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

●心電學英語

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.

詞匯

balloon n.&v.&adj.氣球；使鼓起，使激增，鼓起，激增；像氣球般鼓起的

preclude v.阻止，妨礙，排除

assessable adj.可評價的，可征稅的

contiguous adj.連續(xù)的，相鄰的，接觸的

scintigraphy n.閃爍掃描術(shù)

pheochromocytoma n.嗜鉻細胞瘤

注釋

1.Takotsubo cardiomyopathy指應(yīng)激性心肌病、左心室心尖球囊綜合征，其主要特征為可逆的左心室室壁運動異常而無冠狀動脈的異常。

2.hypokinesis，akinesis，dyskinesis分別指運動低下，運動喪失，反向或異常運動。這三個詞均由kinesis（運動）加不同的前綴構(gòu)成，類似構(gòu)成的詞有hypotonic（低張力的）,atonic（無張力的），dystonic（張力異常的）。

3.Cabrera sequence又稱Cabrera format。我們目前所用心電圖額面六軸系統(tǒng)中，沒有-aVR，只有aVR（210°），而其鏡像虛構(gòu)導(dǎo)聯(lián)即為-aVR（30°），位于Ⅰ（0°）與Ⅱ（60°）正中間，使得Ⅲ、aVF、Ⅱ、-aVR、Ⅰ和aVL之間的夾角均為30°，這種順序關(guān)系即稱為Cabrera sequence或Cabrera format。-aVR的心電圖可由aVR的心電圖作一個上下翻轉(zhuǎn)獲得。-aVR作為標準導(dǎo)聯(lián)最早見于瑞典的相關(guān)文獻中。

4.center around指以…為中心，如center around human being以人為本。

5.bridges the gap between指消除…之間的隔閡，彌合…之間的差異。

參考譯文

第57課急性冠狀動脈綜合征、肺栓塞和應(yīng)激性心肌病T波倒置的差異

T波倒置是非ST段抬高急性冠狀動脈綜合征（ACS）常見的心電圖表現(xiàn)。特別是胸導(dǎo)聯(lián)T波倒置，提示左前降支（LAD）明顯狹窄導(dǎo)致的左心室前壁嚴重缺血。然而，這種心電圖變化也常見于急性肺栓塞（APE）患者，特別是那些有不良后果危險的患者。此外，應(yīng)激性心肌病（TC）是新近發(fā)現(xiàn)的新型心臟綜合征，特征表現(xiàn)為新發(fā)的心電圖異常（ST段抬高，T波倒置），心肌酶增高，一過性左心室心尖球樣擴張而無冠狀動脈阻塞。

對于初始胸導(dǎo)聯(lián)T波倒置的ACS患者，APE和TC應(yīng)包含在鑒別診斷之列。對于這三種疾病，為保證選擇合適的治療方案和改善預(yù)后，快速鑒別至關(guān)重要。12導(dǎo)聯(lián)心電圖是一種簡便、快速、廉價和極為廣泛應(yīng)用的初始臨床診斷檢查。

300例（ACS198例、APE81例、TC 21例）連續(xù)入住ICU的患者，并符合以下標準：（1）胸痛、不適、呼吸困難或其他缺血癥狀發(fā)作48h內(nèi)入院；（2）沒有影響心電圖ST段變化的情況如完全性左或右束支傳導(dǎo)阻滯、左心室肥大、心室起搏或使用影響心電圖的藥物；（3）無明顯的心肺疾病史；（4）入院心電圖符合全面分析，倒置的T波在兩個或以上相鄰的胸導(dǎo)聯(lián)上（V1～V4）至少達1mm。入院時兩個相鄰胸導(dǎo)聯(lián)上ST段抬高至少2mm以上者剔除。

ACS患者不穩(wěn)定癥狀包括靜息、新發(fā)和加劇的心絞痛。罪犯病變定義為血管病變伴造影所見到局部血栓、最嚴重的病變或兩者兼之，位于LAD。APE經(jīng)肺動脈造影、肺灌注閃爍掃描術(shù)或計算機斷層掃描診斷。TC患者呈現(xiàn)以下特征：（1）左心室心尖節(jié)段行短暫運動減弱、運動消失或逆向運動，室壁運動異常區(qū)域超出單一心外膜血管分布區(qū)域；（2）無明顯阻塞性冠狀動脈病變（＞50%）或無急性斑塊破裂血管造影依據(jù)；（3）新發(fā)的心電圖異常（T波倒置）；（4）無嗜鉻細胞瘤或心肌炎。

