Role of Intracoronary OCT in Diagnosis and Treatment of Acute Coronary Syndrome

Coronary angiography is the traditional standard imaging modality for visual evaluation of coronary anatomy and guidance of percutaneous coronary interventions (PCI). However, the 2-dimensional lumenogram cannot depict the arterial vessel per se and plaque characteristics, or directly assess the stenting result. Intracoronary imaging by means of intravascular ultrasound (IVUS) and optical coherence tomography (OCT) provides valuable incremental information that can be used clinically to optimize stent implantation and thereby minimize stent-related problems. Beyond guidance of stent selection and optimisation, imaging provides critical insights into the pathophysiology of acute coronary syndrome (ACS), greater clarity when confronted with angiographically ambiguous lesions and highlights the dynamic nature and significance of atherosclerotic coronary plaque. For several decades, most physicians have believed that ACS is caused by coronary thrombosis resulting from rupture of vulnerable plaque characterized by a thin fibrous cap overlying a large necrotic core and massive inflammatory cell infiltration. However, nearly one-third of ACS cases are caused by plaque erosion characterized by intact fibrous cap, less or absent necrotic core, less inflammation, and large lumen. Because of the limitations of current imaging modalities, including angiography and intravascular ultrasound, the importance of plaque erosion as a cause of acute coronary events is less well known. OCT as an emerging modality with extremely high resolution is the only intravascular imaging modality available for identification of plaque erosion in vivo, which provides new insight into the mechanism of ACS. More importantly, the introduction of OCT to clinical practice enables us to differentiate the patients with ACS caused by plaque erosion from those caused by plaque rupture, thereby providing precise and personalized therapy based on the different underlying mechanisms. This presentation will systematically review the morphological characteristics of plaque erosion identified by OCT and its implications for the management of ACS.