Dynamic nature of nonculprit coronary artery lesion morphology in STEMI: a serial IVUS analysis from the HORIZONS-AMI trial

Exploring new insights in coronary lesion assessment and treatment in patients with diabetes mellitus: the impact of optical coherence tomography

In this review, we summarise new insights into diagnostic approaches and treatment strategies for coronary artery disease (CAD) in patients with diabetes mellitus (DM). Despite the improvements in therapy, the clinical management of DM patients remains challenging as they develop more extensive CAD at a younger age and consistently have worse clinical outcomes than non-DM patients. Current diagnostic modalities as well as revascularisation treatments mainly focus on ischemic lesions. However, the impact of plaque morphology and composition are emerging as strong predictors of adverse cardiac events even in the absence of identified ischemia. In particular, the presence of vulnerable plaques such as thin-cap fibroatheroma (TCFA) lesions has been identified as a very strong predictor of future adverse events. This emphasises the need for an approach combining both functional and morphological methods in the assessment of lesions. In particular, optical coherence tomography (OCT) has proven to be a valuable asset by truly identifying TCFAs. New treatment strategies should consist of individualised and advanced medical regimens and may evolve towards plaque sealing through percutaneous treatment.

Glycemic control is independently associated with rapid progression of coronary atherosclerosis in the absence of a baseline coronary plaque burden: a retrospective case-control study from the PARADIGM registry

BACKGROUND

The baseline coronary plaque burden is the most important factor for rapid plaque progression (RPP) in the coronary artery. However, data on the independent predictors of RPP in the absence of a baseline coronary plaque burden are limited. Thus, this study aimed to investigate the predictors for RPP in patients without coronary plaques on baseline coronary computed tomography angiography (CCTA) images.

METHODS

A total of 402 patients (mean age: 57.6 ± 10.0 years, 49.3% men) without coronary plaques at baseline who underwent serial coronary CCTA were identified from the Progression of Atherosclerotic Plaque Determined by Computed Tomographic Angiography Imaging (PARADIGM) registry and included in this retrospective study. RPP was defined as an annual change of ≥ 1.0%/year in the percentage atheroma volume (PAV).

RESULTS

During a median inter-scan period of 3.6 years (interquartile range: 2.7-5.0 years), newly developed coronary plaques and RPP were observed in 35.6% and 4.2% of the patients, respectively. The baseline traditional risk factors, i.e., advanced age (≥ 60 years), male sex, hypertension, diabetes mellitus, hyperlipidemia, obesity, and current smoking status, were not significantly associated with the risk of RPP. Multivariate linear regression analysis showed that the serum hemoglobin A1c level (per 1% increase) measured at follow-up CCTA was independently associated with the annual change in the PAV (β: 0.098, 95% confidence interval [CI]: 0.048-0.149; P < 0.001). The multiple logistic regression models showed that the serum hemoglobin A1c level had an independent and positive association with the risk of RPP. The optimal predictive cut-off value of the hemoglobin A1c level for RPP was 7.05% (sensitivity: 80.0%, specificity: 86.7%; area under curve: 0.816 [95% CI: 0.574-0.999]; P = 0.017).

CONCLUSION

In this retrospective case-control study, the glycemic control status was strongly associated with the risk of RPP in patients without a baseline coronary plaque burden. This suggests that regular monitoring of the glycemic control status might be helpful for preventing the rapid progression of coronary atherosclerosis irrespective of the baseline risk factors. Further randomized investigations are necessary to confirm the results of our study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02803411.

Inflammation during the life cycle of the atherosclerotic plaque

Inflammation orchestrates each stage of the life cycle of atherosclerotic plaques. Indeed, inflammatory mediators likely link many traditional and emerging risk factors with atherogenesis. Atheroma initiation involves endothelial activation with recruitment of leucocytes to the arterial intima, where they interact with lipoproteins or their derivatives that have accumulated in this layer. The prolonged and usually clinically silent progression of atherosclerosis involves periods of smouldering inflammation, punctuated by episodes of acute activation that may arise from inflammatory mediators released from sites of extravascular injury or infection or from subclinical disruptions of the plaque. Smooth muscle cells and infiltrating leucocytes can proliferate but also undergo various forms of cell death that typically lead to formation of a lipid-rich 'necrotic' core within the evolving intimal lesion. Extracellular matrix synthesized by smooth muscle cells can form a fibrous cap that overlies the lesion's core. Thus, during progression of atheroma, cells not only procreate but perish. Inflammatory mediators participate in both processes. The ultimate clinical complication of atherosclerotic plaques involves disruption that provokes thrombosis, either by fracture of the plaque's fibrous cap or superficial erosion. The consequent clots can cause acute ischaemic syndromes if they embarrass perfusion. Incorporation of the thrombi can promote plaque healing and progressive intimal thickening that can aggravate stenosis and further limit downstream blood flow. Inflammatory mediators regulate many aspects of both plaque disruption and healing process. Thus, inflammatory processes contribute to all phases of the life cycle of atherosclerotic plaques, and represent ripe targets for mitigating the disease.