本研究中，肢體導(dǎo)聯(lián)采用結(jié)構(gòu)上連貫的Cabrera順序排列（Ⅲ、aVF、Ⅱ、-aVR、Ⅰ及aVL）。

入院時心電圖表現(xiàn)見表1。APE較常伴隨肺型P波，S1S2S3和順鐘向轉(zhuǎn)位。電軸右偏和S1Q3T3只見于APE。ACS較常伴隨ST段壓低和較大的ST段壓低總值。在T波倒置的數(shù)量和最大振幅上，TC最大，ACS次之，而APE最低。3組T波倒置的發(fā)生率見圖1。在肢體導(dǎo)聯(lián)上，ACS患者T波倒置常見于Ⅰ和aVL，特別是后者，極少見于下壁導(dǎo)聯(lián)和-aVR。相反，APE患者從Ⅲ到-aVR，T波倒置發(fā)生率逐漸下降，Ⅰ或aVL未見T波倒置。而TC患者，圍繞-aVR T波倒置發(fā)生率高。在胸導(dǎo)聯(lián)，ACS患者T波倒置分布集中圍繞V3。相反，APE患者V1和V2T波始終倒置，從V3到V6，T波倒置發(fā)生率逐漸下降，而TC患者，除V1外，胸導(dǎo)聯(lián)T波倒置發(fā)生率高。Ⅲ和V1T波倒置見于90%APE患者，但只見于3%的ACS或TC患者。-aVR T波倒置（即aVR T波直立）和V1無T波倒置見于95%的TC患者，相反只見于3%的ACS或APE患者。ⅢT波倒置高度預(yù)示APE,結(jié)合V1T波倒置診斷準確性非常高，呈現(xiàn)最高的預(yù)測準確性。-aVR T波倒置（即aVR T波直立）和V1無T波倒置高度預(yù)示TC，但陽性預(yù)測值較低。當兩者結(jié)合時能最大程度上區(qū)分TC。圖2是每組一例患者的代表性心電圖。

ACS T波倒置

本研究中LAD病變引起的ACS患者，倒置T波主要分布在胸導(dǎo)聯(lián)V2～V4，面對左心室前壁區(qū)域，而在肢導(dǎo)聯(lián)aVL，面對的是左心室側(cè)壁區(qū)域。這些患者中63%可于V1見到T波倒置。V1反映的是右側(cè)間隔旁區(qū)，常由LAD的間隔支供應(yīng)。該導(dǎo)聯(lián)T波倒置提示LAD較近端病變導(dǎo)致室間隔嚴重缺血。本研究中多數(shù)（75%）ACS患者為LAD近端病變。相反，-aVR和下壁導(dǎo)聯(lián)T波倒置發(fā)生率非常低。-aVR（+30°）間于Ⅰ（0°）和Ⅱ（60°）之間，也就是說，-aVR面對左心室心尖區(qū)。LAD灌注區(qū)域可能不涉及左心室下壁和心尖區(qū)域，以致面對這些區(qū)域的導(dǎo)聯(lián)T波倒置少見。

APE T波倒置

本研究中，與APE相關(guān)的心電圖表現(xiàn)肺型P波、心電軸右和左偏、S1S2S3和S1Q3T3、低電壓和順鐘向旋轉(zhuǎn)具有特異性，但不敏感。Ⅲ、V1和V2上T波倒置常見于APE患者。Ⅲ面對右心室下壁區(qū)域，而V1和V2面對右心室前壁區(qū)域。隨著右心衰竭加重及心包的限制，右心室向左擴張，因此，T波倒置左移，即肢體導(dǎo)聯(lián)從Ⅲ移向aVF及Ⅱ，胸導(dǎo)聯(lián)從V1移向V6。

對于胸導(dǎo)聯(lián)T波倒置的患者，Ⅲ和V1均為倒置T波可鑒別APE與ACS。

TC T波倒置

TC的心電圖變化類似于前壁急性心肌梗死。與ACS和APE相比，TC的倒置T波振幅和發(fā)生率較高。另外，倒置T波分布較廣，肢體導(dǎo)聯(lián)上圍繞-aVR，胸導(dǎo)聯(lián)上僅V1除外。這些表現(xiàn)的基礎(chǔ)是TC的心室壁運動異常集中圍繞在-aVR面對的左心室心尖區(qū)，很少涉及V1面對的右心室和右側(cè)間隔旁區(qū)。此外，V1少見T波倒置另有原因：TC,而非LAD病變引起的ACS或APE，通常伴隨后外側(cè)區(qū)室壁運動異常，導(dǎo)致這一區(qū)域的T波倒置。

