Multiple plaque ruptures healing assessed by serial optical coherence tomography

A 30-year-old man with hypertension presented to the emergency department with a 30-minute episode of diaphoresis and chest pain, acute inferior myocardial infarction was diagnosed on electrocardiogram.

The effect of colchicine on cholesterol crystal formation, expansion and morphology: a potential mechanism in atherosclerosis

Background

Inflammation is pivotal to the progression of atherosclerosis. Cholesterol crystals (CCs) that grow and enlarge within the plaque core can cause plaque rupture and trigger inflammation as they deposit into the atherosclerotic bed. Thus, agents that affect CC formation, expansion, and morphology may reduce cardiovascular (CV) risk independent of lipid-lowering and anti-inflammatory therapy.

Objective

Because colchicine is highly concentrated in leukocytes that can enter the atherosclerotic plaque core, we tested its effect on the formation and growth of CCs in bench experiments to determine whether it may have direct effects on CCs, independent of its known anti-inflammatory actions.

Method

Different dosages of colchicine mixed with cholesterol (0.05-5 mg/ml/g of cholesterol) were used to influence the formation CCs and volume expansion in vitro. These were compared to control samples with cholesterol in ddH2O without colchicine. In an ex vivo study, fresh atherosclerotic human plaques were incubated with and without colchicine in a water bath at 37°C for 48 h to assess the impact of colchicine on CC morphology. Scanning electron microscopy (SEM) was utilized to analyze CC morphology in samples from the various treatment groups.

Results

The addition of colchicine to cholesterol caused a substantial dose-dependent reduction in volume (p < 0.05). Pairwise comparisons of volume reduction, showed a significant reduction in volume at 5 mg/ml/g when compared to control (p < 0.02) but the calculated Cohen's d effect size was large for five of the six pairwise comparisons. By SEM, CCs from both in vitro and ex vivo samples treated with colchicine had evidence of dissolution and changes in their morphology as evidenced by the loss of their sharp edges. In contrast, CCs in untreated specimens retained their typical geometric structure.

Conclusions

Colchicine can reduce CC formation and expansion and alter CC morphology. These previously unappreciated effects of colchicine may contribute to its clinical benefit in patients with CV disease independent of its anti-inflammatory effects.

Differential Proteoglycan Expression in Atherosclerosis Alters Platelet Adhesion and Activation

Proteoglycans are differentially expressed in different atherosclerotic plaque phenotypes, with biglycan and decorin characteristic of ruptured plaques and versican and hyaluronan more prominent in eroded plaques. Following plaque disruption, the exposure of extracellular matrix (ECM) proteins triggers platelet adhesion and thrombus formation. In this study, the impact of differential plaque composition on platelet function and thrombus formation was investigated. Platelet adhesion, activation and thrombus formation under different shear stress conditions were assessed in response to individual proteoglycans and composites representing different plaque phenotypes. The results demonstrated that all the proteoglycans tested mediated platelet adhesion but not platelet activation, and the extent of adhesion observed was significantly lower than that observed with type I and type III collagens. Thrombus formation upon the rupture and erosion ECM composites was significantly reduced (p < 0.05) compared to relevant collagen alone, indicating that proteoglycans negatively regulate platelet collagen responses. This was supported by results demonstrating that the addition of soluble biglycan or decorin to whole blood markedly reduced thrombus formation on type I collagen (p < 0.05). Interestingly, thrombus formation upon the erosion composite displayed aspirin sensitivity, whereas the rupture composite was intensive to aspirin, having implications for current antiplatelet therapy regimes. In conclusion, differential platelet responses and antiplatelet efficacy are observed on ECM composites phenotypic of plaque rupture and erosion. Proteoglycans inhibit thrombus formation and may offer a novel plaque-specific approach to limit arterial thrombosis.

Clinical Utility of Soluble Lectin Type Oxidized Low-Density Lipoprotein Receptor as a Biomarker for Myocardial Infarction and Stable Angina

Background and objectives Endothelial soluble lectin-type oxidized low-density lipoprotein receptor 1 (sLOX-1) recognizes oxidized low-density lipoprotein (LDL) and triggers downstream signaling leading to atherosclerosis. The objective of this study was to demonstrate the utility of sLOX-1 as a biomarker for detecting acute myocardial infarction (MI) and stable angina (SA) and to develop a diagnostic algorithm for distinguishing coronary vasospasm from coronary plaque rupture. Methods We enrolled 62 patients who underwent diagnostic coronary angiography (CAG) and 30 healthy controls (21 men and nine women) and measured sLOX-1, troponin I, and cardiac myosin-binding protein C (c-MyBPC) using commercial kits. Results Patients with MI exhibited higher sLOX-1 levels (301.55 ± 196.16 pg/ml) than patients with stable angina (220.76 ± 103.65 pg/ml) and healthy controls (121.14 ± 77.10, F: 10.55, p<0.001). Although higher troponin I levels were detected in MI patients (263.00 ± 493.00 vs. 3.19 ± 2.15 ng/ml, p=0.0019), no significant elevation was observed in SA patients (1.91 ± 0.79 ng/ml). Plasma sLOX-1 levels showed a positive association with age (r=0.37, p=0.003), but not with gender (r=0.04, p=0.75). Troponin I showed no association with age (r=0.12, p=0.36) or gender (r=0.06, p=0.62). Receiver operating characteristic (ROC) curves revealed that among the three biomarkers, troponin-I showed a higher area under the curve (AUC) (AUC: 0.941), followed by sLOX-1 (AUC: 0.888), while c-MyBPC showed no clinical utility in the detection of MI (AUC: 0.666). Conclusions A marked elevation of sLOX-1 can detect MI and differentiate the presence or absence of plaque rupture, along with diagnosing stable angina.

Mechanisms of fibrous cap formation in atherosclerosis

The fibrous cap is formed by smooth muscle cells that accumulate beneath the plaque endothelium. Cap rupture is the main cause of coronary thrombosis, leading to infarction and sudden cardiac death. Therefore, the qualities of the cap are primary determinants of the clinical outcome of coronary and carotid atherosclerosis. In this mini-review, we discuss current knowledge about the formation of the fibrous cap, including cell recruitment, clonal expansion, and central molecular signaling pathways. We also examine the differences between mouse and human fibrous caps and explore the impact of anti-atherosclerotic therapies on the state of the fibrous cap. We propose that the cap should be understood as a neo-media to substitute for the original media that becomes separated from the surface endothelium during atherogenesis and that embryonic pathways involved in the development of the arteria media contribute to cap formation.

The Contribution of Vascular Proteoglycans to Atherothrombosis: Clinical Implications

The vascular extracellular matrix (ECM) produced by endothelial and smooth muscle cells is composed of collagens and glycoproteins and plays an integral role in regulating the structure and function of the vascular wall. Alteration in the expression of these proteins is associated with endothelial dysfunction and has been implicated in the development and progression of atherosclerosis. The ECM composition of atherosclerotic plaques varies depending on plaque phenotype and vulnerability, with distinct differences observed between ruptured and erodes plaques. Moreover, the thrombi on the exposed ECM are diverse in structure and composition, suggesting that the best antithrombotic approach may differ depending on plaque phenotype. This review provides a comprehensive overview of the role of proteoglycans in atherogenesis and thrombosis. It discusses the differential expression of the proteoglycans in different plaque phenotypes and the potential impact on platelet function and thrombosis. Finally, the review highlights the importance of this concept in developing a targeted approach to antithrombotic treatments to improve clinical outcomes in cardiovascular disease.

Pathophysiology of Acute Coronary Syndromes-Diagnostic and Treatment Considerations

Coronary artery disease and acute coronary syndromes are accountable for significant morbidity and mortality, despite the preventive measures and technological advancements in their management. Thus, it is mandatory to further explore the pathophysiology in order to provide tailored and more effective therapies, since acute coronary syndrome pathogenesis is more varied than previously assumed. It consists of plaque rupture, plaque erosion, and calcified nodules. The advancement of vascular imaging tools has been critical in this regard, redefining the epidemiology of each mechanism. When it comes to acute coronary syndrome management, the presence of ruptured plaques almost always necessitates emergent reperfusion, whereas the presence of plaque erosions may indicate the possibility of conservative management with potent antiplatelet and anti-atherosclerotic medications. Calcified nodules, on the other hand, are an uncommon phenomenon that has largely gone unexplored in terms of the best management plan. Future studies should further establish the importance of detecting the underlying mechanism and the role of various treatment plans in each of these distinct entities.

