Accuracy of In Vivo Coronary Plaque Morphology Assessment

Inflammation in coronary atherosclerosis: diagnosis and treatment

Coronary atherosclerosis is a chronic condition characterised by the development of an atherosclerotic plaque in the inner layer of the coronary artery, mainly associated with cholesterol accumulation and favoured by endothelial dysfunction related to other cardiovascular risk factors, such as smoking, diabetes and hypertension. A key actor in this process is the systemic inflammatory response, which can make plaques either grow slowly over the course of years (like a 'mountain'), obstructing coronary flow, and causing stable coronary artery disease, or make them explode (like a 'volcano') with subsequent abrupt thrombosis causing an acute coronary syndrome. This central role of inflammation in coronary atherosclerosis has led to its consideration as a modifiable cardiovascular risk factor and a therapeutic target. Classic anti-inflammatory drugs have been tested in clinical trials with some encouraging results, and new drugs specifically designed to tackle inflammation are currently being under investigation in ongoing trials. The objectives of this review are to (1) summarise the role of inflammatory biomarkers and imaging techniques to detect inflammation at each stage of plaque progression, and (2) explore currently available and upcoming anti-inflammatory therapies.

Perspectives in the Diagnosis, Clinical Impact, and Management of the Vulnerable Plaque

Coronary artery disease is a highly prevalent disease that constitutes the leading cause of mortality worldwide. Acute coronary syndromes are the most devastating form of presentation of coronary disease, involving the acute formation of a thrombus within the coronary vessel lumen, further leading to flow limitation and diminished myocardial perfusion. Vulnerable plaques, which are characterized by thin-cap fibroatheroma, a large lipid pool, and macrophage infiltration and spotty calcification of the cap, pose a higher risk of coronary events despite not being flow-limiting. Iterations in intravascular imaging and coronary computed tomography have largely increased the ability to detect and define vulnerable plaques, and its clinical impact in early- and mid-term outcomes has been confirmed in several studies. In this review, we aimed to revise the current concept of vulnerable coronary plaque and its repercussion, to summarize the main pharmacological approaches for its management, and to provide an updated overview of the available evidence on preventive percutaneous interventional strategies in this clinical setting.

Automated Classification of Coronary Plaque on Intravascular Ultrasound by Deep Classifier Cascades

Intravascular ultrasound (IVUS) is the gold standard modality for in vivo visualization of coronary arteries and atherosclerotic plaques. Classification of coronary plaques helps to characterize heterogeneous components and evaluate the risk of plaque rupture. Manual classification is time-consuming and labor-intensive. Several machine learning-based classification approaches have been proposed and evaluated in recent years. In the current study, we develop a novel pipeline composed of serial classifiers for distinguishing IVUS images into five categories: normal, calcified plaque, attenuated plaque, fibrous plaque, and echolucent plaque. The cascades comprise densely connected classification models and machine learning classifiers at different stages. Over 100000 IVUS frames of five different lesion types were collected and labeled from 471 patients for model training and evaluation. The overall accuracy of the proposed classifier is 0.877, indicating that the proposed framework has the capacity to identify the nature and category of coronary plaques in IVUS images. Furthermore, it may provide real-time assistance on plaque identification and facilitate clinical decision-making in routine practice.

Innovations in Intracoronary Imaging: Present Clinical Practices and Future Outlooks

Engaging intracoronary imaging (IC) techniques such as intravascular ultrasound or optical coherence tomography enables the precise description of vessel architecture. These imaging modalities have well-established roles in providing guidance and optimizing percutaneous coronary intervention (PCI) outcomes. Furthermore, IC is increasingly recognized for its diagnostic capabilities, as it has the unique capacity to reveal vessel wall characteristics that may not be apparent through angiography alone. This manuscript thoroughly reviews the contemporary landscape of IC in clinical practice. Focused on current methodologies, the review explores the utility and advancements in IC techniques. Emphasizing their role in clarifying coronary pathophysiology, guiding PCI, and optimizing patient outcomes, the manuscript critically evaluates the strengths and limitations of each modality. Additionally, the integration of IC into routine clinical workflows and its impact on decision-making processes are discussed. By synthesizing the latest evidence, this review provides valuable insights for clinicians, researchers, and healthcare professionals involved in the dynamic field of interventional cardiology.

Endovascular Drug Delivery

Drug-eluting stents (DES) and balloons revolutionize atherosclerosis treatment by targeting hyperplastic tissue responses through effective local drug delivery strategies. This review examines approved and emerging endovascular devices, discussing drug release mechanisms and their impacts on arterial drug distribution. It emphasizes the crucial role of drug delivery in modern cardiovascular care and highlights how device technologies influence vascular behavior based on lesion morphology. The future holds promise for lesion-specific treatments, particularly in the superficial femoral artery, with recent CE-marked devices showing encouraging results. Exciting strategies and new patents focus on local drug delivery to prevent restenosis, shaping the future of interventional outcomes. In summary, as we navigate the ever-evolving landscape of cardiovascular intervention, it becomes increasingly evident that the future lies in tailoring treatments to the specific characteristics of each lesion. By leveraging cutting-edge technologies and harnessing the potential of localized drug delivery, we stand poised to usher in a new era of precision medicine in vascular intervention.

Coronary atherosclerotic plaque phenotype and physiopathologic mechanisms: Is there an influence of sex? Insights from intracoronary imaging

Coronary artery disease (CAD) is the leading cause of disability and death in both women and men; considerable differences in clinical presentation, natural history and prognosis are reported between sexes. Different pathophysiological mechanisms play a major role, including sex-related and gender-related features or a combination of both. Reports from intracoronary imaging studies pointed towards morphological plaque features, which seemed to differ between men and women, albeit results reported so far were not conclusive. The purpose of this review is to shed light on differences in the pathophysiology underlying CAD in women vs men including the description of coronary plaque phenotype and mechanisms of plaque instability, as assessed by intracoronary imaging. We will also discuss potential clinical implications with the aim to move towards a sex and gender-based personalized approach in CAD patients.

Intravascular ultrasonography assisted carotid artery stenting for treatment of carotid stenosis: Two case reports

BACKGROUND

Digital subtraction angiography (DSA), the gold standard of cerebrovascular disease diagnosis, is limited in its diagnostic ability to evaluate arterial diameter. Intravascular ultrasonography (IVUS) has advantages in assessing stenosis and plaque nature and improves the evaluation and effectiveness of carotid artery stenting (CAS).

CASE SUMMARY

Case 1: A 65-year-old man presented with a five-year history of bilateral lower limb weakness due to stroke. Physical examination showed decreased strength (5-/5) in both lower limbs. Carotid artery ultrasound, magnetic resonance angiography, and computed tomography angiography (CTA) showed a right proximal internal carotid artery (ICA) stenosis (70%-99%), acute cerebral infarction, and severe right ICA stenosis, respectively. We performed IVUS-assisted CAS to measure the stenosis and detected a low-risk plaque at the site of stenosis prior to stent implantation. Post-stent balloon dilatation was performed and postoperative IVUS demonstrated successful expansion and adherence. CTA six months postoperatively showed no significant increase in in-stent stenosis. Case 2: A 36-year-old man was admitted with a right common carotid artery (CCA) dissection detected by ultrasound. Physical examination showed no positive neurological signs. Carotid ultrasound and CTA showed lumen dilation in the proximal CCA with an intima-like structure and bulging in the proximal segment of the right CCA with strip-like low-density shadow (dissection or carotid web). IVUS-assisted DSA confirmed right CCA dissection. CAS was performed and intraoperative IVUS suggested a large residual false lumen. Post-stent balloon dilatation was performed reducing the false lumen. DSA three months postoperatively indicated good stent expansion with mild stenosis.