Discordance in the diagnostic assessment of vulnerable plaques between radiofrequency intravascular ultrasound versus optical coherence tomography among patients with acute myocardial infarction: insights from the IBIS-4 study

We aimed to evaluate the diagnostic agreement between radiofrequency (RF) intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for thin-cap fibroatheroma (TCFA) in non-infarct-related coronary arteries (non-IRA) in patients with ST-segment elevation myocardial infarction (STEMI). In the Integrated Biomarker Imaging Study (IBIS-4), 103 STEMI patients underwent OCT and RF-IVUS imaging of non-IRA after successful primary percutaneous coronary intervention and at 13-month follow-up. A coronary lesion was defined as a segment with ≥ 3 consecutive frames (≈1.2 mm) with plaque burden ≥ 40% as assessed by grayscale IVUS. RF-IVUS-derived TCFA was defined as a lesion with > 10% confluent necrotic core abutting to the lumen in > 10% of the circumference. OCT-TCFA was defined by a minimum cap thickness < 65 μm. The two modalities were matched based on anatomical landmarks using a dedicated matching software. Using grayscale IVUS, we identified 276 lesions at baseline (N = 146) and follow-up (N = 130). Using RF-IVUS, 208 lesions (75.4%) were classified as TCFA. Among them, OCT identified 14 (6.7%) TCFA, 60 (28.8%) thick-cap fibroatheroma (ThCFA), and 134 (64.4%) non-fibroatheroma. All OCT-TCFA (n = 14) were confirmed as RF-TCFA. The concordance rate between RF-IVUS and OCT for TCFA diagnosis was 29.7%. The reasons for discordance were: OCT-ThCFA (25.8%); OCT-fibrous plaque (34.0%); attenuation due to calcium (23.2%); attenuation due to macrophage (10.3%); no significant attenuation (6.7%). There was a notable discordance in the diagnostic assessment of TCFA between RF-IVUS and OCT. The majority of RF-derived TCFA were not categorized as fibroatheroma using OCT, while all OCT-TCFA were classified as TCFA by RF-IVUS.

ClinicalTrials.gov Identifier NCT00962416.

Vulnerable plaques and patients: state-of-the-art

Despite advanced understanding of the biology of atherosclerosis, coronary heart disease remains the leading cause of death worldwide. Progress has been challenging as half of the individuals who suffer sudden cardiac death do not experience premonitory symptoms. Furthermore, it is well-recognized that also a plaque that does not cause a haemodynamically significant stenosis can trigger a sudden cardiac event, yet the majority of ruptured or eroded plaques remain clinically silent. In the past 30 years since the term 'vulnerable plaque' was introduced, there have been major advances in the understanding of plaque pathogenesis and pathophysiology, shifting from pursuing features of 'vulnerability' of a specific lesion to the more comprehensive goal of identifying patient 'cardiovascular vulnerability'. It has been also recognized that aside a thin-capped, lipid-rich plaque associated with plaque rupture, acute coronary syndromes (ACS) are also caused by plaque erosion underlying between 25% and 60% of ACS nowadays, by calcified nodule or by functional coronary alterations. While there have been advances in preventive strategies and in pharmacotherapy, with improved agents to reduce cholesterol, thrombosis, and inflammation, events continue to occur in patients receiving optimal medical treatment. Although at present the positive predictive value of imaging precursors of the culprit plaques remains too low for clinical relevance, improving coronary plaque imaging may be instrumental in guiding pharmacotherapy intensity and could facilitate optimal allocation of novel, more aggressive, and costly treatment strategies. Recent technical and diagnostic advances justify continuation of interdisciplinary research efforts to improve cardiovascular prognosis by both systemic and 'local' diagnostics and therapies. The present state-of-the-art document aims to present and critically appraise the latest evidence, developments, and future perspectives in detection, prevention, and treatment of 'high-risk' plaques occurring in 'vulnerable' patients.

Cardiovascular Imaging Techniques for Detection of Vulnerable Plaques

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

Intravascular Molecular Imaging: Near-Infrared Fluorescence as a New Frontier

Despite exciting advances in structural intravascular imaging [intravascular ultrasound (IVUS) and optical coherence tomography (OCT)] that have enabled partial assessment of atheroma burden and high-risk features associated with acute coronary syndromes, structural-based imaging modalities alone do not comprehensively phenotype the complex pathobiology of atherosclerosis. Near-infrared fluorescence (NIRF) is an emerging molecular intravascular imaging modality that allows for in vivo visualization of pathobiological and cellular processes at atheroma plaque level, including inflammation, oxidative stress, and abnormal endothelial permeability. Established intravascular NIRF imaging targets include macrophages, cathepsin protease activity, oxidized low-density lipoprotein and abnormal endothelial permeability. Structural and molecular intravascular imaging provide complementary information about plaque microstructure and biology. For this reason, integrated hybrid catheters that combine NIRF-IVUS or NIRF-OCT have been developed to allow co-registration of morphological and molecular processes with a single pullback, as performed for standalone IVUS or OCT. NIRF imaging is approaching application in clinical practice. This will be accelerated by the use of FDA-approved indocyanine green (ICG), which illuminates lipid- and macrophage-rich zones of permeable atheroma. The ability to comprehensively phenotype coronary pathobiology in patients will enable a deeper understanding of plaque pathobiology, improve local and patient-based risk prediction, and usher in a new era of personalized therapy.