Utility of optical coherence tomography in acute coronary syndromes

Studies utilizing intravascular imaging have replicated the findings of histopathological studies, identifying the most common substrates for acute coronary syndromes (ACS) as plaque rupture, erosion, and calcified nodule, with spontaneous coronary artery dissection, coronary artery spasm, and coronary embolism constituting the less common etiologies. The purpose of this review is to summarize the data from clinical studies that have used high-resolution intravascular optical coherence tomography (OCT) to assess culprit plaque morphology in ACS. In addition, we discuss the utility of intravascular OCT for effective treatment of patients presenting with ACS, including the possibility of culprit lesion-based treatment by percutaneous coronary intervention.

Identification of Optical Coherence Tomography-Defined Coronary Plaque Erosion by Preprocedural Computed Tomography Angiography

Background A previous coronary computed tomography (CT) angiographic study failed to discriminate optical coherence tomography-defined intact fibrous cap culprit lesions (IFC group) from those with ruptured fibrous caps (RFC group) in patients with coronary artery disease. This study aimed to evaluate the diagnostic efficacy of preprocedural coronary CT imaging in identifying subsequently performed optical coherence tomography-defined plaque rupture or erosion at culprit lesions in patients with non-ST-segment-elevation acute myocardial infarction. Methods and Results This study used data from 2 recently published studies that tested the hypothesis that coronary CT angiography (CCTA) before percutaneous coronary intervention may provide diagnostic information on the high-risk atherosclerotic burden in patients with non-ST-segment-elevation acute myocardial infarction. In the analysis of 186 patients, optical coherence tomography identified 106 RFC plaques and 80 IFC plaques as the culprit lesions. On CT, the prevalence of low-attenuation plaque, positive remodeling, napkin-ring sign, and spotty calcification were all significantly lower in the IFC group. The culprit vessel pericoronary adipose tissue inflammation and coronary artery calcium scores were significantly lower in the IFC group than in the RFC group. The absence of low-attenuation plaque, napkin-ring sign, zero coronary artery calcium, and low pericoronary adipose tissue inflammation were independent predictors of IFC. When stratified into 5 subgroups according to the number of these 4 CT factors, the prevalence of IFC was 8.3%, 20.8%, 44.6%, 75.6%, and 100% (P<0.001), respectively. Conclusions Preprocedural comprehensive coronary CT imaging, including coronary artery calcium and pericoronary adipose tissue inflammation assessment, can accurately and noninvasively identify optical coherence tomography-defined IFC or RFC culprit lesions.

Prevalence, Morphology, and Predictors of Intra-Stent Plaque Rupture in Patients with Acute Coronary Syndrome: An Optical Coherence Tomography Study

Previous studies have shown that plaque rupture (PR) is the most important cause of acute coronary syndrome (ACS). However, the potential impact of intra-stent PR on stent failure manifesting as ACS and the optical coherence tomography (OCT) features of these lesions was still less clear. Therefore, we aimed to investigate the characteristics of OCT-defined in-stent PR and identify the potential risk factors for PR in ACS patients. All 213 ACS patients were stratified into two groups according to the occurrence of in-stent PR. The baseline characteristics of all patients were investigated. A multivariable logistic regression was performed to identify factors associated with the formation of PR. OCT findings showed that 80 patients had in-stent PR, and 133 patients were without PR. Patients who suffered in-stent PR had higher blood lipid levels (P < .050) and longer duration of stent failure (P = .001). Moreover, thrombolysis in myocardial infarction (TIMI) 0/1 flow was more prone to the formation of PR (P = .010), and lesions in the PR group harbored more macrophages and cholesterol crystals (P < .001 and P = .024). On multivariate analysis, presentation of myocardial infarction (MI) and OCT findings of lipidic neointima length showed a 3.6-fold (P = .004) and 1.3-fold (P < .001) higher risk for occurrence of in-stent PR. ACS patients who suffered in-stent PR had a longer duration of stent failure and more ISR occurring in non-culprit vessels. Given the distinguishing features between ACS patients with in-stent PR and non-PR, potential targeted therapy was warranted to improve the prognosis of patients with in-stent PR.

Rapid Rise in Cardio-Ankle Vascular Index as a Predictor of Impending Cardiovascular Events -Smooth Muscle Cell Contraction Hypothesis for Plaque Rupture

Predictive factors for vascular events have not been established. The vasculature of the atheroma is supplied by penetration of the vasa vasorum through the smooth muscle cell layer from the adventitia. Smooth muscle cell contraction induces compression of the vasa vasorum, resulting in ischemia in intimal atheromatous lesions. Cardio-ankle vascular index (CAVI) has become known as an index of arterial stiffness of the arterial tree from the origin of the aorta to the ankle. CAVI reflects the progress of arteriosclerosis, and a rapid rise in CAVI indicates arterial smooth muscle cell contraction. We hypothesized that rapidly increased arterial stiffness evaluated by CAVI may be a predictor of impending cardiovascular events.

Prognostic Value of Admission Peak NT-proBNP Combined with Culprit Plaque Types for Predicting Cardiovascular Risk in ST-Segment Elevated Myocardial Infarction: An Optical Coherence Tomography Study

OBJECTIVE

Different culprit plaque phenotypes including plaque rupture (PR) and non-plaque rupture (NPR), and N-Terminal prohormone of brain natriuretic peptide (NT-proBNP) have been reported to influence clinical outcomes in patients with acute coronary syndrome (ACS). We aimed to investigate the prognostic implication of the peak and baseline values at admission for NT-proBNP for major adverse cardiovascular events (MACE) in ST-Segment Elevated Myocardial Infarction (STEMI) patients with different plaque phenotype.

METHODS

A total of 428 patients with STEMI undergoing optical coherence tomography (OCT) were enrolled and divided into four groups: PR/Tertile1-2 NT-proBNP (n = 132), PR/Tertile3 NT-proBNP (n = 65), NPR/Tertile1-2 NT-proBNP (n = 154), NPR/Tertlie3 NT-proBNP (n = 77). Baseline and Peak values of NT-proBNP were obtained in the admission period. The MACEs were defined as the composite of all-cause death, recurrence of myocardial infarction and stroke.

RESULTS

High levels for peak NT-proBNP were significantly associated with a higher incidence of MACE and death (Log rank p = 0.037 and 0.0012, respectively). In the subgroup with NPR, a high level for peak NT-proBNP was significantly associated with higher incidence of death (Log rank p = 0.0022) but this association was not significant in the subgroup of PR (Log rank p = 0.24). Though plaque types were not associated with adverse event, the combination of NPR and a higher peak value for NT-proBNP indicated higher incidence of death compared with other groups (Log rank p = 0.0017). The area under the receiver operating characteristic curve for predicting death to evaluate the diagnostic value of the peak value for NT-proBNP and plaque types combined with traditional risk factors was 0.843 (95% CI: 0.805-0.876), which is superior to solely traditional risk factors: NRI (26.8% [95% CI: 0.4-53.1%], p = 0.046) and IDI (5.1% [95% CI: 1.0-9.2%], p = 0.016).

CONCLUSION

STEMI patients with NPR and a high level for peak NT-proBNP showed higher incidence of death. The peak value of NT-proBNP in combination with plaque types can be used in risk stratification and prediction of death in patients with STEMI.

Distinctive Morphological Patterns of Complicated Coronary Plaques in Acute Coronary Syndromes: Insights from an Optical Coherence Tomography Study

Optical coherence tomography (OCT) is an ideal imaging technique for assessing culprit coronary plaque anatomy. We investigated the morphological features and mechanisms leading to plaque complication in a single-center observational retrospective study on 70 consecutive patients with an established diagnosis of acute coronary syndrome (ACS) who underwent OCT imaging after coronary angiography. Three prominent morphological entities were identified. Type I or intimal discontinuity, which was found to be the most common mechanism leading to ACS and was seen in 35 patients (50%), was associated with thrombus (68.6%; p = 0.001), mostly affected the proximal plaque segment (60%; p = 0.009), and had no distinctive underlying plaque features. Type II, a significant stenosis with vulnerability features (inflammation in 16 patients, 84.2%; thin-cap fibroatheroma (TCFA) in 10 patients, 52.6%) and a strong association with lipid-rich plaques (94.7%; p = 0.002), was observed in 19 patients (27.1%). Type III, a protrusive calcified nodule, which was found to be the dominant morphological pattern in 16 patients (22.9%), was found in longer plaques (20.8 mm vs. 16.8 mm ID vs. 12.4 mm SS; p = 0.04) and correlated well with TCFA (93.8%; p = 0.02) and inflammation (81.3%). These results emphasize the existence of a wide spectrum of coronary morphological patterns related to ACS.