CONCLUSION

IVUS aids decision-making during CAS by accurately assessing carotid artery wall lesions and plaque nature preoperatively, dissection and stenosis morphology intraoperatively, and visualizing and confirming CAS postoperatively.

Isolated Coronary Arteritis in Adults: a Single-Center Experience from China

Isolated coronary arteritis (ICA) is an extremely rare and life-threatening vasculitis with only a limited number of reports in the literature. We retrospectively reviewed the clinical data of 10 ICA patients in our center from 2012 to 2022 and compared them with patients with Takayasu arteritis who presented with coronary arteritis initially (TAK-CA patients). We found that ICA predominantly affected women and most commonly involved the ostium and the proximal segment of the coronary arteries, causing mainly stenotic lesions. The C-reactive protein and erythrocyte sedimentation rate were grossly normal and significantly lower than those of TAK-CA patients (p = 0.027, p = 0.009, respectively). Intravascular ultrasound imaging showed superiority in differentiating coronary vasculitis from atherosclerosis. Restenosis of the coronary arteries occurred rapidly if not treated promptly and appropriately. Systemic glucocorticoid combined with immunosuppressive agents, especially cyclophosphamide, was a promising strategy for treating ICA.

Novel Imaging-Based Biomarkers for Identifying Carotid Plaque Vulnerability

Carotid artery disease has traditionally been assessed based on the degree of luminal narrowing. However, this approach, which solely relies on carotid stenosis, is currently being questioned with regard to modern risk stratification approaches. Recent guidelines have introduced the concept of the "vulnerable plaque," emphasizing specific features such as thin fibrous caps, large lipid cores, intraplaque hemorrhage, plaque rupture, macrophage infiltration, and neovascularization. In this context, imaging-based biomarkers have emerged as valuable tools for identifying higher-risk patients. Non-invasive imaging modalities and intravascular techniques, including ultrasound, computed tomography, magnetic resonance imaging, intravascular ultrasound, optical coherence tomography, and near-infrared spectroscopy, have played pivotal roles in characterizing and detecting unstable carotid plaques. The aim of this review is to provide an overview of the evolving understanding of carotid artery disease and highlight the significance of imaging techniques in assessing plaque vulnerability and informing clinical decision-making.

Invasive Intracoronary Imaging of Cardiac Allograft Vasculopathy: Established Modalities and Emerging Technologies

Despite advances in the care of heart transplant recipients during the past 5 decades, cardiac allograft vasculopathy (CAV) continues to be a major barrier to long-term survival. The early diagnosis and treatment of CAV is crucial for improving long-term outcomes. Coronary angiography, the current gold standard for CAV screening, has low sensitivity for detecting early CAV. Increasingly, invasive intracoronary imaging modalities that provide a more detailed analysis of vessel anatomy and allow for plaque characterization are being used to detect CAV earlier after transplant and uncover mechanistic insights. Studies validating these emerging imaging platforms are needed before their widespread adoption.

Assessing engineered tissues and biomaterials using ultrasound imaging: In vitro and in vivo applications

Quantitative assessment of the structural, functional, and mechanical properties of engineered tissues and biomaterials is fundamental to their development for regenerative medicine applications. Ultrasound (US) imaging is a non-invasive, non-destructive, and cost-effective technique capable of longitudinal and quantitative monitoring of tissue structure and function across centimeter to sub-micron length scales. Here we present the fundamentals of US to contextualize its application for the assessment of biomaterials and engineered tissues, both in vivo and in vitro. We review key studies that demonstrate the versatility and broad capabilities of US for clinical and pre-clinical biomaterials research. Finally, we highlight emerging techniques that further extend the applications of US, including for ultrafast imaging of biomaterials and engineered tissues in vivo and functional monitoring of stem cells, organoids, and organ-on-a-chip systems in vitro.

Quantification of patient-specific coronary material properties and their correlations with plaque morphological characteristics: An in vivo IVUS study

BACKGROUND

A method using in vivo Cine IVUS and VH-IVUS data has been proposed to quantify material properties of coronary plaques. However, correlations between plaque morphological characteristics and mechanical properties have not been studied in vivo.

METHOD

In vivo Cine IVUS and VH-IVUS data were acquired at 32 plaque cross-sections from 19 patients. Six morphological factors were extracted for each plaque. These samples were categorized into healthy vessel, fibrous plaque, lipid-rich plaque and calcified plaque for comparisons. Three-dimensional thin-slice models were constructed using VH-IVUS data to quantify in vivo plaque material properties following a finite element updating approach by matching Cine IVUS data. Effective Young's moduli were calculated to represent plaque stiffness for easy comparison. Spearman's rank correlation analysis was performed to identify correlations between plaque stiffness and morphological factor. Kruskal-Wallis test with Bonferroni correction was used to determine whether significant differences in plaque stiffness exist among four plaque groups.

RESULT

Our results show that lumen circumference change has a significantly negative correlation with plaque stiffness (r = -0.7807, p = 0.0001). Plaque burden and calcification percent also had significant positive correlations with plaque stiffness (r = 0.5105, p < 0.0272 and r = 0.5312, p < 0.0193) respectively. Among the four categorized groups, calcified plaques had highest stiffness while healthy segments had the lowest.

CONCLUSION

There is a close link between plaque morphological characteristics and mechanical properties in vivo. Plaque stiffness tends to be higher as coronary atherosclerosis advances, indicating the potential to assess plaque mechanical properties in vivo based on plaque compositions.

Coronary artery properties in atherosclerosis: A deep learning predictive model

In this work an Artificial Neural Network (ANN) was developed to help in the diagnosis of plaque vulnerability by predicting the Young modulus of the core (E _core ) and the plaque (E _plaque ) of atherosclerotic coronary arteries. A representative in silico database was constructed to train the ANN using Finite Element simulations covering the ranges of mechanical properties present in the bibliography. A statistical analysis to pre-process the data and determine the most influential variables was performed to select the inputs of the ANN. The ANN was based on Multilayer Perceptron architecture and trained using the developed database, resulting in a Mean Squared Error (MSE) in the loss function under 10^-7, enabling accurate predictions on the test dataset for E _core and E _plaque . Finally, the ANN was applied to estimate the mechanical properties of 10,000 realistic plaques, resulting in relative errors lower than 3%.

Intracoronary Imaging of Vulnerable Plaque-From Clinical Research to Everyday Practice

The introduction into clinical practice of intravascular imaging, including intravascular ultrasound (IVUS), optical coherence tomography (OCT) and their derivatives, allowed for the in vivo assessment of coronary atherosclerosis in humans, including insights into plaque evolution and progression process. Intravascular ultrasound, the most commonly used intravascular modality in many countries, due to its low resolution cannot assess many features of vulnerable plaque such as lipid plaque or thin-cap fibroatheroma. Thus, novel methods were introduced to facilitate this problem including virtual histology intravascular ultrasound and later on near-infrared spectroscopy and OCT. Howbeit, none of the currently used modalities can assess all known characteristics of plaque vulnerability; hence, the idea of combining different intravascular imaging methods has emerged including NIRS-IVUS or OCT-IVUS imaging. All of those described methods may allow us to identify the most vulnerable plaques, which are prone to cause acute coronary syndrome, and thus they may allow us to introduce proper treatment before plaque destabilization.

