Advances in mechanisms, imaging and management of the unstable plaque

Antithrombotic Therapy in Acute Coronary Syndrome

Early mechanical reperfusion, primarily via percutaneous coronary intervention, combined with timely antithrombotic drug administration, constitutes the main approach for managing acute coronary syndrome (ACS). Clinicians have access to a variety of antithrombotic agents, necessitating careful selection to balance reducing thrombotic events against increased bleeding risks. This review offers a comprehensive update on current antithrombotic therapy in ACS, emphasizing the need for individualized treatment strategies.

Atherosclerotic Coronary Plaque Features in Patients With Chronic Obstructive Pulmonary Disease and Acute Coronary Syndrome

Previous studies reported a robust relation between chronic obstructive pulmonary disease (COPD) and coronary artery disease (CAD). Systemic inflammation has been proposed as possible pathogenetic mechanism linking these 2 entities, although data on atherosclerotic coronary features in COPD patients are lacking. We studied atherosclerotic coronary plaque features in COPD patients presenting with acute coronary syndrome (ACS) using optical coherence tomography (OCT). ACS patients who underwent intracoronary OCT imaging of the culprit vessel were enrolled. Coronary plaque characteristics and OCT-defined macrophage infiltration (MØI) were assessed by OCT. ACS patients were divided into 2 groups according to the presence of an established diagnosis of COPD, and plaque features at the culprit site and along the culprit vessel were compared between the groups. Of 146 ACS patients (mean age:66.1 ± 12.7 years, 109 men), 47 (32.2%) had COPD. Patients with COPD had significantly higher prevalence of MØI (78.7% vs 54.5%, p = 0.005) and thin cap fibroatheroma (TCFA) (48.9% vs 22.2%, p = 0.001) at the culprit site. In the multivariate logistic regression, COPD was independently associated with MØI (odds ratio [OR] 21.209, 95% confidence interval [CI] 1.679 to 267.910, p = 0.018) and TCFA at the culprit site (OR 5.345, 95% CI 1.386 to 20.616, p = 0.015). Similarly, COPD was independently associated with both MØI (OR 3.570, 95% CI 1.472 to 8.658, p = 0.005) and TCFA (OR 4.088, 95% CI 1.584 to 10.554, p = 0.004) along the culprit vessel. In conclusion, in ACS patients who underwent OCT imaging of the culprit vessel, COPD was an independent predictor of plaque inflammation and vulnerability. These results may suggest that a higher inflammatory milieu in COPD patients might enhance local coronary inflammation, promoting CAD development and plaque vulnerability.

Microvascular complications identify a specific coronary atherosclerotic phenotype in patients with type 2 diabetes mellitus

Background

Patients with type 2 diabetes mellitus (T2DM) are considered as a homogeneous cohort of patients. However, the specific role of diabetic microvascular complications (DMC), in determining the features of coronary plaques is poorly known. We investigated whether the presence of DMC may identify a different phenotype of patients associated to specific clinical, angiographic, optical coherence tomography (OCT) features and different prognosis.

Methods

We prospectively enrolled consecutive T2DM patients with obstructive coronary artery disease (CAD) at their first coronary event. Patients were stratified according to the presence or absence of DMC, including diabetic retinopathy, diabetic neuropathy, and diabetic nephropathy. OCT assessment of the culprit vessel was performed in a subgroup of patients. The incidence of major adverse cardiac events (MACEs) was assessed at follow-up.

Results

We enrolled 320 T2DM patients (mean age 70.3 ± 8.8 years; 234 [73.1%] men, 40% acute coronary syndrome, 60% chronic coronary syndrome). Patients with DMC (172 [53.75%]) presented a different clinical and biochemical profile and, of importance, a higher prevalence of multivessel CAD (109 [63.4%] vs. 68 [45.9%], p = 0.002). At OCT analysis, DMC was associated to a higher prevalence of large calcifications and healed plaques and to a lower prevalence of lipid plaques. Finally, MACEs rate was significantly higher (25 [14.5%] vs. 12 [8.1%], p = 0.007) in DMC patients, mainly driven by a higher rate of planned revascularizations, and DMC predicted the occurrence of MACEs (mean follow-up 33.4 ± 15.6 months).

Conclusions

The presence of DMC identifies a distinct diabetic population with more severe CAD but with a more stable pattern of coronary atherosclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01637-y.

[Clinical and prognostic effect of repeated ten-day courses of low-intensity laser exposure in patients with coronary heart disease]

The deterioration in the prognosis of coronary heart disease (CHD) is due to the influence of numerous pathophysiological factors, which is almost impossible to handle with only medication. Positive results obtained after one course of laser therapy (LT) in patients with angina pectoris substantiate the possibility of prolonging the effect when using repeated courses of low-intensity laser exposure.

PURPOSE OF THE STUDY

To assess the clinical and prognostic value of repeated courses of low-intensity LT in patients with CHD for 24 months.

