Virtual Histology Intravascular Ultrasound Imaging Research Articles

Automated finite element approach to generate anatomical patient-specific biomechanical models of atherosclerotic arteries from virtual histology-intravascular ultrasound.

Despite advancements in early detection and treatment, atherosclerosis remains the leading cause of death across all cardiovascular diseases (CVD). Biomechanical analysis of atherosclerotic lesions has the potential to reveal biomechanically instable or rupture-prone regions. Treatment decisions rarely consider the biomechanics of the stenosed lesion due in-part to difficulties in obtaining this information in a clinical setting. Previous 3D FEA approaches have incompletely incorporated the complex curvature of arterial geometry, material heterogeneity, and use of patient-specific data. To address these limitations and clinical need, herein we present a user-friendly fully automated program to reconstruct and simulate the wall mechanics of patient-specific atherosclerotic coronary arteries. The program enables 3D reconstruction from patient-specific data with heterogenous tissue assignment and complex arterial curvature. Eleven arteries with coronary artery disease (CAD) underwent baseline and 6-month follow-up angiographic and virtual histology-intravascular ultrasound (VH-IVUS) imaging. VH-IVUS images were processed to remove background noise, extract VH plaque material data, and luminal and outer contours. Angiography data was used to orient the artery profiles along the 3D centerlines. The resulting surface mesh is then resampled for uniformity and tetrahedralized to generate the volumetric mesh using TetGen. A mesh convergence study revealed edge lengths between 0.04 mm and 0.2 mm produced constituent volumes that were largely unchanged, hence, to save computational resources, a value of 0.2 mm was used throughout. Materials are assigned and finite element analysis (FEA) is then performed to determine stresses and strains across the artery wall. In a representative artery, the highest average effective stress was in calcium elements with 235 kPa while necrotic elements had the lowest average stress, reaching as low as 0.79 kPa. After applying nodal smoothening, the maximum effective stress across 11 arteries remained below 288 kPa, implying biomechanically stable plaques. Indeed, all atherosclerotic plaques remained unruptured at the 6-month longitudinal follow up diagnosis. These results suggest our automated analysis may facilitate assessment of atherosclerotic plaque stability.

High-intensity statin treatment is associated with reduced plaque structural stress and remodelling of artery geometry and plaque architecture.

AimsPlaque structural stress (PSS) is a major cause of atherosclerotic plaque rupture and major adverse cardiovascular events (MACE). We examined the predictors of changes in peak and mean PSS (ΔPSSpeak, ΔPSSmean) in three studies of patients receiving either standard medical or high-intensity statin (HIS) treatment.Methods and resultsWe examined changes in PSS, plaque size, and composition between 7348 co-registered baseline and follow-up virtual-histology intravascular ultrasound images in patients receiving standard medical treatment (controls, n = 18) or HIS (atorvastatin 80 mg, n = 20, or rosuvastatin 40 mg, n = 22). The relationship between changes in PSSpeak and plaque burden (PB) differed significantly between HIS and control groups (P < 0.001). Notably, PSSpeak increased significantly in control lesions with PB >60% (P = 0.04), but not with HIS treatment. However, ΔPSSpeak correlated poorly with changes in lumen and plaque area or PB, plaque composition, or lipid lowering. In contrast, ΔPSSpeak correlated significantly with changes in lumen curvature, irregularity, and roughness (P < 0.05), all of which were reduced in HIS patients. ΔPSSmean correlated with changes in lumen area, PA, PB, and circumferential calcification, and was unchanged with either treatment.ConclusionOur observational study shows that PSSpeak changes over time were associated with baseline disease severity and treatment. The PSSpeak increase seen in advanced lesions with standard treatment was associated with remodelling artery geometry and plaque architecture, but this was not seen after HIS treatment. Smoothing plaques by reducing plaque/lumen roughness, irregularity, and curvature represents a novel mechanism whereby HIS may reduce PSS and, thus may protect against plaque rupture and MACE.

