Atherosclerotic enlargement of the human abdominal aorta

Evidence Accumulates: Patients with Ascending Aneurysms Are Strongly Protected from Atherosclerotic Disease

Ascending thoracic aortic aneurysms may be fatal upon rupture or dissection and remain a leading cause of death in the developed world. Understanding the pathophysiology of the development of ascending thoracic aortic aneurysms may help reduce the morbidity and mortality of this disease. In this review, we will discuss our current understanding of the protective relationship between ascending thoracic aortic aneurysms and the development of atherosclerosis, including decreased carotid intima-media thickness, low-density lipoprotein levels, coronary and aortic calcification, and incidence of myocardial infarction. We also propose several possible mechanisms driving this relationship, including matrix metalloproteinase proteins and transforming growth factor-β.

Learning-based initialization for correntropy-based level sets to segment atherosclerotic plaque in ultrasound images

Carotid artery atherosclerosis is a significant cause of stroke. Ultrasound imaging has been widely used in the diagnosis of atherosclerosis. Therefore, segmenting the atherosclerotic carotid plaque in an ultrasound image is an important task. Accurate plaque segmentation is helpful for the measurement of carotid plaque burden. This study proposes an automatic method for atherosclerotic plaque segmentation by using correntropy-based level sets (CLS) with learning-based initialization. We introduce the CLS model, containing the point-based local bias-field corrected image fitting method and correntropy-based distance measurement, to overcome the limitations of the ultrasound images. A supervised learning algorithm is employed to solve the automatic initialization problem of the variational methods. The proposed atherosclerotic plaque segmentation method is validated on 29 carotid ultrasound images, obtaining a Dice ratio of 90.6 ± 1.9% and an overlap index of 83.6 ± 3.2%. Moreover, by comparing the standard deviation of each evaluation index, it can be found that the proposed method is more robust for segmenting the atherosclerotic plaque. Our work shows that our proposed method can be more helpful than other variational models for measuring the carotid plaque burden.

HRU-Net: A Transfer Learning Method for Carotid Artery Plaque Segmentation in Ultrasound Images

Carotid artery stenotic plaque segmentation in ultrasound images is a crucial means for the analysis of plaque components and vulnerability. However, segmentation of severe stenotic plaques remains a challenging task because of the heterogeneities of inter-plaques and intra-plaques, and obscure boundaries of plaques. In this paper, we propose an automated HRU-Net transfer learning method for segmenting carotid plaques, using the limited images. The HRU-Net is based on the U-Net encoder−decoder paradigm, and cross-domain knowledge is transferred for plaque segmentation by fine-tuning the pretrained ResNet-50. Moreover, a cropped-blood-vessel image augmentation is customized for the plaque position constraint during training only. Moreover, hybrid atrous convolutions (HACs) are designed to derive diverse long-range dependences for refined plaque segmentation that are used on high-level semantic layers to exploit the implicit discrimination features. The experiments are performed on 115 images; Firstly, the 10-fold cross-validation, using 40 images with severe stenosis plaques, shows that the proposed method outperforms some of the state-of-the-art CNN-based methods on Dice, IoU, Acc, and modified Hausdorff distance (MHD) metrics; the improvements on metrics of Dice and MHD are statistically significant (p < 0.05). Furthermore, our HRU-Net transfer learning method shows fine generalization performance on 75 new images with varying degrees of plaque stenosis, and it may be used as an alternative for automatic noisy plaque segmentation in carotid ultrasound images clinically.

Evaluation of carotid intima media thickness measurement from ultrasound images

A third of deaths in the world are due to cardiovascular diseases [1]. Atherosclerosis is the major cause of myocardial infarction, which occurs by deposition of plaque in the coronary artery. The chance of stroke rises with the thickening of carotid artery due to the plaque. Hence, accurate measurement of the intima-media thickness is necessary for predicting the chance of stroke. The stopping criterion and active resampling are incorporated in greedy snake segmentation technique. This modified algorithm segmented and extracted the intima-media complex in the ultrasound images. The snake control points obtained from the boundary of the region of interest forms the contour and demarcates the boundary of intima-media complex. The thickness ± standard deviation and the intra-observer error values obtained by modified algorithm are in conformity with the measurements by expert. The intra-observer error values for greedy snake segmentation methods were 0.10 and 0.09 for manual snake initialization and automatic snake initialization, respectively. Shapiro-Wilk test and One-way ANOVA test explains there is no statistical difference between group means obtained from these segmentation techniques and the expert measurement. The statistical analysis proves values of the intima-media thickness obtained from both snake segmentation techniques are very close to expert measurements.

