Aortic Plaque Distribution, and Association between Aortic Plaque and Atherosclerotic Risk Factors: An Aortic Angioscopy Study

Calcification and atheroma plaques: is there any impact on the anatomical features of the aortic root and its elements?

OBJECTIVES

Morphometric information of the structures within the borders of the aortic root is a guide for surgical interventions. It is essential to determine the effects of aortic calcification and atheroma plaque findings on the structures of this region. This study aims to establish the normal values of aortic root structures and to investigate the impact of pathologic findings in order to guide diagnosis and treatment in the clinic.

METHODS

The aortic root structures were morphometrically analyzed in fresh hearts of 110 patients (89 males, 21 females) brought to the forensic medicine institution. The distances between the bases of the aortic sinuses, their widths and heights, and the lengths of the commissures were measured to differentiate between pathologic and non-pathologic aortic classes. Parameters were compared according to gender, age, body mass index, and body surface area.

RESULTS

The mean age was 44.71 ± 15.57 years in 21 female patients and 53.66 ± 15.67 years in 89 male patients. The results of the pathologic aorta group with calcification and atheroma plaque findings were higher than the non-pathologic aorta group in all parameters (P < .05).

CONCLUSIONS

Calcification and the presence of atheroma plaque in the aorta increase the size of the structures at the aortic root. Gender, age, body mass index, and body surface area are among the criteria that will cause changes in the structures of this region. These results will help surgeons to know the normal values of aortic root structures and to consider the effects of pathologic findings in aortic valve repair operations.

Association Between Aortic Wall Parameters on Multidetector Computed Tomography and Ruptured Plaques By Nonobstructive General Angioscopy

BACKGROUND

Nonobstructive general angioscopy (NOGA) can identify vulnerable plaques in the aortic lumen that serve as potential risk factors for cardiovascular events such as embolism. However, the association between computed tomography (CT) images and vulnerable plaques detected on NOGA remains unknown.

METHODS AND RESULTS

We investigated 101 patients (67±11 years; women, 13.8%) who underwent NOGA and contrast-enhanced CT before or after 90 days in our hospital. On CT images, the aortic wall thickness, aortic wall area (AWA), and AWA in the vascular area were measured at the thickest point from the 6th to the 12th thoracic vertebral levels. Furthermore, the association between these measurements and the presence or absence of NOGA-derived aortic plaque ruptures (PRs) at the same vertebral level was assessed. NOGA detected aortic PRs in the aortic lumens at 145 (22.1%) of the 656 vertebral levels. The presence of PRs was significantly associated with greater aortic wall thickness (3.3±1.7 mm versus 2.1±1.2 mm), AWA (1.33±0.68 cm2 versus 0.89±0.49 cm2), and AWA in the vascular area (23.2%±9.3% versus 17.2%±7.6%) (P<0.001 for all) on the CT scans compared with the absence of PRs. The frequency of PRs significantly increased as the aortic wall thickness increased. Notably, a few NOGA-derived PRs were detected on CT in near-normal intima.

CONCLUSIONS

The presence of NOGA-derived PRs was strongly associated with increased aortic wall thickness, AWA, and AWA in the vascular area, measured using CT. NOGA can detect PRs in the intima that appear almost normal on CT scans.

Association between aortic thrombi detected using non-obstructive general angioscopy and atrial fibrillation

Atrial fibrillation (AF) is an independent risk factor for stroke and systemic embolism. Cardiogenic and aortogenic emboli are causes of stroke or systemic embolism. Non-obstructive general angioscopy (NOGA) can be used to diagnose aortic intimal findings, including thrombi and atherosclerotic plaques, but little is known about NOGA-derived aortic intimal findings in patients with AF. This study focused on aortic intimal findings in patients with AF and evaluated the association between AF and aortic thrombi detected using NOGA. We enrolled 283 consecutive patients with coronary artery disease who underwent NOGA of the aorta between January 2017 and August 2022. Aortic intimal findings were screened using NOGA after coronary arteriography. The patients were divided into two groups according to their AF history (AF, n = 50 and non-AF, n = 233). Patients in the AF group were older than those in the non-AF group. Sex, body mass index, and coronary risk factors were not significantly different between the two groups. In the NOGA findings, the presence of intense yellow plaques and ruptured plaques was not significantly different between the two groups. Aortic thrombi were more frequent in the AF group than in the non-AF group (92.0 vs. 71.6%, p < 0.001). Multivariate logistic regression found that AF was independently associated with aortic thrombi (odds ratio 3.87 [95% CI 1.28-11.6], p = 0.016). The presence of aortic thrombi observed using NOGA was associated with AF in patients with coronary artery disease. The roles of aortic thrombi as well as cardiogenic embolism may require clarification.

