Symptomatic vs. Asymptomatic 20-40% Internal Carotid Artery Stenosis: Does the Plaque Size Matter?

SMAD3 rs17228212 Polymorphism Is Associated with Advanced Carotid Atherosclerosis in a Slovenian Population

Smad proteins influence the TGFβ signaling pathway, which plays an important role in the progression of atherosclerosis. The aim of our study was to investigate the association between the rs17228212 polymorphism of the SMAD3 gene and advanced carotid atherosclerosis in Slovenian subjects and to investigate the effect of the rs17228212 SMAD3 polymorphism on the expression of SMAD3 in endarterectomy sequesters. In this cross-sectional case-control study, 881 unrelated Caucasians were divided into two groups. The first group included 308 patients with advanced carotid atherosclerosis of the common or internal carotid artery with stenosis greater than 75% that underwent a revascularization procedure (cases). The control group consisted of 573 subjects without hemodynamically significant carotid atherosclerosis. We analyzed the rs17228212 polymorphism of the SMAD3 gene using the StepOne real-time polymerase chain reaction system and TaqMan SNP genotyping assay. The results in the two genetic models showed a statistically significant association, codominant (OR 4.05; CI 1.10-17.75; p = 0.037) and dominant (OR 3.60; CI 1.15-15.45; p = 0.045). An immunohistochemical analysis of SMAD3 expression was conducted for 26 endarterectomy specimens. The T allele of the rs17228212 SMAD3 gene was shown to be associated with an increased numerical area density of SMAD3-positive cells in carotid plaques.

Microstructural and mechanical insight into atherosclerotic plaques: an ex vivo DTI study to better assess plaque vulnerability

Non-invasive microstructural characterisation has the potential to determine the stability, or lack thereof, of atherosclerotic plaques and ultimately aid in better assessing plaques' risk to rupture. If linked with mechanical characterisation using a clinically relevant imaging technique, mechanically sensitive rupture risk indicators could be possible. This study aims to provide this link-between a clinically relevant imaging technique and mechanical characterisation within human atherosclerotic plaques. Ex vivo diffusion tensor imaging, mechanical testing, and histological analysis were carried out on human carotid atherosclerotic plaques. DTI-derived tractography was found to yield significant mechanical insight into the mechanical properties of more stable and more vulnerable microstructures. Coupled with insights from digital image correlation and histology, specific failure characteristics of different microstructural arrangements furthered this finding. More circumferentially uniform microstructures failed at higher stresses and strains when compared to samples which had multiple microstructures, like those seen in a plaque cap. The novel findings in this study motivate diagnostic measures which use non-invasive characterisation of the underlying microstructure of plaques to determine their vulnerability to rupture.

B-mode ultrasound characteristics of carotid plaques in symptomatic and asymptomatic patients with low-grade stenosis

Carotid plaque features assessed using B-mode ultrasound can be useful for the prediction of cerebrovascular symptoms. Therefore, the aim of this retrospective study was to determine the ability of ultrasound B-mode imaging to differentiate between carotid plaques causing less than 50% stenosis in symptomatic and asymptomatic patients. A dataset of 1,593 patients with carotid disease who underwent carotid ultrasound between 2016 and 2021 was evaluated retrospectively between January and April of 2022. A total of 107 carotid plaques from 35 symptomatic and 52 asymptomatic patients causing low-grade stenosis on B-mode images were included in the analysis. Chi-square, independent t-test and Mann-Whitney U test were used to compare the variables. There was a significant association between hypertension and the presence of cerebrovascular symptoms (p = 0.01). Predominantly hypoechoic and hyperechoic carotid plaque were significantly associated with the presence and absence of cerebrovascular symptoms, respectively (predominantly hypoechoic: p = 0.01; predominantly hyperechoic: p = 0.02). Surface irregularity was significantly associated with the presence of cerebrovascular symptoms (p = 0.02). There is was a significant difference in the carotid plaque length and area between the symptomatic and asymptomatic patients (plaque length: symptomatic median 9 mm, interquartile range [IQR] 6 mm; asymptomatic median 6 mm, IQR 4.5 mm, p = 0.01; plaque area: symptomatic median 24 mm, IQR 30 mm; asymptomatic median 14 mm, IQR 17 mm, p = 0.01); however, this difference was not significant for plaque thickness (p = 0.55), or common carotid artery intima-media thickness (p = 0.7). Our findings indicate that hypertension patients with predominantly hypoechoic carotid plaques and plaques with an irregular surface are associated with the presence of cerebrovascular symptoms. In addition, the carotid plaques in symptomatic patients were longer and larger compared to asymptomatic patients.