Culprit Lesion Morphology of Rapidly Progressive and Extensive Anterior-Wall ST-Segment Elevation Myocardial Infarction

BACKGROUND

Rapidly progressive, extensive myocardial injury/infarction (RPEMI) beyond the concept of wave-front phenomenon can be observed even when achieving timely reperfusion; however, the pathogenesis of RPEMI remains unknown. This retrospective study investigated clinical and lesion characteristics of RPEMI, focusing on culprit-lesion morphology (CLM).

METHODS

Among patients with extensive anterior-wall ST-segment elevation myocardial infarction due to proximal left anterior descending artery lesions who had reperfusion within 3 hours of symptom onset, 60 patients undergoing both intravascular ultrasound and cardiac magnetic resonance imaging were enrolled. Myocardial injury/infarction before reperfusion therapy was assessed by QRS scores at hospitalization electrocardiogram, and the extent of myocardial injury/infarction was evaluated by cardiac magnetic resonance imaging, which measured area at risk, infarct size, myocardial salvage index, microvascular obstruction, and left ventricular ejection fraction. RPEMI was defined as lower left ventricular ejection fraction (less median value) with microvascular obstruction.

RESULTS

Despite comparable onset-to-door and onset-to-reperfusion times and area at risk, patients with RPEMI showed higher QRS scores at hospitalization (5 [4.3-6] versus 3 [2-4], P<0.001) and infarct size (26.5±9.1 versus 20.4±10.5%, P=0.04), and a tendency toward lower myocardial salvage index (0.27±0.14 versus 0.36±0.20, P=0.10) compared with those without. Patients with versus without RPEMI more frequently observed specific CLM on intravascular ultrasound, characterized by the combination of vulnerable plaques, plaque ruptures, and/or large thrombi. When stratified by CLM-score composed of these 3 criteria, higher CLM-scores were or tended to be associated with higher QRS scores and incidence of RPEMI. In multivariate analyses including no-reflow phenomenon and final coronary-flow deterioration, increased CLM-score (≥2) was independently associated with high QRS scores and RPEMI (odd ratio 11.25 [95% CI, 2.43-52.00]; P=0.002).

CONCLUSIONS

Vulnerable CLM was a consistent determinant of advanced myocardial injury/infarction both before and after reperfusion therapy and may play a pivotal role in the development of RPEMI.

The effect of plaque morphology, material composition and microcalcifications on the risk of cap rupture: A structural analysis of vulnerable atherosclerotic plaques

Background

The mechanical rupture of an atheroma cap may initiate a thrombus formation, followed by an acute coronary event and death. Several morphology and tissue composition factors have been identified to play a role on the mechanical stability of an atheroma, including cap thickness, lipid core stiffness, remodeling index, and blood pressure. More recently, the presence of microcalcifications (μCalcs) in the atheroma cap has been demonstrated, but their combined effect with other vulnerability factors has not been fully investigated.

Materials and methods

We performed numerical simulations on 3D idealized lesions and a microCT-derived human coronary atheroma, to quantitatively analyze the atheroma cap rupture. From the predicted cap stresses, we defined a biomechanics-based vulnerability index (VI) to classify the impact of each risk factor on plaque stability, and developed a predictive model based on their synergistic effect.

Results

Plaques with low remodeling index and soft lipid cores exhibit higher VI and can shift the location of maximal wall stresses. The VI exponentially rises as the cap becomes thinner, while the presence of a μCalc causes an additional 2.5-fold increase in vulnerability for a spherical inclusion. The human coronary atheroma model had a stable phenotype, but it was transformed into a vulnerable plaque after introducing a single spherical μCalc in its cap. Overall, cap thickness and μCalcs are the two most influential factors of mechanical rupture risk.

Conclusions

Our findings provide supporting evidence that high risk lesions are non-obstructive plaques with softer (lipid-rich) cores and a thin cap with μCalcs. However, stable plaques may still rupture in the presence of μCalcs.

Single-Cell RNA Sequencing of Peripheral Blood Mononuclear Cells From Acute Myocardial Infarction

Background

Acute myocardial infarction (AMI) can occur in patients with atherosclerotic disease, with or without plaque rupture. Previous studies have indicated a set of immune responses to plaque rupture. However, the specific circulating immune cell subsets that mediate inflammatory plaque rupture remain elusive.

Methods

Ten AMI patients were enrolled in our study (five with and five without plaque rupture; plaque characteristics were identified by optical coherence tomography). By single-cell RNA sequencing, we analyzed the transcriptomic profile of peripheral blood mononuclear cells.

Results

We identified 27 cell clusters among 82,550 cells, including monocytes, T cells, NK cells, B cells, megakaryocytes, and CD34⁺ cells. Classical and non-classical monocytes constitute the major inflammatory cell types, and pro-inflammatory genes such as CCL5, TLR7, and CX3CR1 were significantly upregulated in patients with plaque rupture, while the neutrophil activation and degranulation genes FPR2, MMP9, and CLEC4D were significantly expressed in the intermediate monocytes derived from patients without plaque rupture. We also found that CD4⁺ effector T cells may contribute to plaque rupture by producing a range of cytokines and inflammatory-related chemokines, while CD8⁺ effector T cells express more effector molecules in patients without plaque rupture, such as GZMB, GNLY, and PRF1, which may contribute to the progress of plaque erosion. Additionally, NK and B cells played a significant role in activating inflammatory cells and promoting chemokine production in the plaque rupture. Cell–cell communication elaborated characteristics in signaling pathways dominated by inflammatory activation of classical monocytes in patients with plaque rupture.

Conclusions

Our studies demonstrate that the circulating immune cells of patients with plaque rupture exhibit highly pro-inflammatory characteristics, while plaque erosion is mainly associated with intermediate monocyte amplification, neutrophil activation, and degranulation. These findings may provide novel targets for the precise treatment of patients with AMI.

Plaque Structural Stress: Detection, Determinants and Role in Atherosclerotic Plaque Rupture and Progression

Atherosclerosis remains a major cause of death worldwide, with most myocardial infarctions being due to rupture or erosion of coronary plaques. Although several imaging modalities can identify features that confer risk, major adverse cardiovascular event (MACE) rates attributable to each plaque are low, such that additional biomarkers are required to improve risk stratification at plaque and patient level. Coronary arteries are exposed to continual mechanical forces, and plaque rupture occurs when plaque structural stress (PSS) exceeds its mechanical strength. Prospective studies have shown that peak PSS is correlated with acute coronary syndrome (ACS) presentation, plaque rupture, and MACE, and provides additional prognostic information to imaging. In addition, PSS incorporates multiple variables, including plaque architecture, plaque material properties, and haemodynamic data into a defined solution, providing a more detailed overview of higher-risk lesions. We review the methods for calculation and determinants of PSS, imaging modalities used for modeling PSS, and idealized models that explore structural and geometric components that affect PSS. We also discuss current experimental and clinical data linking PSS to the natural history of coronary artery disease, and explore potential for refining treatment options and predicting future events.

Association Between Preinfarction Angina and Culprit Lesion Morphology in Patients With ST-Segment Elevation Myocardial Infarction: An Optical Coherence Tomography Study

BACKGROUND

Previous studies reported the cardiac protection effect of preinfarction angina (PIA) in patients with acute myocardial infarction (AMI). We sought to identify culprit-plaque morphology and clinical outcomes associated with PIA in patients with ST-segment elevation myocardial infarction (STEMI) using optical coherence tomography (OCT).

METHODS AND RESULTS

A total of 279 patients with STEMI between March 2017 and March 2019 who underwent intravascular OCT of the culprit lesion were prospectively included. Of them, 153 (54.8%) patients were presented with PIA. No differences were observed in clinical and angiographic data between the two groups, except STEMI onset with exertion was significantly less common in the PIA group (24.2 vs. 40.5%, p = 0.004). Patients with PIA exhibited a significantly lower incidence of plaque rupture (40.5 vs. 61.9%, p < 0.001) and lipid-rich plaques (48.4 vs. 69.0%, p = 0.001). The thin-cap fibroatheroma (TCFA) prevalence was lower in the PIA group, presenting a thicker fibrous cap thickness, although statistically significant differences were not observed (20.3 vs. 30.2%, p = 0.070; 129.1 ± 92.0 vs. 111.4 ± 78.1 μm, p = 0.088; respectively). The multivariate logistic regression analysis indicated that PIA was an independent negative predictor of plaque rupture (odds ratio: 0.44, 95% CI: 0.268-0.725, p = 0.001). No significant differences in clinical outcomes were observed besides unplanned revascularization.

CONCLUSION

Compared with the non-PIA group, STEMI patients with PIA showed a significantly lower prevalence of plaque rupture and lipid-rich plaques in culprit lesion, implying different mechanisms of STEMI attack in these two groups.

