背景 冠狀動脈左主幹阻塞可引發急性冠心症或死亡，發生率雖低但後果嚴重，最新報告心電圖上 aVR 之 ST 波昇高有助於左主幹阻塞之早期診斷，注意心電圖之改變，有助於評估及治療此一疾病。方法 從1999年到2003年，本院有22位急性冠心症合併左主幹阻塞患者，這些患者均有冠狀動脈攝影證明及介入性治療。這些患者視左主幹冠狀動脈是否為梗塞相關動脈分成兩組，第一組有9位患者，其梗塞相關動脈為左主幹冠狀動脈或左前降枝的開口，第二組有13位患者，其梗塞相關動脈不是左主幹冠狀動脈或左前降枝的開口，但左主幹冠狀動脈有顯著狹窄。臨床病史、心電圖、心肌酵素及冠狀動脈攝影的變化為分析的要點。結果 心電圖上aVR之ST波段在第一組患者全部都上昇，第二組患者僅有7位有此現象。在輻度上，第一組患者有顯著的上昇。輻度大於0.1 mV必須考慮是左主幹冠狀動脈阻塞的急性冠心症。第一組患者有較高的死亡率及CK-MB。右束傳導障礙也在第一組患者中較常見到。結論 急性冠心症合併左主幹阻塞患者，其心電圖之重要表徵為右束傳導障礙及aVR之ST波段昇高。aVR之ST波段昇高，應疑為左主幹有顯著阻塞。急性冠心症合併aVR之ST波段昇高的患者，應行緊急冠狀動脈攝影及介入性治療。

　　　　　Background: Left main coronary artery (LMCA) occlusion may result in acute coronary syndrome (ACS) or sudden death. ST elevation in lead a VR is reported to be valuable in recognizing LM occlusion. Early recognition of electrocardiogram (ECG) changes, such as ST elevation in a VR, is helpful in averting this disaster.Methods: From January 1999 to August 2003, 22 patients with ACS associated with left main (LM) disease who underwent emergent percutaneous coronary intervention (PCI), were included. Patients were grouped according to the infarct-related artery (IRA). Group I consisted of 9 patients having the LM or LM distal portion with extension to the left anterior descending (LAD) artery orifice as its IRA, while group II included 13 patients who had significant LM stenosis but with a different IRA.Results: ST elevation in a VR was noted in all patients in group I and only 7 patients in group Ⅱ. Its amplitude was significantly higher in group I (p=0.003). An elevation of ＞0.1 mV was strongly predictive of LM occlusion (p=0.004). Right bundle branch block (RBBB) was only seen in group I (p=0.003). Creatine kinase-MB (CK-MB) was also higher in group I (p=0.013).Conclusion: Patients with ACS having the LM as culprit lesion are characterized by RBBB and ST elevation in aVR. ST elevation and its amplitude in aVR are strongly related with LM disease. These patients should undergo emergent coronary arteriogram and intervention.