MATERIAL AND METHODS

The study involved 40 men (mean age 56.6±8.2 years) with exertional angina pectoris with high (0-I functional class - 40%) and lower (II-III functional class - 60%) exercise tolerance (according to the classification of the Canadian Heart Association). Duration of the study was 24 months. All patients underwent 10-day courses of skin LT in the infrared radiation range every 6 months. Initially and after each course of LT, a bicycle ergometer test was performed with an assessment of the threshold values of blood pressure (BP), double product (DP=systolic BP×heart rate) and the ratio of DP to load power (DP/W). The blood levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) were studied after each course of LT.

RESULTS

Patients had an improvement in their well-being during LT: a decrease in the number of angina attacks, the need for nitroglycerin, antianginal and antihypertensive drugs. A statistically significant increase in exercise tolerance by 33.2-40.1% was revealed since 1 month after each course of LT, according to the results of stress tests. At the same time, the threshold values of blood pressure remained at the initial level, which was regarded as a manifestation of the hypotensive effect. The decrease in the DP/W index by 18.2-29.6% compared with the initial data indicates the energy economization of cardiac activity. LT was accompanied by a statistically significant decrease in blood cholesterol from 6.15±1.26 to 4.84±1.28-5.25±1.53 mmol/l and LDL-C from 4.70±1.16 to 3, 29±1.26-3.96 mmol/l.

CONCLUSION

Long-term clinical and preventive effect, good tolerability, availability, absence of side effects substantiate the possibility of widespread use of repeated courses of laser exposure in coronary heart disease.

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.

The evolving role of cardiac imaging in patients with myocardial infarction and non-obstructive coronary arteries

Myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA) represents a heterogeneous clinical conundrum accounting for about 6%-8% of all acute MI who are referred for coronary angiography. Current guidelines and consensus documents recommend that these patients are appropriately diagnosed, uncovering the causes of MINOCA, so that specific therapies can be prescribed. Indeed, there are a variety of causes that can result in this clinical condition, and for this reason diagnostic cardiac imaging has an emerging critical role in the assessment of patients with suspected or confirmed MINOCA. In last years, different cardiac imaging techniques have been evaluated in this context, and the comprehension of their strengths and limitations is of the utmost importance for their effective use in clinical practice. Moreover, recent evidence is clearly suggesting that a multimodality cardiac imaging approach, combining different techniques, seems to be crucial for a proper management of MINOCA. However, great variability still exists in clinical practice in the management of patients with suspected MINOCA, also depending on the availability of diagnostic tools and local expertise. Herein, we review the current knowledge supporting the use of different cardiac imaging techniques in patients with MINOCA, underscoring the importance of a comprehensive multimodality cardiac imaging approach and proposing a practical diagnostic algorithm to properly identify and treat the specific causes of MINOCA, in order to improve prognosis and the quality of life in these patients.

Redefining residual inflammatory risk after acute coronary syndrome

Over the last decades, inflammation proved to play a pivotal role in atherosclerotic plaque formation, progression and destabilization. Several studies showed that the patients presenting with acute coronary syndrome are at increased risk of adverse cardiovascular events at both short- and long-term follow-up. Results from different clinical trials highlighted that a residual inflammatory risk exist and targeting inflammation is a successful strategy in selected cases associated to an increased inflammatory burden. Recently, the optimization of intracoronary and multimodality imaging allowed to also assess the entity of local inflammation, thus encouraging the individuation of plaque characteristics that portend a higher risk of future cardiovascular events. In this short review, we aim to highlight the role of systemic and local inflammation in acute coronary syndromes, to provide a summarized overview of the possible medical strategies applicable in selected cases and to underline the diagnostic and prognostic potential of multimodality imaging.

Brain-derived neurotrophic factor in patients with acute coronary syndrome

Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor highly expressed in coronary plaques, particularly in macrophages, and in activated platelets. Thus, a possible role in the pathogenesis of acute coronary syndrome (ACS) has been suggested. We evaluated systemic BDNF levels according to the different clinical presentations of ACS. Moreover, we assessed the relationship between BDNF levels and the presence of optical coherence tomography (OCT)-defined macrophage infiltrates (MØI) and healed plaques along the culprit vessel. We enrolled consecutive patients presenting with ST-elevation myocardial infarction (STEMI) or non-ST-elevation (NSTE)-ACS. Serum BDNF levels were assessed by enzyme-linked immunosorbent assay. Plaque characteristics of the culprit vessel were assessed by OCT. Among 126 ACS patients (median age 68.00, interquartile range [IQR] 59.75-75.25 years, male 74.6%, 71 (56.3%) were NSTE-ACS and 55 (43.7%) were STEMI. BDNF levels were higher in STEMI patients compared to NSTE-ACS. OCT assessment was performed in 53 (42.1%) patients. Patients with MØI (n = 27) had higher BDNF levels compared to patients without MØI. Furthermore, patients with healed plaques (n = 13) had lower BDNF levels than patients without healed plaques. At multivariate regression analysis BDNF levels independently predicted the presence of MØI (odds ratio [OR] = 2.856; 95% confidence interval [CI] [1.151-7.090], P = 0.024) and the absence of healed plaques (OR = 0.438, 95% CI [0.185-0.992], P= 0.050). Among ACS patients, BDNF levels were higher in patients with STEMI. Moreover, BDNF levels were independently associated with MØI and with the absence of healed plaques along the culprit vessel, suggesting a possible role of BDNF in promoting plaque inflammation, destabilization and occlusive thrombosis.

