Cardiovascular Imaging Techniques for Detection of Vulnerable Plaques

Various cardiovascular imaging techniques were developed for the detection of vulnerable atherosclerotic plaques, hoping to be able to predict a cardiovascular event. Plaque vulnerability results from compound pathophysiological mechanisms that lead to structural and morphological changes in lesions. The aim of this review is to present the most recent techniques for the assessment of vulnerable coronary plaques such as cardiac computed tomography angiography (CCTA), optical coherence tomography, or virtual histology intravascular ultra-sound, based on literature data from the last 3 years. CCTA permits direct visualization of the intravascular lumen, together with characterization of the arterial wall. Recent studies maintain that low-attenuation plaques, spotty calcifications, positive vessel remodeling, and the napkin-ring sign are considered main markers of plaque vulnerability and instability. Emerging analytical techniques, such as machine learning or radiomics, will probably demonstrate useful as an auxiliary diagnostic tool for vulnerable plaque detection. The data from the two imaging techniques together provide useful information, especially in patients undergoing a PCI procedure for an acute coronary syndrome. Invasive and noninvasive imaging techniques are able to deliver a large amount of scientific data to assess vulnerable coronary atheromatous plaques. Recent studies demonstrated that information defined by the two techniques is complementary, and using both methods is essential for adequate diagnosis, therapeutic strategy, and prognostic assessment.

Intracoronary Imaging for Assessment of Vascular Healing and Stent Follow-up in Bioresorbable Vascular Scaffolds

Bioresorbable Vascular Scaffolds (BVS) are polymer-based materials implanted in the coronary arteries in order to treat atherosclerotic lesions, based on the concept that once the lesion has been treated, the material of the implanted stent will undergo a process of gradual resorption that will leave, in several years, the vessel wall smooth, free of any foreign material and with its vasomotion restored. However, after the first enthusiastic reports on the efficacy of BVSs, the recently published trials demonstrated disappointing results regarding long-term patency following BVS implantation, which were mainly attributed to technical deficiencies during the stenting procedure. Intracoronary imaging could play a crucial role for helping the operator to correctly implant a BVS into the coronary artery, as well as providing relevant information in the follow-up period. This review aims to summarize the role of intracoronary imaging in the follow-up of coronary stents, with a particular emphasis on the role of intravascular ultrasound and optical coherence tomography for procedural guidance during stent implantation and also for follow-up of bioabsorbable scaffolds.

The Effect of Periplaque Fat on Coronary Plaque Vulnerability in Patients with Stable Coronary Artery Disease – a 128-multislice CT-based Study

Background: The role of periplaque fat (PPF), as a fragment of the total epicardial adipose tissue, measured in the vicinity of a target coronary lesion, more specifically within the close proximity of a vulnerable plaque, has yet to be evaluated.

The study aimed to evaluate the interrelation between PPF and coronary plaque vulnerability in patients with stable coronary artery disease (CAD). Secondary objective: evaluation of the relationship between the total pericardial fat and markers for plaque vulnerability.

Materials and methods: We prospectively enrolled 77 patients with stable CAD, who underwent 128-multislice computed tomography coronary angiography (CTCA), and who presented minimum one lesion with >50% stenosis. CTCA analysis included measurements of: total pericardial fat and PPF volumes, coronary plaque characteristics, markers for plaque vulnerability – positive remodeling (PR), low attenuation plaque (LAP), spotty calcifications (SC,) napkin ring sign (NRS). Study subjects were divided into two categories: Group 1 – 1 marker of plaque vulnerability (n = 36, 46.75%) and Group 2 – ≥1 marker of vulnerability (n = 41, 53.25%).

Results: The mean age of the population was 61.77 ± 11.28 years, and 41 (53.24%) were males. The analysis of plaque characteristics showed that Group 2 presented significantly longer plaques (16.26 ± 4.605 mm vs. 19.09 ± 5.227 mm, p = 0.02), remodeling index (0.96 ± 0.20 vs. 1.18 ± 0.33, p = 0.0009), and vessel volume (p = 0.027), and more voluminous plaques (147.5 ± 71.74 mm3 vs. 207.7 ± 108.9 mm3, p = 0.006) compared to Group 1. Group 2 presented larger volumes of PPF (512.2 ± 289.9 mm3 vs. 710.9 ± 361.9 mm3, p = 0.01) and of thoracic fat volume (1,616 ± 614.8 mm3 vs. 2,000 ± 850.9 mm3, p = 0.02), compared to Group 1, but no differences were found regarding the total pericardial fat (p = 0.49). Patients with 3 or 4 vulnerability markers (VM) presented significantly larges PPF volumes compared to those with 1 or 2 VM, respectively (p = 0.008). There was a significant positive correlation between PPF volume and the non-calcified (r = 0.474, 95% CI 0.2797–0.6311, p <0.0001), lipid-rich (r = 0.316, 95% CI 0.099–0.504, p = 0.005), and fibro-fatty (r = 0.452, 95% CI 0.2541–0.6142, p <0.0001) volumes. The total pericardial fat was significantly correlated only with the volume of lipid-rich plaques (p = 0.02).

