Current Advances in the Diagnostic Imaging of Atherosclerosis: Insights into the Pathophysiology of Vulnerable Plaque

Abstract

Atherosclerosis is a lipoprotein-driven inflammatory disorder leading to a plaque formation at specific sites of the arterial tree. After decades of slow progression, atherosclerotic plaque rupture and formation of thrombi are the major factors responsible for the development of acute coronary syndromes (ACSs). In this regard, the detection of high-risk (vulnerable) plaques is an ultimate goal in the management of atherosclerosis and cardiovascular diseases (CVDs). Vulnerable plaques have specific morphological features that make their detection possible, hence allowing for identification of high-risk patients and the tailoring of therapy. Plaque ruptures predominantly occur amongst lesions characterized as thin-cap fibroatheromas (TCFA). Plaques without a rupture, such as plaque erosions, are also thrombi-forming lesions on the most frequent pathological intimal thickening or fibroatheromas. Many attempts to comprehensively identify vulnerable plaque constituents with different invasive and non-invasive imaging technologies have been made. In this review, advantages and limitations of invasive and non-invasive imaging modalities currently available for the identification of plaque components and morphologic features associated with plaque vulnerability, as well as their clinical diagnostic and prognostic value, were discussed.

Keywords: atherosclerosis; invasive imaging; non-invasive imaging; vulnerable plaque.

Figure 1

The utility of grayscale IVUS, VH-IVUS, OCT, and NIRS in the visualization of a vulnerable plaque. Note: IVUS—intravascular ultrasound; NIRS—near infrared spectroscopy; OCT—optical coherence tomography; PB—plaque burden; TCFA—thin-cap fibroatheroma; VH-IVUS—virtual histology intravascular ultrasound.

Figure 2

Schematic representation of morphological components of a vulnerable plaque that can be detected both by invasive and non-invasive imaging modalities. Note: CT—computed tomography; FLIM—fluorescence lifetime imaging microscopy; IVPA—intravascular photoacoustic imaging; IVUS—intravascular ultrasound; MRI—magnetic resonance imaging; NIRF—near-infrared fluorescence; NIRS—near infrared spectroscopy; OCT—optical coherence tomography; PET—positron emission tomography.