Expression level and diagnostic value of exosomal NEAT1/miR-204/MMP-9 in acute ST-segment elevation myocardial infarction

Acute myocardium infarction (AMI) is one of the main causes of cardiovascular death, and timely intervention and diagnosis are essential. Owing to the irreversible apoptosis and death of myocardial cells, which ultimately causes heart failure, the problem of myocardial repair after myocardial infarction needs to be urgently addressed. Exosomes can act as messengers between cells, delivering large amounts of proteins, RNA, and lipids to receptor cells, and regulating target cell functions. Studies have shown that exosomes can repair infarcted myocardium. We aimed to investigate the relationship between long non-coding RNA NEAT1 in serum exosomes of patients and AMI and its underlying mechanism. Subjects were divided into control, UA, and STEMI groups. RNA was extracted from the serum exosomes, and the expressions of lncRNA NEAT1 and miR-204 were detected by qRT-PCR. MMP-9 was detected by western blot, Spearman test was used to analyze the correlation among the three. Logistic regression and Receiver-operating characteristic curve (ROC) were used to evaluate the prediction of acute myocardial infarction. The expressions of NEAT1 and MMP-9 in serum exosomes of patients with acute ST-segment elevation myocardial infarction were up-regulated and positively correlated, miR-204 expression was down-regulated, there were no correlations between miR-204 with NEAT1, or MMP-9. Exosomal NEAT1, miR-204, and MMP-9 displayed potent biomarkers for diagnosis of acute ST-segment elevation myocardial infarction.

Macrophage infiltrates in coronary plaque erosion and cardiovascular outcome in patients with acute coronary syndrome

BACKGROUND AND AIMS

Plaque erosion (PE) is responsible for at least one-third of acute coronary syndrome (ACS), and inflammation plays a key role in plaque instability. We assessed the presence of optical coherence tomography (OCT)-defined macrophage infiltrates (MØI) at the culprit site in ACS patients with PE, evaluating their clinical and OCT correlates, along with their prognostic value.

METHODS

ACS patients undergoing OCT imaging and presenting PE as culprit lesion were retrospectively selected. Presence of MØI at culprit site was assessed. The incidence of major adverse cardiac events (MACEs), defined as the composite of cardiac death, recurrent myocardial infarction and target-vessel revascularization (TVR), was assessed [follow-up median (interquartile range, IQR) time 2.5 (2.03-2.58) years].

RESULTS

We included 153 patients [median age (IQR) 64 (53-75) years, 99 (64.7%) males]. Fifty-one (33.3%) patients presented PE with MØI and 102 (66.7%) PE without MØI. Patients having PE with MØI compared with PE patients without MØI had more vulnerable plaque features both at culprit site and at non-culprit segments. MACEs were significantly more frequent in PE with MØI patients compared with PE without MØI [11 (21.6%) vs. 6 (5.9%), p = 0.008], mainly driven by a higher risk of cardiac death and TVR. At multivariable Cox regression, PE with MØI was an independent predictor of MACEs [HR = 2.95, 95% CI (1.09-8.02), p = 0.034].

CONCLUSIONS

Our study demonstrates that among ACS patients with PE the presence of MØI at culprit lesion is associated with more vulnerable plaque features, along with a worse prognosis at a long-term follow-up.

Management of non-culprit coronary plaques in patients with acute coronary syndrome

Approximately 50% of patients with ST-segment elevation myocardial infarction (STEMI) have multivessel coronary artery disease, a condition associated with an increased incidence of recurrent ischaemic events and higher mortality. Based on recent evidences, a strategy of staged percutaneous coronary intervention (PCI) of obstructive non-culprit lesions should be considered the gold standard for the management of these patients. However, several issues remain still unresolved. Indeed, what is the optimal timing of staged PCI is not completely defined. Moreover, assessment of intermediate non-culprit lesions represent still a clinical conundrum, as pressure-wire indexes do not seem able to correctly identify those patients in whom deferral is safe. Intracoronary imaging may help to identify untreated non-culprit lesions containing vulnerable plaques that may portend a higher risk of future cardiovascular events. However, there are hitherto no studies demonstrating that preventive PCI of vulnerable plaques or more intensive pharmacological treatment is associated with an improved clinical outcome. In this review, we discuss the recent evolving concepts about management of non-culprit plaques in STEMI patients, proposing a diagnostic and therapeutic algorithm to guide physicians in clinical practice. We also underscore the several knowledge gaps to address in future studies.