Cholesterol Crystal Embolism in a Patient with Spontaneous Ruptured Aortic Plaques Identified by Non-Obstructive General Angioscopy

Cholesterol crystal (CC) embolism is a disease in which CCs from atherosclerotic lesions embolize peripheral arteries, causing organ dysfunction. In this case, a patient with spontaneously ruptured aortic plaques (SRAPs) identified by non-obstructive general angioscopy (NOGA) may have developed a CC embolism. This is the first report of a CC embolism in a patient with SRAPs identified using NOGA, which further supports the previously speculated pathogenesis of CC embolism due to SRAPs.

Thoracic aortic aneurysm and atrial fibrillation: clinical associations with the risk of stroke from a global federated health network analysis

BACKGROUND

An association with aortic aneurysm has been reported among patients with atrial fibrillation (AF). The aims of this study were to investigate the prevalence of thoracic aorta aneurysm (TAA) among patients with AF and to assess whether the co-presence of TAA is associated with a higher risk of adverse clinical outcomes.

METHODS AND RESULTS

Using TriNetX, a global federated health research network of anonymised electronic medical records, all adult patients with AF, were categorised into two groups based on the presence of AF and TAA or AF alone. Between 1 January 2017 and 1 January 2019, 874,212 people aged ≥ 18 years with AF were identified. Of these 17,806 (2.04%) had a TAA. After propensity score matching (PSM), 17,805 patients were included in each of the two cohorts. During the 3 years of follow-up, 3079 (17.3%) AF patients with TAA and 2772 (15.6%) patients with AF alone, developed an ischemic stroke or transient ischemic attack (TIA). The risk of ischemic stroke/TIA was significantly higher in patients with AF and TAA (HR 1.09, 95% CI 1.04-1.15; log-rank p value < 0.001) The risk of major bleeding was higher in patients with AF and TAA (OR 1.07, 95% CI 1.01-1.14), but not significant in time-dependent analysis (HR 1.04, 95% CI 0.98-1.10; log-rank p value = 0.187), CONCLUSION: This retrospective analysis reports a clinical concomitance of the two medical conditions, and shows in a PSM analysis an increased risk of ischemic events in patients affected by TAA and AF compared to AF alone.

Acute Ischemic Stroke and Transient Ischemic Attack in ST-Segment Elevation Myocardial Infarction Patients Who Underwent Primary Percutaneous Coronary Intervention

BACKGROUND

Acute ischemic stroke (AIS) is a rare but critical complication following ST-elevation myocardial infarction (STEMI). The risk of AIS or transient ischemic attack (TIA) may be amplified by invasive procedures, including primary percutaneous coronary intervention (PCI). This study aimed to investigate the factors associated with in-hospital AIS/TIA in patients with STEMI who required primary PCI.

METHODS

We included 941 STEMI patients who underwent primary PCI and divided them into an AIS/TIA group (n = 39) and a non-AIS/TIA group (n = 902), according to new-onset AIS/TIA. The primary interest was to find the factors associated with AIS/TIA by multivariate logistic regression analysis. We also compared clinical outcomes between the AIS/TIA and non-AIS/TIA groups.

RESULTS

The incidence of in-hospital deaths was significantly higher in the AIS/TIA group (46.2%) than in the non-AIS/TIA group (6.3%) (p < 0.001). Multivariate analysis revealed that cardiogenic shock (OR 3.228, 95% CI 1.492-6.986, p = 0.003), new-onset atrial fibrillation (AF) (OR 2.280, 95% CI 1.033-5.031, p = 0.041), trans-femoral approach (OR 2.336, 95% CI 1.093-4.992, p = 0.029), use of ≥4 catheters (OR 3.715, 95% CI 1.831-7.537, p < 0.001), and bleeding academic research consortium (BARC) type 3 or 5 bleeding (OR 2.932, 95% CI 1.256-6.846, p = 0.013) were significantly associated with AIS/TIA.