Abstract P125: IL-6-induced Signaling In PD-1 + CD4 Effector Memory T Cells Is Associated With Human Coronary Pathology

Objective: Murine data, prospective epidemiological studies, and genetic association data support a potential causal role of IL-6 signaling in atherosclerosis development. IL-6 inhibitors have emerged as potential therapeutics for reducing events in both stable coronary artery disease (CAD) and acute coronary syndromes. IL-6-induced immune regulation plays an important role in atherosclerosis, however, a comprehensive map of IL-6 signaling in human immune cells is currently lacking. We developed a 32-antibody custom mass cytometry (CyTOF) panel to characterize IL-6 signaling across all major human immune cell subsets and applied it to identify IL-6-induced immune signatures linked with unstable atherosclerotic plaque. Methods: Peripheral blood mononuclear cells from healthy donors and subjects with CAD undergoing virtual histology-intravascular ultrasound imaging (IVUS-VH) were stimulated with vehicle and IL-6, stained, and ran in CyTOF. Unsupervised analysis algorithms (SPADE, UMAP, and Leiden clustering) were used to identify immune cell subsets and IL-6-induced intracellular phosphorylation status. Results: IL-6 induced STAT1 and STAT3 activation in CD4 and CD8 naïve T cell subsets and CD4 memory T subsets. Notably, we identified that IL-6 also activates STAT5 within the CD4 and CD8 naïve T subsets. IL-6 induced a much more robust activation of STAT1 as compared to STAT3 and STAT5. Other cell types such as CD14 + monocytes, and CD11c + , and CD123 + dendritic cells also showed IL-6-induced STAT activation. IL-6-induced phosphorylation of STAT1 and STAT3 in a novel PD-1 + CD4 + effector memory T cell subtype was associated with higher CAD burden and unstable plaque features. Conclusions: Findings are significant for mechanistic insights into IL-6-induced inflammation and may enable discovery of new approaches to reduce inflammation in CAD and other pathologies.

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.

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.

Matrix Metalloproteinase 9 as a Predictor of Coronary Atherosclerotic Plaque Instability in Stable Coronary Heart Disease Patients with Elevated Lipoprotein(a) Levels.

We sought to investigate whether levels of matrix metalloproteinases (MMPs) and their inhibitors predict coronary atherosclerotic plaque instability, as assessed by intravascular ultrasound (IVUS) virtual histology during coronary angiography. Blood samples were collected before angiography in 32 subjects (mean age 56 ± 8 years) with stable coronary heart disease (CHD) and elevated lipoprotein(a) (Lp(a), 94 ± 35 mg/dL). Levels of high-sensitivity C-reactive protein (hsCRP), apolipoprotein B100 (apoB100), MMP-7, MMP-9, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 were determined using commercially available enzyme-linked immunosorbent assay kits. Results. The morphology of a total of sixty coronary lesions was assessed by virtual histology IVUS imaging. Eleven (18%) plaques in nine (28%) patients were classified as plaques with an unstable phenotype or a thin-cap fibroatheroma. Age, low-density lipoprotein cholesterol, apoB100, MMP-7, and MMP-9 levels were positively associated with necrotic core volume. Conversely, there was a negative relationship between MMP-7 and -9 levels and fibrous and fibro-fatty tissue volume. Multivariate regression analysis revealed that MMP-9 is a strong independent predictor of atherosclerotic plaque instability in stable CHD patients. In stable CHD patients with elevated Lp(a), MMP-9 levels are positively associated with the size of the necrotic core of coronary atherosclerotic plaques.