Multivessel Versus Culprit-Only Revascularization in STEMI and Multivessel Coronary Artery Disease: Meta-Analysis of Randomized Trials

OBJECTIVES

The goal of this systematic review and meta-analysis was to provide a comprehensive evaluation of contemporary randomized trials addressing the efficacy and safety of multivessel versus culprit vessel-only percutaneous coronary intervention (PCI) among patients presenting with ST-segment elevation myocardial infarction and multivessel coronary artery disease.

BACKGROUND

Multivessel coronary artery disease is present in about one-half of patients with ST-segment elevation myocardial infarction. Randomized controlled trials comparing multivessel and culprit vessel-only PCI produced conflicting results regarding the benefits of a multivessel PCI strategy.

METHODS

A comprehensive search for published randomized controlled trials comparing multivessel PCI with culprit vessel-only PCI was conducted on ClinicalTrials.gov, PubMed, Web of Science, EBSCO Services, the Cochrane Central Register of Controlled Trials, Google Scholar, and scientific conference sessions from inception to September 15, 2019. A meta-analysis was performed using a random-effects model to calculate the risk ratio (RR) and 95% confidence interval (CI). Primary efficacy outcomes were all-cause mortality and reinfarction.

RESULTS

Ten randomized controlled trials were included, representing 7,030 patients: 3,426 underwent multivessel PCI and 3,604 received culprit vessel-only PCI. Compared with culprit vessel-only PCI, multivessel PCI was associated with no significant difference in all-cause mortality (RR: 0.85; 95% CI: 0.68 to 1.05) and lower risk for reinfarction (RR: 0.69; 95% CI: 0.50 to 0.95), cardiovascular mortality (RR: 0.71; 95% CI: 0.50 to 1.00), and repeat revascularization (RR: 0.34; 95% CI: 0.25 to 0.44). Major bleeding (RR: 0.92; 95% CI: 0.50 to 1.67), stroke (RR: 1.15; 95% CI: 0.65 to 2.01), and contrast-induced nephropathy (RR: 1.25; 95% CI: 0.80 to 1.95) were not significantly different between the 2 groups.

CONCLUSIONS

Multivessel PCI was associated with a lower risk for reinfarction, without any difference in all-cause mortality, compared with culprit vessel-only PCI in patients with ST-segment elevation myocardial infarction.

Machine Learning Framework to Identify Individuals at Risk of Rapid Progression of Coronary Atherosclerosis: From the PARADIGM Registry

Background

Rapid coronary plaque progression (RPP) is associated with incident cardiovascular events. To date, no method exists for the identification of individuals at risk of RPP at a single point in time. This study integrated coronary computed tomography angiography–determined qualitative and quantitative plaque features within a machine learning (ML) framework to determine its performance for predicting RPP.

Methods and Results

Qualitative and quantitative coronary computed tomography angiography plaque characterization was performed in 1083 patients who underwent serial coronary computed tomography angiography from the PARADIGM (Progression of Atherosclerotic Plaque Determined by Computed Tomographic Angiography Imaging) registry. RPP was defined as an annual progression of percentage atheroma volume ≥1.0%. We employed the following ML models: model 1, clinical variables; model 2, model 1 plus qualitative plaque features; model 3, model 2 plus quantitative plaque features. ML models were compared with the atherosclerotic cardiovascular disease risk score, Duke coronary artery disease score, and a logistic regression statistical model. 224 patients (21%) were identified as RPP. Feature selection in ML identifies that quantitative computed tomography variables were higher‐ranking features, followed by qualitative computed tomography variables and clinical/laboratory variables. ML model 3 exhibited the highest discriminatory performance to identify individuals who would experience RPP when compared with atherosclerotic cardiovascular disease risk score, the other ML models, and the statistical model (area under the receiver operating characteristic curve in ML model 3, 0.83 [95% CI 0.78–0.89], versus atherosclerotic cardiovascular disease risk score, 0.60 [0.52–0.67]; Duke coronary artery disease score, 0.74 [0.68–0.79]; ML model 1, 0.62 [0.55–0.69]; ML model 2, 0.73 [0.67–0.80]; all P<0.001; statistical model, 0.81 [0.75–0.87], P=0.128).

Conclusions

Based on a ML framework, quantitative atherosclerosis characterization has been shown to be the most important feature when compared with clinical, laboratory, and qualitative measures in identifying patients at risk of RPP.

Predicting Locations of High-Risk Plaques in Coronary Arteries in Patients Receiving Statin Therapy