A pilot and ex-vivo study of examination of endometrium tissue by catheter based optical coherence tomography

Objective

This study aimed to distinguish ex-vivo normal and abnormal endometrium tissue samples histologically by catheter based optical coherence tomography (OCT).

Methods

A total of 72 ex-vivo endometrium specimens were obtained from June 2018 to March 2021 and were imaged fresh after hysterectomy. The scanned region of endometrium was excised for histological examination and endometrium OCT images were precisely compared to corresponding histological images. Meanwhile endometrium OCT images were analyzed quantitatively with intensity of backscattered light in region of interest (ROI) and maximum penetration depth of the OCT signal. Blinded qualitative analysis on endometrium OCT images was performed by 2 assessors to determine accuracy rate and inter-rating reliability on the histopathological diagnosis.

Results

OCT images were performed successfully in 72 endometrium specimens. Five endometrium specimens developed OCT interpretation criteria and the rest 67 endometrium specimens validated qualitatively and analyzed quantitatively. We defined an OCT criteria to distinguish normal endometrium and five different abnormal endometrium phases including proliferative endometrium, secretory phase endometrium, atrophic endometrium, endometrial hyperplasia with atypia and endometrial carcinoma based on OCT imaging features. The overall diagnosis accuracy achieved by the two assessors was 72.4% based on the OCT criteria. The inter-rater reliability between assessors on overall OCT images was substantial (Kendall τb of 0.720, p < 0.05). The changes in ROI minimum intensity, ROI maximum intensity, ROI average intensity and OCT signal maximum penetration depth of five different abnormal endometrium phases were significantly different (all p < 0.001). These parameters of endometrium carcinomas were significantly different from the other four endometrium phases (all p < 0.001).

Conclusion

OCT has the advantage of noninvasive and rapid diagnosis, which can contribute to the diagnosis of endometrial cancer and will be an indispensable complement to traditional biopsy. Future studies in vivo with larger samples are needed to confirm this conclusion.

Detection of Vulnerable Coronary Plaques Using Invasive and Non-Invasive Imaging Modalities

Acute coronary syndrome (ACS) mostly arises from so-called vulnerable coronary plaques, particularly prone for rupture. Vulnerable plaques comprise a specific type of plaque, called the thin-cap fibroatheroma (TFCA). A TCFA is characterized by a large lipid-rich necrotic core, a thin fibrous cap, inflammation, neovascularization, intraplaque hemorrhage, microcalcifications or spotty calcifications, and positive remodeling. Vulnerable plaques are often not visible during coronary angiography. However, different plaque features can be visualized with the use of intracoronary imaging techniques, such as intravascular ultrasound (IVUS), potentially with the addition of near-infrared spectroscopy (NIRS), or optical coherence tomography (OCT). Non-invasive imaging techniques, such as computed tomography coronary angiography (CTCA), cardiovascular magnetic resonance (CMR) imaging, and nuclear imaging, can be used as an alternative for these invasive imaging techniques. These invasive and non-invasive imaging modalities can be implemented for screening to guide primary or secondary prevention therapies, leading to a more patient-tailored diagnostic and treatment strategy. Systemic pharmaceutical treatment with lipid-lowering or anti-inflammatory medication leads to plaque stabilization and reduction of cardiovascular events. Additionally, ongoing studies are investigating whether modification of vulnerable plaque features with local invasive treatment options leads to plaque stabilization and subsequent cardiovascular risk reduction.

Understanding the predictive value and methods of risk assessment based on coronary computed tomographic angiography in populations with coronary artery disease: a review

Risk assessment in coronary artery disease plays an essential role in the early identification of high-risk patients. However, conventional invasive imaging procedures all require long intraprocedural times and high costs. The rapid development of coronary computed tomographic angiography (CCTA) and related image processing technology has facilitated the formulation of noninvasive approaches to perform comprehensive evaluations. Evidence has shown that CCTA has outstanding performance in identifying the degree of stenosis, plaque features, and functional reserve. Moreover, advancements in radiomics and machine learning allow more comprehensive interpretations of CCTA images. This paper reviews conventional as well as novel diagnostic and risk assessment tools based on CCTA.

Elevated Serum Levels of Soluble ST2 Are Associated With Plaque Vulnerability in Patients With Non-ST-Elevation Acute Coronary Syndrome

Background: Recent studies have suggested that soluble suppression of tumorigenicity-2 (sST2), an inflammation-related protein receptor, is associated with atherosclerotic diseases. This study aimed to investigate the potential predictive value of sST2 on plaque vulnerability by assessing whether elevated serum levels of sST2 are associated with vulnerable plaque features in patients with non-ST-elevation acute coronary syndrome (ACS).

Methods: A total of 120 patients with non-ST-elevation ACS (167 lesions) were prospectively enrolled and evaluated by standard coronary computed tomography angiography (CCTA) and coronary angiography in this study. Serum sST2 levels were measured by ELISA (Presage^® ST2 Assay Kit, Critical Diagnostics), and semiautomated software (QAngioCT, Medis) was used to quantify coronary plaques.

Results: The included patients were divided into 4 groups by serum sST2 level quartiles. Volumetric analysis of the whole lesion revealed that patients with higher sST2 levels had a larger absolute necrotic core (NC) volume (Quartile 4 vs. Quartile 1, 86.16 ± 59.71 vs. 45.10 ± 45.80 mm³, P = 0.001; Quartile 4 vs. Quartile 2, 86.16 ± 59.71 vs. 50.22 ± 42.56 mm³, P = 0.002) and a higher NC percentage (Quartile 4 vs. Quartile 1, 35.16 ± 9.82 vs. 23.21 ± 16.18%, P < 0.001; Quartile 4 vs. Quartile 2, 35.16 ± 9.82% vs. 22.50 ± 14.03%, P < 0.001; Quartile 4 vs. Quartile 3, 35.16 ± 9.82% vs. 25.04 ± 14.48%, P < 0.001). Correlation analysis revealed that serum sST2 levels were positively correlated with the NC (r = 0.323, P < 0.001) but negatively correlated with dense calcium (r = −0.208, P = 0.007). Furthermore, among those with plaque calcification, patients with spotty calcification exhibited higher serum sST2 levels than those with large calcification (26.06 ± 16.54 vs. 17.55 ± 7.65 ng/mL, P = 0.002). No significant differences in plaque components at the level of the minimal lumen area (MLA) were found among the groups.

Conclusions: Serum sST2 levels were correlated with different coronary plaque components in patients with non-ST-elevation ACS. A higher serum level of sST2 was correlated with plaque vulnerability.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT04797819.

Vascular Lesion-Specific Drug Delivery Systems: JACC State-of-the-Art Review

Drug delivery is central to modern cardiovascular care, where drug-eluting stents, bioresorbable scaffolds, and drug-coated balloons all aim to restore perfusion while inhibiting exuberant healing. The promise and enthusiasm of these devices has in some cases exceeded demonstration of efficacy and even understanding of driving mechanisms. The authors review the means of drug delivery in each device, outlining how the technologies affect vascular behavior. They focus on how drug retention and response are governed by lesion morphology: lipid displacing drug-specific binding sites, calcium inhibiting diffusion, blocking thrombi or promoting luminal washout, and vascular healing steering hyperplastic developments. In this regard, the authors outline the fundamental impact of vascular structure on drug delivery and review the development of contemporary and future devices for coronary and peripheral intervention. They look toward a future where incorporating information on lesion distribution is central to therapeutic success and envision a transition toward lesion-specific treatment for improved interventional outcomes.

