Characterization of coronary atherosclerosis by intravascular imaging modalities

Abstract

Coronary artery disease (CAD) is highly prevalent in Western countries and is associated with morbidity, mortality, and a significant economic burden. Despite the development of anti-atherosclerotic medical therapies, many patients still continue to suffer from coronary events. This residual risk indicates the need for better risk stratification and additional therapies to achieve more reductions in cardiovascular risk.Recent advances in imaging modalities have contributed to visualizing atherosclerotic plaques and defining lesion characteristics in vivo. This innovation has been applied to refining revascularization procedure, assessment of anti-atherosclerotic drug efficacy and the detection of high-risk plaques. As such, intravascular imaging plays an important role in further improvement of cardiovascular outcomes in patients with CAD.The current article reviews available intravascular imaging modalities with regard to its method, advantage and disadvantage.

Coronary Atherosclerosis Imaging

“…Calcified plaques appear echo-dense (hyperechoic) and brighter than the surrounding adventitia. Some grey-scale IVUS signal intensity features have been associated with histological features of plaque instability and high risk of CAD: plaque with ultrasonic attenuation (echoattenuated plaque), associated with fibroatheroma containing large necrotic core; echo-lucent plaque, containing an intraplaque zone of absent echogenicity, correlated with small necrotic core; spotty calcification and calcified nodule, both associated with acute coronary events [104,105]. However, the grey-scale atheromatous plaque classification is limited by the IVUS axial and lateral resolution (about 200 microns), not sufficient to visualize some components of the vulnerable plaque, such as microcalcifications or the TCFA which are usually smaller than 60 microns.…”

“…It is also limited by the inability to penetrate calcification and to assess the composition and inflammatory state of the fibrous cap [106]. To improve the IVUS analysis of atherosclerotic plaque components, computer-assisted radiofrequency analysis of the reflected ultrasound signals have been developed in recent years to visualize color-coded plaque composition, including fibroatheroma, necrotic core, TCFA and dense calcification [104][105][106]. In addition to the greyscale IVUS, the colour coded virtual histology IVUS (VH-IVUS), based on the modulation of the frequency of the backscattered ultrasound waves, provides a detailed analysis of plaque composition and has been validated in vivo and in postmortem specimens.…”

“…In addition to the greyscale IVUS, the colour coded virtual histology IVUS (VH-IVUS), based on the modulation of the frequency of the backscattered ultrasound waves, provides a detailed analysis of plaque composition and has been validated in vivo and in postmortem specimens. [104,[107][108][109].…”

“…High sensitivity and specificity has been demonstrated for fibrous, fibrocalcific, and lipid-rich plaques [112]. Also, OCT is considered the only imaging modality that can directly measure TCFA and quantify the presence of macrophages and cholesterol crystal in the atherosclerotic plaque [20,104,[113][114][115]. OCT imaging of contemporary presence of macrophages and microcalcifications in the same plaque with reciprocal distance smaller than 1 mm (termed co-localization), has been shown to be associated with more vulnerable plaque features [116,117].…”

Prediction of cardiovascular outcomes by imaging coronary atherosclerosis

“…As detailed reviews on various invasive and non-invasive imaging modalities for coronary atherosclerosis have been reported in this issue of the journal (1,2), this article will focus on their prognostic value. The main outcomes can be divided into long-term outcomes, such subsequent major adverse cardiovascular event (MACE); and more immediate peri-procedural outcomes such as distal embolization, peri-procedural myocardial infraction and no reflow.…”