Features of high-risk coronary artery plaques prone to major adverse cardiac events (MACE) were identified by intravascular ultrasound (IVUS) virtual histology (VH). These plaque features are: thin-cap fibroatheroma (TCFA), plaque burden PB ≥ 70%, or minimal luminal area MLA ≤ 4 mm². Identification of arterial locations likely to later develop such high-risk plaques may help prevent MACE. We report a machine learning method for prediction of future high-risk coronary plaque locations and types in patients under statin therapy. Sixty-one patients with stable angina on statin therapy underwent baseline and one-year follow-up VH-IVUS non-culprit vessel examinations followed by quantitative image analysis. For each segmented and registered VH-IVUS frame pair ( ), location-specific ( mm) vascular features and demographic information at baseline were identified. Seven independent support vector machine classifiers with seven different feature subsets were trained to predict high-risk plaque types one year later. A leave-one-patient-out cross-validation was used to evaluate the prediction power of different feature subsets. The experimental results showed that our machine learning method predicted future TCFA with correctness of 85.9%, 81.7%, and 77.0% (G-mean) for baseline plaque phenotypes of TCFA, thick-cap fibroatheroma, and non-fibroatheroma, respectively. For predicting PB ≥ 70%, correctness was 80.8% for baseline PB ≥ 70% and 85.6% for 50% ≤ PB < 70%. Accuracy of predicted MLA ≤ 4 mm² was 81.6% for baseline MLA ≤ 4 mm² and 80.2% for 4 mm² < MLA ≤ 6 mm². Location-specific prediction of future high-risk coronary artery plaques is feasible through machine learning using focal vascular features and demographic variables. Our approach outperforms previously reported results and shows the importance of local factors on high-risk coronary artery plaque development.

Plaque volume and plaque risk profile in diabetic vs. non-diabetic patients undergoing lipid-lowering therapy: a study based on 3D intravascular ultrasound and virtual histology

Background

Coronary atherosclerosis progresses faster in patients with diabetes mellitus (DM) and causes higher morbidity and mortality in such patients compared to non-diabetics ones (non-DM). We quantify changes in plaque volume and plaque phenotype during lipid-lowering therapy in DM versus non-DM patients using advanced intracoronary imaging.

Methods

We analyzed data from 61 patients with stable angina pectoris included to the PREDICT trial searching for prediction of plaque changes during intensive lipid-lowering therapy (40 mg rosuvastatin daily). Geometrically correct, fully 3-D representation of the vascular wall surfaces and intravascular ultrasound virtual histology (IVUS-VH) defined tissue characterization was obtained via fusion of two-plane angiography and IVUS-VH. Frame-based indices of plaque morphology and virtual histology analyses were computed and averaged in 5 mm long baseline/follow-up registered vessel segments covering the entire length of the two sequential pullbacks (baseline, 1-year). We analyzed 698 5-mm-long segments and calculated the Liverpool active plaque score (LAPS).

Results

Despite reaching similar levels of LDL cholesterol (DM 2.12 ± 0.91 mmol/l, non-DM 1.8 ± 0.66 mmol/l, p = 0.21), DM patients experienced, compared to non-DM ones, higher progression of mean plaque area (0.47 ± 1.15 mm² vs. 0.21 ± 0.97, p = 0.001), percent atheroma volume (0.7 ± 2.8% vs. − 1.4 ± 2.5%, p = 0.007), increase of LAPS (0.23 ± 1.66 vs. 0.13 ± 1.79, p = 0.018), and exhibited more locations with TCFA (Thin-Cap Fibro-Atheroma) plaque phenotype in 5 mm vessel segments (20.3% vs. 12.5%, p = 0.01). However, only non-DM patients reached significant decrease of LDL cholesterol. Plaque changes were more pronounced in PIT (pathologic intimal thickening) compared to TCFA with increased plaque area in both phenotypes in DM patients.

Conclusion

Based on detailed 3D analysis, we found advanced plaque phenotype and further atherosclerosis progression in DM patients despite the same reached levels of LDLc as in non-DM patients.

Trial registration ClinicalTrials.gov identifier: NCT01773512

Serial 3-Vessel Optical Coherence Tomography and Intravascular Ultrasound Analysis of Changing Morphologies Associated With Lesion Progression in Patients With Stable Angina Pectoris

Background—

Optical coherence tomographic (OCT) morphologies associated with lesion progression are not well studied. The aim of this study was to determine the morphological change for untreated lesion progression using both OCT and intravascular ultrasound (IVUS).

Methods and Results—

We used baseline and 8-month follow-up 3-vessel OCT and IVUS to assess 127 nonculprit lesions (IVUS plaque burden ≥40%) in 45 patients with stable angina after target lesion treatment. Lesion progression was defined as an IVUS lumen area decrease >0.5 mm 2 . A layered pattern was identified as a superficial layer that had a different optical intensity and a clear demarcation from underlying plaque. Lesion progression was observed in 19% (24/127) lesions, and its pattern was characterized into 3 types: type I, new superficial layered pattern at follow-up that was not present at baseline (n=9); type II, a layered pattern at baseline whose layer thickness increased at follow-up (n=7); or type III, no layered pattern at baseline or follow-up (n=8). The increase of IVUS plaque+media area was largest in type I and least in type III (1.9 mm 2 [1.6–2.1], 1.1 mm 2 [0.9–1.4], and 0.3 mm 2 [−0.2 to 0.8], respectively; P =0.002). Type III, but not types I or II, showed negative remodeling during follow-up (IVUS vessel area; from 14.3 mm 2 [11.4–17.2] to 13.5 mm 2 [10.4–16.7]; P =0.02). OCT lipidic plaque was associated with lesion progression (odds ratio, 13.6; 95% confidence interval, 3.7–50.6; P <0.001).

Conclusions—

Lesion progression was categorized to distinct OCT morphologies that were related to changes in plaque mass or vessel remodeling.

