●心電學英語

Lesson Fifty-eight Is ST elevation in aVR a marker of LMCA or ostial LAD stenosis?

The lead aVR is oriented to'look'at the right upper side of the heart,and can provide specific information about the right ventricle outflow tract and basal part of the septum.Because of its location and the fact that it displays reciprocal information covered by leads aVL,Ⅱ,V5and V6,lead aVR is often ignored,even when considering complex ECGs.

Figure 1Initial（A）and follow-up（B）electrocardiograms of a 44-year-old man presenting with chest heaviness and shortness of breath.Angiogram revealed a total proximal occlusion of the left anterior coronary artery without other significant disease.Note the ST elevation in aVR than V1.Also note the hyperacute T waves in the precardial leads and the ST abnormalities in the inferiolateral leads.

AcuteCoronarySyndromeandSTElevationinaVR

Studies by Engelen et al found that ST segment elevation in aVR strongly predicted LAD occlusion proximal to the first septal perforator（Figure 1）.Yamaji et al observed that aVR ST segment elevation greater than the

ST segment elevation in V1predicts acute left main coronary artery（LMCA）occlusion with a sensitivity of

81%and a specificity of 80%（Figure 2）.This finding also predicts clinical outcomes.Gaitonde et al demonstrated in a prospective study that in acute myocardial infarction,patients with an ST segment elevation that is greater in lead aVR than in lead V1prompted early angiography,withholding of clopidogrel and early referral to coronary artery bypass grafting,resulting in improved clinical outcomes1.

Kosuge et al found that in patients with non-ST segment elevation myocardial infarction,ST segment elevation of 0.5 mm or greater in aVR was a useful predictor of LMCA or three-vessel coronary artery disease（sensitivity 78%,specificity 86%）（Figure 3）.Furthermore,they found that aVR ST segment elevation was the strongest predictor of adverse events at 90 days in patients with non-ST segment elevation myocardial infarction.Barrabes et al,in a study of 775 patients with theirfirst non-ST segment elevation myocardial infarction, showed that aVR ST segment elevation was associated with higher rates of in-hospital death,recurrent ischemia and heart failure.

Figure 2Electrocardiogram of a 71-year-old woman presenting with chest pain.Angiogram revealed high-grade stenosis of the distal left main coronary artery involving the take-offs of the left anterior descending and circumflex coronary arteries.Note the ST elevation in aVR and the diffuse ST depressions.

Figure 3Electrocardiogram of a 54-year-old man with chest pain and a history of coronary artery bypass surgery.Angiogram revealed an occluded left main coronary artery,a subtotal occlusion of the left anterior descending coronary artery after the anastamosis of left internal mammary artery,an ostial stenosis of saphenous vein graft to the obtuse marginal artery,and a diffuse moderate disease of the right coronary artery.Note the ST elevation in aVR and the ST depressions in the anterior and inferior leads.

Kotoku et al reported on the relationship between the ST segment level in lead aVR and the length of the LAD.ST segment levels（especially in leadsⅡand V6）,the site of LAD occlusion and the length of the LAD affect the ST segment level in lead aVR in patients with a first ST elevation acute anterior wall myocardial infarction.Proximal LAD occlusion is associated with ST segment elevation in lead aVR,while a long LAD occlusion is associated with ST segment depression in lead aVR.Kotoku et al also reported that a prominent Q wave in lead-aVR in anterior wall acute myocardial infarction is related to severe regional wall motion abnormality in the apical and inferior regions,with an LAD wrapping around the apex2.

LMCA occlusion is another clinical situation in which prompt diagnosis by the clinician can help initiate life-saving invasive therapy.The typical electrocardiographic finding in patients with preserved flow through the LMCA is widespread ST segment depression maximally in leads V4to V6,with inverted T waves and ST segment elevation in lead aVR.ST elevation in lead aVR,when accompanied by either anterior ST elevationor widespread ST segment depression,may indicate LMCA occlusion.Figure 4 showed ECG changes of complete ostial occlusion of LMCA determined by emergent angiography.The ECG shows marked ST elevation in aVR>>V1and ST depression in multiple leads（V2～V6,Ⅰ,Ⅱ,aVL,aVF）.

