左主冠狀動脈急性阻塞的心電圖變化

研究背景:左主冠狀動脈急性阻塞引發心肌梗塞，在臨床上並不多見，根據以前的研究，發生率約0.8%-2.4%。臨床表現常併發心因性休克、急性肺水腫、呼吸衰竭及致命心律不整(心室顫動)，有極高的猝死機率，為心肌梗塞中最嚴重的一型。也由於低發生率及高猝死率，目前已發表的相關研究依然很少；倘若能經由發病初期的心電圖早期預測梗塞病灶為左主冠狀動脈，可以提供第一線醫師重要的參考依據，而採取更為積極的醫療緊急處置 :包括立即心導管檢查、照會心臟外科醫師及相關人員、設備Intra-aortic balloon pump (IABP)、Extra-corporeal membrane oxygenation (ECMO)緊急待命，隨時接手施行冠狀動脈繞道手術，方能有效提升病患的存活率。研究方法:研究對象:從2003年3月至2009年2月之間在澄清醫院、中山醫學大學附設醫院、彰化基督教醫院及義守大學附設醫院共四間醫院，因心肌梗塞住院，經緊急心導管檢查證實病灶為左主冠狀動脈的病人，連續選擇共19名患者為病例組；另病灶為左前降枝近端的病人，共45名患者為對照組。研究材料:收集心導管檢查前的十二導程心電圖進行分析。統計方法：使用SPSS 14版統計軟體進行分析。連續變項以Student t- test檢定，來較兩組之間是否有統計學上的差異。類別變項以卡方檢定或Fisher exact test，來比較兩組差異。多變項分析，以逐段區別分析方法( stepwise discriminant analysis)來比較相關變數的預測能力。研究結果: 兩組患者的臨床基本特性，包括性別、年齡及冠心病的危險因子，在統計上無明顯差異；但左主冠狀動脈組心因性休克的發生率較高(68% versus 10%，P<0.001)，死亡率也較高(68% versus 7%，P<0.001)。左主冠狀動脈組導程aVR ST段上升(>0.05mV)的發生率為95%，明顯高於左前降枝組的18% (P<0.001)。左主冠狀動脈組導程aVR ST段的平均值+標準差為0.13+0.07mV，左前降枝組為-0.02+0.06mV，有明顯差異(p<0.001)。導程I、II、 aVF、 V1-V6 ST段下降的發生率，左主冠狀動脈組明顯高於左前降枝組(p<0.01)。多變項分析結果顯示，導程aVR、V1、II的ST段變化在二組之間有顯著差異，3個預測變項中以導程aVR的區別係數絕對值最大，為判別左主冠狀動脈阻塞最重要的預測指標。左主冠狀動脈組預後(死亡率)相關的變項分析，死亡有13位、存活者有6位，12導程心電圖ST段的偏移程度二組沒有明顯差異; 但心電圖呈現右束支傳導阻滯(RBBB)，在死亡的患者中發生率較高(54% versus 0%，p=0.044)，心因性休克亦然(92% versus 17%，p=0.003)。若依歐洲及美國心臟學會(ESC/ACC) ST段上升心肌梗塞心電圖診斷標準，19位左主冠狀動脈阻塞的患者中，有4位（21%）ST段上升僅在導程aVL、aVR或aVR、V1；另外，有3位(16%)患者心電圖ST段上升僅出現在導程I、aVL、aVR。結論: 本次研究結果顯示，心電圖導程aVR ST段上升是診斷左主冠狀動脈急性阻塞最重要的預測指標。可以提供臨床醫師在診斷左主冠狀動脈急性阻塞患者非常好用的參考依據。另外，若合併下壁導程(II、aVF)ST段下降或導程aVL ST段上升、心軸左偏、右束支傳導阻滯，也有輔助的參考價值。在左主冠狀動脈急性阻塞患者臨床預後相關的變項分析中，合併心因性休克或心電圖呈現右束支傳導阻滯，在死亡的患者中發生率較高，值得重視；但因樣本數較少，仍有待較大規模前瞻性的研究進一步分析. 若依ESC/ACC ST段上升心肌梗塞心電圖診斷標準，所收集19位左主冠狀動脈阻塞的患者中，有4位（21%）ST段上升僅在導程aVL、aVR或aVR、V1，須歸類至非ST段上升心肌梗塞。另外，有3位(16%)患者ST段上升僅出現在導程I、aVL、aVR，合計共7位(37%)患者，我們將其歸類為少數導程ST段上升(I、AVL、aVR)併廣泛ST段下降型左主冠狀動脈阻塞，常被誤認為單純的側壁或非ST段上升心肌梗塞，輕忽其嚴重性而造成臨床處置的延誤，值得急診醫師及心臟科醫師提高警覺。