Relationship Between Serum Inflammatory Marker Levels and the Dynamic Changes in Coronary Plaque Characteristics After Statin Therapy

BACKGROUND

The mechanism of statin for atheroma stabilization remains unclear. We aimed to assess the relationship between on-treatment changes in serum inflammatory biomarker levels and plaque composition in differed nonculprit coronary lesions.

METHODS AND RESULTS

The changes in serum biochemical values, and intravascular ultrasound data were evaluated in 218 patients with virtual histology (VH)-intravascular ultrasound-defined fibroatheroma-containing segments after 12-month rosuvastatin treatment. When stratifying patients into quartiles according to the change in high-sensitivity C-reactive protein (hsCRP), there was a significant positive linear relationship for the changes in %necrotic core (coefficient, 1.31; standard error, 0.54) and %dense calcium volumes (coefficient, 0.80; standard error, 0.27), but a negative linear relationship for the changes in %fibrous (coefficient, -0.94; standard error, 0.45) and %fibrofatty volumes (coefficient, -1.17; standard error, 0.56; all P<0.05). The decrease in hsCRP (-1.2±3.9 versus 0.5±3.4 mg/L; P=0.02) was greater in those without VH-defined thin-cap fibroatheroma (TCFA, defined as >30° of necrotic core abutting the lumen in 3 consecutive slices) than those with VH-TCFA at follow-up. Diabetes mellitus, a larger normalized total atheroma volume, and the presence of VH-TCFA at baseline predicted the presence of VH-TCFA at follow-up (odds ratio, 4.01, 1.18, and 9.21, respectively; all P<0.05), whereas the change in hsCRP showed a trend (odds ratio, 1.19; P=0.07). The change in low-density lipoprotein-cholesterol had no relationship with the changes in hsCRP or plaque compositions.

CONCLUSIONS

With 12-month rosuvastatin therapy, a greater hsCRP reduction (not low-density lipoprotein-cholesterol) was associated with a greater decrease in %necrotic core volume and the absence of VH-TCFA, indicating a link between the anti-inflammatory action of statin and plaque stabilization by reducing NC and reinforcing fibrous cap.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00997880.

Intravascular imaging in cardiovascular ageing

Ageing is related to complex molecular, inflammatory and biochemical changes that affect coronary pathology and often lead to coronary artery disease and cardiovascular events. Intravascular imaging is considered as the ideal technique to study coronary plaque morphology and assess its burden. Over the recent years several studies have been performed that investigated the association between pathophysiological mechanisms that promote vascular ageing and plaque morphology. In addition, several reports have compared plaque pathology in different age groups and a few studies included serial intravascular imaging to assess changes in the atheroma burden and compositional characteristics of the plaque. This review article summarizes the evidence derived from intravascular imaging studies about the implications of vascular ageing on coronary artery morphology and discusses the potential of coronary imaging in assessing atherosclerotic evolution.

Early Detection and Treatment of the Vulnerable Coronary Plaque

Early identification and treatment of the vulnerable plaque, that is, a coronary artery lesion with a high likelihood of rupture leading to an acute coronary syndrome, have gained great interest in the cardiovascular research field. Postmortem studies have identified clear morphological characteristics associated with plaque rupture. Recent advances in invasive and noninvasive coronary imaging techniques have empowered the clinician to identify suspected vulnerable plaques in vivo and paved the way for the evaluation of therapeutic agents targeted at reducing plaque vulnerability. Local treatment of vulnerable plaques by percutaneous coronary intervention and systemic treatment with anti-inflammatory and low-density lipoprotein–lowering drugs are currently being investigated in large randomized clinical trials to assess their therapeutic potential for reducing adverse coronary events. Results from these studies may enable a more patient-tailored strategy for the treatment of coronary artery disease.

The Role of Virtual Histology Intravascular Ultrasound in the Identification of Coronary Artery Plaque Vulnerability in Acute Coronary Syndromes

Markers of coronary plaque vulnerability, such as a high lipid burden, increased inflammatory activity, and a thin fibrous cap, have been identified in histological studies. In vivo, grayscale intravascular ultrasound (IVUS) provides more in-depth information on coronary artery plaque burden than conventional angiography but is unable to accurately distinguish between noncalcific tissue types within the plaque. An analysis of IVUS radiofrequency backscatter based on spectral pattern recognition, such as virtual histology IVUS, allows detailed scrutiny of plaque composition and classification of coronary lesions. This review discusses the virtual histology IVUS technology and its accuracy in identifying vulnerable plaque features, focusing on its use in predicting patient outcomes after acute coronary syndrome, and its limitations in clinical practice.

Evolution of nonculprit coronary atherosclerotic plaques assessed by serial virtual histology intravascular ultrasound in patients with ST-segment elevation myocardial infarction and chronic total occlusion

OBJECTIVE

The pathophysiology and natural course of coronary nonculprit plaques remain unclear. We investigated whether the short-term natural course of nonculprit plaques differs between ST-segment elevation myocardial infarction (STEMI) and chronic total occlusion (CTO) patients.

METHODS

We performed serial virtual histology intravascular ultrasound on nonculprit plaques in 26 STEMI and 11 CTO lesions at baseline and the 6-month follow-up.