The impact of computed tomography-derived aortic atheroma volume on prognosis after transcatheter aortic valve replacement

BACKGROUND

The impact of the extent of aortic atheroma on patients' prognosis after transcatheter aortic valve replacement (TAVR) has not been completely evaluated. This study aimed to evaluate the prognostic value of the aortic atheroma volume (AAV) derived from computed tomography, and the effect of its differences among the segments of the aorta, in patients undergoing TAVR.

METHODS

In total, 143 patients with symptomatic severe aortic stenosis who underwent pre-procedural computed tomography before TAVR procedure indication were evaluated. AAV was calculated by measuring the aortic lumen and vessel volume using every 1-mm axial image and was further divided into thoracic (TAAV) and abdominal segments (AbAAV).

RESULTS

During a median follow-up of 651 days, 24 all-cause and 14 cardiac deaths occurred. In the Kaplan-Meier analysis, the high AAV group had significantly higher all-cause and cardiac mortalities than the low AAV group (p = 0.016 and 0.023, respectively). Regarding segmental AAV, all-cause and cardiac mortalities did not have significant differences between the high and low TAAV groups. Moreover, all-cause and cardiac mortalities were significantly higher in the high AbAAV group than in the low AbAAV group (p = 0.0043 and 0.023, respectively). The multivariable analysis showed that only AbAAV was an independent predictor for all-cause mortality (hazard ratio: 1.06, p = 0.046).

CONCLUSION

AAV was significantly associated with the mortality after TAVR. The current study suggests the pre-procedural assessment of AAV is valuable in predicting prognosis after TAVR. However, further investigation with a larger sample size is needed to validate our findings.

Role of pregnancy on insulin-induced vasorelaxation: the influence of angiotensin II receptors

Insulin resistance is a feature of pregnancy and is associated with increased levels of angiotensin II (Ang II) and insulin. Therefore, pregnancy may change insulin-induced vasodilation through changes in Ang II receptors. Insulin-induced vasorelaxation was evaluated in phenylephrine-precontracted aortic rings of pregnant and non-pregnant rats, using a conventional isolated organ preparation. Experiments were performed in thoracic or abdominal aorta rings with or without endothelium in the presence and absence of N^G-nitro-L-arginine methyl ester (L-NAME) (10^-5 M), losartan (10^-7 M), or PD123319 (10^-7 M). AT1 and AT2 receptor expressions were detected by immunohistochemistry. Insulin-induced vasodilation was endothelium- and nitric oxide-dependent and decreased in the thoracic aorta but increased in the abdominal segment of pregnant rats. The insulin's vasorelaxant effect was increased by losartan mainly on the thoracic aorta. PD123319 decreased insulin-induced vasorelaxation mainly in the pregnant rat abdominal aorta. AT1 receptor expression was decreased while AT2 receptor expression was increased by pregnancy. In conclusion, pregnancy changes insulin-induced vasorelaxation. Moreover, insulin vasodilation is tonically inhibited by AT1 receptors, while AT2 receptors appear to have an insulin-sensitizing effect. The role of pregnancy and Ang II receptors differ depending on the aorta segment. These results shed light on the role of pregnancy and Ang II receptors on the regulation of insulin-mediated vasodilation.

Morphological and Histopathological Study of Autopsied Patients with Atherosclerosis and HIV

BACKGROUND

Chronic infection by HIV evolves with a vascular inflammatory action causing endothelial dysfunction. The action of the virus, as well as the side effects of antiretroviral drugs, contribute to the progression of cardiovascular diseases. The present study aimed to evaluate the percentage of collagen fibers and the density of mast cells, chymase and tryptase, in aortas of patients with and without HIV, and also patients with and without atherosclerosis.