Thin Cap Fibroatheroma Detection in Virtual Histology Images Using Geometric and Texture Features

Atherosclerotic plaque rupture is the most common mechanism responsible for a majority of sudden coronary deaths. The precursor lesion of plaque rupture is thought to be a thin cap fibroatheroma (TCFA), or “vulnerable plaque”. Virtual Histology-Intravascular Ultrasound (VH-IVUS) images are clinically available for visualising colour-coded coronary artery tissue. However, it has limitations in terms of providing clinically relevant information for identifying vulnerable plaque. The aim of this research is to improve the identification of TCFA using VH-IVUS images. To more accurately segment VH-IVUS images, a semi-supervised model is developed by means of hybrid K-means with Particle Swarm Optimisation (PSO) and a minimum Euclidean distance algorithm (KMPSO-mED). Another novelty of the proposed method is fusion of different geometric and informative texture features to capture the varying heterogeneity of plaque components and compute a discriminative index for TCFA plaque, while the existing research on TCFA detection has only focused on the geometric features. Three commonly used statistical texture features are extracted from VH-IVUS images: Local Binary Patterns (LBP), Grey Level Co-occurrence Matrix (GLCM), and Modified Run Length (MRL). Geometric and texture features are concatenated in order to generate complex descriptors. Finally, Back Propagation Neural Network (BPNN), kNN (K-Nearest Neighbour), and Support Vector Machine (SVM) classifiers are applied to select the best classifier for classifying plaque into TCFA and Non-TCFA. The present study proposes a fast and accurate computer-aided method for plaque type classification. The proposed method is applied to 588 VH-IVUS images obtained from 10 patients. The results prove the superiority of the proposed method, with accuracy rates of 98.61% for TCFA plaque.

Automatic plaque segmentation based on hybrid fuzzy clustering and k nearest neighborhood using virtual histology intravascular ultrasound images

Thin cap fibroatheroma (TCFA) or “vulnerable plaque” is responsible for the majority of coronary artery death. Virtual Histology Intravascular Ultrasound (VH-IVUS) image is a clinically available method for visualizing color coded tissue maps. However, this technique has considerable limitations in providing medical relevant information for identifying vulnerable plaque. The aim of this paper is to improve the identification of TCFA in VH-IVUS image. Therefore, this paper proposes a set of algorithms for segmentation, feature extraction, and plaque type classification to accurately identify TCFA. A hybrid model using the FCM and kNN (HFCM-kNN) is proposed to accurately segment the VH-IVUS image. The proposed technique is capable of eliminating outliers and detecting clusters with different densities in VH-IVUS image. The next process is extracting plaque features to provide an accurate definition of the unstable (vulnerable) plaque. To achieve the above contribution, five algorithms are proposed to extract significant features from VH-IVUS images. Machine learning approaches are applied for training 440 in-vivo images obtained from 8 patients. Results proved the dominance of the proposed method for TCFA detection with accuracy rate of 98.02% compared with the 76.5% obtained by the cardiologist decision. Moreover, by validation of VH-IVUS images and their corresponding Optical Coherence Tomography (OCT) images, accuracy of 92.85% is achieved.

Potential contribution of virtual histology plaque composition to hemodynamic–morphologic dissociation in patients with non-ST elevation acute coronary syndrome

ObjectiveHistologic plaque characteristics may influence the hemodynamic effect generated by physiologically significant unstable coronary lesions where plaque content and surface related factors are expected to contribute to the maximum translesional pressure drop. In this study, we aimed to identify local lesion specific virtual histological characteristics that may potentially affect hemodynamic outcome measures. MethodsForty-eight consecutive patients with non-ST-elevation acute coronary syndrome (NSTEACS) having paired hemodynamic and morphological data were enrolled. A dual sensor guide-wire was used for the assessment of fractional flow reserve (FFR) and stenosis resistance (HSR) in the culprit vessel. Virtual histology intravascular ultrasound imaging was performed after obtaining hemodynamic data. ResultsIn a hemodynamically significant lesion subset (FFR<0.75 [n=34]), after controlling for lesion length, MLA and coronary artery compliance, FFR correlated with necrotic core (NC) area (r=−0.423, p=0.028) at MLA and NC volume (r=−0.497, p=0.008) and dense calcium (DC) volume (r=−0.332, p=0.03) across the entire lesion segment. Likewise, NC (r=−0.544, p=0.005) and DC (r=0.376, p=0.03) areas at MLA and NC (r=0.545, p=0.005) and DC (r=0.576, p=0.003) volumes across the entire lesion segment were associated with HSR in the hemodynamically significant lesion group (HSR>0.80 [n=33]). However, no correlation has been observed between intracoronary hemodynamic end-points and plaque components in hemodynamically insignificant lesions. ConclusionsThis study demonstrated that for a given coronary stenosis geometry and arterial compliance, plaque composition may influence hemodynamic outcome measures in functionally significant stenoses in patients with NSTEACS.