Figure 4This patient presented to ED with severe ischaemic chest pain,vomiting,syncope（due to runs of VT）and cardiogenic shock.He was taken for emergent angiography and found to have a complete ostial occlusion of left main coronary artery.

Kanei et al reported in a study of 106 patients that ST segment depression in lead aVR in inferior wall ST segment elevation myocardial infarction predicts left circumflex infarction or larger right coronary artery infarction involving a large posterolateral branch.

Stress Testing and ST Elevation in aVR

Data regarding the significance of STE in lead aVR in the setting of exercise treadmill testing（ETT）are limited.In the present study,Uthamalingam S et al tested the hypothesis that ETT-induced STE in lead aVR is a useful indicator of hemodynamically significant LMCA or ostial LAD stenosis.

A database search of patients undergoing cardiac catheterization at his institution between January 2008 and July 2009 was performed to identify 3 groups of patients∶1）those with significant LMCA or ostial LAD disease（≥50%luminal diameter reduction）in addition to any other coronary lesions（≥70%luminal diameter reduction for mid and distal LAD segments）;2）those with coronary artery disease（CAD）（≥70%luminal diameter reduction）but not LMCA or ostial LAD disease;and 3）those free of significant CAD（LMCA and all 3 major vessels free of any stenosis≥50%）. Ostial LAD stenosis included any lesion proximal to the first septal perforator.All patients（n=454）had undergone ETT according to the standard Bruce protocol≤6months beforetheclinicallyindicatedcardiac catheterization.LMCA（n=38）or ostial LAD stenosis（n=42）was present in 75 patients（5 patients had both）.The remainder had either CAD of varying severity that did not involve the LMCA or ostial LAD（n= 276）or no significant CAD（n=103）.

Patients with acute coronary syndromes or prior coronary artery bypass grafting were excluded.Patients who had undergone pharmacological stress also were excluded,as were those whose baseline ECG studies indicated left bundle branch block,intraventricular conduction delays≥120ms,left ventricular hypertrophy with marked strain pattern（down-sloping ST-segment depression[STD]≥1 mm with biphasic or inverted T waves）,or marked anterior T-wave inversions（the Wellens pattern3）concerning for active ischemia or possible LMCA or proximal LAD stenosis.

ECG data（rest and stress）

In addition to lead aVR,lead aVL,the inferior leads（Ⅱ，Ⅲ,and aVF）,and pre-cordial leads V1and V4to V6were evaluated,and the amount of STD or STE at 80 ms after the J point both at rest and during peak stress was tested in univariate regression analysis.In lead aVR,only horizontal or up-sloping STE was con-sidered indicative of ischemia.J-point elevation only with down-sloping ST segment was not.

Univariate logistic regression analysis was performed of patients with 1VD,2VD,and 3VD without LMCA or ostial LAD stenosis to determine the correlation of each with STE in lead aVR.There was no significant correlation between 1VD,2VD,or 3VD without LMCA or ostial LAD stenosis and STE in lead aVR.In contrast,STE in lead aVR was a significant（P＜0.0001,AUC∶0.76）positively correlated predictor of selected cases of pure,isolated LMCA or ostial LAD stenosis（n=34）.Because leads V5and V6are reciprocal to lead aVR,STD in either of these leads as a univariate predictor of LMCA or ostial LAD stenosis was determined.Although both were correlated strongly（lead V5：P＜0.0001,AUC∶0.69；lead V6：P＜0.0001,AUC：0.70）,the AUC for each was significantly less than that for STE in lead aVR（0.82）（both P＜0.001）.Finally, although stress-induced STE in lead V1was also a significant predictor of LMCA or ostial LAD stenosis（P＜0.0001,AUC∶0.59）it too was significantly less than that for STE in lead aVR（P＜0.0001 for AUC comparison）and did not add independent information in multivariate analysis.