CONCLUSION

In STEMI patients with primary PCI, new-onset AIS/TIA was significantly associated with cardiogenic shock, new-onset AF, trans-femoral approach, the use of ≥4 catheters, and BARC type 3 or 5 bleeding. We should recognize these modifiable and unmodifiable risk factors for AIS/TIA in the treatment of STEMI.

Serial Changes of Aortic Vulnerable Plaques Observed via Non-Obstructive General Angioscopy

Stabilization of aortic vulnerable plaques has not been fully elucidated. Non-obstructive general angioscopy (NOGA) is a novel method for the detailed evaluation of atheromatous plaques in the aortic intimal wall. A 57-year-old man presenting with acute myocardial infarction underwent percutaneous coronary intervention (PCI). NOGA was performed for the evaluation of aortic atherosclerosis, and vulnerable puff-chandelier plaques in the aortic arch were identified. After a strictly controlled low-density lipoprotein cholesterol lowering therapy with a strong statin for 8 months after the primary PCI, NOGA revealed stabilized aortic plaques in the same lesions. Therefore, NOGA may be helpful in evaluating the effects of lipid-lowering therapy on aortic plaque stabilization.

Diagnosis of Atherosclerotic Plaques Using Vascular Endothelial Growth Factor Receptor-2 Targeting Antibody Nano-microbubble as Ultrasound Contrast Agent

The atherosclerotic plaque is characterized by narrowing of blood vessels and reduced blood flow leading to the insufficient blood supply to the brain. The hemodynamic changes caused by arterial stenosis increase the shearing force of the fibrous cap on the surface of the plaque, thereby reducing the stability of the plaque. Unstable plaques are more likely to promote angiogenesis and increase the risk of patients with cerebrovascular diseases. A timely understanding of the formation and stability of the arterial plaque can guide in taking targeted measures for reducing the risk of acute stroke in patients. It has been confirmed that nano-microbubbles can enter these plaques through the gaps in the patient's vascular endothelial cells, thereby enhancing the acquisition of ultrasound information for plaque visualization. Therefore, we aim to investigate the diagnostic value of targeted nano-microbubbles for atherosclerotic plaques. This study constructed vascular endothelial growth factor receptor-2 (VEGFR-2) targeting antibody nano-microbubbles and compared its diagnostic value with that of blank nano-microbubbles for atherosclerotic plaques. Studies have found that VEGFR-2 targeting antibody nano-microbubbles can accurately detect the position of plaques. Its detection rate, sensitivity, and specificity for plaques are higher than those of blank nano-microbubbles. Similarly, the peak intensity and average transit time of VEGFR-2 targeting antibody nano-microbubbles were greater than those of blank nano-microbubbles. Therefore, we believe that the combination of VEGFR-2 antibody and nano-microbubbles can enhance the acquisition of ultrasound information on atherosclerotic plaque neovascularization, thereby improving the early diagnosis of unstable plaque.

Efficacy of non-obstructive aortic angioscopy for detecting a thoracic aortic graft rupture: a case report

Background

Non-anastomotic thoracic aortic graft rupture is extremely rare and difficult to diagnose. Non-obstructive general angioscopy can help monitor the aortic intima and detect the locations of abnormal findings, while aortic angioscopy can detect vulnerable plaques in the aorta, which are difficult to visualize using conventional diagnostic methods. Herein, we report the case of a patient with non-anastomotic thoracic aortic graft rupture diagnosed using non-obstructive aortic angioscopy.

Case presentation

An 85-year-old man who had undergone total arch replacement 5 years prior complained of chest pain. Emergent contrast-enhanced computed tomography (CT) revealed an intra-mediastinal hematoma around the vascular graft of the ascending aorta and angiography revealed pooling of contrast medium on the dorsal side of the vascular graft. We suspected extravasation of the thoracic vascular graft. Aortic angioscopic examination revealed a red vascular graft defect that matched extravasation at the contralateral level of the prosthetic left common carotid artery branch. Subsequently, non-anastomotic thoracic aortic graft rupture was diagnosed. The patient underwent a two-debranching thoracic endovascular aortic repair (Zone 0) with a right subclavian artery-left common carotid artery-left subclavian artery bypass. Postoperative angiography revealed disappearance of the extravasation from the graft rupture site, patent grafted vessels with flow, and no endoleak. Follow-up CT at 6 months postoperatively showed no extravasation.