Contribution of atherosclerotic plaque location and severity to the near-wall hemodynamics of the carotid bifurcation: an experimental study and FSI modeling

Atherosclerosis is initiated by endothelial injury that is related to abnormal values of hemodynamic parameters such as wall shear stress (WSS), oscillatory shear index (OSI) and stress phase angle (SPA), which are more common in arterial bifurcations due to the complex structure. An experimental model of human carotid bifurcation with accurate geometrical and mechanical features was set up, and using realistic pulsatile flow rates, the inlet and outlet pressure pulses were measured for normal and stenosed models with 40% and 80% severities at common carotid (CCA), internal carotid (ICA) and external carotid (ECA) arteries. Based on the obtained experimental data, fluid-structure models were developed to obtain WSS, OSI, and SPA and evaluate pathological consequences at different locations. Mild severity had minor impact, however, inducing severe 80% stenosis in each branch led to considerable localized changes of hemodynamic parameters both in the stenosis site and other locations. This included sharp increases in WSS values accompanied by very low values close to zero before and after the peaks. Severe stenosis not only caused significant changes in the local artery, but also in other branches. OSI and SPA were less sensitive to stenosis, although high peaks were observed on bifurcation site for the stenosis at ECA. The interconnection of arteries at carotid bifurcation results in altered pressure/flow patterns in all branches when a stenosis is applied in any site. Such effect confirms pathological findings that atherosclerotic plaques are observed simultaneously in different carotid branches, although with different degrees of plaque growth and severity.

Association of culprit lesion plaque characteristics with flow restoration post-fibrinolysis in ST-segment elevation myocardial infarction: an intravascular ultrasound-virtual histology study

Background

Not every patient achieves normal coronary flow following fibrinolysis in STEMI (ST-segment elevation myocardial infarction). The culprit lesion plaque characteristics play a prominent role in the coronary flow before and during percutaneous coronary intervention. The main purpose was to determine the culprit lesion plaque features by virtual histology-intravascular ultrasound (VH-IVUS) in patients with STEMI following fibrinolysis in relation to baseline coronary angiogram TIMI (thrombolysis in myocardial infarction) flow. Pre-intervention IVUS was undertaken in 61 patients with STEMI after successful fibrinolysis. After the coronary angiogram, they were separated into the TIMI1–2 flow group (n = 31) and TIMI 3 flow group (n = 30). Culprit lesion plaque composition was evaluated by VH-IVUS.

Results

On gray-scale IVUS, the lesion external elastic membrane cross-sectional area (EEM CSA) was significantly higher in the TIMI 1–2 groups as compared to the TIMI 3 group (15.71 ± 3.73 mm² vs 13.91 ± 2.94 mm², p = 0.041) with no significant difference in plaque burden (82.42% vs. 81.65%, p = 0.306) and plaque volume (108.3 mm³ vs. 94.3 mm³, p = 0.194). On VH-IVUS, at the minimal luminal area site (MLS), the fibrous area (5.83 mm² vs. 4.37 mm², p = 0.024), necrotic core (NC) area (0.95 mm² vs. 0.59 mm², p < 0.001), and NC percentage (11% vs. 7.1%, p = 0.024) were higher in the TIMI 1–2 groups in contrast to the TIMI 3 group. The absolute necrotic core (NC) volume (8.3 mm³ vs. 3.65 mm³, p < 0.001) and NC percentage (9.3% vs. 6.0%, p = 0.007) were significantly higher in the TIMI 1–2 groups as compared to the TIMI 3 group. Absolute dense calcium (DC) volume was higher in TIMI 1–2 groups with a trend towards significance (1.0 mm³ vs.0.75 mm³, p = 0.051). In multivariate analysis, absolute NC volume was the only independent predictor of TIMI 1–2 flow (odds ratio = 1.561; 95% CI 1.202–2.026, p = 0.001). Receiver operating characteristic curves showed absolute NC volume has best diagnostic accuracy (AUC = 0.816, p < 0.001) to predict TIMI 1–2 flow with an optimal cutoff value of 4.5 mm³ with sensitivity and specificity of 79% and 61%, respectively.

Conclusions

This study exemplifies that the necrotic core component of the culprit lesion plaque in STEMI is associated with the coronary flow after fibrinolysis. The absolute necrotic core volume is a key determinant of flow restoration post-fibrinolysis and aids in prognostication of less than TIMI 3 flow.

A Domain Enriched Deep Learning Approach to Classify Atherosclerosis using Intravascular Ultrasound Imaging

Intravascular ultrasound (IVUS) imaging is widely used for diagnostic imaging in interventional cardiology. The detection and quantification of atherosclerosis from acquired images is typically performed manually by medical experts or by virtual histology IVUS (VH-IVUS) software. VH-IVUS analyzes backscattered radio frequency (RF) signals to provide a color-coded tissue map, and is the method of choice for assessing atherosclerotic plaque in situ. However, a significant amount of tissue cannot be analyzed in reasonable time because the method can be applied just once per cardiac cycle. Furthermore, only hardware and software compatible with RF signal acquisition and processing may be used. We present an image-based tissue characterization method that can be applied to entire acquisition sequences post hoc for the assessment of diseased vessels. The pixel-based method utilizes domain knowledge of arterial pathology and physiology, and leverages technological advances of convolutional neural networks to segment diseased vessel walls into the same tissue classes as virtual histology using only grayscale IVUS images. The method was trained and tested on patches extracted from VH-IVUS images acquired from several patients, and achieved overall accuracy of 93.5% for all segmented tissue. Imposing physically-relevant spatial constraints driven by domain knowledge was key to achieving such strong performance. This enriched approach offers capabilities akin to VH-IVUS without the constraints of RF signals or limited once-per-cycle analysis, offering superior potential information acquisition speed, reduced hardware and software requirements, and more widespread applicability. Such an approach may well yield promise for future clinical and research applications.

In vivo imaging of vulnerable plaque with intravascular modalities: its advantages and limitations

In vivo imaging of plaque instability has been considered to have a great potential to predict future coronary events and evaluate the stabilization effect of novel anti-atherosclerotic medical therapies. Currently, there are several intravascular imaging modalities which enable to visualize plaque components associated with its vulnerability. These include virtual histology intravascular ultrasound (VH-IVUS), integrated backscatter IVUS (IB-IVUS), optical coherence tomography (OCT), near-infrared spectroscopy and coronary angioscopy. Recent studies have shown that these tools are applicable for risk stratification of cardiovascular events as well as drug efficacy assessment. However, several limitation exists in each modality. The current review paper will outline advantages and limitation of VH-IVUS, IB-IVUS, OCT, NIRS and coronary angioscopy imaging.

Advances in IVUS/OCT and Future Clinical Perspective of Novel Hybrid Catheter System in Coronary Imaging

Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) have been developed and improved as both diagnostic and guidance tools for interventional procedures over the past three decades. IVUS has a resolution of 100 μm with a high tissue penetration and capability of assessing the entire structure of a coronary artery including the external elastic membrane, whereas OCT has a higher resolution of 10–20 μm to assess endoluminal structures with a limited tissue penetration compared to IVUS. Recently, two companies, CONAVI and TERUMO, integrated IVUS and OCT into a single catheter system. With their inherent strength and limitations, the combined IVUS and OCT probes are complementary and work synergistically to enable a comprehensive depiction of coronary artery. In this review, we summarize the performance of the two intracoronary imaging modalities—IVUS and OCT—and discuss the expected potential of the novel hybrid IVUS–OCT catheter system in the clinical field.