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Association Between Unstable Angina and CXCL17: a New Potential Biomarker

Atherosclerosis and chemokines are strongly related, but the role of the chemokine CXCL17 in atherogenesis is still poorly understood. We aim to investigate the serum CXCL17 levels in different stages of patients with coronary heart disease and explore whether these differences contribute to atherosclerosis. In the current prospective study, we enrolled 48 patients with unstable angina (UA), 51 patients with stable angina (SA) and 41 patients for the control group (CG). All subjects were diagnosed by coronary angiography and Gensini score was used to evaluate the severity of coronary artery disease. The CXCL17 levels were determined using ELISA, while lipid metabolism indicators and high sensitivity C-reactive protein (hs-CRP) were detected by automatic biochemical analyzer. We observed that the unstable angina group had higher CXCL17 levels compared with the stable angina and the control group. The logistic regression analysis showed that CXCL17 was an independent risk factor for unstable angina. Our results showed that CXCL17 was also statistically correlated with hs-CRP, while it was irrelevant with Gensini score. CXCL17 levels were associated with activity of inflammatory response and the instability of atherosclerotic plaques. These results suggest that CXCL17 elevation may be a potential new biomarker of unstable angina.

Alterations of Hyaluronan Metabolism in Acute Coronary Syndrome: Implications for Plaque Erosion

BACKGROUND

Superficial erosion currently causes at least one-third of acute coronary syndromes (ACS), and its incidence is increasing. Yet, the underlying mechanisms in humans are still largely unknown.

OBJECTIVES

The authors sought to assess the role of hyaluronan (HA) metabolism in ACS.

METHODS

Peripheral blood mononuclear cells were collected from ACS (n = 66), stable angina (SA) (n = 55), and control (CTRL) patients (n = 45). The authors evaluated: 1) gene expression of hyaluronidase 2 (HYAL2) (enzyme degrading high-molecular-weight HA to its proinflammatory 20-kDa isoform) and of CD44v1, CD44v4, and CD44v6 splicing variants of HA receptor; and 2) HYAL2 and CD44 protein expression. Moreover, they compared HYAL2 and CD44 gene expression in ACS patients with plaque erosion (intact fibrous cap and thrombus) and in ACS patients with plaque rupture, identified by optical coherence tomography analysis.

RESULTS

Gene expression of HYAL2, CD44v1, and CD44v6 were significantly higher in ACS as compared with SA (p = 0.003, p < 0.001, and p = 0.033, respectively) and CTRL subjects (p < 0.001, p < 0.001, and p = 0.009, respectively). HYAL2 protein expression was significantly higher in ACS than in SA (p = 0.017) and CTRL (p = 0.032), whereas no differences were found in CD44 protein expression. HYAL2 and CD44v6 gene expression was significantly higher in patients with plaque erosion than in those with plaque rupture (p = 0.015 and p = 0.029, respectively).

CONCLUSIONS

HYAL2 and CD44v6 splicing variants seem to play an important role in ACS, in particular when associated with plaque erosion. After further validation, HYAL2 might represent a potentially useful biomarker for the noninvasive identification of this mechanism of coronary instability.

Association of some hemostasis and endothelial dysfunction factors with probability of presence of vulnerable atherosclerotic plaques in patients with coronary atherosclerosis

Objective

The study was dedicated to investigation of some hemostasis and endothelial dysfunction factors association with probability of presence of vulnerable atherosclerotic plaques in coronary arteries in men with atherosclerosis.

Results

The blood levels of factor VII, factor XII and MCP-1 were higher, and concentration of sVCAM-1 lower in men with vulnerable atherosclerotic plaques in the coronary arteries, compared to men who had stable plaques. Have been revealed correlation links between the blood levels of factor II, factor XII, MCP-1 and the presence of vulnerable atherosclerotic plaques in the coronary arteries. Results of logistic regression analysis showed that the relative risk of present of vulnerable atherosclerotic plaques in the coronary arteries is associated with an elevated blood level of factor XII and MCP-1.

Rapamycin: A Bacteria-Derived Immunosuppressant That Has Anti-atherosclerotic Effects and Its Clinical Application

Atherosclerosis (AS) is the leading cause of stroke and death worldwide. Although many lipid-lowering or antiplatelet medicines have been used to prevent the devastating outcomes caused by AS, the serious side effects of these medicines cannot be ignored. Moreover, these medicines are aimed at preventing end-point events rather than addressing the formation and progression of the lesion. Rapamycin (sirolimus), a fermentation product derived from soil samples, has immunosuppressive and anti-proliferation effects. It is an inhibitor of mammalian targets of rapamycin, thereby stimulating autophagy pathways. Several lines of evidence have demonstrated that rapamycin possess multiple protective effects against AS through various molecular mechanisms. Moreover, it has been used successfully as an anti-proliferation agent to prevent in-stent restenosis or vascular graft stenosis in patients with coronary artery disease. A thorough understanding of the biomedical regulatory mechanism of rapamycin in AS might reveal pathways for retarding AS. This review summarizes the current knowledge of biomedical mechanisms by which rapamycin retards AS through action on various cells (endothelial cells, macrophages, vascular smooth muscle cells, and T-cells) in early and advanced AS and describes clinical and potential clinical applications of the agent.

