Most acute coronary syndromes (ACS) are caused by plaque complications triggering thrombotic events in the culprit plaques. Plaque complications include plaque rupture (Ruptured Fibrous Cap-RFC) with exposure of highly thrombogenic substrate to the flow and plaque erosion (Intact Fibrous Cap-IFC) a condition characterized by endothelial/intimal damage occurring over non-ruptured plaques. Far less commonly (\<5%), calcified nodules (CN) may trigger acute coronary thrombosis. Plaque rupture accounts for 75% of fatal AMI in autopsy series, while erosion is found in about 25% of cases. These proportions have been supported by in vivo invasive studies (OCT) and OCT-pathology correlation studies. However, it remains unclear whether OCT findings consistently align with in vivo pathology-based evidence of RFC in ACS. Guidelines addressing treatments of ACS unanimously indicate percutaneous coronary intervention (PCI) to restore the coronary flow. Pre-PCI thrombus aspiration is not currently indicated by most guidelines, with the exception of cases with very high thrombus burden. The samples retrieved from thrombus aspiration can be suitable for pathology investigation and aim to evaluate the presence of plaque components in the context of the thrombotic material, a finding that demonstrates plaque rupture as the substrate for the acute coronary event. These studies are uniquely qualified to provide information on the correct OCT-based interpretation of plaque complications in ACS and require OCT imaging quality suitable to classify RFC, IFC, and CN. Therefore, a prospective OCT-pathology study was designed using the pre-PCI aspirated material from patients with high thrombus burden, to explore the contribution of pathology study in OCT-based classification of plaque complications.