RESULTS

At baseline, more lesions in the STEMI group were virtual histology intravascular ultrasound-derived thin-cap fibroatheromas (TCFA; 76.9 vs. 18.1%, P=0.002). During the follow-up period, the plaque composition changed dynamically in the STEMI group (fibrofatty: 9.8±1.9 to 17.3±2.9%, P=0.030; dense calcium: 12.7±1.8 to 8.1±1.7%, P=0.026; necrotic core: 21.1±1.8 to 15.4±2.2%, P=0.052), with a consistent plaque size. In the CTO group, the plaque composition and plaque size remained consistent without a significant change. Also, more lesions in the STEMI group remained as or progressed to TCFA, compared with the CTO group (67 vs. 11%, P=0.089). Factors associated with a persistent TCFA or with a new development of TCFA were a large necrotic core volume index and the diagnosis of STEMI, whereas new statin usage was a protective factor.

CONCLUSION

Nonculprit lesions in STEMI patients were more unstable at the baseline compared with those in CTO patients. During follow-up, nonculprit lesions in STEMI and CTO patients showed a distinct pattern of change; the former were stabilized in plaque composition, whereas the latter remained consistent. The diagnosis of STEMI and a large necrotic core volume were predictors of evolution to a TCFA, and new statin usage was a protective factor.

Usefulness of the Baseline Syntax Score to Predict 3-Year Outcome After Complete Revascularization by Percutaneous Coronary Intervention

Although we strive to achieve complete revascularization (CR) in those receiving percutaneous coronary intervention, it is uncertain which of these patients are at increased risk of clinical events. In this study, we aimed to investigate whether the baseline SYNTAX score (bSS) can predict adverse clinical events in patients receiving CR. From the Efficacy of Xience/Promus Versus Cypher in Reducing Late Loss After Stenting registry, the 3-year patient-oriented composite end point (POCE; all cause death, any myocardial infarction, and any revascularization) was compared according to bSS tertiles (1 ≤ low bSS < 6, 6 ≤ mid-bSS < 10, high bSS ≥ 10). Of the 5,088 patients, CR was achieved in 2,173 by percutaneous coronary intervention. The 3-year POCE increased significantly along with bSS tertile (7.3% vs 8.4% vs 14.8%, p <0.001). Multivariate analysis showed that, despite having the same residual SS of 0, the bSS was an independent predictor of 3-year POCE (hazard ratio 1.038, 95% confidence interval 1.018 to 1.058, p <0.001 per bSS point). In subgroup analysis, bSS was a predictor for 3-year POCE in multivessel diseases (hazard ratio 1.029, 95% confidence interval 1.004 to 1.054, p = 0.025 per bSS point), whereas in single-vessel diseases, the discriminative value of bSS was less significant. Also the clinical SYNTAX score, which added age, creatinine level, and ejection fraction to the bSS, was superior to the bSS in predicting 3-year POCE (area under the curve 0.595 vs 0.649, p = 0.008). In conclusion, the bSS was an independent predictor of long-term clinical outcomes in patients receiving CR, especially in those with multivessel coronary artery disease. Adding clinical factors to the bSS could increase the predictive power of clinical outcomes.

Prognostic Determinants of Coronary Atherosclerosis in Stable Ischemic Heart Disease

Risk stratification in patients with stable ischemic heart disease is essential to guide treatment decisions. In this regard, whether coronary anatomy, physiology, or plaque morphology is the best determinant of prognosis (and driver an effective therapeutic risk reduction) remains one of the greatest ongoing debates in cardiology. In the present report, we review the evidence for each of these characteristics and explore potential algorithms that may enable a practical diagnostic and therapeutic strategy for the management of patients with stable ischemic heart disease.

The vulnerable artery: early and rapid deposition of lipid in coronary arteries is associated with subsequent development of thin-cap fibroatheromas

AIMS

We aimed to determine whether intravascular ultrasound (IVUS) and near infrared spectroscopy (NIRS) could identify arteries which would subsequently develop a thin-cap fibroatheroma (TCFA).

METHODS AND RESULTS

Three-vessel angiography, IVUS and NIRS evaluations were performed at three, six and nine months after induction of diabetes mellitus and hypercholesterolaemia in 13 Yorkshire pigs (n=37 arteries). In vivo total arterial plaque plus media (P+M) area, echo-attenuated plaque (AP) area by IVUS, and lipid core burden index (LCBI) by NIRS were compared to histology at nine months. P+M mean area increased over time (3 vs. 6 months p<0.01; 6 vs. 9 months p<0.01), as did the AP area and mean LCBI between three and six months (p<0.01). There were 69 TCFAs within 18 arteries. The mean LCBI at six months was greater in arteries containing a TCFA (77.8±17.4 vs. 34.3±11.4; p=0.04) as was the ∆LCBI from three to six months (55.3±16.9 vs. 3.3±16.0; p=0.03). Arteries which contained TCFA at nine months had greater AP area by IVUS at six months (p=0.007).

CONCLUSIONS

The early and persistent accumulation of total arterial lipid detected by NIRS was associated with the future development of TCFAs.