Age-Related Effects of Smoking on Coronary Artery Disease Assessed by Gray Scale and Virtual Histology Intravascular Ultrasound

Although smoking is a risk factor for coronary atherosclerosis, the age-related impact on lesion morphology has not been studied. The aim of this study was to assess the age-related impact of smoking on the extent of atherosclerosis and arterial remodeling. In Providing Regional Observations to Study Predictors of Events in the Coronary Tree, 687 patients with acute coronary syndrome underwent 3-vessel gray scale and virtual histology intravascular ultrasound imaging of 3,185 nonculprit lesions. In 207 patients ≤65 years, current (smoking within 1 month) and former (no smoking for >1 month) smokers showed significantly smaller normalized volumes of external elastic membrane (EEM), lumen, and P + M (plaque + media) compared with nonsmokers. At the minimal lumen area site, current and former smokers had significantly smaller EEM, lumen, and P + M areas than nonsmokers. Conversely, in 480 patients >65 years, current smokers had greater normalized P + M volumes than nonsmokers with no difference in normalized EEM or lumen volumes. Finally, in patients >65 years (but not in patients ≤65 years), current smokers showed more plaque ruptures (4.7% vs 1.8%, p = 0.05) and echolucent plaques (8.3% vs 3.9%, p = 0.05) compared with nonsmokers. On multivariable analysis, a history of smoking (combining current and former smoking) predicted smaller normalized EEM volumes compared with nonsmokers ≤65 years. In conclusion, in patients ≤65 years, but not in patients >65 years, smoking had a vascular constrictive effect that contributed to severe luminal stenosis. Conversely, smokers >65 years had more plaque with greater plaque instability.

Framework to Co-register Longitudinal Virtual Histology-Intravascular Ultrasound Data in the Circumferential Direction

Considerable efforts have been directed at identifying prognostic markers for rapidly progressing coronary atherosclerotic lesions that may advance into a high-risk (vulnerable) state. Intravascular ultrasound (IVUS) has become a valuable clinical tool to study the natural history of coronary artery disease (CAD). While prospectively IVUS studies have provided tremendous insight on CAD progression, and its association with independent markers (e.g., wall shear stress), they are limited by the inability to examine the focal association between spatially heterogeneous variables (in both circumferential and axial directions). Herein, we present a framework to automatically co-register longitudinal (in-time) virtual histology-intravascular ultrasound (VH-IVUS) imaging data in the circumferential direction (i.e., rotate follow-up image so circumferential basis coincides with corresponding baseline image). Multivariate normalized cross correlation was performed on paired images (n = 636) from five patients using three independent VH-IVUS defined parameters: artery thickness, VH-IVUS defined plaque constituents, and VH-IVUS perivascular imaging data. Results exhibited high correlation between co-registration rotation angles determined automatically versus manually by an expert reader ( r(2) = 0.90). Furthermore, no significant difference between automatic and manual co-registration angles was observed ( 91.31 ±1.04(°) and 91.07 ±1.04(°), respectively; p = 0.48) and Bland-Altman analysis yielded excellent agreement ( bias = 0.24(°), 95% CI +/- 16.33(°)). In conclusion, we have developed, verified, and validated an algorithm that automatically co-registers VH-IVUS imaging data that will allow for the focal examination of CAD progression.