Using a cut-point of 1-mm STE in lead aVR, chi-square tests were used to compare the prediction of LMCA or ostial LAD stenosis with 1VD,2VD,and 3VD without LMCA or ostial LAD stenosis.Thus,76%of patients with LMCA or ostial LAD stenosis had 1-mm STE in lead aVR with stress,compared with 17%,27%,and 39%,respectively,with 1VD,2VD,and 3VD without LMCA or ostial LAD stenosis Only 8 patients（8%）without significant CAD had 1-mm STE in lead aVR with stress.

Optimal ECG lead aVR cut-point and Bayesian analysis

The optimal cut-point for the amount of stress-induced STE in lead aVR was defined by the greatest sum of sensitivity and specificity for the detection of significant LMCA or ostial LAD stenosis.Cut-points of 0.5-, 1.0-,1.5-,and 2.0-mm horizontal STE were tested. The greatest sensitivity-specificity sum（1.56）was reached at 1.0-mm STE.Thus,sensitivity was 75%, specificity was 81%,positive predictive accuracy was 44%,negative predictive accuracy was 94%,and overall predictive accuracy was 80%.

詞匯

ignore v.忽視,不顧,不理會,駁回

withhold v.克制,使...停止,把...留下,拒給

wrap n.&v.包裹物,包裝,披肩,毯子,外衣;包,包上,包扎,纏繞,覆蓋,用...包

circumflex adj.&v.音調(diào)符號的,卷曲的,彎曲的;使...彎曲

univariate adj.單變量的

logistic n.&adj.算術(shù)；邏輯的,計算的

注釋

1.句子“Gaitonde et al demonstrated…prompted early angiography,withholding of clopidogrel and early referral to coronary artery bypass grafting,resulting in improved clinical outcomes.”中，“withholding”是動名詞作prompted的賓語，而“resulting…”是分詞短語用作伴隨狀語。

2.句子“Kotoku et al also reported…the apical and inferior regions,with an LAD wrapping around the apex.”中的“wrapping…”分詞短語是with賓語“LAD”的補語，而“with…”整個介詞短語是“anterior wall acute myocardial infarction”的名詞修飾語。

3.Wellens pattern指前降支嚴重狹窄的特異性心電圖表現(xiàn)，V2～V3上出現(xiàn)對稱性T波深倒置（＞2mm）（A型Wellens T波），或T波呈先正后負的正負雙相改變（B型Wellens T波）。

參考譯文

第58課aVR ST段抬高是左冠狀動脈主干或前降支開口狹窄的特征嗎？

aVR面對心臟右上方，可提供右心室流出道和間隔基底部的特別信息。由于它的位置及其顯示的信息與aVL、Ⅱ、V5和V6所覆蓋的彼此相反，因此，即使分析復雜的心電圖時,也常常忽視aVR。

急性冠狀動脈綜合征與aVR ST段抬高

Engelen等研究發(fā)現(xiàn)aVR ST段抬高強烈預示前降支（LAD）阻塞部位位于第一穿間隔支之前（圖1）。Yamaji等觀察到aVR ST段抬高超過V1預測急性左冠狀動脈主干（LMCA）阻塞的敏感性為81%，特異性為80%（圖2）。這種表現(xiàn)還能預測臨床預后。Gaitonde等在一前瞻性研究中證實，急性心肌梗死時aVR ST段抬高超過V1者，促使早期造影、停用波利維及早期轉(zhuǎn)向冠狀動脈搭橋術(shù)，結(jié)果是臨床預后得到改善。