Multimodality Imaging-Based Characterization of Regional Material Properties in a Murine Model of Aortic Dissection

Chronic infusion of angiotensin-II in atheroprone (ApoE-/-) mice provides a reproducible model of dissection in the suprarenal abdominal aorta, often with a false lumen and intramural thrombus that thickens the wall. Such lesions exhibit complex morphologies, with different regions characterized by localized changes in wall composition, microstructure, and properties. We sought to quantify the multiaxial mechanical properties of murine dissecting aneurysm samples by combining in vitro extension-distension data with full-field multimodality measurements of wall strain and thickness to inform an inverse material characterization using the virtual fields method. A key advance is the use of a digital volume correlation approach that allows for characterization of properties not only along and around the lesion, but also across its wall. Specifically, deformations are measured at the adventitial surface by tracking motions of a speckle pattern using a custom panoramic digital image correlation technique while deformations throughout the wall and thrombus are inferred from optical coherence tomography. These measurements are registered and combined in 3D to reconstruct the reference geometry and compute the 3D finite strain fields in response to pressurization. Results reveal dramatic regional variations in material stiffness and strain energy, which reflect local changes in constituent area fractions obtained from histology but emphasize the complexity of lesion morphology and damage within the dissected wall. This is the first point-wise biomechanical characterization of such complex, heterogeneous arterial segments. Because matrix remodeling is critical to the formation and growth of these lesions, we submit that quantification of regional material properties will increase the understanding of pathological mechanical mechanisms underlying aortic dissection.

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

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.

Design and rationale of a randomized control trial testing the effectiveness of combined therapy with STAtin plus FENOfibrate and statin alone in non-diabetic, combined dyslipidemia patients with non-intervened intermediate coronary artery disease - STAFENO study

Background

Despite the chronicled success of low-density lipoprotein cholesterol (LDLc)-lowering statin therapy, substantial residual cardiovascular (CV) disease risk remains a problem worldwide, highlighting the need to for combination therapies targeting non-LDLc factors, such as with fenofibrate.

Methods/design

The STAFENO trial is a prospective, randomized, open-label, multi-center trial to compare the effect of statin plus fenofibrate with statin alone on the reduction and stabilization of plaque in non-diabetic, combined dyslipidemia patients with non-intervened, intermediate coronary artery disease (CAD) using virtual histology-intravascular ultrasound at 12 months. A total of 106 eligible patients are planned to be randomized to receive either a combination therapy (rosuvastatin 10 mg plus fenofibrate 160 mg/day) or monotherapy (rosuvastatin 10 mg/day) for 12 months. The primary endpoint of this study is the percentage change in the necrotic core volume. Secondary endpoints include changes in tissue characteristics and 1-year major CV events, including all-cause mortality, CV mortality, nonfatal myocardial infarction, stroke, and revascularization of the intervened and non-intervened lesions.

Discussion

The STAFENO trial will address whether combination treatment of statin and fenofibrate has an additive beneficial effect compared to statin alone on the reduction and stabilization of plaque and CV events in non-diabetic, combined dyslipidemia patients with non-intervened intermediate CAD.

Trial registration

ClinicalTrials.gov, NCT02232360. Registered 9 February 2014.

https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S0004ULE&selectaction=Edit&uid=U00023SZ&ts=2&cx=juppd2

Coronary Atherosclerosis Imaging

Identifying patients at increased risk of coronary artery disease, before the atherosclerotic complications become clinically evident, is the aim of cardiovascular prevention. Imaging techniques provide direct assessment of coronary atherosclerotic burden and pathological characteristics of atherosclerotic lesions which may predict the progression of disease. Atherosclerosis imaging has been traditionally based on the evaluation of coronary luminal narrowing and stenosis. However, the degree of arterial obstruction is a poor predictor of subsequent acute events. More recent techniques focus on the high-resolution visualization of the arterial wall and the coronary plaques. Most acute coronary events are triggered by plaque rupture or erosion. Hence, atherosclerotic plaque imaging has generally focused on the detection of vulnerable plaque prone to rupture. However, atherosclerosis is a dynamic process and the plaque morphology and composition may change over time. Most vulnerable plaques undergo progressive transformation from high-risk to more stable and heavily calcified lesions, while others undergo subclinical rupture and healing. Although extensive plaque calcification is often associated with stable atherosclerosis, the extent of coronary artery calcification strongly correlates with the degree of atherosclerosis and with the rate of future cardiac events. Inflammation has a central role in atherogenesis, from plaque formation to rupture, hence in the development of acute coronary events. Morphologic plaque assessment, both invasive and non-invasive, gives limited information as to the current activity of the atherosclerotic disease. The addition of nuclear imaging, based on radioactive tracers targeted to the inflammatory components of the plaques, provides a highly sensitive assessment of coronary disease activity, thus distinguishing those patients who have stable disease from those with active plaque inflammation.

Automated classification of dense calcium tissues in gray-scale intravascular ultrasound images using a deep belief network

Background

IVUS is widely used to quantitatively assess coronary artery disease. The purpose of this study was to automatically characterize dense calcium (DC) tissue in the gray scale intravascular ultrasound (IVUS) images using the image textural features.

Methods

A total of 316 Gy-scale IVUS and corresponding virtual histology images from 26 patients with acute coronary syndrome who underwent IVUS along with X-ray angiography between October 2009 to September 2014 were retrospectively acquired and analyzed. One expert performed all procedures and assessed their IVUS scans. After image acquisition, the DC candidate and corresponding acoustic shadow regions were automatically determined. Then, nine image-base feature groups were extracted from the DC candidates. In order to reduce the dimensionalities, principal component analysis (PCA) was performed, and selected feature sets were utilized as an input for a deep belief network. Classification results were validated using 10-fold cross validation.

Results

The dimensionality of the feature map was efficiently reduced by 50% (from 66 to 33) without any performance decrease using PCA method. Sensitivity, specificity, and accuracy of the proposed method were 92.8 ± 0.1%, 85.1 ± 0.1%, and 88.4 ± 0.1%, respectively (p < 0.05). We found that the window size could largely influence the characterization results, and selected the 5 × 5 size as the best condition. We also validated the performance superiority of the proposed method with traditional classification methods.

Conclusions

These experimental results suggest that the proposed method has significant clinical applicability for IVUS-based cardiovascular diagnosis.

Prediction of Major Adverse Cardiovascular Events and Slow/No-Reflow by Virtual Histology Imaging After Percutaneous Interventions on Saphenous Vein Grafts

Saphenous vein grafts disease (SVGD) is a common complication after coronary artery bypass graft (CABG) and usually treated by percutaneous coronary intervention (PCI). In this prospective cohort study, we performed virtual histology-intravascular ultrasound to investigate whether plaque composition and morphological characteristics were associated with post-PCI major adverse cardiac events (MACEs) and slow/no-reflow in patients with SVGD. Patients (n = 90) were studied (76.7% men, mean age 64.9 ± 8.2 years and mean duration of SVG 8.0 ± 3.6 years). There were 77.8% lesions with a plaque burden of at least 70%; 18 MACE incidences accumulated in 14 patients over 12 months post-PCI and slow/no-reflow was observed in 12 patients. On adjusted multivariate analysis, lesion length (hazard ratio [HR] = 1.05; 95% confidence interval [CI]: 1.01-1.08]); age of CABG (HR = 1.51 [95% CI: 1.11-2.05], and absolute necrotic core (NC) area (HR = 8.04 [95% CI: 1.86-34.73]) were independently associated with MACEs. Factors independently associated with slow/no-reflow post-PCI were preprocedure systolic blood pressure (odds ratio [OR] = 0.98; 95% CI: 0.96-0.99) and absolute NC area (OR = 2.47 (95% CI: 1.14-5.36). A cutoff value of absolute NC area at ≥1.1 mm² may serve as a significant risk predictor for no-reflow after SVG-PCI. Factors associated with MACEs and the slow/no-reflow phenomenon following PCI of the SVG can be used in risk assessment of SVG.