Identification of Carotid Artery Microstructure and Plaque Rupture Using C-Arm Cone-Beam CT: A Case Report

C-arm cone-beam computed tomography (CBCT) offers a high imaging resolution with a wide range of contrast to visualize vessels, soft tissue, and bone. We report the usefulness of CBCT in observing neovascularization, microcalcification, and plaque rupture. A 56-year-old man presented with vertigo and complain of an unsteady gait for 5 months. Catheter angiography demonstrated right severe carotid stenosis with irregular filling defect, which on high-resolution MRI showed vessel wall enhancement. The CBCT showed high density structures and linear contrast enhancement from the vascular lumen to the plaque, related to microstructure and plaque rupture. Carotid endarterectomy was performed, and histopathology confirmed that the high-density areas represented neovascularization and microcalcification, with linear enhancement representing plaque rupture. This is the first report showing that microcalcifications and plaque rupture can be identified by CBCT. Thus, CBCT can be used as a promising supplement to current imaging modalities to evaluate plaque components more accurately.

CD74 in Apoptotic Macrophages Is Associated with Inflammation, Plaque Progression and Clinical Manifestations in Human Atherosclerotic Lesions

The aim of this study was to investigate whether CD74 levels in atherosclerotic lesions are associated with inflammation, apoptosis, plaque severity, and clinical symptoms among patients with carotid atherosclerosis. We further studied whether CD74 expression is associated with apoptosis in macrophages induced by 7ketocholesterol (7keto). Sixty-one carotid samples (39 males and 22 females) were immunostained with macrophages, smooth muscle cells, CD74, ferritin, TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling), and thrombin receptors. Double immunocytochemistry of CD74 and caspase 3 or CD74 and Annexin V was performed on THP-1 macrophages exposed to 7keto. In human carotid plaques, CD74 expression is lesion-dependently increased and is associated with necrotic core formation and plaque rupture, clinical symptoms, macrophage apoptosis, ferritin, and thrombin receptors. CD74 levels were inversely correlated to high-density lipoproteins and statin treatment, and positively correlated to triglycerides. In THP-1 macrophages, 7keto induced a significant increase in levels of CD74, ferritin, and apoptotic cell death. This study suggests that CD74 in apoptotic macrophages is linked to inflammation and thrombosis in progression of human atherosclerotic plaques, lipid metabolism, and clinical manifestation in atherosclerosis. Surface CD74 in apoptotic macrophages and ferritin production induced by oxidized lipids may contribute to inflammation and plaque vulnerability in atherosclerosis.

Use of Optical Coherence Tomography in MI with Non-obstructive Coronary Arteries

MI with non-obstructive coronary arteries (MINOCA) comprises an important minority of cases of acute MI. Many different causes have been implicated in the pathogenetic mechanism of MINOCA. Optical coherence tomography (OCT) is an indispensable tool for recognising the underlying pathogenetic mechanism when epicardial pathology is suspected. OCT can reliably identify coronary lesions not apparent on conventional coronary angiography and discriminate the various phenotypes. Plaque rupture and plaque erosion are the most frequently found atherosclerotic causes of MINOCA. Furthermore, OCT can contribute to the identification of ischaemic non-atherosclerotic causes of MINOCA, such as spontaneous coronary artery dissection, coronary spasm and lone thrombus. Recognition of the exact cause will enable therapeutic management to be tailored accordingly. The combination of OCT with cardiac magnetic resonance can set a definite diagnosis in the vast majority of MINOCA patients.

Synopsis of Biomarkers of Atheromatous Plaque Formation, Rupture and Thrombosis in the Diagnosis of Acute Coronary Syndromes

Acute coronary syndrome is the main cause of mortality and morbidity worldwide and early diagnosis is a challenge for clinicians. Though cardiac Troponin, the most commonly used biomarker, is the gold standard for myocardial necrosis, it is blind for ischemia without necrosis. Therefore, ideal biomarkers are essential in the care of patients presenting with symptoms suggestive of cardiac ischemia. The ideal biomarker or group of biomarkers of atheromatous plaque formation, rupture and thrombosis for timely and accurate diagnosis of acute coronary syndrome is a current need. Therefore, we discuss the existing understanding and future of biomarkers of atheromatous plaque formation, rupture and thrombosis of acute coronary syndrome in this review. Keywords were searched from Medline, ISI, IBSS and Google Scholar databases. Further, the authors conducted a manual search of other relevant journals and reference lists of primary articles. The development of high-sensitivity troponin assays facilitates earlier exclusion of acute coronary syndrome, contributing to a reduced length of stay at the emergency department, and earlier treatment resulting in better outcomes. Although researchers have investigated biomarkers of atheromatous plaque formation, rupture and thrombosis to help early diagnosis of cardiac ischemia, most of them necessitate validation from further analysis. Among these biomarkers, pregnancy-associated plasma protein-A, intercellular adhesion molecule-1, and endothelial cell-specific molecule- 1(endocan) have shown promising results in the early diagnosis of acute coronary syndrome but need further evaluation. However, the use of a combination of biomarkers representing varying pathophysiological mechanisms of cardiac ischemia will support risk assessment, diagnosis and prognosis in these patients and this is the way forward.

[Numerical simulation study of fracture mechanics of the atherosclerotic plaque]

Atherosclerotic plaque rupture is the main cause of many cardiovascular diseases, and biomechanical factors play an important role in the process of plaque rupture. In the study of plaque biomechanics, there are relatively few studies based on fatigue fracture failure theory, and most of them mainly focus on the whole fatigue propagation process from crack initiation to plaque rupture, while there are few studies on the influence of crack on plaque rupture at a certain time in the process of fatigue propagation. In this paper, a two-dimensional plaque model with crack was established. Based on the theory of fracture mechanics and combined with the finite element numerical simulation method, the stress intensity factor (SIF) and related influencing factors at the crack tip in the plaque were studied. The SIF was used to measure the influence of crack on plaque rupture. The results show that the existence of crack can lead to local stress concentration, which increases the risk of plaque rupture. The SIF at the crack tip in the plaque was positively correlated with blood pressure, but negatively correlated with fibrous cap thickness and lipid pool stiffness. The effect of the thickness and angle of lipid pool on the SIF at the crack tip in the plaque was less than 4%, which could be ignored. This study provides a theoretical basis for the risk assessment of plaque rupture with cracks.

Optical Coherence Tomography-Derived Changes in Plaque Structural Stress Over the Cardiac Cycle: A New Method for Plaque Biomechanical Assessment

Introduction: Cyclic plaque structural stress has been hypothesized as a mechanism for plaque fatigue and eventually plaque rupture. A novel approach to derive cyclic plaque stress in vivo from optical coherence tomography (OCT) is hereby developed. Materials and Methods: All intermediate lesions from a previous OCT study were enrolled. OCT cross-sections at representative positions within each lesion were selected for plaque stress analysis. Detailed plaque morphology, including plaque composition, lumen and internal elastic lamina contours, were automatically delineated. OCT-derived vessel and plaque morphology were included in a 2-dimensional finite element analysis, loaded with patient-specific intracoronary pressure tracing data, to calculate the changes in plaque structural stress (ΔPSS) on vessel wall over the cardiac cycle. Results: A total of 50 lesions from 41 vessels were analyzed. A significant ΔPSS gradient was observed across the plaque, being maximal at the proximal shoulder (45.7 [32.3, 78.6] kPa), intermediate at minimal lumen area (MLA) (39.0 [30.8, 69.1] kPa) and minimal at the distal shoulder (35.1 [28.2, 72.3] kPa; p = 0.046). The presence of lipidic plaques were observed in 82% of the diseased segments. Larger relative lumen deformation and ΔPSS were observed in diseased segments, compared with normal segments (percent diameter change: 8.2 ± 4.2% vs. 6.3 ± 2.3%, p = 0.04; ΔPSS: 59.3 ± 48.2 kPa vs. 27.5 ± 8.2 kPa, p < 0.001). ΔPSS was positively correlated with plaque burden (r = 0.37, p < 0.001) and negatively correlated with fibrous cap thickness (r = -0.25, p = 0.004). Conclusions: ΔPSS provides a feasible method for assessing plaque biomechanics in vivo from OCT images, consistent with previous biomechanical and clinical studies based on different methodologies. Larger ΔPSS at proximal shoulder and MLA indicates the critical sites for future biomechanical assessment.