Conclusions

To our knowledge, this is the first report of non-anastomotic thoracic aortic graft rupture detected using non-obstructive aortic angioscopy. Aortic angioscopy can help establish a definitive diagnosis in patients with aortic graft rupture.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40792-022-01394-w.

Aortic plaque burden predicts vascular events in patients with cardiovascular disease: The EAST-NOGA study

BACKGROUND

Non-obstructive general angioscopy (NOGA) can be used to diagnose aortic atherosclerotic plaques. We examine the association between the number of aortic plaques detected by NOGA and the risk of subsequent cardiovascular events.

METHODS

The Evaluation of AtheroScleroTic and rupture events by Non-Obstructive General Angioscopy (EAST-NOGA) was a prospective cohort study of patients with suspected coronary artery disease who underwent NOGA.

RESULTS

Of the 577 patients who underwent NOGA, 532 (92%) completed the follow-up (median follow-up: 13 months, interquartile range: 12-16). The median number of plaques per person was 6 (interquartile range: 3-12), and 567 (98%) had at least one aortic plaque. During the 13-month follow-up, 38 (7.1%) patients had a primary composite endpoint [including cardiovascular death, myocardial infarction, stroke, peripheral artery disease (PAD), or worsening renal function], which was significantly associated with chronic kidney disease, a history of PAD, a lower hemoglobin level, and large numbers of aortic plaques [11 (5-17) vs. 6 (2-11), p = 0.003]. A receiver operating characteristic curve analysis for the number of aortic plaques predicting composite endpoints revealed that the cut-off value of aortic plaques was 12. After multivariate adjustment, the presence of ≥12 aortic plaques remained a significant predictor for composite endpoint events (hazard ratio 2.53, 95% confidence interval 1.26-5.04, p = 0.010).

CONCLUSIONS

The number of aortic plaques detected by NOGA may predict subsequent clinical events.

Abdominal aorta plaques are better in predicting future cardiovascular events compared to carotid intima-media thickness: A 20-year prospective study

BACKGROUND AND AIMS

Both carotid intima-media thickness (IMT) and arterial plaques have been shown to predict future CV events. Since there are no previous studies on the subject, our objective was to compare carotid IMT and the length of plaques in abdominal-pelvic main arteries in CV risk assessment in a prospective study setting with a follow-up of over 20 years.

METHODS

A total of 1007 patients (50% men), aged 51 ± 6.0 years, participated in the current study. Carotid IMT and the summarized plaque length (SUM) from abdominal aorta to common femoral arteries were ultrasonographically assessed. Patients were followed-up a median (1st-3rd quartile) of 22.5 (17.5-23.2) years for CV events.

RESULTS

SUM significantly predicted CV events (HR per every 10 mm increase: 1.035, 95% CI: 1.027-1.044, p < 0.001). Those in the highest SUM tertile had over 3-fold risk for CV event (HR: 3.392, 95% CI: 2.427-4.741, p < 0.001) when compared to those in the lowest tertile. SUM significantly predicted CV events even after adjusting for age, sex, hypertension, diabetes, smoking (pack-years), LDL cholesterol and IMT. Adding SUM to the established model improved C-index (95% CI) from 0.706 (0.674-0.738) to 0.718 (0.688-0.747) as well as both discrimination (p < 0.001) and reclassification (p < 0.001) of the patients. In contrast, IMT predicted cardiovascular events only in univariate analysis and it did not improve discrimination or reclassification of the patients.

CONCLUSIONS

In light of our findings, SUM is a superior indicator and clinical tool for evaluating the overall CV risk compared to carotid IMT.