Correlation between CD4+CD28null T lymphocytes, regulatory T cells and plaque rupture: An Optical Coherence Tomography study in Acute Coronary Syndromes

BACKGROUND

A sizeable proportion of patients with Acute Coronary Syndromes (ACS) shows a unique adaptive immune system profile, associated to a worse outcome, characterized by higher CD4⁺CD28^null T-cells, lower regulatory T-cells (Treg) and increased CD4⁺CD28^null/Treg ratio. We sought to investigate the correlation between CD4⁺CD28^null T-cells, Treg, CD4⁺CD28^null/Treg ratio and plaque phenotype as assessed by Optical Coherence Tomography (OCT).

METHODS

Peripheral blood mononuclear cells (PBMC) were collected from 30 Non-ST Elevation Myocardial Infarction (NSTEMI) patients, sub-grouped according to OCT analysis of culprit lesions into two cohorts: Ruptured Fibrous Cap (NSTEMI-RFC, n = 12) and Intact Fibrous Cap (NSTEMI-IFC, n = 18). Stable Angina patients (SA, n = 18) were used as controls. We examined the frequency of CD4⁺CD28^null and Treg (defined as CD4⁺CD25^highCD127^lowFoxp3⁺ T-cells) by flow-cytometry.

RESULTS

CD4⁺CD28^null frequency (median, range) was significantly higher in NSTEMI-RFC patients (17.3%, 12.5-33.8) as compared with NSTEMI-IFC (3.8%, 0.3-14.1) and SA (3%, 0.6-17.7) (P < 0.001 for all comparisons). We also found a higher CD4⁺CD28^null/Treg ratio in NSTEMI-RFC patients (6.6%, 3.7-13.9) than in NSTEMI-IFC (1.6%, 0.3-5.2) and SA (1.2%, 0.3-8.7) (P < 0.001 for all comparisons). Finally, there was an inverse correlation between CD4⁺CD28^null/Treg ratio and cap-thickness (R = -0.44; P = 0.002).

CONCLUSION

Patients with NSTEMI presenting with RFC as culprit lesion at OCT evaluation have a specific perturbation of adaptive immunity, mostly involving CD4⁺CD28^null T- cells and Tregs, as compared with patients with IFC and SA. This specific imbalance of T-cells might play a key role in fibrous cap thinning, predisposing atherosclerotic plaque to rupture.

Not all plaque ruptures are born equal: an optical coherence tomography study

Aims

Plaque rupture (PR) represents the most common substrate of coronary thrombosis, in at least 50% of cases. Chronic low grade inflammation is a common background for atherosclerosis development; however, increased plaque inflammation may predispose by itself to PR. In the last decade, studies performed by optical coherence tomography (OCT) have allowed to establish the severity of plaque inflammation by assessing macrophage infiltration (MØI). Our retrospective study aimed at assessing the role of plaque inflammation in PR among patients with acute coronary syndrome (ACS) using OCT.

Methods and results

We enrolled 56 patients with ACS exhibiting PR at the site of the culprit stenosis identified by OCT. Patients were divided into two cohorts according to the presence of MØI at OCT analysis, defined as signal-rich, distinct, or confluent punctate regions that exceed the intensity of background speckle noise. Serum high-sensitivity C-reactive protein (CRP) was measured on admission by latex-enhanced immunophelometric assay. Thirty-seven (66%) patients had MØI at the site of PR, whereas 19 (34%) patients had no evidence of MØI. Patients with MØI showed a higher rate of CRP values >3 mg/dL as compared with those without MØI (92% vs. 47%, P = 0.004). In contrast, patients without MØI had a higher prevalence of hypertension compared with those with MØI (89% vs. 59%, P = 0.021). Furthermore, the group with MØI exhibited a significantly higher rate of lipid-rich plaques (86% vs. 50%, P = 0.008), a higher rate of multifocal disease (59% vs. 10%, P < 0.001), and an MØI in both culprit and remote lesions (97% vs. 0%, P < 0.001) compared with those without MØI. At multivariate analysis, CRP value >3 mg/dL was the only independent predictor of MØI in the culprit plaque (OR 8.72, 95% CI 1.78-41.67, P= 0.007).

Conclusions

In conclusion, PR can be caused by predominant inflammatory or non-inflammatory mechanisms, over a common low-grade chronic inflammatory background well known from pathology observations.

Coronary versus carotid artery plaques. Similarities and differences regarding biomarkers morphology and prognosis

Carotid and coronary artery disease are two major atherosclerotic conditions that have shown an increased prevalence in the last three decades that is associated with high morbidity and mortality. Recent data have revealed that the development of the atherosclerotic plaque-the basic entity in both diseases-may share similar characteristics and mechanisms irrespective of the location site. Even though the biology of atherosclerotic process is similar, there are differences in plaque morphology and characteristics. Indeed, plaque erosion, calcified nodules, fibrous cap thickness and macrophage accumulation may be different in the setting of coronary and carotid artery disease. The perivascular adipose tissue surrounding the coronary arteries (but not carotids) could also affect plaque biology. In this review we focus on comparative the characteristics of both types of atherosclerotic plaques and summarize existing knowledge to provide useful conclusions about current and future treatment strategies.