Development of a Collagen Fibre Remodelling Rupture Risk Metric for Potentially Vulnerable Carotid Artery Atherosclerotic Plaques

Atherosclerotic plaque rupture in carotid arteries can lead to stroke which is one of the leading causes of death or disability worldwide. The accumulation of atherosclerotic plaque in an artery changes the mechanical properties of the vessel. Whilst healthy arteries can continuously adapt to mechanical loads by remodelling their internal structure, particularly the load-bearing collagen fibres, diseased vessels may have limited remodelling capabilities. In this study, a local stress modulated remodelling algorithm is proposed to explore the mechanical response of arterial tissue to the remodelling of collagen fibres. This stress driven remodelling algorithm is used to predict the optimum distribution of fibres in healthy and diseased human carotid bifurcations obtained using Magnetic Resonance Imaging (MRI). In the models, healthy geometries were segmented into two layers: media and adventitia and diseased into four components: adventitia, media, plaque atheroma and lipid pool (when present in the MRI images). A novel meshing technique for hexahedral meshing of these geometries is also demonstrated. Using the remodelling algorithm, the optimum fibre patterns in various patient specific plaques are identified and the role that deviations from these fibre configurations in plaque vulnerability is shown. This study provides critical insights into the collagen fibre patterns required in carotid artery and plaque tissue to maintain plaque stability.

Plaque Rupture, Compared With Plaque Erosion, Is Associated With a Higher Level of Pancoronary Inflammation

OBJECTIVES

The aim of this study was to compare the level of coronary inflammation between plaque rupture and plaque erosion using pericoronary adipose tissue (PCAT) attenuation.

BACKGROUND

Vascular inflammation plays a key role in plaque rupture, while the role of inflammation in plaque erosion remains less well defined. PCAT attenuation determined using computed tomography has emerged as a marker specific for coronary artery inflammation.

METHODS

Patients with non-ST-segment elevation acute coronary syndromes who underwent preintervention coronary computed tomographic angiography and optical coherence tomographic culprit lesion imaging were enrolled. PCAT attenuation was measured around the culprit lesion and in the proximal 40 mm of all coronary arteries.

RESULTS

Among 198 patients, plaque rupture was the underlying mechanism in 107 (54.0%) and plaque erosion in 91 (46.0%). Plaque rupture had higher PCAT attenuation than plaque erosion both at the culprit plaque level (-65.8 ± 7.5 HU vs -69.5 ± 11.4 HU; P = 0.010) and at the culprit vessel level (-67.1 ± 7.1 HU vs -69.6 ± 8.2 HU; P = 0.024). The mean PCAT attenuation of all 3 coronary arteries was also significantly higher in patients with plaque rupture than in plaque erosion, indicating a higher level of inflammation (-67.9 ± 5.7 HU vs -69.9 ± 6.8 HU; P = 0.030). In multivariable analysis, plaque rupture was significantly associated with high PCAT attenuation.

CONCLUSIONS

PCAT attenuation in culprit plaque, culprit vessel, and all 3 coronary arteries was higher in plaque rupture than in plaque erosion. The results suggest that pancoronary inflammation plays a more significant role in plaque rupture than in plaque erosion. (Massachusetts General Hospital and Tsuchiura Kyodo General Hospital Coronary Imaging Collaboration; NCT04523194).

A Novel Monocyte Subset as a Unique Signature of Atherosclerotic Plaque Rupture

The evaluation of monocyte subset distribution among acute coronary syndrome (ACS) patients according to culprit coronary plaque morphology has never been explored. We evaluated whether there were significant differences in frequency of circulating monocyte subsets isolated from ACS patients according to optical coherence tomography (OCT) investigation of plaque erosion and rupture. We enrolled 74 patients with non-ST-elevation ACS (NSTE-ACS), 21 of them underwent OCT investigation of the culprit coronary plaque and local macrophage infiltration (MØI) assessment. As control, we enrolled 30 chronic coronary syndrome (CCS) patients. We assessed the frequency of monocyte subsets in the whole study population, in reliance on their CD14 and CD16 expression (classical, CM: CD14⁺⁺CD16^–; intermediates, IM: CD14⁺⁺CD16⁺; non-classical, NCM: CD14⁺CD16⁺⁺). Then, we tested the effect of lipopolysaccharide (LPS) (a CD14 ligand) on peripheral blood mononuclear cells (PBMCs) of NSTE-ACS patients, quantifying the inflammatory cytokine levels in cell-culture supernatants. Our data proved that monocyte subsets isolated from NSTE-ACS patients represent a peculiar biological signature of the pathophysiological mechanism lying beneath atherosclerotic plaque with a ruptured fibrous cap (RFC) as compared with plaque erosion. Moreover, the magnitude of LPS-mediated effects on IL-1β, IL-6, and IL-10 cytokine release in cell-culture supernatants appeared to be greater in NSTE-ACS patients with RFC. Finally, we described a fourth monocyte population never explored before in this clinical setting (pre-classical monocytes, PCM: CD14⁺CD16^–) that was prevalent in NSTE-ACS patients as compared with CCS and, especially, in patients with RFC and culprit plaque with MØI.

Plaque Erosion: A Distinctive Pathological Mechanism of Acute Coronary Syndrome

Plaque erosion (PE) is one of the most important pathological mechanisms underlying acute coronary syndrome (ACS). The incidence of PE is being increasingly recognized owing to the development and popularization of intracavitary imaging. Unlike traditional vulnerable plaques, eroded plaques have unique pathological characteristics. Moreover, recent studies have revealed that there are differences in the physiopathological mechanisms, biomarkers, and clinical outcomes between PE and plaque rupture (PR). Accurate diagnosis and treatment of eroded plaques require an understanding of the pathogenesis of PE. In this review, we summarize recent scientific discoveries of the pathological characteristics, mechanisms, biomarkers, clinical strategies, and prognosis in patients with PE.

Air Pollution and Coronary Plaque Vulnerability and Instability: An Optical Coherence Tomography Study

OBJECTIVES

We assessed the relationship between exposure to air pollutants and mechanisms of coronary instability evaluated by optical coherence tomography (OCT) in patients with acute coronary syndrome (ACS).

BACKGROUND

Air pollution is an emerging key player in determining the residual risk of coronary events. However, pathophysiological mechanisms linking air pollution and coronary events have been not adequately investigated.

METHODS

Patients with ACS undergoing OCT imaging were retrospectively selected. Mechanism of culprit lesion instability was classified as plaque rupture (PR) or intact fibrous cap (IFC) by OCT, and the presence of macrophage infiltrates (MØI) and thin-cap fibroatheroma (TCFA) at the culprit site was also assessed. Based on each case's home address, exposure to several pollutants was evaluated, including particulate matter 2.5 (PM2.5), PM10, and carbon monoxide (CO). Only patients with >2 years of available data on air pollution exposure prior to ACS were enrolled.

RESULTS

We included 126 patients (median age: 67.0 years of age; interquartile range: 55.5-76.0; 97 male patients [77.0%]). Sixty-six patients (52.4%) had PR as the mechanism of plaque instability. Patients with PR were exposed to significantly higher PM2.5 levels than to IFC, and PM2.5 was independently associated with PR (odds ratio: 1.194; 95% CI: 1.036 to 1.377; P = 0.015). Moreover, exposure to higher levels of PM2.5 was independently associated with the presence of TCFA and of MØI at the culprit site. Interestingly, PM2.5, PM10, and Co levels were positively and significantly correlated with serum levels of C-reactive protein.

CONCLUSIONS

We provide novel insights into the missing link between air pollution and increased risk of coronary events. In particular, exposure to higher concentrations of air pollutants is associated with the presence of vulnerable plaque features and with plaque rupture as a mechanism of coronary instability. An enhanced systemic and plaque inflammatory activation may explain these findings.

Optical Coherence Tomography of Plaque Vulnerability and Rupture: JACC Focus Seminar Part 1/3

Plaque rupture is the most common cause of acute coronary syndromes and sudden cardiac death. Characteristics and pathobiology of vulnerable plaques prone to plaque rupture have been studied extensively over 2 decades in humans using optical coherence tomography (OCT), an intravascular imaging technique with micron scale resolution. OCT studies have identified key features of plaque vulnerability and described the in vivo characteristics and spatial distribution of thin cap fibroatheromas as major precursors to plaque rupture. In addition, OCT data supports the evolving understanding of coronary heart disease as a panvascular process associated with inflammation. In the setting of high atherosclerotic burden, plaque ruptures often occur at multiple sites in the coronary arteries, and plaque progression and healing are dynamic processes modulated by systemic risk factors. This review details major investigations with intravascular OCT into the biology and clinical implications of plaque vulnerability and plaque rupture.