Kosuge等發(fā)現(xiàn)非ST段抬高患者aVR ST段抬高0.5mm或以上是LMCA或多支冠狀動脈病變的有效預測指標（敏感性78%，特異性86%）（圖3）。此外，他們發(fā)現(xiàn)aVR ST段抬高是非ST段抬高心肌梗死患者90d不良事件的最強預測指標。Barrabes等對775例首次發(fā)生非ST段抬高心肌梗死患者的研究表明，aVR ST段抬高患者的住院死亡、再發(fā)心肌缺血及心力衰竭發(fā)生率較高。

Kotoku等對ST段水平與LAD長度之間的關(guān)系作了報道。對于首次ST段抬高急性前壁心肌梗死患者，ST段水平（特別是Ⅱ和V6）、LAD阻塞部位及LAD長度影響aVR ST段水平。LAD近端阻塞與aVR ST段抬高有關(guān)，而長的LAD阻塞與aVR ST段壓低有關(guān)。Kotoku等也報道，在LAD包繞心尖部的急性前壁心肌梗死，aVR上明顯的Q波與心尖及下壁區(qū)域嚴重局部心室壁運動異常相關(guān)。

LMCA阻塞是另一種臨床狀態(tài)，臨床醫(yī)師的即時診斷將有助于啟動挽救生命的創(chuàng)傷性治療。保留LMCA血流的患者，典型心電圖表現(xiàn)為廣泛ST段壓低，V4～V6最明顯，伴隨aVR T波倒置和ST段抬高。aVR ST抬高，如伴隨前壁ST段抬高或廣泛ST段壓低，提示LMCA阻塞。圖4為經(jīng)緊急血管造影證實LMCA開口完全阻塞的心電圖變化。心電圖顯示aVR ST段明顯抬高，明顯超過V1，同時多個導聯(lián)（V2～V6，Ⅰ，Ⅱ,aVL,aVF）ST段壓低。

Kanei等對106例下壁ST段抬高心肌梗死患者研究顯示，aVR ST段壓低預示左旋支梗死或右冠狀動脈梗死累及粗大的后外側(cè)分支血管。

應力測試與aVR ST段抬高

有關(guān)運動平板試驗（ETT）中涉及aVR ST段抬高意義的資料有限。本研究中，Uthamalingam等對ETT誘發(fā)的aVR ST段抬高是血流動力學上顯著的LMCA或LAD開口狹窄的有效預測指標這一假設作了測試。

檢索2008年1月至2009年7月他所在機構(gòu)進行心導管檢查的患者資料庫，確定3組患者：（1）除其他冠狀動脈病變LAD中遠段狹窄≥70%外，有顯著的LMCA或LAD開口病變（管腔狹窄≥50%）；（2）有冠狀動脈病變（狹窄≥70%），但無LMCA或LAD開口病變；（3）無明顯冠狀動脈病變（LMCA和所有三支血管無任何≥50%的狹窄）。LAD開口狹窄是指第一穿間隔支之前的任何LAD病變。所有患者（n=454）于臨床心導管檢查前≤6個月內(nèi)按照Bruce方案進行ETT測試。LMCA（n=38）或LAD開口狹窄（n=42）者共75例（其中5例兩者并存）。其余為未累及LMCA或LAD開口的各種嚴重程度的冠狀動脈病變者（n=276），或無明顯冠狀動脈病變者（n=103）。

排除急性冠狀動脈綜合征或以前冠狀動脈搭橋術(shù)。接受藥物應力測試的、基礎心電圖提示左束支傳導阻滯、室內(nèi)傳導延遲≥120ms、左心室肥大伴明顯勞損性改變（下斜型ST段壓低≥1mm伴T波雙相或倒置）、或明顯前壁T波倒置提示活動性缺血或LMCA或LAD近端狹窄可能的患者也排除在外。

ECG資料（靜息與應力）

評估aVR及aVL、下壁導聯(lián)（Ⅱ，Ⅲ，aVF）和胸前V1、V4～V6。對靜息和峰值負荷時J點后80ms處ST段壓低或ST段抬高數(shù)值作單因素回歸分析。aVR上，認為只有水平型或上斜型ST段抬高為缺血表現(xiàn)。僅有J點抬高伴下斜型ST段抬高不考慮缺血。