Detection and characterization of early plaque formations by Raman probe spectroscopy and optical coherence tomography: an in vivo study on a rabbit model

Intravascular imaging techniques provide detailed specification about plaque appearance and morphology, but cannot deliver information about the biochemical composition of atherosclerotic plaques. As the biochemical composition is related to the plaque type, important aspects such as the risk of a plaque rupture and treatment are still difficult to assess. Currently, various spectroscopic techniques are tested for potential applications for the chemical analysis of plaque depositions. Here, we employ Raman spectroscopy in combination with optical coherence tomography (OCT) for the characterization of plaques on rabbits in vivo. Experiments were carried out on New Zealand white rabbits treated with a fat- and cholesterol-enriched diet, using a Raman probe setup with a 785-nm multimode laser as an excitation source. Subsequently, OCT images were acquired with a swept source at 1305±55  nm at 22.6 mW. Raman spectra were recorded from normal regions and regions with early plaque formations. The probe positioning was monitored by x-ray angiography. The spectral information identified plaque depositions consisting of lipids, with triglycerides as the major component. Afterward, OCT images of the spectroscopically investigated areas were obtained. The spectral information correlates well with the observed intravascular morphology and is in good agreement with histology. Raman spectroscopy can provide detailed biochemical specification of atherosclerotic plaques.

Intracranial Atherosclerosis: From Microscopy to High-Resolution Magnetic Resonance Imaging

Intracranial atherosclerosis is one of the leading causes of ischemic stroke and occurs more commonly in patients of Asian, African or Hispanic origin than in Caucasians. Although the histopathology of intracranial atherosclerotic disease resembles extracranial atherosclerosis, there are some notable differences in the onset and severity of atherosclerosis. Current understanding of intracranial atherosclerotic disease has been advanced by the high-resolution magnetic resonance imaging (HRMRI), a novel emerging imaging technique that can directly visualize the vessel wall pathology. However, the pathological validation of HRMRI signal characteristics remains a key step to depict the plaque components and vulnerability in intracranial atherosclerotic lesions. The purpose of this review is to describe the histological features of intracranial atherosclerosis and to state current evidences regarding the validation of MR vessel wall imaging with histopathology.

Decreased cathepsin K levels in human atherosclerotic plaques are associated with plaque instability

Investigating the determinants and dynamics of atherosclerotic plaque instability is a key area of current cardiovascular research. Extracellular matrix degradation from excessive proteolysis induced by enzymes such as cathepsin K (Cat K) is implicated in the pathogenesis of unstable plaques. The current study assessed the expression of Cat K in human unstable atherosclerotic plaques. Specimens of popliteal arteries with atherosclerotic plaques were classified as stable (<40% lipid core plaque area; n=6) or unstable (≥40% lipid core plaque area; n=14) based on histopathological examinations of hematoxylin and eosin stained sections. The expression of Cat K and cystatin C (Cys C) were assessed by immunohistochemical examination and levels of Cat K mRNA were detected by semi-quantitative reverse transcriptase polymerase chain reaction. Morphological changes including a larger lipid core, endothelial proliferation with foam cells and destruction of internal elastic lamina were observed in unstable atherosclerotic plaques. In unstable plaques, the expression of Cat K protein and mRNA was upregulated, whereas Cys C protein expression was downregulated. The interplay between Cat K and Cys C may underlie the progression of plaques from stable to unstable and the current study indicated that Cat K and Cys C are potential targets for preventing and treating vulnerable atherosclerotic plaque ruptures.

Relationship between Serum Inflammatory Biomarkers and Thrombus Characteristics in Patients with ST Segment Elevation Myocardial Infarction

OBJECTIVES

To compare angiographic and optical coherence tomography (OCT) data pertinent to thrombi, along with the histologic characteristics of aspirated thrombi in patients presenting with ST elevation myocardial infarction (STEMI) with or without inflammation, as assessed by C-reactive protein (CRP) and myeloperoxidase (MPO).

METHODS

In the OCTAVIA (Optical Coherence Tomography Assessment of Gender Diversity in Primary Angioplasty) study, 140 patients with STEMI referred for primary percutaneous intervention were enrolled. The patients underwent OCT assessment of the culprit vessel, along with blood sampling of CRP and MPO, and histologic analysis of the thrombus.

RESULTS

Biomarkers were available for 129 patients, and histology and immunohistochemistry of the thrombi were available for 78 patients. Comparisons were made using the median thresholds of CRP and MPO (2.08 mg/L and 604.124 ng/mL, respectively). There was no correlation between CRP and MPO levels in the whole population (p = 0.685). Patients with high CRP levels had higher thrombus grades and more frequent TIMI flow 0/1 compared with those with low CRP levels (5 [1st quartile 3; 3rd quartile 5] vs. 3.5 mg/L [1; 5], p = 0.007, and 69.3 vs. 48.5%, p = 0.04, respectively). Patients with high MPO levels more commonly had early thrombi than had those with low MPO levels (42.5 vs. 20.0%, p = 0.04).