Plasma Pentraxin-3 Combined with Plaque Characteristics Predict Cardiovascular Risk in ST-Segment Elevated Myocardial Infarction: An Optical Coherence Tomography Study

Background

Culprit‑plaque morphology [plaque rupture (PR) and plaque erosion (PE) identified by optical coherence tomography (OCT)] and biomarker of vascular inflammation, pentraxin-3 (PTX3), have been reported to influence clinical outcomes in coronary diseases. We aimed to investigate the prognostic implication of culprit-plaque morphology and plasma PTX3 for major adverse cardiovascular events (MACE) in patients with ST-segment elevation myocardial infarction (STEMI).

Methods

A total of 236 patients were enrolled and divided into four groups: PE/low-PTX3 (n = 57), PE/high-PTX3 (n = 47), PR/low-PTX3 (n = 78) and PR/high-PTX3 (n = 54). MACE was defined as the composite of all-cause death, recurrence of myocardial infarction, stroke and unplanned revascularization of any coronary artery.

Results

During the follow-up of 1.9 years, a total of 40 (16.9%) MACE were observed: 5.3% (3 patients) among patients with PE/low-PTX3, 21.3% (10 patients) among patients with PE/high-PTX3, 17.9% (14 patients) among patients with PR/low-PTX3 and 24.1% (13 patients) among patients with PR/high-PTX3 (Log rank P = 0.013). In fully adjusted analyses, patients with high-PTX3 were associated with higher MACE risk (HR: 2.40, 95% CI: 1.26–4.57, P = 0.008). Patients with PR/high-PTX3 (HR: 5.63, 95% CI: 1.57–20.16, P = 0.008) and PE/high-PTX3 (HR: 5.44, 95% CI: 1.46–20.29, P = 0.012) presented higher MACE risk than those with PE/low-PTX3. Adding plasma PTX3 levels and PR to the risk prediction model increased the area under curves to 76.1% (95% CI: 67.6–84.5%) and the NRI (28.1%, 95% CI: 0.3–48.3%, P=0.040) and IDI (2.4%, 95% CI: 0.1–12.9%, P = 0.040).

Conclusion

Patients with PR/high-PTX3 and PE/high-PTX3 presented a poorer prognosis than those with PE/low-PTX3. Combining the culprit-plaque morphology with PTX3 enhanced the predictive ability for MACE and contributed to better identification of high-risk patients.

Trial Registration Number

This study is registered at clinical trials.gov as NCT03593928.

Targeting non-coding RNAs in unstable atherosclerotic plaques: Mechanism, regulation, possibilities, and limitations

Cardiovascular diseases (CVDs) caused by arteriosclerosis are the leading cause of death and disability worldwide. In the late stages of atherosclerosis, the atherosclerotic plaque gradually expands in the blood vessels, resulting in vascular stenosis. When the unstable plaque ruptures and falls off, it blocks the vessel causing vascular thrombosis, leading to strokes, myocardial infarctions, and a series of other serious diseases that endanger people's lives. Therefore, regulating plaque stability is the main means used to address the high mortality associated with CVDs. The progression of the atherosclerotic plaque is a complex integration of vascular cell apoptosis, lipid metabolism disorders, inflammatory cell infiltration, vascular smooth muscle cell migration, and neovascular infiltration. More recently, emerging evidence has demonstrated that non-coding RNAs (ncRNAs) play a significant role in regulating the pathophysiological process of atherosclerotic plaque formation by affecting the biological functions of the vasculature and its associated cells. The purpose of this paper is to comprehensively review the regulatory mechanisms involved in the susceptibility of atherosclerotic plaque rupture, discuss the limitations of current approaches to treat plaque instability, and highlight the potential clinical value of ncRNAs as novel diagnostic biomarkers and potential therapeutic strategies to improve plaque stability and reduce the risk of major cardiovascular events.

Plaque Vulnerability Index Predicts Cardiovascular Events: A Histological Study of an Endarterectomy Cohort

Background

The balance between stabilizing and destabilizing atherosclerotic plaque components is used in experimental studies and in imaging studies to identify rupture prone plaques. However, we lack the evidence that this balance predicts future cardiovascular events. Here we explore whether a calculated histological ratio, referred to as vulnerability index (VI), can predict patients at higher risk to suffer from future cardiovascular events.

Methods and Results

Carotid plaques and clinical information from 194 patients were studied. Tissue sections were used for histological analysis to calculate the VI (CD68 [cluster of differentiation 68], alpha‐actin, Oil red O, Movat pentachrome, and glycophorin A). Postoperative cardiovascular events were identified through the Swedish National Inpatient Health Register (2005–2013). During the follow‐up (60 months) 45 postoperative cardiovascular events were registered. Patients with a plaque VI in the fourth quartile compared with the first to third quartiles had significantly higher risk to suffer from a future cardiovascular event (P=0.0002). The VI was an independent predictor and none of the 5 histological variables analyzed separately predicted events. In the 13 patients who underwent bilateral carotid endarterectomy, the VI of the right plaque correlated with the VI of the left plaque and vice versa (r=0.7, P=0.01).

Conclusions

Our findings demonstrate that subjects with a high plaque VI have an increased risk of future cardiovascular events, independently of symptoms and other known cardiovascular risk factors . This strongly supports that techniques which image such plaques can facilitate risk stratification for subjects in need of more intense treatment.

In vivo correlation between morphological characteristics of coronary plaques and functional characteristics of carotid arteries in acute coronary syndrome

BACKGROUND

Carotid artery temperature heterogeneity (ΔΤ) measured by microwave radiometry (MWR) has been associated with future cardiovascular events including acute coronary syndromes. The vulnerable plaques of the coronary arterial tree, that can be ideally depicted by intracoronary imaging such as optical coherence tomography (OCT) have anatomical characteristics such as the thin fibrous cap (TCFA), that make them vulnerable to rupture. The scope of the study was to assess the implication of the carotid artery temperature heterogeneity on the culprit coronary plaque morphology in patients presenting with acute myocardial infarction.

METHODS

34 patients presented with an acute myocardial infarction were enrolled in the study. All patients underwent percutaneous coronary intervention (PCI) and OCT for the evaluation of the anatomical characteristics of the culprit lesion. After the completion of the PCI all patients underwent carotid ultrasound and MWR of both carotid arteries and thermal heterogeneity of the carotid arteries was assessed. Blood samples were collected for high sensitivity C-reactive protein (CRP) analysis.

RESULTS

Thirty four patients, 21 with STEMI (61.76%) and 13 (38.23%) with NSTEMI, were included in the study. Patients with ruptured plaques had significantly increased hsCRP compared to patients that did not have a ruptured plaque (14.41±4.02 vs 9.9±2.5, P<0.005). Thermal heterogeneity, was significantly increased in ruptured plaques compared to no ruptured ones (1.01±0.31 vs 0.51±0.14°C, P=0.001), and in plaques with TCFA compared to those without a TCFA (0.82±0.37 vs 0.60±0.05°C, P=0.001). Diabetes mellitus, ΔΤ and hsCRP, were entered in the multivariate analysis, from which DM (OR 4.12; 95% CI 0.77-22.07; P=0.07) and ΔΤ (OR for 0.1°C increase 1.43; 95% CI 1.03-1.98; P=0.03) remained in the final analysis, and only ΔΤ was independently associated with the presence of the TCFA. Regarding plaque rupture, STEMI, hsCRP, and ΔT were entered in the multivariate analysis from which hsCRP (OR 1.51; 95% CI 0.99-2.28; P=0.051) and ΔΤ (OR for 0.1°C increase 3.40; 95% CI 1.29-8.96; P=0.013) remained in the final analysis with the ΔT being the only variable.

Circulating Biomarkers Reflecting Destabilization Mechanisms of Coronary Artery Plaques: Are We Looking for the Impossible?

Despite significant strides to mitigate the complications of acute coronary syndrome (ACS), this clinical entity still represents a major global health burden. It has so far been well-established that most of the plaques leading to ACS are not a result of gradual narrowing of the vessel lumen, but rather a result of sudden disruption of vulnerable atherosclerotic plaques. As most of the developed imaging modalities for vulnerable plaque detection are invasive, multiple biomarkers were proposed to identify their presence. Owing to the pivotal role of lipids and inflammation in the pathophysiology of atherosclerosis, most of the biomarkers originated from one of those processes, whereas recent advancements in molecular sciences shed light on the use of microRNAs. Yet, at present there are no clinically implemented biomarkers or any other method for that matter that could non-invasively, yet reliably, diagnose the vulnerable plaque. Hence, in this review we summarized the available knowledge regarding the pathophysiology of plaque instability, the current evidence on potential biomarkers associated with plaque destabilization and finally, we discussed if search for biomarkers could one day bring us to non-invasive, cost-effective, yet valid way of diagnosing the vulnerable, rupture-prone coronary artery plaques.