METHODS

Aortic fragments were obtained from autopsied patients aged 22-69 years and selected regardless of the cause of death or underlying disease. The samples were divided into four groups, (1) Group with HIV and with atherosclerosis; (2) Group with HIV and without atherosclerosis; (3) Group without HIV and with atherosclerosis; (4) Group without HIV and without atherosclerosis (Control). The percentage of collagen fibers was analyzed in the intima-media layer and the density of mast cells was analyzed in all aortic layers. Graphpad Prism 5.0^® software was used for statistical analysis.

RESULTS

There were more collagen fibers in HIV patients, with or without atherosclerosis. The group with HIV and atherosclerosis presented a higher density of chymase and tryptase mast cells. The correlation between collagen fibers and age was negative in the non-HIV group and with atherosclerosis.

CONCLUSION

The inflammatory process resulting from HIV infection may be relevant in the alteration of aortic collagen fibers and in triggering or accelerating atherosclerosis. The study is important because HIV patients have increased risks for the development of cardiovascular diseases, and follow-up is necessary to prevent such diseases.

An unexpected paradox: wall shear stress in the aorta is less in patients with severe atherosclerosis regardless of obesity

BACKGROUND

Obesity is a widespread condition that is more prevalent in Western countries compared to others. Aortic atherosclerosis (AA) is a condition that frequently has been associated with obesity. An obesity paradox, where morbidly obese decedents had either no or minimal AA compared to nonobese decedents, recently has been described by some of us. The explanation for this almost counterintuitive paradox has yet to be determined, but a number of hypotheses were advanced, including hemodynamic factors producing aortic wall shear stress (WSS). The purpose of the present study was to determine if there was a relationship between AA and WSS, as determined by postmortem measurement of aortic wall diameters.

METHODS

Circumferences of the aorta at the levels of the ascending, thoracic and abdominal aorta were measured in 274 consecutive autopsies over 2-year period of time. AA was assessed using a previously described grading scale as either mild or severe. Circumferences were mathematically converted to diameters and WSS was calculated using the Hagen-Poiseuille formula. Two different methods to estimate cardiac output were used, both based on literature methods, one of which was body mass index (BMI) dependent, and the other BMI independent. Univariate and multivariable analyses of the relationship between WSS, age, BMI, gender, race and severity of AA were performed.

RESULTS

Of the 274 decedents, 140 had mild and 134 had moderate to severe AA. BMI <35 was associated with moderate to severe AA. WSS was inversely correlated with AA in all these segments of the aorta in each BMI subgroup with the exception of the ascending aorta for decedents with BMI ≤35 kg/m². Contrary to what we had hypothesized, WSS was not a determinant of the obesity paradox. However, among all the variables analyzed, a history of hypertension, diabetes mellitus and age were significant factors for developing AA (relative risk [RR] 0.35, P = .039; RR 1.51, P = .0006, RR 1.19, P = .0001, respectively).

CONCLUSIONS

Our data demonstrate that WSS was unexpectedly lower in decedents with moderate and severe AA as compared to those with mild AA. This observation, which requires further investigations, was seen in all BMI ranges and was confirmed by 2 methods to calculate WSS.

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.

Diffusion Limited Cryopreservation of Tissue with Radiofrequency Heated Metal Forms