Ruptured plaque and large plaque burden are risks of distal embolisation during percutaneous coronary intervention: evaluation by angioscopy and virtual histology intravascular ultrasound imaging

Slow flow and no flow phenomena have been associated with distal embolisation, especially of plaque debris, and with unfavourable clinical outcomes. However, patients at high risk of distal embolisation for whom distal protection might be beneficial have not been adequately identified. We examined the frequency of distal embolisation and its predicting factors, including both ACS and non-ACS patients. Consecutive patients (n=98) with or without ACS who had received PCI with a filter-type distal protection device and successful angioscopic and VH-IVUS examination were prospectively enrolled. The presence of yellow plaque and plaque rupture was evaluated by angioscopy. Tissue classification and plaque burden was evaluated by VH-IVUS. Distal embolisation was evaluated by pathological examination of material collected in the filter. Distal embolisation of plaque debris was more frequently detected in patients with ACS (48% vs. 25%, p=0.02), in those with ruptured plaque (86% vs. 13%, p<0.001), in those with large (>75%) plaque burden (50% vs. 23%, p=0.006), and in those with grade 2/3 yellow plaque (52% vs. 7%, p<0.001), as compared to those without it. The presence of ruptured yellow plaque and of large plaque burden, rather than the setting of ACS, was highly predictive of distal embolisation of plaque debris.

Quantification of new structural features of coronary plaques by computational post-hoc analysis of virtual histology-intravascular ultrasound images

Cardiovascular disease and complications are often mediated by the development and rupture of atherosclerotic plaques. Plaque composition is a major factor that determines plaque vulnerability. Intravascular ultrasound (IVUS) and spectral analysis of the radio frequency signal provide an in vivo tissue characterisation of atherosclerotic plaques, known as virtual histology (VH–IVUS). In VH–IVUS analysis, four histological tissue components are classified: fibrous, fibro/fatty, necrotic core and calcium. Existing technology determines only the area of each component within the plaque. Quantitative, objective characterisation of other plaque components' patterns within the plaque is lacking. The aim of this study was to determine new compositional and structural indices which indicate spatial distribution, heterogeneity and dispersity of each VH–IVUS-derived component within the plaque area and also with respect to the plaque–lumen border. We developed an automated computational system in Java for the analysis of both single cross-sectional segments and the whole length of the examined plaque (volumetric analysis). The following parameters were computed: the number of different solid segments and the area of the largest solid segment of each component within the plaque, the per cent of the lumen border that is surrounded by each component, the number of different solid segments and the largest area of a solid segment of each component that adjoins the lumen border. Especially components' localisation in relation to the lumen border may significantly influence plaque vulnerability and plaque–stent interaction, which should be investigated in future clinical studies.

Vascular Response of the Segments Adjacent to the Proximal and Distal Edges of the ABSORB Everolimus-Eluting Bioresorbable Vascular Scaffold: 6-Month and 1-Year Follow-Up Assessment: A Virtual Histology Intravascular Ultrasound Study From the First-in-Man ABSORB Cohort B Trial