CONCLUSIONS

CRP and MPO were not correlated in STEMI patients, possibly reflecting different pathogenic mechanisms, with CRP more related to thrombus burden and MPO to thrombus age.

Contrast-enhanced ultrasound imaging of intraplaque neovascularization and its correlation to plaque echogenicity in human carotid arteries atherosclerosis

BACKGROUND

Currently the most widely accepted predictor of stroke risk in patients with carotid atherosclerosis is the degree of stenoses. Plaque echogenicity on ultrasound imaging (US) and intraplaque neovascularization (IPNV) are becoming recognized as factors of plaque vulnerability. Aim of the study was to investigate the correlation between the echogenicity of the carotid atherosclerosis by standard US and the degree of IPNV by contrast enhanced US (CEUS).

METHODS

We recruited 45 consecutive subjects with an asymptomatic ≥50% carotid artery stenoses. Carotid plaque echogenicity at standard US was visually graded according to Gray-Weale classification (GW) and measured by the grayscale median (GSM), a semi-automated measurement performed by Adobe Photoshop©. On CEUS imaging IPNV was graded by different point scales according to the visual appearance of contrast within the plaque as follows: CEUS_A (1=absent; 2=present); CEUS_B (increasing IPNV from 1 to 3); and CEUS_C (increasing IPNV from 0 to 3).

RESULTS

The correlation between echogenicity by GW and IPNV grading was as follows: CEUS_B (-0.130 p .423), CEUS_C (-0.108, p .509), CEUS_A (0.021, p .897). The correlation between echogenicity by GSM measurement and IPNV was as follows: using a CEUS_A (-0.125, p .444), CEUS_C (-0.021, p .897) (0.005, p .977). No correlation was found statistically significant.

CONCLUSION

Our results display that there is no significant correlation between plaque echogenicity and IPNV. The small sample number and the multifaceted pathophysiology of the atherosclerotic plaque may explain the absence of statistically significantly correlation. Curtailing vulnerability explanation to either IPNV or echolucency may be misleading.

Frequency Analysis of the Photoacoustic Signal Generated by Coronary Atherosclerotic Plaque

The identification of unstable atherosclerotic plaques in the coronary arteries is emerging as an important tool for guiding percutaneous coronary interventions and may enable preventive treatment of such plaques in the future. Assessment of plaque stability requires imaging of both structure and composition. Spectroscopic photoacoustic (sPA) imaging can visualize atherosclerotic plaque composition on the basis of the optical absorption contrast. It is an established fact that the frequency content of the photoacoustic (PA) signal is correlated with structural tissue properties. As PA signals can be weak, it is important to match the transducer bandwidth to the signal frequency content for in vivo imaging. In this ex vivo study on human coronary arteries, we combined sPA imaging and analysis of frequency content of the PA signals. Using a broadband transducer (-3-dB one-way bandwidth of 10-35 MHz) and a 1-mm needle hydrophone (calibrated for 1-20 MHz), we covered a large frequency range of 1-35 MHz for receiving the PA signals. Spectroscopic PA imaging was performed at wavelengths ranging from 1125 to 1275 nm with a step of 2 nm, allowing discrimination between plaque lipids and adventitial tissue. Under sPA imaging guidance, the frequency content of the PA signals from the plaque lipids was quantified. Our data indicate that more than 80% of the PA energy of the coronary plaque lipids lies in the frequency band below 8 MHz. This frequency information can guide the choice of the transducer element used for PA catheter fabrication.

Lipoprotein (a) is related to coronary atherosclerotic burden and a vulnerable plaque phenotype in angiographically obstructive coronary artery disease

BACKGROUND

Lipoprotein Lp(a) has been shown to be an independent risk factor for coronary artery disease (CAD). However, its association with CAD burden in patients with ACS is largely unknown, as well as the association of Lp(a) with lipid rich plaques prone to rupture.

AIM

We aim at assessing CAD burden by coronary angiography and plaque features including thin cap fibroatheroma (TCFA) by optical coherence tomography (OCT) in consecutive patients presenting with acute coronary syndrome (ACS) and obstructive CAD along with serum Lp(a) levels.

METHODS

This study comprises an angiographic and an OCT cohort. A total of 500 ACS patients (370 men, average age 66 ± 11) were enrolled for the angiographic cohort and 51 ACS patients (29 males, average age 65 ± 11) were enrolled for the OCT cohort. Angiographic CAD severity was assessed by Sullivan score and by Bogaty score including stenosis score and extent index. OCT plaque features were evaluated at the site of the minimal lumen area and along the culprit segment.