Conclusions: Periplaque fat volume was associated with a higher degree of coronary plaque vulnerability. PPF was correlated with lipid-rich, fibro-fatty, and non-calcified plaque-related volumes, as markers for enhanced plaque vulnerability. PPF volume, assessed with native cardiac computed tomography, could become a novel marker for coronary plaque vulnerability.

Intracoronary Imaging in the Management of a Complex and Recurrent Acute Coronary Syndrome Associated With Multiple Comorbidities. A Case Report

Coronary artery disease represents a major cause of morbidity and mortality around the world. Unstable angina pectoris is a serious manifestation of ischemic heart disease and represents an acute condition caused by the narrowing of the coronary lumen as the result of an atheromatous plaque formation. In most cases the trigger of this process is represented by the rupture of a plaque that has become vulnerable or unstable. The first-line intracoronary imaging technique for the evaluation of plaque vulnerability is optical coherence tomography, which can measure the thickness of the fibrous cap (a significant predictor of plaque vulnerability) and can also assess other characteristics of plaque vulnerability (macrophage infiltration, lipid pool, intracoronary thrombus, or neointimal rupture). We present the case of a 67-year-old male with symptoms suggestive of unstable angina pectoris, caused by the presence of a vulnerable plaque on the left main coronary artery, where optical coherence tomography had a significant contribution in identifying the etiology of chest pain.

Original research. The Assessment of Epicardial Adipose Tissue in Acute Coronary Syndrome Patients. A Systematic Review

Background: This systematic review seeks to evaluate the role of epicardial adipose tissue (EAT), quantified either by thickness, assessed by transthoracic echocardiography, or by volume, assessed by cardiac computed tomography (CT), in the follow-up of patients with acute coronary syndromes (ACS). Method: One-hundred forty-four articles were screened, from which 56 were reviewed in full-text. From those, 47 studies were excluded for the following reasons: they did not meet the inclusion criteria; they were either reviews or meta-analyses; the study cohorts included only stable coronary artery disease patients; they did not state a clear and concise study design, endpoints, or follow-up. The final draft included nine studies for systematic evaluation. Results: Of the 2,306 patients included in the review, 170 underwent cardiac CT while the remaining 2,136 underwent transthoracic echocardiography for the measurement of EAT. The analysis found that the EAT thickness was significantly associated with major adverse cardiovascular events (MACE) rates during hospitalization (OR: -1.3, 95% CI: 1.05-1.62, p = 0.020) and at three years (HR: 1.524, 95% CI: 1.0-2.2, p = 0.038). The included studies found that EAT was correlated with the following clinical and angiographic risk scores for ACS: GRACE (r = 0.438, p <0.001), TIMI risk score (r = 0.363, p = 0.001), SYNTAX score (r = 0.690, p <0.0001; r = 0.610, p <0.01), and Gensini score (r = 0.438, p = 0.001). There was an inverse correlation between ST-segment resolution of <70% after revascularization and EAT (r = −0.414, p = 0.01), and the myocardial blush grade (r = −0.549, p <0.001). The EF aggregation ranged between 2.65 mm and 4.7 mm within the included studies. Conclusions: EAT, evaluated either by echocardiography or cardiac CT, correlates with the severity of coronary lesions, with the clinical and angiographic risk scores for acute coronary syndromes, with indicators for coronary reperfusion, and with short- and long-term MACE rates. Further studies are required to fully elucidate the role of this extensively studied but still novel cardiovascular biomarker as part of a risk prediction tool.

Review. Automatic Segmentation Techniques of the Coronary Artery Using CT Images in Acute Coronary Syndromes

Coronary artery disease represents one of the leading reasons of death worldwide, and acute coronary syndromes are their most devastating consequences. It is extremely important to identify the patients at risk for developing an acute myocardial infarction, and this goal can be achieved using noninvasive imaging techniques. Coronary computed tomography angiography (CCTA) is currently one of the most reliable methods used for assessing the coronary arteries; however, its use in emergency settings is sometimes limited due to time constraints. This paper presents the main characteristics of plaque vulnerability, the role of CCTA in the assessment of vulnerable plaques, and automatic segmentation techniques of the coronary artery tree based on CT angiography images. A detailed inventory of existing methods is given, representing the state-of-the-art of computational methods applied in vascular system segmentation, focusing on the current applications in acute coronary syndromes.