Cryopreserved tissues are increasingly needed in biomedical applications. However, successful cryopreservation is generally only reported for thin tissues (≤1 mm). This work presents several innovations to reduce cryoprotectant (CPA) toxicity and improve tissue cryopreservation, including 1) improved tissue warming rates through radiofrequency metal form and field optimization and 2) an experimentally verified predictive model to optimize CPA loading and rewarming to reduce toxicity. CPA loading is studied by microcomputed tomography (µCT) imaging, rewarming by thermal measurements, and modeling, and viability is measured after loading and/or cryopreservation by alamarBlue and histology. Loading conditions for three common CPA cocktails (6, 8.4, and 9.3 m) are designed, and then fast cooling and metal forms rewarming (up to 2000 °C min-1 ) achieve ≥90% viability in cryopreserved 1-2 mm arteries with various CPAs. Despite high viability by alamarBlue, histology shows subtle changes after cryopreservation suggesting some degree of cell damage especially in the central portions of thicker arteries up to 2 mm. While further studies are needed, these results show careful CPA loading and higher metal forms warming rates can help reduce CPA loading toxicity and improve outcomes from cryopreservation in tissues while also offering new protocols to preserve larger tissues ≥1 mm in thickness.

Phylogenic Determinants of Cardiovascular Frailty, Focus on Hemodynamics and Arterial Smooth Muscle Cells

The evolution of the circulatory system from invertebrates to mammals has involved the passage from an open system to a closed in-parallel system via a closed in-series system, accompanying the increasing complexity and efficiency of life’s biological functions. The archaic heart enables pulsatile motion waves of hemolymph in invertebrates, and the in-series circulation in fish occurs with only an endothelium, whereas mural smooth muscle cells appear later. The present review focuses on evolution of the circulatory system. In particular, we address how and why this evolution took place from a closed, flowing, longitudinal conductance at low pressure to a flowing, highly pressurized and bifurcating arterial compartment. However, although arterial pressure was the latest acquired hemodynamic variable, the general teleonomy of the evolution of species is the differentiation of individual organ function, supported by specific fueling allowing and favoring partial metabolic autonomy. This was achieved via the establishment of an active contractile tone in resistance arteries, which permitted the regulation of blood supply to specific organ activities via its localized function-dependent inhibition (active vasodilation). The global resistance to viscous blood flow is the peripheral increase in frictional forces caused by the tonic change in arterial and arteriolar radius, which backscatter as systemic arterial blood pressure. Consequently, the arterial pressure gradient from circulating blood to the adventitial interstitium generates the unidirectional outward radial advective conductance of plasma solutes across the wall of conductance arteries. This hemodynamic evolution was accompanied by important changes in arterial wall structure, supported by smooth muscle cell functional plasticity, including contractility, matrix synthesis and proliferation, endocytosis and phagocytosis, etc. These adaptive phenotypic shifts are due to epigenetic regulation, mainly related to mechanotransduction. These paradigms actively participate in cardio-arterial pathologies such as atheroma, valve disease, heart failure, aneurysms, hypertension, and physiological aging.

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

Aim: Knowledge of subclinical plaque morphology and plaque distribution in the aorta in vivo remains unclear. This study aimed to increase the body of knowledge in this area.

Methods: We enrolled 37 consecutive patients with stable angina pectoris patients who underwent non-obstructive angioscopy for both the coronary artery and aorta immediately after percutaneous coronary intervention. We evaluated the presence of aortic plaques and the distribution of plaque instability. Patients were allocated into two groups according to the number of vulnerable plaques in whole aorta (a low [0–11] and high [≥ 12] group). We evaluated the relationships between the two groups in terms of cardiovascular risk factors.

Results: Aortic plaques were identified using non-obstructive angioscopy in all patients, and the greatest number of plaques was found at the infrarenal abdominal aorta (IAA) (the aortic arch, the descending thoracic aorta, the suprarenal abdominal aorta, the IAA, and common iliac artery; 65%, 76%, 65%, 95%, and 49%, respectively; p < 0.001). The maximum yellow grade, and the number of intense yellow plaques, ruptured plaques, and thrombi were highest at the IAA (p < 0.001). The prevalence of diabetes mellitus and peripheral arterial disease was higher in the high vulnerable plaque group (83.3% vs. 40.0%, p = 0.010, 50.0% vs. 8.0%, p = 0.005, respectively).

Conclusions: Aortic atherosclerosis was the most severe at the IAA, and aortic plaque vulnerability and distribution were associated with the prevalence of diabetes mellitus and peripheral artery disease in patients with stable angina pectoris. Non-obstructive angioscopy may identify patients at high risk of future aortic events.