Virtual histology intravascular ultrasound evaluation of coronary artery lesions within 1 year and more than 10 years after the onset of Kawasaki disease

BACKGROUND

Coronary artery evaluation by virtual histological intravascular ultrasonography (VH-IVUS) late in Kawasaki disease (KD) shows intimal thickening, calcification, fatty components, and necrosis of regressed coronary artery lesions (CALs). However, it is not clear when these VH-IVUS findings start to occur. Therefore, we evaluated coronary arteries using VH-IVUS in patients with early-stage KD and tried to determine whether these atherosclerotic findings on VH-IVUS were different from that in patients with late-stage KD.

METHODS

Eighteen patients with KD aged between 1 and 32 years who had CALs and underwent cardiac catheterization between January 1, 2008 and December 31, 2014 were included. They were divided into 2 groups-those with the disease for <1 year (group A) and those with it for >10 years (group B). VH-IVUS findings were compared between the groups. The coronary arteries were divided based on coronary angiography findings into normal, regressed (dilated CALs regressed to a normal size), and aneurysmal lesions. The Wilcoxon signed-rank test was used in the statistical analysis.

RESULTS

In both regressed and aneurysmal lesions, marked intimal proliferation and atherosclerotic findings (fibro-fatty and necrotic core lesions) were observed. In addition, there was no difference in the area percentage of atherosclerosis between the groups.

CONCLUSIONS

VH-IVUS revealed that atherosclerotic-like findings exist in CALs in patients with KD, even within a year of onset. The findings were almost the same in those with the disease for >10 years. Because there is no histological evidence of atherosclerosis in KD, these VH-IVUS findings may indicate complex histological findings of KD. Nevertheless, early interventions to help reduce the risk factors of atherosclerosis may be required in these patients.

Effect of Everolimus Initiation and Calcineurin Inhibitor Elimination on Cardiac Allograft Vasculopathy in De Novo Heart Transplant Recipients

Background Cardiac allograft vasculopathy (CAV) limits survival after heart transplantation, and the effect of different immunosuppressive regimens on CAV is not fully understood. The randomized SCHEDULE trial (Scandinavian Heart Transplant Everolimus De Novo Study With Early Calcineurin Inhibitors Avoidance) evaluated whether initiation of the proliferation signal inhibitor everolimus and early cyclosporine elimination can reduce CAV development. Methods and Results The SCHEDULE trial was a multicenter Scandinavian trial, where 115 de novo heart transplantation recipients were randomized to everolimus with complete cyclosporine withdrawal 7 to 11 weeks after heart transplantation or standard cyclosporine-based immunosuppression. Seventy-six (66%) patients had matched intravascular ultrasound examinations at baseline and 12 and 36 months. Intravascular ultrasound analysis evaluated maximal intimal thickness, percent atheroma volume, and total atheroma volume. Qualitative plaque analysis using virtual histology assessed fibrous, fibrofatty, and calcified tissue as well as necrotic core. Serum inflammatory markers were measured in parallel. The everolimus group (n=37) demonstrated significantly reduced CAV progression as compared with the cyclosporine group (n=39) at 36 months (Δ maximal intimal thickness, 0.09±0.05 versus 0.15±0.16 mm [ P=0.03]; Δ percent atheroma volume, 5.3±2.8% versus 7.6±5.9% [ P=0.03]; and Δ total atheroma volume, 33.9±71.2 versus 54.2±96.0 mm³ [ P=0.34], respectively]. At 36 months the number of everolimus patients with rejection graded ≥2R was 15 (41%) as compared with 5 (13%) in the cyclosporine group ( P=0.01). Everolimus did not affect CAV morphology or immune marker activity during the follow-up period. Conclusions The SCHEDULE trial demonstrates that everolimus initiation and early cyclosporine elimination significantly reduces CAV progression at 12 months, and this beneficial effect is clearly sustained at 36 months. Clinical trial registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT01266148.

Long-term clinical outcomes in patients with untreated non-culprit intermediate coronary lesion and evaluation of predictors by using virtual histology-intravascular ultrasound; a prospective cohort study

Background

It is uncertain whether the coronary lesion with intermediate stenosis is more likely to cause cardiovascular events than a normal or minimal lesion. We conducted a single-center, prospective cohort study to identify long-term clinical outcomes of patients with untreated non-culprit intermediate lesion and evaluate its predictor of cardiovascular events by using virtual histology-intravascular ultrasound (VH-IVUS).

Methods

Subjects with non-culprit intermediate lesion underwent VH-IVUS were prospectively registered after percutaneous coronary intervention at the culprit lesion. Intermediate lesion was defined as 30 to 70% stenosis in coronary angiography and primary outcome was an occurrence of major adverse cardiovascular events (MACE) defined as all-cause death, intermediate lesion revascularization (InLR), minimal lesion revascularization (MnLR, unplanned revascularization elsewhere in the target vessel or in other coronary arteries which looked normal or minimal stenosis), cerebrovascular events, or non-fatal myocardial infarction (MI). The mean follow-up period was 4.2 years.

Results

Total 25 MACE, approximately 7% incidence annually, were identified during a follow-up period in 86 patients with 89 intermediate lesions. InLR (n = 13) was a most common event followed by MnLR (n = 6), non-fatal MI (n = 4), all-cause death (n = 3), and cerebrovascular events (n = 1). Diameter stenosis (OR 1.07, 95% CI 1.01–1.12, p = 0.015), plaque burden (PB, OR 1.07, 95% CI 1.00–1.15, p = 0.040), fibrofatty area (FFA, OR 1.61, 95% CI 1.10–2.38, p = 0.016), PB ≥ 70% (OR 3.93, 95% CI 1.28–12.07, p = 0.018), and area stenosis ≥ 50% (OR 2.94, 95% CI 1.01–8.56, p = 0.042) showed significant relationships with an occurrence of MACE. In multivariable Cox-proportional hazard analysis, FFA in intermediate lesion was an only independent predictor of MACE (HR 1.36, 95% CI 1.05–1.77, p = 0.019).

Conclusions

Untreated intermediate lesions had a significantly higher chance for requiring revascularization compared with a normal or minimal lesion. And also, a large FFA in intermediate lesion was a significant predictor of cardiovascular events and which finding was mainly driven by coronary-related events, in particularly intermediate lesion progression.

Intravascular ultrasound assisted carotid artery stenting: randomized controlled trial. Preliminary results on 60 patients

AIMS

The primary aim is the evaluation of the usefulness of intravascular ultrasound (IVUS) in the identification of otherwise unnoticed complications during carotid stenting. The secondary aim is the evaluation of the impact of IVUS assistance in the procedural outcomes and long-term patency rates of carotid artery stenting.