關鍵字

左主冠狀動脈；心肌梗塞；心電圖；導程aVR

並列摘要

Electrocardiographic features in patients with acute left main coronary artery obstruction Backgrounds: Myocardial infarction caused by acute left main coronary artery (LM) obstruction is rare, approximately 0.8–2.4% according to previous reports. Patients usually presented as cardiogenic shock, acute pulmonary edema, respiratory failure and life-threatening arrhythmia. It is one of the most severe forms of myocardial infarction. Due to rare incidence and high sudden death rate, reports about acute left main coronary artery obstruction have been scarce. Early diagnosis of left main coronary artery obstruction by specific electrocardiogram (ECG) changes is important and may alert the physician to admit the patient for aggressive therapies including immediate cardiac catheterization and cardiovascular surgeon consultation with equipment of Intra-aortic balloon pump (IABP) and Extra-corporeal membrane oxygenation (ECMO) standby. Urgent coronary artery bypass grafting surgery (CABG) may be preformed to improve clinical outcome. The aim of this study was to analyze electrocardiographic changes in patients with acute myocardial infarction related to left main coronary artery obstruction. Methods: (1) Study population: From March 2003 to February 2009, 19 patients with acute myocardial infarction caused by left main coronary artery obstruction were selected from 4 hospitals as left main disease group (LM group). Another 45 consecutive patients with the culprit lesion located at proximal segment of left anterior descending coronary artery were selected as control group (left anterior descending group, LAD group). (2) Study material: 12-lead electrocardiograms were obtained before emergency coronary angiography and compared between the 2 groups. Statistical analysis: All analyses were performed using statistical software, SPSS 14.0. Continuous variables were compared using an unpaired Student’s t-test. Categorical variables were compared with aχ2 test or Fisher’s exact test. For multivariate analysis, stepwise discriminant analysis was used to compare those dependent variables between the 2 groups. Results: There were no differences between the two groups in baseline characteristics including sex, age, and coronary artery risk factors. Cardiogenic shock occurred with significantly higher incidence in the LM group (68%) than in the LAD group (10%). (p<0.001) In-hospital mortality was significantly higher in the LM group (68% versus 7%, p<0.001). Lead aVR ST-segment elevation (>0.05mV) occurred with a higher incidence in the LM group than in the LAD group (95% versus 18%, p<0.001). Lead aVR ST-segment elevation was significantly higher in the LM group (0.13+0.07mV) than in the LAD group (-0.02+0.06mV). (p<0.001) Lead I, II, aVF, V1-V6 ST-segment depression occurred in higher incidence in the LM group.(p<0.01) Multivariate analysis selected leads aVR, II, and V1 as leads in which ST-segment shift significantly contributed to distinguishing the 2 groups. Among the 3 leads, lead aVR was the strongest predictor of LM obstruction. We attempted to identify predictive factors of mortality in patients with acute LM obstruction. Six of 19 patients survived in the LM group. The incidences of RBBB (54% versus 0%, p =0.044) or cardiogenic shock (92% versus 17%, p=0.003) was significantly higher in the non-survival group. But there were no significant differences between the survival and non-survival groups in baseline characteristics and 12-lead ECG ST-segment shift. Conclusion: In our study, lead aVR ST-segment elevation is the strongest predictor in acute left main coronary artery obstruction. Lead II, aVF ST-segment depression, left axis deviation, RBBB, and lead aVL ST-segment elevation are also ECG features of LM obstruction and may assist in diagnosis. A RBBB pattern in the ECG and cardiogenic shock are significant predictors of in-hospital mortality. However, the sample size in this study is small, further prospective studies with large numbers of patients will be needed to determine predictors for prognosis. According to the ESC/ACC ECG criteria of ST-segment elevation myocardial infarction (STEMI), 4 patients (21%) of the LM group with ST-segment elevation in leads aVL, aVR or AVR, V1 may be classified as Non-ST-segment elevation myocardial infarction (NSTEMI). Another 3 patients (16%) of the LM group with ST-segment elevation in leads I, aVL, aVR may be treated as isolated lateral wall MI or NSTEMI. It is important for emergency physicians and cardiologists to understand the above ECG patterns in acute LM obstruction to avoid misdiagnosis and delay in treatment.

並列關鍵字

Left main coronary artery ； myocardial infarction ； electrocardiogram ； lead aVR

參考文獻

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左主冠狀動脈急性阻塞的心電圖變化

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