Diabetes Mellitus: Is It Protective against Aneurysm? A Narrative Review

Objectives: In the course of extensive clinical aortic surgery, we noticed that the aorta was quite thick and fibrotic in diabetic patients. We thought the diabetic aortic aorta might be inimitable to aortic dissection. On this basis, we set out to review information in the literature regarding aortic growth and dissection in diabetic patients. Methods: We used a 2-step search approach to the available literature on diabetes and aneurysm. Firstly, databases including PubMed, Cochrane, Embase and TRIP were searched. Secondly, relevant studies were identified through secondary sources including references of initially selected articles. We address the relationship between diabetes and the incidence, prevalence, growth, mortality and rupture of an aneurysm. Results: Diabetes is thought to exert a protective role in both thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA). Diabetics were shown to have a slower aneurysm growth rate, lower rupture rate, delayed (> 65 years) age of rupture, decreased rate of mortality from an aneurysm and a decreased length of hospital stay. There was also noted a decreased rate of incidence and prevalence of TAA and AAA in diabetics, smaller aneurysm diameter, reduction in matrix metalloproteinases and an increased aortic wall stress in diabetics. Antidiabetic agents like metformin, thiazolidinediones and dipeptidyl peptidase-4 inhibitors may protect against an aneurysm. Conclusion: Our literature review provides strong (but often circumstantial) evidence that diabetic patients exhibit slower growth of aortic aneurysms and a lower rate of aortic dissection. Furthermore, clinical and experimental studies indicate that common antidiabetic medications on their own inhibit growth of aortic aneurysms. These findings indicate a paradoxically beneficial effect of the otherwise highly detrimental diabetic state.

Mechanical and geometrical determinants of wall stress in abdominal aortic aneurysms: A computational study

An aortic aneurysm (AA) is a focal dilatation of the aortic wall. Occurrence of AA rupture is an all too common event that is associated with high levels of patient morbidity and mortality. The decision to surgically intervene prior to AA rupture is made with recognition of significant procedural risks, and is primarily based on the maximal diameter and/or growth rate of the AA. Despite established thresholds for intervention, rupture occurs in a notable subset of patients exhibiting sub-critical maximal diameters and/or growth rates. Therefore, a pressing need remains to identify better predictors of rupture risk and ultimately integrate their measurement into clinical decision making. In this study, we use a series of finite element-based computational models that represent a range of plausible AA scenarios, and evaluate the relative sensitivity of wall stress to geometrical and mechanical properties of the aneurysmal tissue. Taken together, our findings encourage an expansion of geometrical parameters considered for rupture risk assessment, and provide perspective on the degree to which tissue mechanical properties may modulate peak stress values within aneurysmal tissue.

Exposure of tropoelastin to peroxynitrous acid gives high yields of nitrated tyrosine residues, di-tyrosine cross-links and altered protein structure and function

Elastin is an abundant extracellular matrix protein in elastic tissues, including the lungs, skin and arteries, and comprises 30-57% of the aorta by dry mass. The monomeric precursor, tropoelastin (TE), undergoes complex processing during elastogenesis to form mature elastic fibres. Peroxynitrous acid (ONOOH), a potent oxidising and nitrating agent, is formed in vivo from superoxide and nitric oxide radicals. Considerable evidence supports ONOOH formation in the inflamed artery wall, and a role for this species in the development of human atherosclerotic lesions, with ONOOH-damaged extracellular matrix implicated in lesion rupture. We demonstrate that TE is highly sensitive to ONOOH, with this resulting in extensive dimerization, fragmentation and nitration of Tyr residues to give 3-nitrotyrosine (3-nitroTyr). This occurs with equimolar or greater levels of oxidant and increases in a dose-dependent manner. Quantification of Tyr loss and 3-nitroTyr formation indicates extensive Tyr modification with up to two modified Tyr per protein molecule, and up to 8% conversion of initial ONOOH to 3-nitroTyr. These effects were modulated by bicarbonate, an alternative target for ONOOH. Inter- and intra-protein di-tyrosine cross-links have been characterized by mass spectrometry. Examination of human atherosclerotic lesions shows colocalization of 3-nitroTyr with elastin epitopes, consistent with TE or elastin modification in vivo, and also an association of 3-nitroTyr containing proteins and elastin with lipid deposits. These data suggest that exposure of TE to ONOOH gives marked chemical and structural changes to TE and altered matrix assembly, and that such damage accumulates in human arterial tissue during the development of atherosclerosis.

