为血管病变伴造影所见到局部血栓、最严重的病变或两者兼之，位于LAD。APE经肺动脉造影、肺灌注闪烁扫描术或计算机断层扫描诊断。TC患者呈现以下特征：（1）左心室心尖节段行短暂运动减弱、运动消失或逆向运动，室壁运动异常区域超出单一心外膜血管分布区域；（2）无明显阻塞性冠状动脉病变（＞50%）或无急性斑块破裂血管造影依据；（3）新发的心电图异常（T波倒置）；（4）无嗜铬细胞瘤或心肌炎。

本研究中，肢体导联采用结构上连贯的Cabrera顺序排列（Ⅲ、aVF、Ⅱ、-aVR、Ⅰ及aVL）。

入院时心电图表现见表1。APE较常伴随肺型P波，S1S2S3和顺钟向转位。电轴右偏和S1Q3T3只见于APE。ACS较常伴随ST段压低和较大的ST段压低总值。在T波倒置的数量和最大振幅上，TC最大，ACS次之，而APE最低。3组T波倒置的发生率见图1。在肢体导联上，ACS患者T波倒置常见于Ⅰ和aVL，特别是后者，极少见于下壁导联和-aVR。相反，APE患者从Ⅲ到-aVR，T波倒置发生率逐渐下降，Ⅰ或aVL未见T波倒置。而TC患者，围绕-aVR T波倒置发生率高。在胸导联，ACS患者T波倒置分布集中围绕V3。相反，APE患者V1和V2T波始终倒置，从V3到V6，T波倒置发生率逐渐下降，而TC患者，除V1外，胸导联T波倒置发生率高。Ⅲ和V1T波倒置见于90%APE患者，但只见于3%的ACS或TC患者。-aVR T波倒置（即aVR T波直立）和V1无T波倒置见于95%的TC患者，相反只见于3%的ACS或APE患者。ⅢT波倒置高度预示APE,结合V1T波倒置诊断准确性非常高，呈现最高的预测准确性。-aVR T波倒置（即aVR T波直立）和V1无T波倒置高度预示TC，但阳性预测值较低。当两者结合时能最大程度上区分TC。图2是每组一例患者的代表性心电图。

ACS T波倒置

本研究中LAD病变引起的ACS患者，倒置T波主要分布在胸导联V2～V4，面对左心室前壁区域，而在肢导联aVL，面对的是左心室侧壁区域。这些患者中63%可于V1见到T波倒置。V1反映的是右侧间隔旁区，常由LAD的间隔支供应。该导联T波倒置提示LAD较近端病变导致室间隔严重缺血。本研究中多数（75%）ACS患者为LAD近端病变。相反，-aVR和下壁导联T波倒置发生率非常低。-aVR（+30°）间于Ⅰ（0°）和Ⅱ（60°）之间，也就是说，-aVR面对左心室心尖区。LAD灌注区域可能不涉及左心室下壁和心尖区域，以致面对这些区域的导联T波倒置少见。

APE T波倒置

本研究中，与APE相关的心电图表现肺型P波、心电轴右和左偏、S1S2S3和S1Q3T3、低电压和顺钟向旋转具有特异性，但不敏感。Ⅲ、V1和V2上T波倒置常见于APE患者。Ⅲ面对右心室下壁区域，而V1和V2面对右心室前壁区域。随着右心衰竭加重及心包的限制，右心室向左扩张，因此，T波倒置左移，即肢体导联从Ⅲ移向aVF及Ⅱ，胸导联从V1移向V6。

对于胸导联T波倒置的患者，Ⅲ和V1均为倒置T波可鉴别APE与ACS。

TC T波倒置

TC的心电图变化类似于前壁急性心肌梗死。与ACS和APE相比，TC的倒置T波振幅和发生率较高。另外，倒置T波分布较广，肢体导联上围绕-aVR，胸导联上仅V1除外。这些表现的基础是TC的心室壁运动异常集中围绕在-aVR面对的左心室心尖区，很少涉及V1面对的右心室和右侧间隔旁区。此外，V1少见T波倒置另有原因：TC,而非LAD病变引起的ACS或APE，通常伴随后外侧区室壁运动异常，导致这一区域的T波倒置。

