Acute Coronary Syndrome: Insights Based on Intravascular Imaging

Intravascular imaging devices can offer information about vessels that cannot be depicted by angiography. Intravascular ultrasound (IVUS) can image the trilaminar structure of vessel walls and not only enable quantitative analysis, but also tissue characterization by radiofrequency data analysis. Coronary angioscopy provides full color images as direct visualization of the coronary lumen, and the images are applicable to the macroscopic diagnosis of intracoronary structures. Optical coherence tomography (OCT) is a novel optical imaging technology that provides cross-sectional tomographic images that yield detailed structural information superior to any other currently available modality. These intravascular imaging devices have played an important role both in the elucidation of the pathology of coronary artery disease and in the guidance of clinical treatment. Rupture of atherosclerotic plaque and the overlying thrombus is often observed in culprit lesions of acute coronary syndrome (ACS). In vivo, intravascular imaging devices can show detailed morphology of the culprit lesion that is associated with the clinical presentation and the prognosis. Rupture-prone plaques are called “vulnerable plaques.” Identification of vulnerable plaques has been attempted over the years. Prospective studies have shown that thin cap fibroatheroma (TCFA), defined by different intravascular imaging devices, is related to future cardiac events. Furthermore, multiple vulnerable plaques are often observed in non–culprit arteries of ACS patients. Therefore, ACS is recognized to represent a pan-coronary process of vulnerable plaque development. In addition, the multiplicity of vulnerable plaques was also demonstrated to be a predictor of ACS events. Some cardiac biomarkers, which are reported to be predictors of ACS events, are associated with the characterization of culprit and non-culprit arteries in ACS patients. On the other hand, the detailed findings obtained by intravascular imaging devices play an important role to prove the validity of noninvasive coronary artery studies. Near-infrared spectroscopy and coronary thermography can reveal plaque vulnerability by detecting inflammation and by quantifying the molecular composition of the plaque. The introduction of new technologies will increase our understanding of the pathophysiology and prevention of ACS.