An integrated method for atherosclerotic carotid plaque segmentation in ultrasound image

BACKGROUND AND OBJECTIVE

Carotid artery atherosclerosis is an important cause of stroke. Ultrasound imaging has been widely used in the diagnosis of atherosclerosis. Therefore, segmenting atherosclerotic carotid plaque in ultrasound image is an important task. Accurate plaque segmentation is helpful for the measurement of carotid plaque burden. In this paper, we propose and evaluate a novel learning-based integrated framework for plaque segmentation.

METHODS

In our study, four different classification algorithms, along with the auto-context iterative algorithm, were employed to effectively integrate features from ultrasound images and later also the iteratively estimated and refined probability maps together for pixel-wise classification. The four classification algorithms were support vector machine with linear kernel, support vector machine with radial basis function kernel, AdaBoost and random forest. The plaque segmentation was implemented in the generated probability map. The performance of the four different learning-based plaque segmentation methods was tested on 29 B-mode ultrasound images. The evaluation indices for our proposed methods were consisted of sensitivity, specificity, Dice similarity coefficient, overlap index, error of area, absolute error of area, point-to-point distance, and Hausdorff point-to-point distance, along with the area under the ROC curve.

RESULTS

The segmentation method integrated the random forest and an auto-context model obtained the best results (sensitivity 80.4 ± 8.4%, specificity 96.5 ± 2.0%, Dice similarity coefficient 81.0 ± 4.1%, overlap index 68.3 ± 5.8%, error of area -1.02 ± 18.3%, absolute error of area 14.7 ± 10.9%, point-to-point distance 0.34 ± 0.10 mm, Hausdorff point-to-point distance 1.75 ± 1.02 mm, and area under the ROC curve 0.897), which were almost the best, compared with that from the existed methods.

CONCLUSIONS

Our proposed learning-based integrated framework investigated in this study could be useful for atherosclerotic carotid plaque segmentation, which will be helpful for the measurement of carotid plaque burden.

Implications of alcoholic cirrhosis in atherosclerosis of autopsied patients

Introduction:

Alcoholism is a major public health problem, which has a high social cost and affects many aspects of human activity. Liver disease is one of the first consequences of alcohol abuse, and steatosis, liver cirrhosis and hepatitis may occur. Other organs are also affected with pathological changes, such as pancreatitis, cardiomyopathies, dyslipidemias and atherosclerosis.

Objective:

To identify the occurrence and degree of atherosclerosis in alcohol-dependent individuals with liver cirrhosis, observing macroscopic and microscopic changes in lipid and collagen deposits and in the liver. We also aimed to verify the association of lipid and collagen fiber deposits with gender, age and body mass index, and to relate alcoholism, liver cirrhosis and atherosclerosis.

Method:

We performed a study based on autopsy reports of patients with alcoholic liver cirrhosis, with analysis of aorta and liver fragments to verify the occurrence and degree of atherosclerosis, as well as collagen contents.

Results:

Microscopic atherosclerosis was higher in young subjects (early injury) and in patients with alcoholic liver cirrhosis. The macroscopic analysis of atherosclerosis in aortas showed that patients in more advanced age groups presented more severe classifications. Atherosclerosis, both micro and macroscopically, and the percentage of fibrosis in the liver and aorta were more expressive in females.

Conclusion:

Cirrhotic patients presented a higher percentage of fibrosis and lipidosis, and may represent a group susceptible to the accelerated progression of cardiovascular diseases. Investigative studies contribute to targeting health-promoting interventions, reducing the mortality and costs of treating cardiovascular disease.