MATERIALS AND METHODS

Sixty patients who underwent carotid artery stenting (CAS) during a 14-month period were evaluated prospectively. Thirty patients (50%) underwent IVUS assisted CAS, 30 patients (50%) underwent CAS using angiography as the unique diagnostic tool. All patients were enrolled through a primary duplex ultrasound evaluation; as a secondary evaluation, 54 patients (90%) underwent a preprocedural magnetic resonance angiography, whereas six patients (10%) underwent computed tomography-angiography. Patients with preocclusive stenoses (>85%) were excluded. Mean follow-up was 23 W 5.3 months.

RESULTS

No periprocedural or late complications were observed. No statistical significance was observed in long-term stent patency between the two groups. Mean procedural time length of IVUS-assisted procedures was 10.3 W 5 min longer than non-IVUS-assisted procedures. Virtual histology (VH) IVUS evaluation of plaque morphology led to a different stent choice in three patients. In two cases, the IVUS assessment revealed a suboptimal stent deployment, solved by angioplasty; in one patient VH-IVUS detected plaque protrusion through stent cells, immediately treated by manual aspiration.

CONCLUSIONS

Though not recommended as a routine intraprocedural evaluation, IVUS may be useful for a real-time CAS control when treating challenging plaques, such as 'soft' or lipidic ones or those prone to rupture, or whenever an intraprocedural morphologic evaluation is required for the appropriate stent choice, or when higher embolic risk is evaluated.

High shear stress on the coronary arterial wall is related to computed tomography-derived high-risk plaque: a three-dimensional computed tomography and color-coded tissue-characterizing intravascular ultrasonography study

Low wall shear stress (WSS) is associated with plaque formation. However, the relationship between WSS and coronary plaque vulnerability remains unclear. Therefore, this study aimed to clarify the in vivo relationship between luminal WSS derived from three-dimensional (3D) computed tomography (CT) and plaque vulnerability within the coronary artery. Forty-three consecutive patients with ischemic heart disease and coronary stenotic lesions were enrolled and underwent coronary angiography and color-coded intravascular ultrasonography (iMap™) followed by multi-slice coronary CT angiography. CT-derived high-risk plaque was defined by specific CT characteristics, including low CT intensity (< 30 HU) and positive remodeling. The Student's t test, Mann-Whitney U test, χ² test, repeated measures analysis of variance, and logistic and multiple regression were used for statistical analyses. CT-derived high-risk plaque (n = 15) had higher values of maximum and average shear stress than CT-derived stable plaque (474 ± 453 vs. 158 ± 138 Pa, p = 0.018; 4.2 ± 3.1 vs. 1.6 ± 1.2 Pa, p = 0.007, respectively). Compared with patients with CT-derived stable plaque, those with CT-derived high-risk plaque had a higher prevalence of necrotic and lipidic characteristics (44 ± 13 vs. 31 ± 11%, p = 0.001) based on iMap™. Multivariate logistic regression analysis showed that the average WSS and necrotic plus lipidic content were independent determinants of CT-derived high-risk plaque (average WSS: odds ratio 2.996, p = 0.014; necrotic plus lipidic content: odds ratio 1.306, p = 0.036). Our findings suggested that CT-derived high-risk plaque may coexist with high shear stress on the plaque surface.

Long-term darapladib use does not affect coronary plaque composition assessed using multimodality intravascular imaging modalities: a randomized-controlled study

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) may play a role in plaque progression and vulnerability. We aimed to define plaque characteristics on multimodality intravascular imaging in patients with coronary endothelial dysfunction in response to long-term inhibition of Lp-PLA2 by darapladib.

PATIENTS AND METHODS

This is a double-blinded, randomized study screening 70 patients, and enrolling 54 patients with suspected ischemia, without obstructive disease on angiography and with coronary endothelial dysfunction by invasive assessment. Patients were randomized to receive darapladib or placebo for 6 months. Forty patients underwent multimodality intravascular imaging at baseline and after 6 months of therapy. Several parameters of plaque vulnerability were measured, including maximum value of lipid core burden index for any of the 4-mm segment (maxLCBI4 mm) by near-infrared spectroscopy. Microchannels and macrophages were assessed using optical coherence tomography and necrotic core volume by virtual histology intravascular ultrasound.

RESULTS

There was no significant difference in maxLCBI4 mm [64.56 (7.74, 128.56) vs. 22.43 (0, 75.63), P=0.522] or in macrophage images angle [-9.5° (-25.53°, 12.68°) vs. -16.7° (-28.6°, -4.8°), P=0.489] between groups. There was a trend toward shorter microchannel length in the darapladib arm [0, (-4.4, 0.2) mm vs. 0.8 (-0.15, 1.9) mm, P=0.08]. Percentage of necrotic core volume was not significantly different.

CONCLUSION

Thus, long-term inhibition of endogenous Lp-PLA2 activity with darapladib was not associated with a change in plaque progression and vulnerability indices after 6 months of therapy, and the endogenous Lp-PLA2 pathway may not play a direct role in the progression of early atherosclerosis in humans.

A novel intensity-based multi-level classification approach for coronary plaque characterization in intravascular ultrasound images

Background

Intravascular ultrasound (IVUS) is a commonly used diagnostic imaging method for coronary artery disease. Virtual histology (VH) characterizes the plaque components into fibrous tissue (FT), fibro-fatty tissue (FFT), necrotic core (NC), or dense calcium (DC). However, VH can obtain only a single-frame image in one cardiac cycle, and specific software is needed to obtain the radio frequency data. This study proposed a novel intensity-based multi-level classification model for plaque characterization.

Methods

The plaque-containing regions between the intima and the media-adventitia were segmented manually for all IVUS frames. A total of 54 features including first order statistics, grey level co-occurrence matrix, Law’s energy measures, extended grey level run length matrix, intensity, and local binary pattern were estimated from the plaque-containing regions. After feature extraction, optimal features were selected using principle component analysis (PCA), and these were utilized as the input for the classification models. Plaque components were classified into FT, FFT, NC, or DC using an intensity-based multi-level classification model consisting of three different nets. Net 1 differentiated low-intensity components into FT/FFT and NC/DC groups. Then, net 2 subsequently divided FT/FFT into FT or FFT, whereas the remainder and high-intensity components were classified into NC or DC via net 3. To improve classification accuracy, each net utilized three different input features obtained by PCA. Classification performance was evaluated in terms of sensitivity, specificity, accuracy, and receiver operating characteristic curve.

Results

Quantitative results indicated that the proposed method showed significantly high classification accuracy for all tissue types. The classifiers had classification accuracies of 85.1%, 71.9%, and 77.2%, respectively, and the areas under the curve were 0.845, 0.704, and 0.783. In particular, the proposed method achieved relatively high sensitivity (82.0%) and specificity (87.1%) for differentiating between the FT/FFT and NC/DC groups.

Conclusions

These results confirmed the clinical applicability of the proposed approach for IVUS-based tissue characterization.

Combining cholesterol-lowering strategies with imaging data: a visible benefit?

Coronary artery disease is characterised by the development of atherosclerotic plaques and is associated with significant morbidity and mortality on a global level. However, many patients with atherosclerosis are asymptomatic and the prediction of acute coronary events is challenging. The role of imaging studies in characterising plaque morphology and stability is emerging as a valuable prognostic tool, while providing evidence for the beneficial effects of cholesterol-lowering therapy on plaque burden. This review provides an overview of contemporary studies describing the value of imaging strategies for atherosclerotic plaques. Coronary angiography is commonly used in the clinical setting, but requires a significant radiation dose (similar to computed tomography). Magnetic resonance imaging evaluation of coronary vessels would avoid exposure to ionising radiation, but is not yet feasible due to motion artefacts. The roles of alternative imaging techniques, including grey-scale intravascular ultrasound, optical coherence tomography and near-infrared spectroscopy have emerged in recent years. In particular, grey-scale intravascular ultrasound has been effectively applied to detect changes in plaque burden and features of plaques predictive of rupture, as well as plaque characteristics during cholesterol-lowering therapy, providing novel insights into factors that may contribute to treatment effectiveness. Challenges and limitations to the use of imaging techniques are considered in this context, along with future imaging strategies.

