Today's concept of vulnerable plaque has evolved primarily from the early pioneering work uncovering the pivotal role of plaque rupture and coronary thrombosis as the major cause of acute myocardial infarction and sudden cardiac death. Since the first historical description of plaque rupture in 1844, several key studies by leading researchers and clinicians have lead to the current accepted views on lesion instability. Important to the complex paradigm of plaque destabilization and thrombosis are many discoveries beginning with the earliest descriptions of advanced plaques, reminiscent of abscesses encapsulated by fibrous tissue capable of rupture. It was not until the late 1980s that studies of remodeling provided keen insight into the growth of advanced plaques, beyond the simple accumulation of lipid. The emphasis in the next decade, however, was on a focused shift toward the mechanisms of lesion vulnerability based on the contribution of tissue proteolysis by matrix metalloproteinases as an essential factor responsible for thinning and rupture of the fibrous cap. In an attempt to unify the understanding of what constitutes a vulnerable plaque, morphological studies, mostly from autopsy, suggest the importance of necrotic core size, inflammation, and fibrous cap thickness. Definitive proof of the vulnerable plaque, however, remains elusive because animal or human data supporting a cause-and-effect relationship are lacking. Although emerging imagining technologies involving optical coherence tomography, high-resolution MRI, molecular biomarkers, and other techniques have far surpassed the limits of the early days of angiography, advancing the field will require establishing relevant translational animal models that produce vulnerable plaques at risk for rupture and further testing of these modalities in large prospective clinical trials.

Concept of Vulnerable/Unstable Plaque

Multislice computed tomographic characteristics of coronary lesions in acute coronary syndromes.

https://www.incor.usp.br/sites/cardiopneumo.259/images/Assessment_of_Culprit_Lesion_Morphology_in_Acute_Myocardial_Infarction.pdf

Assessment of culprit lesion morphology in acute myocardial infarction: ability of optical coherence tomography compared with intravascular ultrasound and coronary angioscopy.

Optical coherence tomography (OCT) is a novel intravascular imaging modality, based on infrared light emission, that enables a high resolution arterial wall imaging, in the range of 10-20 microns. This feature of OCT allows the visualization of specific components of the atherosclerotic plaques. The aim of the present Expert Review Document is to address the methodology, terminology and clinical applications of OCT for qualitative and quantitative assessment of coronary arteries and atherosclerosis.

/pdf/expert-review-document-on-methodology-terminology-and-4ad06l4hyg.pdf

Expert review document on methodology, terminology, and clinical applications of optical coherence tomography: Physical principles, methodology of image acquisition, and clinical application for assessment of coronary arteries and atherosclerosis

The purpose of this study was to analyze the ability of optical coherence tomography (OCT) to identify coronary arterial plaque diagnosed by histologic examination. We examined 166 sections from 108 coronary arterial segments of 40 consecutive human cadavers (24 men and 16 women; mean age 74 ± 7 years). The plaque type was classified as fibrous (n = 43), fibrocalcific (n = 82), or lipid-rich (n = 41). The accuracy of OCT and intravascular ultrasound (IVUS) in characterizing the plaque type was studied, with the histologic consensus diagnosis serving as the gold standard. OCT, as well as IVUS, had high sensitivity and specificity for characterizing the different types of atherosclerotic plaque. OCT had a higher sensitivity for characterizing lipid-rich plaques than IVUS (85% vs 59%, p = 0.03). In conclusion, the high resolution of OCT permitted evaluation of lipid-rich plaques more accurately than IVUS.

Assessment of Coronary Arterial Plaque by Optical Coherence Tomography

Background— The current understanding of the pathophysiology of coronary artery disease is based largely on postmortem studies. Optical coherence tomography (OCT) is a high-resolution (≈10 μm), catheter-based imaging modality capable of investigating detailed coronary plaque morphology in vivo. Methods and Results— Patients undergoing cardiac catheterization were enrolled and categorized according to their clinical presentation: recent acute myocardial infarction (AMI), acute coronary syndromes (ACS) constituting non-ST-segment elevation AMI and unstable angina, or stable angina pectoris (SAP). OCT imaging was performed with a 3.2F catheter. Two observers independently analyzed the images using the previously validated criteria for plaque characterization. Of 69 patients enrolled, 57 patients (20 with AMI, 20 with ACS, and 17 with SAP) had analyzable images. In the AMI, ACS, and SAP groups, lipid-rich plaque (defined by lipid occupying ≥2 quadrants of the cross-sectional area) was observed in 90%, 75%, an...

Nicusor Iftima

Papers

In Vivo Characterization of Coronary Atherosclerotic Plaque by Use of Optical Coherence Tomography