 Current guideline for treating acute STEMI is primarily PCI and stent placement in the infarct-related coronary artery. But, the underlying plaque morphology is not routinely identified due to the limited resolution of conventional imagine modalities. However, autopsy studies have shown that there are different atherosclerotic plaque morphologies involving in acute thrombotic occlusion of coronary arteries other than atherosclerotic plaque rupture, such as plaque erosion, calcified nodule, etc. Some studies have suggested that PCI and stenting might not always be necessary in about 30 - 40 of ACS patients, and an alternative treatment strategy is needed for these patients based on the characteristics of plaque morphology. 