Morphological Features and Plaque Composition in Culprit Atheromatous Plaques of Patients with Acute Coronary Syndromes

Background: The independent role of each plaque feature in relation to plaque vulnerability is still the subject of ongoing research. This study aimed to compare the morphologic characteristics of vulnerable atheromatous coronary plaques with the ones of stable, non-vulnerable plaques, and in plaques with different locations in the coronary tree, in order to identify the most relevant imaging-based biomarkers associated with coronary plaque vulnerability.

Material and methods: This was a prospective observational, non-randomized study that included 50 patients with unstable angina who underwent computed tomography angiography for assessment of the entire coronary artery tree followed by complex morphologic analysis of all lesions, divided into two groups: group 1 – 25 patients with vulnerable plaque (VP) and group 2 – 25 age- and gender-matched patients with non-vulnerable plaque (NVP).

Results: Lesions with a stenosis degree >70% were significantly longer than those with a stenosis degree <70% (8.27 ± 2.74 mm vs. 5.56 ± 4.11 mm, p = 0.04). VP presented significantly higher values of plaque thickness (p = 0.0005), plaque burden (p = 0.0004), and higher total plaque volume (p = 0.0005) than NVP. The remodeling index was not significantly different between the groups (p = 0.6), but the eccentricity index was (0.24 ± 0.14 compared to 0.14 ± 0.17, p = 0.023). Linear regression analysis revealed a significant correlation between plaque burden and plaque components in VP (r = 0.76, p <0.0001 for necrotic core; r = 0.62, p = 0.0008 for fibro-fatty tissue; and r = 0.5, p = 0.01 for fibrotic tissue volume). Culprit plaques located in the right coronary artery presented significantly larger plaque burden volumes (91.17 ± 4.88 mm3 vs. 83.35 ± 8.47 mm3, p = 0.04), larger volumes of necrotic core (82.03 ± 47.85 mm3 vs. 45.84 ± 43.72 mm3, p = 0.02) and fibrofatty tissue (53.23 ± 31.92 mm3 vs. 23.76 ± 20.90 mm3, p = 0.02) than the ones situated in the left coronary artery.

Conclusions: VPs from the culprit lesions exhibit a different phenotype than non-vulnerable ones, and vulnerability features are present in a significantly larger extent in VPs from the right coronary artery as compared to those from the left coronary artery.

In vivo tissue characterization of human atherosclerotic plaques by optical coherence tomography: A directional coronary atherectomy study with histopathologic confirmation

BACKGROUND

The histopathological validation of optical coherence tomography (OCT) in visualizing atherosclerotic plaques has been reported only in ex vivo studies. We sought to evaluate the accuracy of OCT in tissue characterization in vivo.

METHODS AND RESULTS

A total of 25 patients with stable angina pectoris who underwent directional coronary atherectomy (DCA) were included in the investigation, whereby OCT was performed before and after a single debulking. The debulked region was determined on OCT and classified into fibrous tissue, lipid, calcification, thrombus, and macrophage accumulation, which were compared with histology. Changes in OCT signal intensity in the deeper intimal region after DCA were also visually evaluated. Fibrous tissues were detected in all cases, while thrombus was identified only in 1 case, by both OCT and histology. The sensitivity, specificity, positive and negative predictive values, and predictive accuracy for lipid detection by OCT were 88.9%, 75.0%, 66.7%, 92.3%, and 80.0%; those for calcification were 50.0%, 100%, 100%, 91.3%, and 92.0%; and those for macrophage accumulation were 85.7%, 88.9%, 75.0%, 94.1%, and 88.0%, respectively. The false positive diagnoses for lipid were mostly attributed to the extracellular matrix accumulation containing less collagen. The false negative diagnoses for calcification were explained by the presence of lipid around the calcification. The OCT signal intensity in the deeper intimal region substantially increased after DCA in all cases.

CONCLUSIONS

The current study showed excellent predictive accuracy of in vivo OCT in tissue characterization, whereas the limitations of OCT were highlighted by an over-detection of lipid, under-detection of calcification, and underestimation of the deeper intimal matrix.

A higher volume of fibrotic tissue on virtual histology prior to coronary stent implantation predisposes to more pronounced neointima proliferation

BACKGROUND

Since neointima smooth muscle cells (SMC) mainly originate from the vessel wall, we investigated whether atherosclerotic plaque composition influences subsequent in-stent neointima proliferation and restenosis.

METHODS

We performed intravascular ultrasound (IVUS) with virtual histology in 98 patients prior to elective bare-metal stent (BMS) implantation in de novo coronary artery lesions. Virtual histology variables pre-percutaneous coronary intervention (PCI) were related to in-stent neointima proliferation six months after implantation assessed as late luminal loss of 0.88 mm (interquartile range (IQR) 0.37-1.23 mm) on angiography and as maximal percentage area stenosis of 42% (IQR 33-59%) and percentage volume intima hyperplasia of 27% (IQR 20-36%) on IVUS. A ridge-trace based multiple linear regression model was constructed to account for multicollinearity of the virtual histology variables and was corrected for implanted stent length (18 mm, IQR 15-23 mm), stent diameter (3.0 mm, IQR 2.75-3.5 mm) and lesion volume (146 mm³, IQR 80-201 mm³) prior to PCI.

RESULTS

Fibrous tissue volume prior to PCI (49 mm³, IQR 30-77 mm³) was significantly and independently related to late luminal loss (p = .038), maximal percentage area stenosis (p = .041) and percentage volume intima hyperplasia (p = .004). Neither absolute nor relative amounts of fibrofatty, calcified or necrotic core tissue appeared related to any of the restenosis parameters. Subgroup analysis after exclusion of acute coronary syndrome (ACS) patients yielded similar results.

CONCLUSION

Lesions with more voluminous fibrotic tissue pre-PCI show more pronounced in-stent neointima proliferation, even after correction for lesion plaque volume.

Coronary Artery Plaque Imaging

PURPOSE OF REVIEW

This short review summarizes the recent development in clinical and experimental imaging techniques for coronary atherosclerosis.

RECENT FINDINGS

Coronary atherosclerosis is the underlying disease of myocardial infarction, the leading cause of death in the industrialized world. Conventional ways of risk assessment, including evaluation of traditional risk factors and interrogation of luminal stenosis, have proven imprecise for the prediction of major events. Rapid advances in noninvasive imaging techniques including MRI, CT, and PET, as well as catheter-based methods, have opened the doors to more in-depth interrogation of plaque burden, composition, and many crucial pathological processes such as inflammation and hemorrhage. These emerging imaging modalities and methodologies, combined with conventional imaging evidences of anatomy and ischemia, offer the promises to provide comprehensive information of the disease status. There is tremendous clinical potential for imaging to improve the current management of coronary atherosclerosis, including the identification of high-risk patients for aggressive therapies and guiding personalized treatment. In this review, we provide an overview of the state-of-the-art coronary plaque imaging techniques focusing on their respective strengths and weaknesses, as well as their clinical outlook.