Rupture of a Vulnerable Plaque in a Hazy Angiographic Culprit Lesion During Acute Coronary Syndrome

In the presence of an equivocal culprit lesion in the context of an acute coronary syndrome, the optical coherence tomography (OCT) scan defines the severity and composition of the plaque, elucidating (as in this pathognomonic case) the mechanism related to plaque rupture. Furthermore, OCT analysis allowed stent implantation with adequate sizing and length, and subsequent final optimization of the result. In the presence of non-unequivocal lesions, in the context of acute coronary syndrome, the use of OCT imaging defined the etiology and mechanism of plaque instability, reducing cardiovascular events. In this clinical scenario, it is necessary to have a low threshold for the use of intracoronary imaging methods. In a challenging scenario, resorting to intracoronary imaging when possible can reduce the risk of procedural and postprocedural complication.

Coronary plaque composition influences biomechanical stress and predicts plaque rupture in a morpho-mechanic OCT analysis

Plaque rupture occurs if stress within coronary lesions exceeds the protection exerted by the fibrous cap overlying the necrotic lipid core. However, very little is known about the biomechanical stress exerting this disrupting force. Employing optical coherence tomography (OCT), we generated plaque models and performed finite-element analysis to simulate stress distributions within the vessel wall in 10 ruptured and 10 non-ruptured lesions. In ruptured lesions, maximal stress within fibrous cap (peak cap stress [PCS]: 174 ± 67 vs. 52 ± 42 kPa, p<0.001) and vessel wall (maximal plaque stress [MPS]: 399 ± 233 vs. 90 ± 95 kPa, p=0.001) were significantly higher compared to non-ruptured plaques. Ruptures arose in the immediate proximity of maximal stress concentrations (angular distances: 21.8 ± 30.3° for PCS vs. 20.7 ± 23.7° for MPS); stress concentrations excellently predicted plaque rupture (area under the curve: 0.940 for PCS, 0.950 for MPS). This prediction of plaque rupture was superior to established vulnerability features such as fibrous cap thickness or macrophage infiltration. In conclusion, OCT-based finite-element analysis effectively assesses plaque biomechanics, which in turn predicts plaque rupture in patients. This highlights the importance of morpho-mechanic analysis assessing the disrupting effects of plaque stress.

Heart attacks are caused by a blockage in arteries that supply oxygen to the heart. This often happens when fatty deposits (or ‘plaques’) that line blood vessels break off and create a clot. To identify individuals most at risk of this occurring, physicians currently use symptoms, family history, blood tests, imaging and surgical procedures. But better methods are needed.

Imaging blockages in the arteries of individuals who died from heart attacks highlighted certain plaque characteristics that increase the risk of a rupture. Further understanding the forces that lead to these fatty deposits breaking off may help scientists to develop improved heart attack prediction methods.

Using patient-specific computer simulations, Milzi et al. show it is possible to predict where plaques are most likely to rupture in an individual, based on biomechanical stresses on the deposits in the artery. The models also showed how forces on the external layers of the plaque played a pivotal role in breakages.

More research is needed to confirm the results of this study and to develop automated ways for measuring the stress exerted on plaques in the arteries. If that research is successful, biomechanical analyses of artery plaques in routine patient assessments may one day allow physicians to predict heart attacks and provide life-saving preventive care.

Bee Attack or Heart Attack: Kounis Syndrome

Kounis syndrome (KS) is defined as an allergic or hypersensitivity reaction leading to coronary vasospasm and acute coronary syndrome. The inflammatory mediators released during the body's reaction to an allergen causes vasoconstriction, plaque rupture, platelet aggregation, and even thrombosis of an existing coronary stent. Over the years, many allergens including drugs, environmental exposures, and animal and insect bites have been implicated in KS. Patients may present with elevated cardiac enzymes and electrocardiographic changes. We describe a case of a patient with no prior cardiac history who presented to the emergency department seeking treatment after multiple bee stings. The patient had non-specific electrocardiogram (ECG) changes and elevated cardiac enzymes consistent with a non-ST-elevation myocardial infarction. The patient underwent a pharmacologic stress test and myocardial perfusion imaging, which showed a perfusion defect consistent with ischemia. Selective right and left coronary angiography revealed a critical lesion at the proximal left circumflex artery. This was managed with percutaneous coronary intervention utilizing a bare-metal stent.

Evaluation of coronary plaques and atherosclerosis using optical coherence tomography

Introduction: Coronary angiography (CAG) is the standard modality for assessing coronary stenosis; however, it has limitations in assessing coronary plaque morphology. Optical coherence tomography (OCT) is a high-resolution (10-20 μm) light-based intravascular imaging technique that can identify more detailed coronary plaque morphology compared to other intravascular imaging modalities. OCT is remarkable for characterizing fibrous, fibrocalcific, and lipid-rich plaques. The capabilities of OCT are well suited for discriminating three types of unstable plaque morphologies underlying coronary thrombosis, such as plaque rupture, erosion, and calcified nodules. The high resolution of OCT makes it possible to identify important features of vulnerable plaques, such as thin-cap (<65 μm thick) fibroatheroma, macrophages, vasa vasorum, and cholesterol crystals.Areas covered: This review summarizes the clinical impact of OCT and its efficacy in identifying plaque components and morphological features associated with plaque vulnerability.Expertopinion: The unique properties of OCT as a tool for investigating high-risk lesions have greatly contributed to a better understanding of plaque vulnerability. Consequently, OCT has led to significant changes in medical treatment and percutaneous coronary intervention strategies for acute coronary syndrome. Further development and investigation of OCT are necessary to better predict and manage acute coronary events in the future.

Atherothrombosis in Acute Coronary Syndromes-From Mechanistic Insights to Targeted Therapies

The atherothrombotic substrates for acute coronary syndromes (ACS) consist of plaque ruptures, erosions and calcified nodules, while the non-atherothrombotic etiologies, such as spontaneous coronary artery dissection, coronary artery spasm and coronary embolism are the rarer causes of ACS. The purpose of this comprehensive review is to (1) summarize the histopathologic insights into the atherothrombotic plaque subtypes in acute ACS from postmortem studies; (2) provide a brief overview of atherogenesis, while mainly focusing on the events that lead to plaque destabilization and disruption; (3) summarize mechanistic data from clinical studies that have used intravascular imaging, including high-resolution optical coherence tomography, to assess culprit plaque morphology and its underlying pathobiology, especially the newly described role of innate and adaptive immunity in ACS secondary to plaque erosion; (4) discuss the utility of intravascular imaging for effective treatment of patients presenting with ACS by percutaneous coronary intervention; and (5) discuss the opportunities that these mechanistic and imaging insights may provide for more individualized treatment of patients with ACS.

The Spectrum of ACS: Towards a More Personalized Approach

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Establishment of a Novel Mouse Model for Atherosclerotic Vulnerable Plaque

Background and Aims: Acute coronary syndrome (ACS) is a group of clinical syndromes characterized by rupture or erosion of atherosclerotic unstable plaques. Effective intervention for vulnerable plaques (VP) is of great significance to reduce adverse cardiovascular events.

Methods: Fbn1^C1039G+/− mice were crossbred with LDLR^−/− mice to obtain a novel model for atherosclerotic VP. After the mice were fed with a high-fat diet (HFD) for 12 or 24 weeks, pathological staining and immunohistochemistry analyses were employed to evaluate atherosclerotic lesions.

Results: Compared to control mice, Fbn1^C1039G+/−LDLR^−/− mice developed more severe atherosclerotic lesions, and the positive area of oil red O staining in the aortic sinus was significantly increased after 12 weeks (21.7 ± 2.0 vs. 6.3 ± 2.1) and 24 weeks (32.6 ± 2.5 vs. 18.7 ± 2.6) on a HFD. Additional vulnerable plaque characteristics, including significantly larger necrotic cores (280 ± 19 vs. 105 ± 7), thinner fiber caps (14.0 ± 2.8 vs. 32.6 ± 2.7), apparent elastin fiber fragmentation and vessel dilation (3,010 ± 67 vs. 1,465 ± 49), a 2-fold increase in macrophage number (8.5 ± 1.0 vs. 5.0 ± 0.6), obviously decreased smooth muscle cell number (0.6 ± 0.1 vs. 2.1 ± 0.2) and an ~25% decrease in total collagen content (33.6 ± 0.3 vs. 44.9 ± 9.1) were observed in Fbn1^C1039G+/−LDLR^−/− mice compared with control mice after 24 weeks. Furthermore, spontaneous plaque rupture, neovascularization, and intraplaque hemorrhage were detected in the model mouse plaque regions but not in those of the control mice.

