Along with symptoms of chest pain, the presence of ST segment elevations on ECG is the criterion usually used in practice to identify patients with acute coronary artery occlusion and is essential for the direct and acute referral of patients for primary PCI. However, ECG does not always reflect changes in the posterior wall of the heart, often equivalent to the left circumflex coronary artery's (LCX) supply area, resulting in an underrepresentation of LCX as culprit artery in STEMI populations. There is a general concern that some patients with genuine acute occlusion of LCX may present without ST segment elevation and be denied reperfusion therapy, resulting in larger infarction and worse outcome.