This study sought to investigate in vivo the vascular response at the proximal and distal edges of the second-generation ABSORB everolimus-eluting bioresorbable vascular scaffold (BVS). The edge vascular response after implantation of the BVS has not been previously investigated. The ABSORB Cohort B trial enrolled 101 patients and was divided into B(1) (n = 45) and B(2) (n = 56) subgroups. The adjacent (5-mm) proximal and distal vessel segments to the implanted ABSORB BVS were investigated at either 6 months (B(1)) or 1 year (B(2)) with virtual histology intravascular ultrasound (VH-IVUS) imaging. At the 5-mm proximal edge, the only significant change was modest constrictive remodeling at 6 months (Δ vessel cross-sectional area: -1.80% [-3.18; 1.30], p < 0.05), with a tendency to regress at 1 year (Δ vessel cross-sectional area: -1.53% [-7.74; 2.48], p = 0.06). The relative change of the fibrotic and fibrofatty (FF) tissue areas at this segment were not statistically significant at either time point. At the 5-mm distal edge, a significant increase in the FF tissue of 43.32% [-19.90; 244.28], (p < 0.05) 1-year post-implantation was evident. The changes in dense calcium need to be interpreted with caution since the polymeric struts are detected as "pseudo" dense calcium structures with the VH-IVUS imaging modality. The vascular response up to 1 year after implantation of the ABSORB BVS demonstrated some degree of proximal edge constrictive remodeling and distal edge increase in FF tissue resulting in nonsignificant plaque progression with adaptive expansive remodeling. This morphological and tissue composition behavior appears to not significantly differ from the behavior of metallic drug-eluting stents at the same observational time points.

TCT-627: Risk Evaluation of Distal Embolization During Percutaneous Coronary Intervention by Angioscopy and Virtual Histology Intravascular Ultrasound Imaging

TCT-627: Risk Evaluation of Distal Embolization During Percutaneous Coronary Intervention by Angioscopy and Virtual Histology Intravascular Ultrasound Imaging

Endovascular treatment is effective against acute mesenteric ischemia complicated with metabolic diseases.

A 77-year-old man with hypertension, diabetes mellitus, ischemic heart disease and a smoking habit presented at our hospital with sudden abdominal pain. Computed tomography indicated edematous swelling and pneumatosis of the intestinal wall in a localized area of the ascending colon with inflamed adipose tissue. Acute mesenteric ischemia was diagnosed. Abdominal angiography showed stenosis of the mesenteric arteries. Virtual histology-intravascular ultrasound imaging indicated a fibrous change in the superior mesenteric artery with a necrotic core. Endovascular treatment with stent placement after percutaneous transluminal angioplasty was effective. Surgery would usually be considered as the first choice for treating patients with acute mesenteric ischemia; however, when this condition is complicated with metabolic diseases, stenotic changes in the mesenteric arteries that would normally be found in patients with chronic mesenteric ischemia need to be considered to ensure optimal treatment.

076 Dual source computed tomography for characterisation of coronary atherosclerotic plaques. A comparison with virtual histology intravascular ultrasound

<h3>Background</h3> Non invasive plaque characterisation is important for risk stratification. Dual Source CT (DSCT) offers a significant improvement in temporal resolution over single source CT and may be a non invasive method to classify plaque components. Although CT plaque images have previously been compared with greyscale IVUS they have not been validated against virtual histology intravascular ultrasound (VH-IVUS), a technology which involves spectral analysis of IVUS radiofrequency signals. VH-IVUS is the gold standard for in vivo plaque classification, with proven validation against histology. Our aim was to show that DSCT could distinguish between plaque components as defined by VH-IVUS on the basis of their attenuation values in Hounsfield units (HU). <h3>Methods</h3> Twenty-one patients underwent DSCT and VH-IVUS prior to coronary stenting. Twenty-six plaques with VH-IVUS plaque burden &gt;40% were chosen. Plaques were either homogenous for fibrous plaque or contained large confluent areas of calcified plaque or a necrotic core. The VH- IVUS images were co-registered with the corresponding CT image by an unblinded observer. Accurate matching of lesions was performed by using measurements of distance from the coronary ostia. The images were orientated using fiduciary markers (side branches or characteristic calcifications). Multiple regions of interest (ROI) were placed within the plaque components and lumen on the cross sectional CT images in areas that had been pre-classified on the VH-IVUS images (Abstract 76 Figure 1). The density of these ROIs were measured (expressed in HU) and assigned to the relative plaque type or lumen. <h3>Results</h3> Attenuation values for 171 ROIs (necrotic core 28, fibrous plaque 38, calcified plaque 29 and lumen 76) were measured from the 26 plaques. Mean and standard deviation attenuation values were 35+/−17 HU, 128+/−49 HU, 719+/−237 HU and 362+/−51 respectively (Abstract 76 Table 1). There were statistically highly significant differences in the attenuation values among the four groups (necrotic core, fibrous plaque, calcified plaque and lumen) by nonparametric Kruskal–Wallis test (p&lt;0.0001) (Abstract 76 Figure 2). <h3>Conclusions</h3> VH-IVUS-defined plaque components have characteristic attenuation values that differ significantly enough to be differentiated by DSCT. This classification may facilitate non-invasive coronary plaque characterisation using DSCT for both therapeutic drug trials and assessment of vascular risk.