Role of biomechanical forces in the natural history of coronary atherosclerosis

Atherosclerosis remains a major cause of morbidity and mortality worldwide, and a thorough understanding of the underlying pathophysiological mechanisms is crucial for the development of new therapeutic strategies. Although atherosclerosis is a systemic inflammatory disease, coronary atherosclerotic plaques are not uniformly distributed in the vascular tree. Experimental and clinical data highlight that biomechanical forces, including wall shear stress (WSS) and plaque structural stress (PSS), have an important role in the natural history of coronary atherosclerosis. Endothelial cell function is heavily influenced by changes in WSS, and longitudinal animal and human studies have shown that coronary regions with low WSS undergo increased plaque growth compared with high WSS regions. Local alterations in WSS might also promote transformation of stable to unstable plaque subtypes. Plaque rupture is determined by the balance between PSS and material strength, with plaque composition having a profound effect on PSS. Prospective clinical studies are required to ascertain whether integrating mechanical parameters with medical imaging can improve our ability to identify patients at highest risk of rapid disease progression or sudden cardiac events.

Intravascular imaging of coronary calcification and its clinical implications

Calcium impacts the natural history and treatment of coronary artery disease in many ways. Intravascular imaging studies, mostly intravascular ultrasound, but more recently studies using optical coherence tomography, have been instrumental in increasing our understanding of the relationship between calcium and coronary atherosclerosis, the predictors, the natural history of this relationship, and the impact on treatment. On one hand, stable coronary lesions are associated with more calcium than unstable lesions; and the amount of calcium may affect the success of percutaneous coronary intervention. On the other hand, calcium correlates with plaque burden; unstable lesions are associated with focal calcium deposits; and calcific nodules are one of the morphologies of vulnerable plaque. This review focuses on more than 20 years of intravascular imaging studies of the relationship between calcium and coronary atherosclerosis.

Near-infrared spectroscopy for intracoronary detection of lipid-rich plaques to understand atherosclerotic plaque biology in man and guide clinical therapy

Ischaemic heart disease is the leading cause of death worldwide. The common denominator for plaques causing acute coronary syndrome (ACS) is lipid accumulation, either as a lipid core or lipid pools. An intracoronary imaging device to detect lipid-rich plaques (LRPs) could therefore identify most of the plaques causing ACS and sudden death. Near-infrared spectroscopy combined with intravascular ultrasound (NIRS-IVUS) is a promising new intracoronary imaging method that is able to specifically quantify lipid accumulation measured as the lipid core burden index (LCBI). NIRS-IVUS is highly specific for the identification of ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) culprit plaques usually in the form of a circular LRP. NIRS-IVUS may assist in defining the aetiology of coronary events. The effect of cholesterol-lowering therapy on the lipid core can be measured in coronary plaques in patients, and NIRS-IVUS may be a useful tool for drug development in phase II studies as a surrogate end-point for future ACS. Plaques with a high LCBI have an increased risk of peri-procedural events. NIRS-IVUS can help to define the diameter and length of stents to avoid procedure-related complications. Increased coronary LCBI predicts a higher risk of future cardiovascular events. Lipid core detection using NIRS may help to identify vulnerable plaques to treat them before they cause ACS or sudden death.

Echogenicity as a surrogate for bioresorbable everolimus-eluting scaffold degradation: analysis at 1-, 3-, 6-, 12- 18, 24-, 30-, 36- and 42-month follow-up in a porcine model

The objective of the study is to validate intravascular quantitative echogenicity as a surrogate for molecular weight assessment of poly-l-lactide-acid (PLLA) bioresorbable scaffold (Absorb BVS, Abbott Vascular, Santa Clara, California). We analyzed at 9 time points (from 1- to 42-month follow-up) a population of 40 pigs that received 97 Absorb scaffolds. The treated regions were analyzed by echogenicity using adventitia as reference, and were categorized as more (hyperechogenic or upperechogenic) or less bright (hypoechogenic) than the reference. The volumes of echogenicity categories were correlated with the measurements of molecular weight (Mw) by gel permeation chromatography. Scaffold struts appeared as high echogenic structures. The quantification of grey level intensity in the scaffold-vessel compartment had strong correlation with the scaffold Mw: hyperechogenicity (correlation coefficient = 0.75; P < 0.01), upperechogenicity (correlation coefficient = 0.63; P < 0.01) and hyper + upperechogenicity (correlation coefficient = 0.78; P < 0.01). In the linear regression, the R² for high echogenicity and Mw was 0.57 for the combination of hyper and upper echogenicity. IVUS high intensity grey level quantification is correlated to Absorb BVS residual molecular weight and can be used as a surrogate for the monitoring of the degradation of semi-crystalline polymers scaffolds.

Culprit vessel only vs immediate complete revascularization in patients with acute ST-segment elevation myocardial infarction: systematic review and meta-analysis