Conclusions: Plaques in Fbn1^C1039G+/−LDLR^−/− mice fed a HFD show many features of human advanced atherosclerotic unstable plaques. These results suggest that the Fbn1^C1039G+/−LDLR^−/− mouse is a novel model for investigating the pathological and physiological mechanisms of advanced atherosclerotic unstable plaques.

Analysis of MicroRNAs Associated With Carotid Atherosclerotic Plaque Rupture With Thrombosis

Atherosclerosis is a progressive vascular wall inflammatory disease, and the rupture of atherosclerotic vulnerable plaques is the leading cause of morbidity and mortality worldwide. This study intended to explore the potential mechanisms behind plaque rupture and thrombosis in ApoE knockout mice. The spontaneous plaque rupture models were established, and left carotid artery tissues at different time points (1-, 2-, 4-, 6-, 8-, 12-, and 16-week post-surgery) were collected. By the extent of plaque rupture, plaque was defined as (1) control groups, (2) atherosclerotic plaque group, and (3) plaque rupture group. Macrophage (CD68), MMP-8, and MMP-13 activities were measured by immunofluorescence. Cytokines and inflammatory markers were measured by ELISA. The left carotid artery sample tissue was collected to evaluate the miRNAs expression level by miRNA-microarray. Bioinformatic analyses were conducted at three levels: (2) vs. (1), (3) vs. (2), and again in seven time series analysis. The plaque rupture with thrombus and intraplaque hemorrhage results peaked at 8 weeks and decreased thereafter. Similar trends were seen in the number of plaque macrophages and lipids, the expression of matrix metalloproteinase, and the atherosclerotic and plasma cytokine levels. MiRNA-microarray showed that miR-322-5p and miR-206-3p were specifically upregulated in the atherosclerotic plaque group compared with those in the control group. Meanwhile, miR-466h-5p was specifically upregulated in the plaque rupture group compared with the atherosclerotic plaque group. The highest incidence of plaque rupture and thrombosis occurred at 8 weeks post-surgery. miR-322-5p and miR-206-3p may be associated with the formation of atherosclerotic plaques. miR-466h-5p may promote atherosclerotic plaque rupture via apoptosis-related pathways.

Prevalence, Features, and Prognosis of Artery-to-Artery Embolic ST-Segment-Elevation Myocardial Infarction: An Optical Coherence Tomography Study

Background The major underlying mechanisms contributing to acute coronary syndrome are plaque rupture, plaque erosion, and calcified nodule. Artery-to-artery embolic myocardial infarction (AAEMI) was defined as ST-segment-elevation myocardial infarction caused by migrating thrombus formed at the proximal ruptured plaque. The aim of this study was to investigate the prevalence and clinical features of AAEMI by using optical coherence tomography. Methods and Results This study retrospectively enrolled 297 patients with ST-segment-elevation myocardial infarction who underwent optical coherence tomography before percutaneous coronary intervention. Patients were divided into 4 groups consisting of plaque rupture, plaque erosion, calcified nodule, and AAEMI according to optical coherence tomography findings. The prevalence of AAEMI was 3.4%. The culprit vessel in 60% of patients with AAEMI was right coronary artery. Minimum lumen area at the culprit site was larger in AAEMI compared with plaque rupture, plaque erosion, and calcified nodule (4.0 mm² [interquartile range (IQR), 2.2-4.9] versus 1.0 mm² [IQR, 0.8-1.3] versus 1.0 mm² [IQR, 0.8-1.2] versus 1.1 mm² [IQR, 0.7-1.6], P<0.001). Lumen area at the rupture site was larger in patients with AAEMI compared with patients with plaque rupture (4.4 mm² [IQR, 2.5-6.7] versus 1.5 mm² [IQR, 1.0-2.4], P<0.001). In patients with AAEMI, the median minimum lumen area at the occlusion site was 1.2 mm² (IQR, 1.0-2.1), 40% of them had nonstent strategy, and the 3-year major adverse cardiac event rate was 0%. Conclusions AAEMI is a rare cause for ST-segment-elevation myocardial infarction and has unique morphological features of plaque including larger lumen area at rupture site and smaller lumen area at the occlusion site.

NIRS-IVUS for Differentiating Coronary Plaque Rupture, Erosion, and Calcified Nodule in Acute Myocardial Infarction

OBJECTIVES

This study sought to investigate the ability of combined near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS) to differentiate plaque rupture (PR), plaque erosion (PE), or calcified nodule (CN) in acute myocardial infarction (AMI).

BACKGROUND

Most acute coronary syndromes occur from coronary thrombosis based on PR, PE, or CN. In vivo differentiation among PR, PE, and CN is a major challenge for intravascular imaging.

METHODS

The study enrolled 244 patients with AMI who had a de novo culprit lesion in a native coronary artery. The culprit lesions were assessed by both NIRS-IVUS and optical coherence tomography (OCT). Maximum lipid core burden index in 4 mm (maxLCBI_4mm) was measured by NIRS. Plaque cavity and convex calcium was detected by IVUS. The OCT diagnosis of PR (n = 175), PE (n = 44), and CN (n = 25) was used as a reference standard.

RESULTS

In the development cohort, IVUS-detected plaque cavity showed a high specificity (100%) and intermediate sensitivity (62%) for identifying OCT-PR. IVUS-detected convex calcium showed a high sensitivity (93%) and specificity (100%) for identifying OCT-CN. NIRS-measured maxLCBI_4mm was largest in OCT-PR (705 [interquartile range (IQR): 545 to 854]), followed by OCT-CN (355 [IQR: 303 to 478]) and OCT-PE (300 [IQR: 126 to 357]) (p < 0.001). The optimal cutoff value of maxLCBI_4mm was 426 for differentiating between OCT-PR and -PE; 328 for differentiating between OCT-PE and -CN; and 579 for differentiating between OCT-PR and -CN. In the validation cohort, the NIRS-IVUS classification algorithm using plaque cavity, convex calcium, and maxLCBI_4mm showed a sensitivity and specificity of 97% and 96% for identifying OCT-PR, 93% and 99% for OCT-PE, and 100% and 99% for OCT-CN, respectively.

CONCLUSIONS

By evaluating plaque cavity, convex calcium, and maxLCBI_4mm, NIRS-IVUS can accurately differentiate PR, PE, and CN.

Pancoronary Plaque Characteristics in STEMI Caused by Culprit Plaque Erosion Versus Rupture: 3-Vessel OCT Study

OBJECTIVES

This study sought to investigate nonculprit plaque characteristics in patients with ST-segment elevation myocardial infarction (STEMI) presenting with plaque erosion (PE) and plaque rupture (PR). Pancoronary vulnerability was considered at nonculprit sites: 1) the CLIMA (Relationship Between OCT Coronary Plaque Morphology and Clinical Outcome) study (NCT02883088) defined high-risk plaques with simultaneous presence of 4 optical coherence tomography (OCT) features (minimum lumen area <3.5 mm²; fibrous cap thickness [FCT] <75 μm; maximum lipid arc >180º; and macrophage accumulation); and 2) the presence of plaque ruptures or thin-cap fibroatheromas (TCFA).

BACKGROUND

PE is a unique clinical entity associated with better outcomes than PR. There is limited evidence regarding pancoronary plaque characteristics of patients with culprit PE versus culprit PR.

METHODS

Between October 2016 and September 2018, 523 patients treated by 3-vessel OCT at the time of primary percutaneous intervention were included with 152 patients excluded from final analysis.

RESULTS

Overall, 458 nonculprit plaques were identified in 202 STEMI patients with culprit PE; and 1,027 nonculprit plaques were identified in 321 STEMI patients with culprit PR. At least 1 CLIMA-defined OCT nonculprit high-risk plaque was seen in 11.4% of patients with culprit PE, but twice as many patients were seen with culprit PR (25.2%; p < 0.001). This proportion was also seen when individual high-risk features were analyzed separately. When patients with PE were divided by a heterogeneous substrate (fibrous or lipid-rich plaque) underlying the culprit site, the prevalence of nonculprits with FCT <75 μm, macrophages, and TCFA showed a significant gradient from PE_(Fibrous) to PE_{lipid-rich plaque (LRP)} to PR. Interestingly, nonculprit rupture was rarely found in patients with culprit PE_(Fibrous) (1.9%), although it was exhibited with comparable prevalence in patients with culprit PE_(LRP) (16.3%) versus PR (17.8%). Culprit PE predicted decreased pancoronary vulnerability independent of conventional risk factors.

CONCLUSIONS

STEMI patients with culprit PE have a limited pancoronary vulnerability that may explain better outcomes in these patients than in STEMI patients with culprit PR.