106 Which virtual histology intravascular ultrasound properties discriminate better between stable angina pectoris and troponin positive acute coronary syndrome: assessment of plaques or analysis of the whole coronary artery vasculature?

<h3>Introduction</h3> Previous work has examined the relationship between plaque virtual-histology intravascular ultrasound (VH-IVUS) appearances (local coronary factors) and patient presentation. However, little is known about the relationship between patient presentation and VH-IVUS appearances of the whole coronary vascular tree (global coronary factors), which may be a better ‘barometer’ of patients9 cardiovascular risk. This study aims to determine which VH-IVUS coronary factors, local or global, discriminate better between stable angina and troponin-positive acute coronary syndrome (ACS). <h3>Methods</h3> This 200 patient cross-sectional study examined the VH-IVUS appearances of the whole coronary vascular tree (full 3-vessel VH-IVUS) in patients referred for percutaneous coronary intervention (PCI) with either stable angina or ACS. VH-IVUS imaging preceded PCI. Results are presented as mean±SD unless stated. <h3>Results</h3> There were no differences in baseline demographics between stable angina and ACS groups including age, sex, blood pressure, previous MI, diabetes, serum cholesterol/HDL ratio and smoking. On full 3-vessel VH-IVUS, diabetic patients had a greater necrotic core volume (238±168 mm³ vs 120±77 mm³, p=0.022) and plaque burden (1673±645 mm³ vs 1102±445 mm³, p=0.006) than non-diabetics. After adjusting for total plaque volume, diabetics still had more necrotic core volume than non-diabetics: 12.9±5.0% vs 10.3±4.1%, p=0.045. Full 3-vessel VH-IVUS necrotic core volume did not differ between stable angina and ACS groups, even after adjusting for total plaque volume: 10.1±4.0% vs 11.6±4.6%, p=0.10, indicating that plaque composition throughout the whole arterial tree could not predict presentation. However, ACS patients were more likely to have at least one VH-IVUS derived thin-capped fibroatheroma (ID-TCFA) in the target vessel than stable angina patients: OR 2.2 (95% CI 0.9 to 5.4), p=0.048. Abstract 106 Figure 1 shows ID-TCFA (FI=fibrous tissue, FF=fibrofatty tissue, NC=necrotic core, DC=dense calcium). <h3>Conclusion</h3> Although global coronary factors (whole coronary artery plaque burden and necrotic core volume) may define high-risk patient populations such as diabetics, local plaque structure such as presence of ID-TCFAs in the target vessel may be more important in governing mode of patient presentation.