Ischemic Stroke Patients with Non-Valvular Atrial Fibrillation have a Risk for Aortogenic Embolizations

We have a great interest in the article in Journal of Atherosclerosis and Thrombosis by Suzuki et al. titled Complex Aortic Arch Atherosclerosis in Acute Ischemic Stroke Patients with Non-Valvular Atrial Fibrillation. The authors demonstrated that 38.7% transesophageal echocardiography-derived complex aortic arch plaques (CAPs) among 106 patients with acute ischemic strokes with atrial fibrillation (AF), suggesting that patients with acute ischemic stroke and AF often had CAPs. The atheromatous lesions at the aortic arch are one of the causes of ischemic strokes. The cause of acute ischemic strokes in patients with AF could not only be cardiogenic embolisms due to AF but also aortogenic embolisms due to CAPs. The possibility of concomitant CAPs should be considered for stroke patients with AF. Non-obstructive general angioscopy has the possibility to detect aortic plaques in the aortic arch more accurately than TEE and might help to diagnose atheromatous plaques and embolic materials in the aortic arch. Further studies are needed to elucidate the causes of ischemic strokes and are expected to improve the outcomes for acute ischemic strokes in patients with AF.

Partitioning risk factors for embolic stroke of undetermined source using exploratory factor analysis

Background

Embolic stroke of undetermined source (ESUS) accounts for up to 25% of strokes. Understanding risk factors associated with ESUS is important in reducing stroke burden worldwide. However, ESUS patients are younger and present with fewer traditional risk factors. Significant global variation in ESUS populations also exists making the clinical picture of this type of stroke unclear.

Methods and results

ESUS patients were pair matched for age, sex, and ethnicity with a group of all other strokes (both n = 331). Exploratory factor analysis was applied in both groups to 14 risk and clinical factors to identify latent factors. In ESUS patients, two latent factors emerged consisting primarily of heart-related variables such as left ventricular wall motion abnormalities, reduced ejection fraction, and increased left atrial volume index, as well as aortic arch atherosclerosis. This is in comparison to the all other strokes group, which was dominated by traditional stroke risk factors.

Conclusions

Our findings support the existence of a unique pattern of risk factors specific to ESUS. We show that LVWMA and corresponding changes in left heart function are a potential source of emboli in these patients. In addition, the clustering of aortic arch atherosclerosis with left heart factors suggests a causal link. Through the application of exploratory factor analysis, this work contributes to a further understanding of stroke mechanisms in ESUS.

Consensus document on the standard of coronary angioscopy examination and assessment from the Japanese Association of Cardiovascular Intervention and Therapeutics

Coronary angioscopy (CAS) is a unique diagnostic device that allows direct visualization of the vascular luminal surface in living patients. CAS contributes to elucidate the pathology of coronary artery disease. This consensus document provides a standard for CAS examination and assessment.

Clinical insights of non-obstructive general angioscopy for assessing atherosclerotic pathology of aortic valve in vivo

Non-obstructive general angioscopy (NOGA) images of severe aortic valve stenosis (AS) and atherosclerotic aorta were documented. Atheromatous embolization is known as an important complication of endovascular therapy for severe AS. However, it is hard to detect atherosclerotic changes of the aortic valve and atheromatous aorta related to them in the in-vivo setting. NOGA, which is a novel imaging modality for the aorta and aortic valves, can visualize atherosclerosis of aortic intima vividly. NOGA may play a role in risk stratification for atheromatous embolism with endovascular therapy. We reported a case of severe AS and atheromatous aorta to evaluate before an operation with NOGA.

Upregulated Kynurenine Pathway Enzymes in Aortic Atherosclerotic Aneurysm: Macrophage Kynureninase Downregulates Inflammation

AIMS

Inflammation and hypertension contribute to the progression of atherosclerotic aneurysm in the aorta. Vascular cell metabolism is regarded to modulate atherogenesis, but the metabolic alterations that occur in atherosclerotic aneurysm remain unknown. The present study aimed to identify metabolic pathways and metabolites in aneurysmal walls and examine their roles in atherogenesis.

METHODS

Gene expression using microarray and metabolite levels in the early atherosclerotic lesions and aneurysmal walls obtained from 42 patients undergoing aortic surgery were investigated (early lesion n=11, aneurysm n=35) and capillary electrophoresis-time-of-flight mass spectrometry (early lesion n=14, aneurysm n=38). Using immunohistochemistry, the protein expression and localization of the identified factors were examined (early lesion n=11, non-aneurysmal advanced lesion n=8, aneurysm n=11). The roles of the factors in atherogenesis were analyzed in macrophages derived from human peripheral blood mononuclear cells.