RESULTS

In the angiographic cohort, at multivariate analysis, Lp(a) was a weak independent predictor of Sullivan score (p < 0.0001), stenosis score (p < 0.0001) and extent index (p < 0.0001). In the OCT cohort, patients with higher Lp(a) levels (≥ 30 md/dl) compared to patients with lower Lp(a) levels (<30 md/dl) exhibited a higher prevalence of lipidic plaque at the site of the culprit stenosis (67% vs. 27%; P = 0.02), a wider lipid arc (135 ± 114 vs 59 ± 111; P = 0.03) and a higher prevalence of TCFA (38% vs. 10%; P = 0.04).

CONCLUSIONS

Among patients with ACS, raised Lp(a) levels are associated with an increased atherosclerotic burden and it identifies a subset of patients with features of high risk coronary atherosclerosis.

Emerging Technology Update Intravascular Photoacoustic Imaging of Vulnerable Atherosclerotic Plaque

The identification of vulnerable atherosclerotic plaques in the coronary arteries is emerging as an important tool for guiding atherosclerosis diagnosis and interventions. Assessment of plaque vulnerability requires knowledge of both the structure and composition of the plaque. Intravascular photoacoustic (IVPA) imaging is able to show the morphology and composition of atherosclerotic plaque. With imminent improvements in IVPA imaging, it is becoming possible to assess human coronary artery disease in vivo. Although some challenges remain, IVPA imaging is on its way to being a powerful tool for visualising coronary atherosclerotic features that have been specifically associated with plaque vulnerability and clinical syndromes, and thus such imaging might become valuable for clinical risk assessment in the catheterisation laboratory.

Investigation of the composition of arterial plaques based on arterial waveforms and material properties

Stroke is mainly caused by a narrowing of the carotid artery from a build-up of plaque. The risk of plaque rupture and subsequent stroke is dependent on plaque composition. Advances in imaging modalities offer a non-invasive means to assess the health of blood vessels and detect damage. However, the current diagnosis fails to identify patients with soft lipid plaque that are more susceptible to fissure, resulting in stroke. The aim of this study was to use waveform analysis to identify plaque composition and the risk of rupture. We have investigated pressure and flow by combining an artificial blood flow circuit with tubing containing different materials, to simulate plaques in a blood vessel. We used fat and bone to model lipid and calcification respectively to determine if the composition of plaques can be identified by arterial waveforms. We demonstrate that the arterial plaque models with different percentages of calcification and fat, results in significantly different arterial waveforms. These findings imply that arterial waveform analysis has the potential for further development to identify the vulnerable plaques prone to rupture. These findings could have implications for improved patient prognosis by speed of detection and a more appropriate treatment strategy.

Imaging coronary artery disease and the myocardial ischemic cascade: clinical principles and scope

On a subcellular level, atherogenesis is characterized by the translocation of proatherogenic lipoproteins into the arterial wall. An inflammatory response involving complex repair mechanisms subsequently causes maladaptive vascular changes resulting in coronary stenosis or occlusion. The chronology of the underlying processes occurring from atherosclerosis to myocardial ischemia affect the selection and interpretation of diagnostic testing. An understanding of the ischemic cascade, atherosclerosis, coronary remodeling, plaque morphology, and their relationship to clinical syndromes is essential in determining which diagnostic modalities are useful in clinical practice.

Plaque rupture and intact fibrous cap assessed by optical coherence tomography portend different outcomes in patients with acute coronary syndrome

AIMS

Patients presenting with acute coronary syndrome (ACS) may have different plaque morphologies at the culprit lesion. In particular, plaque rupture (PR) has been shown as the more frequent culprit plaque morphology in ACS. However, its prognostic value is still unknown. In this study, we evaluated the prognostic value of PR, compared with intact fibrous cap (IFC), in patients with ACS.

METHODS AND RESULTS

We enrolled consecutive patients admitted to our Coronary Care Unit for ACS and undergoing coronary angiography followed by interpretable optical coherence tomography (OCT) imaging. Culprit lesion was classified as PR and IFC by OCT criteria. Prognosis was assessed according to such culprit lesion classification. Major adverse cardiac events (MACEs) were defined as the composite of cardiac death, non-fatal myocardial infarction, unstable angina, and target lesion revascularization (follow-up mean time 31.58 ± 4.69 months). The study comprised 139 consecutive ACS patients (mean age 64.3 ± 12.0 years, male 73.4%, 92 patients with non-ST elevation ACS and 47 with ST-elevation ACS). Plaque rupture was detected in 82/139 (59%) patients. There were no differences in clinical, angiographic, or procedural data between patients with PR when compared with those having IFC. Major adverse cardiac events occurred more frequently in patients with PR when compared with those having IFC (39.0 vs. 14.0%, P = 0.001). Plaque rupture was an independent predictor of outcome at multivariable analysis (odds ratio 3.735, confidence interval 1.358-9.735).

CONCLUSION

Patients with ACS presenting with PR as culprit lesion by OCT have a worse prognosis compared with that of patients with IFC. This finding should be taken into account in risk stratification and management of patients with ACS.