Endothelial function and arterial stiffness indexes in subjects with carotid plaque and carotid plaque length: A subgroup analysis showing the relationship with hypertension and diabetes

BACKGROUND

Stroke is a leading cause of death and disability globally. A large proportion of ischemic strokes are caused by carotid atherosclerotic plaques. However, the relationship between vascular health status (arterial stiffness and endothelial dysfunction) and carotid plaque remains unclear.

OUR STRATEGY

Here, we recruited 991 subjects with carotid plaques and 1170 subjects without carotid plaques to measure arterial stiffness and endothelial dysfunction, using a logistic regression model and multiple linear regression models to predict the relationship between them and carotid plaques.

MAIN RESULTS

The data revealed that patients with carotid plaques presented a significantly higher mean of cf-PWV and lower mean RHI values. Age, male gender, diabetes, hypertension, and smoking contributed to plaque formation. Carotid plaques and their lengths were negatively associated with RHI values and positively associated with cf-PWV values; diabetes combined with hypertension showed a cumulative effect on arteriosclerosis.

CONCLUSION

RHI combined with cf-PWV could improve the efficacy of predicting the presence of carotid plaques and their lengths.

The role of non-stenosing carotid artery plaques in embolic stroke of undetermined source, is it a silent offender? A review of literature

PURPOSE

Atherosclerotic cervical internal carotid artery disease is one of the major causes of ischemic stroke and transient ischemic attacks. The risk of stroke from mild to moderate stenoses (i.e. <50% stenosis) might be underestimated. There is increasing evidence that plaque morphological features reflect plaque instability that may harbor high risk for embolization. In this narrative review, we will review the literature on plaque features that predict vulnerability beyond the degree of stenosis, discuss the clinical association with stroke, and evaluate the evidence that these lesions serve as a source for embolic stroke of unknown source (ESUS).

METHODS

We performed a literature search using PubMed, EMBASE, and Web of Science. The terms "embolic stroke of undetermined source" and "plaque morphology" were used either alone or in combination with "non-flow limiting stenosis," "non-stenosing plaques," "high-risk plaque features" or "internal carotid artery plaque." Data on plaque morphology and ESUS were mainly taken from review articles, observational studies including retrospective cohort and cross-sectional studies, meta-analyses, and systematic reviews.

CONCLUSION

Nonstenosing carotid artery plaques with high-risk features carry a remarkable risk for stroke occurrence and randomized clinical trials are warranted for further evaluation of using carotid artery stenting or carotid endarterectomy to mitigate the risk of stroke.

Imaging High-Risk Atherothrombosis Using a Novel Fibrin-Binding Positron Emission Tomography Probe

BACKGROUND AND PURPOSE

High-risk atherosclerosis is an underlying cause of cardiovascular events, yet identifying the specific patient population at immediate risk is still challenging. Here, we used a rabbit model of atherosclerotic plaque rupture and human carotid endarterectomy specimens to describe the potential of molecular fibrin imaging as a tool to identify thrombotic plaques.

METHODS

Atherosclerotic plaques in rabbits were induced using a high-cholesterol diet and aortic balloon injury (N=13). Pharmacological triggering was used in a group of rabbits (n=9) to induce plaque disruption. Animals were grouped into thrombotic and nonthrombotic plaque groups based on gross pathology (gold standard). All animals were injected with a novel fibrin-specific probe ⁶⁸Ga-CM246 followed by positron emission tomography (PET)/magnetic resonance imaging 90 minutes later. ⁶⁸Ga-CM246 was quantified on the PET images using tissue-to-background (back muscle) ratios and standardized uptake value.

RESULTS

Both tissue-to-background (back muscle) ratios and standardized uptake value were significantly higher in the thrombotic versus nonthrombotic group (P<0.05). Ex vivo PET and autoradiography of the abdominal aorta correlated positively with in vivo PET measurements. Plaque disruption identified by ⁶⁸Ga-CM246 PET agreed with gross pathology assessment (85%). In ex vivo surgical specimens obtained from patients undergoing elective carotid endarterectomy (N=12), ⁶⁸Ga-CM246 showed significantly higher binding to carotid plaques compared to a D-cysteine nonbinding control probe.

CONCLUSIONS

We demonstrated that molecular fibrin PET imaging using ⁶⁸Ga-CM246 could be a useful tool to diagnose experimental and clinical atherothrombosis. Based on our initial results using human carotid plaque specimens, in vivo molecular imaging studies are warranted to test ⁶⁸Ga-CM246 PET as a tool to stratify risk in atherosclerotic patients.

Correlation between calcium, water contents and ultrasonographic appearance of atherosclerotic lesions of carotid artery lesions

Background

We tested the hypothesis whether there is a correlation between the echogenicity and calcium and water contents of carotid plaques.