RESULTS

Enrichment analysis using 35 significantly upregulated genes (log2 ratio, ＞3) revealed the alteration of the kynurenine pathway. Metabolite levels of tryptophan, kynurenine, and quinolinic acid and the kynurenine-to-tryptophan ratio were increased in the aneurysmal walls. Gene and protein expression of kynureninase and kynurenine 3-monooxygenase were upregulated and localized in macrophages in the aneurysmal walls. The silencing of kynureninase in the cultured macrophages enhanced the expression of interleukin-6 and indoleamine 2,3-dioxygenase 1.

CONCLUSION

Our study suggests the upregulation of the kynurenine pathway in macrophages in aortic atherosclerotic aneurysm. Kynureninase may negatively regulate inflammation via the kynurenine pathway itself in macrophages.

High Wall Shear Stress Is Related to Atherosclerotic Plaque Rupture in the Aortic Arch of Patients with Cardiovascular Disease: A Study with Computational Fluid Dynamics Model and Non-Obstructive General Angioscopy

Aims: Wall shear stress (WSS) has been considered a major determinant of aortic atherosclerosis. Recently, non-obstructive general angioscopy (NOGA) was developed to visualize various atherosclerotic pathologies, including in vivo ruptured plaque (RP) in the aorta. However, the relationship between aortic RP and WSS distribution within the aortic wall is unclear. This study aimed to investigate the relationship between aortic NOGA-derived RP and the stereographic distribution of WSS by computational fluid dynamics (CFD) modeling using three-dimensional computed tomography (3D-CT) angiography.

Methods: We investigated 45 consecutive patients who underwent 3D-CT before coronary angiography and NOGA during coronary angiography. WSS in the aortic arch was measured by CFD analysis based on the finite element method using uniform inlet and outlet flow conditions. Aortic RP was detected by NOGA.

Results: Patients with a distinct RP showed a significantly higher maximum WSS value in the aortic arch than those without aortic RP (56.2±30.6 Pa vs 36.2±19.8 Pa, p =0.017), no significant difference was noted in the mean WSS between those with and without aortic RP. In a multivariate logistic regression analysis, the presence of a maximum WSS value more than a specific value was a significant predictor of aortic RP (odds ratio 7.21, 95% confidence interval 1.78-37.1, p =0.005).

Conclusions: Aortic RP detected by NOGA was strongly associated with a higher maximum WSS in the aortic arch derived by CFD using 3D-CT. The maximum WSS value may have an important role in the underlying mechanism of not only aortic atherosclerosis, but also aortic RP.

Complex Aortic Arch Atherosclerosis in Acute Ischemic Stroke Patients with Non-Valvular Atrial Fibrillation

Aim: Aortic arch atherosclerosis, particularly complex aortic arch plaques (CAPs), is an important source of cerebral emboli. CAPs and atrial fibrillation (AF) often co-exist; however, the prevalence and risk of CAPs in acute ischemic stroke patients with AF is unclear.

Methods: In patients with acute ischemic stroke with non-valvular AF admitted to Jichi Medical University Hospital during April 2016 to September 2019, we retrospectively evaluated the presence of CAPs on transesophageal echocardiography (TEE).

Results: CAPs were observed in 41 (38.7 %) of 106 patients with non-valvular AF. Older age, diabetes mellitus, chronic kidney disease, low high-density lipoprotein cholesterol (HDL-C) levels, higher levels of glycohemoglobin A1c (HbA1c), higher CHADS ₂ and CHA ₂ DS ₂ -VASc scores, and intracranial or carotid artery stenosis were more frequently observed in CAPs-positive than in CAPs-negative patients. In multivariable analyses, older age (odds ratio [OR]: 1.2 per year increase; 95% confidence interval [CI]: 1.07–1.24; P ＜0.0001), diabetes mellitus (OR: 4.7; 95%CI: 1.27-17.35; P ＜0.05), and low HDL-C (OR: 0.95 per 1 mg/dl increase; 95%CI: 0.92-0.99; P ＜0.01) were independent risk factors for CAPs. The prevalence of CAPs was age-dependent, and there was a significantly higher risk in patients aged either 75–84 years or ＞84 years than in those aged ＜65 (OR: 7.6; 95%CI: 1.50-38.62, and OR: 32.1; 95%CI: 5.14-200.11, respectively).