Age-related differences in virtual histology-intravascular ultrasound findings in patients with coronary artery disease

We assessed the age-related differences in pre-intervention virtual histology-intravascular ultrasound (VH-IVUS) findings at target lesion sites in patients with coronary artery disease. A total of 553 patients who underwent pre-intervention VH-IVUS imaging were grouped according to age: non-elderly (< or = 70 years, n=429) and elderly (>70 years, n=124); 191 had stable angina and 362 acute coronary syndrome. VH-IVUS classified the tissue into: fibrotic, fibro-fatty, dense calcium (DC), and necrotic core (NC). Overall, the absolute and percent volumes of DC (11.0 + or - 11.0mm(3) vs. 9.7 + or - 11.9 mm(3), P=0.033; 11.7 + or - 8.1% vs. 9.8 + or - 7.2%, P=0.014, respectively) and NC (18.5 + or - 17.6mm(3) vs. 16.6 + or - 18.9 mm(3), P=0.020; 18.8 + or - 8.8% vs. 16.5 + or - 9.3%, P=0.026, respectively) were significantly greater in the elderly than in the non-elderly. In stable angina patients, the absolute and percent volumes of DC (10.4 + or - 9.9 mm(3) vs. 7.2 + or - 7.6 mm(3), P=0.022; 13.4 + or - 10.0% vs. 9.2 + or - 6.5%, P=0.011, respectively) and NC (14.8 + or - 11.2 mm(3) vs. 12.0 + or - 11.9 mm(3), P=0.035; 19.6 + or - 8.8% vs. 15.5 + or - 8.4%, P=0.006, respectively) were significantly greater in the elderly. However, in acute coronary syndrome patients, there were no significant differences in absolute and percent volumes of DC (11.4 + or - 11.6 mm(3) vs. 10.9 + or - 13.4 mm(3), P=0.8; 10.7 + or - 6.5% vs. 10.1 + or - 7.5%, P=0.5, respectively) and NC (24.1 + or - 20.3 mm(3) vs. 23.9 + or - 21.2 mm(3), P=0.9; 22.0 + or - 8.8% vs. 21.3 + or - 9.6%, P=0.6, respectively) between the elderly and non-elderly groups. Myocardial infarction (OR: 2.56, 95% CI: 1.45-4.12, P=0.003), diabetes mellitus (OR: 2.23, 95% CI: 1.30-3.53, P=0.009), and high-sensitivity C-reactive protein (OR: 1.44, 95% CI: 1.06-2.45, P=0.042), but not age, were independent predictors of percent NC volume >20% in lesion site. Myocardial infarction, diabetes mellitus, and high-sensitivity C-reactive protein, but not age, were associated with NC-rich lesions. Clinical presentation, risk factors, and inflammatory status, but not age, are important factors for plaque components.

Target Lesion Thin-Cap Fibroatheroma Defined by Virtual Histology Intravascular Ultrasound Affects Microvascular Injury During Percutaneous Coronary Intervention in Patients With Angina Pectoris

Several reports suggest that virtual histology intravascular ultrasound (VH-IVUS) assessment could predict microvascular damage during percutaneous coronary intervention (PCI). A novel index of microcirculatory resistance (IMR) has been developed as a reproducible and less hemodynamic-dependent index. The purpose of this study was to investigate the relationship between thin-cap fibroatheroma (TCFA) defined by VH-IVUS and a change in the IMR during PCI in patients with angina pectoris (AP). The study investigated 30 lesions from 28 AP patients. VH-IVUS imaging was performed before PCI. TCFA was defined as the presence of confluent necrotic core (>10%) without detectable overlying fibrous cap segment. Patients were divided into 2 groups according to the presence of TCFA. Using a pressure guidewire, IMR were measured before and after PCI. After successful PCI, patients were prospectively followed up clinically. TCFA was detected in 9 lesions (30%). IMR tended to improve after PCI in the non-TCFA group, but tended to worsen in the TCFA group. DeltaIMR (=IMR after PCI-IMR before PCI) was significantly higher in the TCFA group compared with the non-TCFA group (13.2+/-29.9 vs -4.4+/-16.0, P=0.04). During follow-up (mean 20 months), survival free of major adverse cardiac events was significantly less in the TCFA group than in the non-TCFA group. Target lesion TCFA may be related to both microvascular injury and the long-term clinical outcome after successful PCI in patients with AP.