Patients and methods

Ninety carotid befurcations from 45 deceased patients were removed during autopsy. Thirty-four plaques were categorized as homogenous echolucent (HEL), homogenous echogenic (HEG) and heterogenous (HE) plaques based on premortem B-mode image. Water content was expressed in % of wet weight. Ca was determined by proton-induced X-ray emission and expressed in ppm. Relative optical density of the B-mode images was analyzed offline using a computer program.

Results

HEL plaques had lower Ca content (medians and IQRs: 6,145 [4,465–6,536 ppm]) compared to HEG (74,100 [15,300–1,44,500−ppm]), P ≤ 0.001). HE plaques showed an intermediate calcium content (7,310 [4,840–9,920 ppm]) that was statistically not different from echolucent plaques. Water content of HEG plaques was statistically not different from HEL and HE (HEG:53.5 [35.5–64%], HEL: 73.5 [69.7–78.5%], HE: 70.6 [67.4–73.9%]). HEG plaques had the highest relative optical densities (196 [188–217%]). HEL and HE had similar relative optical densities (HEL: 176 [164–187%], HE: 164 [144–188%], respectively). A significant positive correlation was found between the Ca content and relative optical density of plaques.

Conclusions

Echogenicity of carotid plaques increases along with their calcium content. Water content may be an important factor in differentiation of different plaques.

Tryptophan Metabolism, Inflammation, and Oxidative Stress in Patients with Neurovascular Disease

Atherosclerosis is a leading cause of major vascular events, myocardial infarction, and ischemic stroke. Tryptophan (TRP) catabolism was recognized as an important player in inflammation and immune response having together with oxidative stress (OS) significant effects on each phase of atherosclerosis. The aim of the study is to analyze the relationship of plasma levels of TRP metabolites, inflammation, and OS in patients with neurovascular diseases (acute ischemic stroke (AIS), significant carotid artery stenosis (SCAS)) and in healthy controls. Blood samples were collected from 43 patients (25 with SCAS, 18 with AIS) and from 25 healthy controls. The concentrations of twelve TRP metabolites, riboflavin, neopterin (NEO, marker of inflammation), and malondialdehyde (MDA, marker of OS) were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Concentrations of seven TRP metabolites (TRP, kynurenine (KYN), 3-hydroxykynurenine (3-HK), 3-hydroxyanthranilic acid (3-HAA), anthranilic acid (AA), melatonin (MEL), tryptamine (TA)), NEO, and MDA were significantly different in the studied groups. Significantly lower concentrations of TRP, KYN, 3-HAA, MEL, TA, and higher MDA concentrations were found in AIS compared to SCAS patients. MDA concentration was higher in both AIS and SCAS group (p < 0.001, p = 0.004, respectively) compared to controls, NEO concentration was enhanced (p < 0.003) in AIS. MDA did not directly correlate with TRP metabolites in the study groups, except for 1) a negative correlation with kynurenine acid and 2) the activity of kynurenine aminotransferase in AIS patients (r = -0.552, p = 0.018; r = -0.504, p = 0.033, respectively). In summary, TRP metabolism is clearly more deregulated in AIS compared to SCAS patients; the effect of TRP metabolites on OS should be further elucidated.

Association between rs2107595 HDAC9 gene polymorphism and advanced carotid atherosclerosis in the Slovenian cohort

Background

Histone deacetylase 9 (HDAC9) plays an important role in transcriptional regulation, cell cycle progression and developmental events; moreover, it has been investigated as a candidate gene in a number of conditions, including the onset and progression of atherosclerosis. We hypothesized that the rs2107595 HDAC9 gene polymorphism may be associated with advanced carotid artery disease in a Slovenian cohort. We also investigated the effect of this polymorphism on HDAC9 receptor expression in the internal carotid artery (ICA) specimens obtained by endarterectomy.

Methods

This case-control study enrolled 619 unrelated Slovenian patients: 311 patients with ICA stenosis > 75% as the study group and 308 patients with ICA stenosis < 50% as the control group. Patient laboratory and clinical data were obtained from the medical records. The rs2107595 polymorphisms were genotyped using TaqMan SNP Genotyping assay. HDAC9 expression was assessed by immunohistochemistry in 30 ICA specimens from patients with ICA atherosclerosis > 75%, and the numerical areal density of HDAC9 positive cells was calculated.

Results

The occurrence of advanced ICA atherosclerosis in the Slovenian cohort was 3.81 times higher in the codominant genetic model (OR = 3.81, 95%CI = 1.06–13.77, p = 0.04), and 3.10 times higher in the recessive genetic model (OR = 3.10, 95%CI = 1.16–8.27, p = 0.02). In addition, the A allele of rs2107595 was associated with increased HDAC9 expression in the ICA specimens obtained by endarterectomy.

Conclusions

We observed a significant association between the AA genotype of rs2107595 with the advanced carotid artery disease in our Slovenian cohort, indicating that this polymorphism may be a genetic risk factor for ICA atherosclerosis.