表1尖峰頭盔征患者的臨床和心電圖特征

圖1 ACS,APE和TC患者倒置T波發(fā)生率。

圖2 ACS,APE和TC的代表性心電圖。A.ACS：倒置T波見于aVL和V1～V4。當肢體導(dǎo)聯(lián)按結(jié)構(gòu)上連貫的Cabrera順序排列，倒置T波只見于aVL，該導(dǎo)聯(lián)面對左心室上外側(cè)區(qū)域。冠狀動脈造影顯示LAD近端90%狹窄。B.APE：倒置T波見于Ⅲ、aVF和V1～V4。當肢體導(dǎo)聯(lián)按Cabrera順序排列，面對右心室下壁區(qū)域的Ⅲ倒置T波最深，aVF較淺。ⅡT波淺倒置。胸部CT掃描顯示左右側(cè)大的肺動脈多發(fā)充盈缺損。肺灌注閃爍掃描術(shù)顯示右上中肺和左上肺充盈缺損。C. TC：倒置T波見于Ⅰ，Ⅱ，Ⅲ，aVF和V2～V6。aVR上T波直立。當肢體導(dǎo)聯(lián)按Cabrera順序排列時，倒置T波廣泛分布于除面向左心室上側(cè)壁的aVL外的所有導(dǎo)聯(lián)。心臟超聲顯示左心室心尖和中段短暫的運動消失，冠狀動脈造影顯示無明顯冠狀動脈狹窄。

[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.

（童鴻）

●思考與分析

本例心電圖為12導(dǎo)聯(lián)與雙極食管導(dǎo)聯(lián)（EB）同步記錄。圖中前半部分未見P波，代之以大小、形態(tài)、間距不規(guī)則的“f”波，R-R間期絕對不規(guī)則，明確為心房顫動。細小的“f”波持續(xù)至R7前后時轉(zhuǎn)變?yōu)榇执蟮摹癴”波，并由R8前的一次粗“f”波誘發(fā)其后的窄QRS波群心動過速。R-R間期絕對規(guī)則，頻率180次/min，12導(dǎo)聯(lián)心電圖ST段上隱約可見P-波，難以肯定，對照雙極食管導(dǎo)聯(lián)明確每個QRS波群后均有固定的P-波，R-PE-間期120ms，從而明確為順向型房室折返性心動過速。另外，心房顫動時未見心室預(yù)激圖形，心動過速時P-波在Ⅰ倒置，V1直立，以及R-PE-間期＜R-PV1-間期，基本明確為左側(cè)隱匿性房室旁道參與逆?zhèn)鞯捻樝蛐头渴艺鄯敌孕膭舆^速。

心房顫動絕對不規(guī)則的心室率突然轉(zhuǎn)為規(guī)則時，需考慮：（1）恢復(fù)竇性心律：其心率往往有一個由慢至快的“溫醒”過程，并可見竇性P波，本例圖中未見，且心率很快，可鑒別。（2）合并三度房室傳導(dǎo)阻滯：心房顫動合并三度房室傳導(dǎo)阻滯時，心室率往往由房室交接區(qū)或心室逸搏心律控制，頻率往往較慢，本例窄QRS波群心動過速心率達180次/min，可排除。（3）轉(zhuǎn)變?yōu)樾姆繐鋭樱盒姆繐鋭拥念l率一般在250～400次/min，偶可＜250次/min，本例心動過速時心率僅180次/min，可基本排除。（4）轉(zhuǎn)變?yōu)榉啃孕膭舆^速：不少見，但是房性心動過速時往往因頻率較快會出現(xiàn)P’-R間期不固定的房室文氏傳導(dǎo)，尤其是顫動波剛剛轉(zhuǎn)變?yōu)榉啃訮波時，本例轉(zhuǎn)變后未見R-P-間期變化，可以此鑒別。當然明確診斷需心內(nèi)電生理檢查證實。（5）轉(zhuǎn)變?yōu)槭疑闲孕膭舆^速：較少見，本例主要需明確是慢-快型房室結(jié)折返性心動過速，還是順向型房室折返性心動過速。圖中因有雙極食管導(dǎo)聯(lián)同步記錄，明確R-PE-間期120ms，從而可以與慢-快型房室結(jié)折返性心動過速時R-PE-間期＜70ms鑒別。

綜上所述，本例心電圖的診斷為：心房顫動，誘發(fā)順向型房室折返性心動過速（提示隱匿性左側(cè)房室旁道參與逆?zhèn)鳎?/p>

編者按《思考心電圖之131》共收到20份答案，以下同志的答案正確或基本正確：張敏徐立文李興杰國衛(wèi)民龐曰同閭文德王兆玉梁興國邸成業(yè)齊治平耿學軍李志勤汪寧曹慶生叢鵬許燕

（蔡衛(wèi)勛）