Although multivessel coronary artery disease has been associated with poor health outcomes in patients with acute ST-segment elevation myocardial infarction (STEMI), the optimal approach to revascularization remains uncertain. The objective of this review was to determine the benefits and harms of culprit vessel only vs immediate complete percutaneous coronary intervention (PCI) in patients with acute STEMI. We searched MEDLINE, EMBASE, the Cochrane Register of Controlled Trials, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) for randomized controlled trials (RCTs). Teams of 2 reviewers, independently and in duplicate, screened titles and abstracts, completed full-text reviews, and abstracted data. We calculated pooled risk ratios (RRs) and associated 95% confidence intervals (CIs) using random-effect models for nonfatal myocardial infarction (MI), revascularization, cardiovascular mortality, all-cause mortality, and adverse events, and used the GRADE approach to rate confidence in estimates of effect. Of 341 patients randomized to complete revascularization and followed to study conclusion, 31 experienced revascularization, as did 80 of 324 randomized to culprit vessel only revascularization (RR: 0.35, 95% CI: 0.24-0.53). Ten patients in the complete revascularization group and 28 patients in the culprit vessel only revascularization group experienced nonfatal MI (RR: 0.35, 95% CI: 0.17-0.72). All-cause mortality and cardiac deaths did not differ between groups (RR: 0.69, 95% CI: 0.40-1.21 for all-cause mortality; RR: 0.48, 95% CI: 0.22-1.04 for cardiac deaths). Pooled data from 3 RCTs suggest that immediate complete revascularization probably reduces revascularization in patients with acute STEMI; although results suggest possible benefits on MI and death, confidence in estimates is low.

Clinical utility of intravascular imaging and physiology in coronary artery disease

Intravascular imaging and physiology techniques and technologies are moving beyond the framework of research to inform clinical decision making. Currently available technologies and techniques include fractional flow reserve; grayscale intravascular ultrasound (IVUS); IVUS radiofrequency tissue characterization; optical coherence tomography, the light analogue of IVUS; and near-infrared spectroscopy that detects lipid within the vessel wall and that has recently been combined with grayscale IVUS in a single catheter as the first combined imaging device. These tools can be used to answer questions that occur during daily practice, including: Is this stenosis significant? Where is the culprit lesion? Is this a vulnerable plaque? What is the likelihood of distal embolization or periprocedural myocardial infarction during stent implantation? How do I optimize acute stent results? Why did thrombosis or restenosis occur in this stent? One of the legacies of coronary angiography is to presume that one technique will answer all of these questions; however, that often has been proved inaccurate in contemporary practice.

Consideration of a new definition of clinically relevant myocardial infarction after coronary revascularization: an expert consensus document from the Society for Cardiovascular Angiography and Interventions (SCAI)

Numerous definitions have been proposed for the diagnosis of myocardial infarction (MI) after coronary revascularization. The universal definition for MI designates post procedural biomarker thresholds for defining percutaneous coronary intervention (PCI)-related MI (type 4a) and coronary artery bypass grafting (CABG)-related MI (type 5), which are of uncertain prognostic importance. In addition, for both the MI types, cTn is recommended as the biomarker of choice, the prognostic significance of which is less well validated than CK-MB. Widespread adoption of a MI definition not clearly linked to subsequent adverse events such as mortality or heart failure may have serious consequences for the appropriate assessment of devices and therapies, may affect clinical care pathways, and may result in misinterpretation of physician competence. Rather than using an MI definition sensitive for small degrees of myonecrosis (the occurrence of which, based on contemporary large-scale studies, are unlikely to have important clinical consequences), it is instead recommended that a threshold level of biomarker elevation which has been strongly linked to subsequent adverse events in clinical studies be used to define a "clinically relevant MI." The present document introduces a new definition for "clinically relevant MI" after coronary revascularization (PCI or CABG), which is applicable for use in clinical trials, patient care, and quality outcomes assessment.

In vivo detection of high-risk coronary plaques by radiofrequency intravascular ultrasound and cardiovascular outcome: results of the ATHEROREMO-IVUS study

AIMS

Acute coronary syndromes (ACS) are mostly caused by plaque rupture. This study aims to investigate the prognostic value of in vivo detection of high-risk coronary plaques by intravascular ultrasound (IVUS) in patients undergoing coronary angiography.

METHODS AND RESULTS

Between November 2008 and January 2011, IVUS of a non-culprit coronary artery was performed in 581 patients who underwent coronary angiography for ACS (n = 318) or stable angina (n = 263). Primary endpoint was major adverse cardiac events (MACEs) defined as mortality, ACS, or unplanned coronary revascularization. Culprit lesion-related events were not counted. Cumulative Kaplan-Meier incidence of 1-year MACE was 7.8%. The presence of IVUS virtual histology-derived thin-cap fibroatheroma (TCFA) lesions (present 10.8% vs. absent 5.6%; adjusted HR: 1.98, 95% CI: 1.09-3.60; P = 0.026) and lesions with a plaque burden of ≥70% (present 16.2% vs. absent 5.5%; adjusted HR: 2.90, 95% CI: 1.60-5.25; P < 0.001) were independently associated with a higher MACE rate. Thin-cap fibroatheroma lesions were also independently associated with the composite of death or ACS only (present 7.5% vs. absent 3.0%; adjusted HR: 2.51, 95% CI: 1.15-5.49; P = 0.021). Thin-cap fibroatheroma lesions with a plaque burden of ≥70% were associated with a higher MACE rate within (P = 0.011) and after (P < 0.001) 6 months of follow-up, while smaller TCFA lesions were only associated with a higher MACE rate after 6 months (P = 0.033).

CONCLUSION

In patients undergoing coronary angiography, the presence of IVUS virtual histology-derived TCFA lesions in a non-culprit coronary artery is strongly and independently predictive for the occurrence of MACE within 1 year, particularly of death and ACS. Thin-cap fibroatheroma lesions with a large plaque burden carry higher risk than small TCFA lesions, especially on the short term.