對無LMCA或LAD開口狹窄的單支、雙支和三支血管病變與aVR ST段抬高之間的相關(guān)性作單因素邏輯回歸分析。無LMCA或LAD開口狹窄的單支、雙支和三支血管病變與aVR ST段抬高之間無明顯相關(guān)性。相反，aVR ST段抬高是所選患者（n=34）單純LMCA或LAD開口狹窄的顯著正相關(guān)指標（P＜0.0001，AUC∶0.76）。因為V5和V6與aVR互為對應，因此，其中任一導聯(lián)的ST段壓低是LMCA或LAD開口狹窄的單變量預測指標。雖然兩者均高度相關(guān)（V5：P＜0.0001，AUC：0.69；V6：P＜0.0001，AUC：0.70），但各自的AUC均顯著低于aVR的ST段抬高（0.82）（均P＜0.001）。最后，雖然應力誘發(fā)的V1ST段抬高也是LMCA或LAD開口狹窄的重要指標（P＜0.0001，AUC∶0.59），但也是顯著低于aVR ST段抬高（P＜0.0001，由AUC對照），且不能為多變量分析增加獨立的信息。

采用aVR ST段抬高1-mm作為分割點，作χ2檢驗來比較LMCA或LAD開口狹窄與無LMCA或LAD開口狹窄的單支、雙支和三支血管病變的預測。這樣，76%LMCA或LAD開口狹窄患者應力測試時出現(xiàn)1-mm ST段抬高。相比之下，無LMCA或LAD開口狹窄的單支、雙支和三支血管病變患者分別為17%，27%和39%。只有8例無冠狀動脈病變患者（8%）應力測試時aVR出現(xiàn)1-mm ST段抬高。

最佳心電圖aVR分割點和貝葉斯分析

通過計算探測嚴重LMCA或LAD開口狹窄的敏感性和特異性的最大合計值確定應力測試誘發(fā)的aVR ST段抬高的最佳分割點。測試水平型ST段抬高0.5-,1.0-,1.5-,和2.0-mm的分割點。于ST段抬高1.0-mm點，敏感性和特異性合計值達到最大（1.56）。這樣，敏感性為75%,特異性為81%,陽性預測準確性44%,陰性預測準確性94%,總體預測準確性80%。

圖11例44歲男性因胸部沉悶和呼吸短促就診時初始（A）和隨訪（B）心電圖。造影顯示LAD近端完全阻塞而無其他明顯病變。注意aVR ST段抬高大于V1。另外，注意胸導聯(lián)超急期T波和下壁導聯(lián)ST段異常。

圖271歲女性因胸痛就診時的心電圖。造影顯示LMCA遠端高度狹窄，累及LAD和LCX起始部位。注意aVR ST段抬高和廣泛ST段壓低。

圖31例胸痛并有冠狀動脈搭橋史的54歲男性心電圖。造影顯示LMCA阻塞、LAD內(nèi)乳動脈吻合口遠端次全阻塞，鈍緣支大隱靜脈口狹窄，RCA彌漫性中度病變。注意aVR ST段抬高及前壁和下壁ST段壓低。

圖4患者因嚴重缺血性胸痛、嘔吐、暈厥（短陣室性心動過速所致）和心源性休克急診。立即行血管造影檢查發(fā)現(xiàn)LMCA開口完全阻塞。

[1]George A,Arumugham P S,Figueredo V M,et al.aVR-the forgotten lead[J].Exp Clin Cardiol,2010,15（2）:e36-e44.

[2]Uthamalingam S,Zheng H,Leavitt M,et al.Exercise-Induced ST-Segment Elevation in ECG Lead aVR Is a Useful Indicator of Significant Left Main or Ostial LAD Coronary Artery Stenosis[J].J Am Coll Cardiol Img，2011，4（2）:176-186.

（童鴻）