Coronary Artery Lesions at the Same Site Presenting With Different Electrocardiogram Patterns

Acute total occlusion of the LMCA is a rare and catastrophic event often accompanied by cardiogenic shock and malignant ventricular arrhythmias and can lead to death. For patients with acute total occlusion of the LMCA, and especially those with cardiogenic shock, the primary goal is to perform emergency reperfusion under stabilizing measures, such as insertion of an intra-aortic balloon pump.¹

A literature review showed that there are 3 main ECG patterns of acute total occlusion of the LMCA. The first is typical STEMI. This pattern constitutes typical anterior STE with varying numbers of affected precordial leads, usually with accompanying STE in leads I and aVL.² Additionally, STE starts from V₂ rather than from V₁ in patients with acute total occlusion of the LMCA. In contrast, in cases of ostial occlusion of the proximal left anterior descending coronary artery (LAD), STE is also present in V₁.³ The reason for this discrepancy is that both the LAD and left circumflex coronary artery are occluded in acute total occlusion of the LMCA. As the occlusion of left circumflex coronary artery results in posterior wall myocardial ischemia, STE occurs in leads V₇ to V₉ and reciprocal STD occurs in leads V₁ to V₃, which counteracts STE in lead V₁ caused by LAD occlusion. Therefore, the presence of STE in V₁ supports the diagnosis of isolated proximal LAD occlusion, whereas its absence supports the diagnosis of acute total occlusion of the LMCA. The ECG changes in the present case coincided with this ECG pattern.