表1尖峰头盔征患者的临床和心电图特征

图1 ACS,APE和TC患者倒置T波发生率。

图2 ACS,APE和TC的代表性心电图。A.ACS：倒置T波见于aVL和V1～V4。当肢体导联按结构上连贯的Cabrera顺序排列，倒置T波只见于aVL，该导联面对左心室上外侧区域。冠状动脉造影显示LAD近端90%狭窄。B.APE：倒置T波见于Ⅲ、aVF和V1～V4。当肢体导联按Cabrera顺序排列，面对右心室下壁区域的Ⅲ倒置T波最深，aVF较浅。ⅡT波浅倒置。胸部CT扫描显示左右侧大的肺动脉多发充盈缺损。肺灌注闪烁扫描术显示右上中肺和左上肺充盈缺损。C. TC：倒置T波见于Ⅰ，Ⅱ，Ⅲ，aVF和V2～V6。aVR上T波直立。当肢体导联按Cabrera顺序排列时，倒置T波广泛分布于除面向左心室上侧壁的aVL外的所有导联。心脏超声显示左心室心尖和中段短暂的运动消失，冠状动脉造影显示无明显冠状动脉狭窄。

[1]Kosuge M,Ebina T,Hibi K,et al.Differences in negative T waves among acute coronary syndrome,acute pulmonary embolism,and Takotsubo cardiomyopathy[J].European Heart Journal:Acute Cardiovascular Care，2012，1（4）：349-357.

（童鸿）

●思考与分析

本例心电图为12导联与双极食管导联（EB）同步记录。图中前半部分未见P波，代之以大小、形态、间距不规则的“f”波，R-R间期绝对不规则，明确为心房颤动。细小的“f”波持续至R7前后时转变为粗大的“f”波，并由R8前的一次粗“f”波诱发其后的窄QRS波群心动过速。R-R间期绝对规则，频率180次/min，12导联心电图ST段上隐约可见P-波，难以肯定，对照双极食管导联明确每个QRS波群后均有固定的P-波，R-PE-间期120ms，从而明确为顺向型房室折返性心动过速。另外，心房颤动时未见心室预激图形，心动过速时P-波在Ⅰ倒置，V1直立，以及R-PE-间期＜R-PV1-间期，基本明确为左侧隐匿性房室旁道参与逆传的顺向型房室折返性心动过速。

心房颤动绝对不规则的心室率突然转为规则时，需考虑：（1）恢复窦性心律：其心率往往有一个由慢至快的“温醒”过程，并可见窦性P波，本例图中未见，且心率很快，可鉴别。（2）合并三度房室传导阻滞：心房颤动合并三度房室传导阻滞时，心室率往往由房室交接区或心室逸搏心律控制，频率往往较慢，本例窄QRS波群心动过速心率达180次/min，可排除。（3）转变为心房扑动：心房扑动的频率一般在250～400次/min，偶可＜250次/min，本例心动过速时心率仅180次/min，可基本排除。（4）转变为房性心动过速：不少见，但是房性心动过速时往往因频率较快会出现P’-R间期不固定的房室文氏传导，尤其是颤动波刚刚转变为房性P波时，本例转变后未见R-P-间期变化，可以此鉴别。当然明确诊断需心内电生理检查证实。（5）转变为室上性心动过速：较少见，本例主要需明确是慢-快型房室结折返性心动过速，还是顺向型房室折返性心动过速。图中因有双极食管导联同步记录，明确R-PE-间期120ms，从而可以与慢-快型房室结折返性心动过速时R-PE-间期＜70ms鉴别。

综上所述，本例心电图的诊断为：心房颤动，诱发顺向型房室折返性心动过速（提示隐匿性左侧房室旁道参与逆传）。

编者按《思考心电图之131》共收到20份答案，以下同志的答案正确或基本正确：张敏徐立文李兴杰国卫民庞曰同闾文德王兆玉梁兴国邸成业齐治平耿学军李志勤汪宁曹庆生丛鹏许燕

（蔡卫勋）