Conclusions: Even in patients with ischemic stroke with non-valvular AF, concomitant CAPs should be considered in older individuals and those who have diabetes or low HDL-C.

Mechanical and structural properties of different types of human aortic atherosclerotic plaques

Atherosclerotic plaques are characterized by structural heterogeneity affecting aortic behaviour under mechanical loading. There is evidence of direct connections between the structural plaque arrangement and the risk of plaque rupture. As a consequence of aortic plaque rupture, plaque components are transferred by the bloodstream to smaller vessels, resulting in acute cardiovascular events with a poor prognosis, such as heart attacks or strokes. Hence, evaluation of the composition, structure, and biochemical profile of atherosclerotic plaques seems to be of great importance to assess the properties of a mechanically induced failure, indicating the strength and rupture vulnerability of plaque. The main goal of the research was to determine experimentally under uniaxial loading the mechanical properties of different types of the human abdominal aorta and human aortic atherosclerotic plaques identified based on vibrational spectra (ATR-FTIR and FT-Raman spectroscopy) analysis and validated by histological staining. The potential of spectroscopic techniques as a useful histopathological tool was demonstrated. Three types of atherosclerotic plaques - predominantly calcified (APC), lipid (APL), and fibrotic (APF) - were distinguished and confirmed by histopathological examinations. Compared to the normal aorta, fibrotic plaques were stiffer (median of E_H for circumferential and axial directions, respectively: 8.15 MPa and 6.56 MPa) and stronger (median of σ_M for APLc = 1.57 MPa and APLa = 1.64 MPa), lipidic plaques were the weakest (median of σ_M for APLc = 0.76 MPa and APLa = 0.51 MPa), and calcified plaques were the stiffest (median of E_H for circumferential and axial directions, respectively: 13.23 MPa and 6.67 MPa). Therefore, plaques detected as predominantly lipid and calcified are most prone to rupture; however, the failure process reflected by the simplification of the stress-stretch characteristics seems to vary depending on the plaque composition.

Spontaneous ruptured aortic plaque and injuries: insights for aging and acute aortic syndrome from non-obstructive general angioscopy

Recent advances in non-obstructive general angioscopy (NOGA) have enabled the detection of aortic atherosclerosis. The incidence of spontaneous ruptured aortic plaques (SRAPs) and aortic injuries was found to be high in patients diagnosed with or suspected of having coronary artery disease. These facts may result in a paradigm shift for diseases such as aging and acute aortic syndrome because the incidence of systemic embolic diseases and aortic disease are assumed be high. Aortic thromboembolism has been thought to be mainly iatrogenic and is referred to as "cholesterol embolization syndrome" or "cholesterol crystal embolization", although the cholesterol crystals (CCs) were not demonstrated routinely as real images. Atheromatous materials, fibrins, calcifications, macrophages, and a mixture of such substances are released through a puff or puff-chandelier rupture. Among atheromatous materials, CCs can be easily detected clinically in sampled blood via polarized light microscopy. Atheromatous materials include rich CCs and free monolayers, and multilayer CCs are released when the atheromatous materials from vulnerable plaques break into pieces, such as in puff or puff-chandelier rupture. Released SRAPs seem to be asymptomatic; however, accumulation of SRAPs referred to as accumulated spontaneous asymptomatic plaques may cause aging through systemic "embolic" processes, such as mechanical obstruction and an inflammasome pathway. Unique findings in "atherosclerotic" acute aortic syndrome, such as a clear boundary between the dissected lesion and the normal lesion, fissure/fissure bleeding suggesting an entry or a reentry, and subintimal blood flow detected through NOGA are reported. Fissure/fissure bleeding and subintimal blood flow may be the first or last triggers of "atherosclerotic" acute aortic syndrome. Pre-emptive diagnosis and risk stratification of acute "atherosclerotic" aortic dissection and feedback for endovascular therapy may be enabled through the use of NOGA in the future.