Molecular imaging of the extracellular matrix in the context of atherosclerosis

This review summarizes the current status of molecular imaging of the extracellular matrix (ECM) in the context of atherosclerosis. Apart from cellular components, the ECM of the atherosclerotic plaque plays a relevant role during the initiation of atherosclerosis and its' subsequent progression. Important structural and signaling components of the ECM include elastin, collagen and fibrin. However, the ECM not only plays a structural role in the arterial wall but also interacts with different cell types and has important biological signaling functions. Molecular imaging of the ECM has emerged as a new diagnostic tool to characterize biological aspects of atherosclerotic plaques, which cannot be characterized by current clinically established imaging techniques, such as X-ray angiography. Different types of molecular probes can be detected in vivo by imaging modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT). The modality specific signaling component of the molecular probe provides information about its spatial location and local concentration. The successful introduction of molecular imaging into clinical practice and guidelines could open new pathways for an earlier detection of disease processes and a better understanding of the disease state on a biological level. Quantitative in vivo molecular parameters could also contribute to the development and evaluation of novel cardiovascular therapeutic interventions and the assessment of response to treatment.

Morphometric evaluation of the aortic root in stillborns

OBJECTIVE

To describe the dimensions and amount of collagen in the aortic root of autopsied fetuses at different gestational ages.

MATERIAL AND METHODS

40 samples of aortic roots were selected from autopsied fetuses with gestational ages ranging between 20 and 40 weeks. The thickness and the area of the aortic wall were analyzed on slides stained with Hematoxylin and Eosin, and the collagen was quantified on slides stained with Picrosirius, by using an image analyzing system.

RESULTS

A positive correlation was observed between the thickness of the media layer of the aortic wall and the gestational age. There was a positive and significant correlation between the percentage of collagen in the aortic wall with gestational age and fetal weight. The correlation between gestational age and the area of the aortic root circumference was positive and significant. And the correlation between the aortic diameter and the gestational age as well as fetal length was positive and significant.

CONCLUSION

The thickness of the media layer, the amount of collagen in the aortic wall, the area of the aortic root circumference and the aortic diameter rose with the increase of the gestational age. Thus, the morphological analysis of the aortic root may help as a parameter during the follow-up of inter-uterine growth and fetal development.

Association Between Thoracic Aorta Calcium and Thoracic Aorta Geometry in a Cohort of Asymptomatic Participants at Increased Cardiovascular Risk

INTRODUCTION AND OBJECTIVES

Thoracic aorta calcium detection is known to improve cardiovascular risk prediction for cardiac and noncardiac events beyond traditional risk factors. We investigated the influence of thoracic aorta morphometry on the presence and extent of aortic calcifications.

METHODS

Nonenhanced computed tomography heart scans were performed in 970 asymptomatic participants at increased cardiovascular risk. An automated algorithm estimated the geometry of the entire thoracic aorta and quantified the aortic calcium Agatston score. A nonparametric model was used to analyze the percentiles of calcium score by age. Logistic regression models were calculated to identify anatomical associations with calcium levels.

RESULTS

Calcifications were concentrated in the aortic arch and descending portions. Higher amounts of calcium were associated with an enlarged, unfolded, less tapered and more tortuous aorta. The size of the ascending aorta was not correlated with aortic calcium score, whereas enlargement of the descending aorta had the strongest association: the risk of having a global calcium score > 90th percentile was 3.62 times higher (confidence interval, 2.30-5.91; P < .001) for each 2.5-mm increase in descending aorta diameter. Vessel taper, tortuosity, unfolding and aortic arch and descending volumes were also correlated with higher amounts of calcium.

CONCLUSIONS

Thoracic aorta calcium was predominantly found at the arch and descending aorta and was positively associated with the size of the descending aorta and the aortic arch, but not with the size of the ascending aorta. These findings suggest that aortic dilatation may have different mechanisms and may consequently require different preventive strategies according to the considered segments.

Evidence of deregulated cholesterol efflux in abdominal aortic aneurysm

Previous studies indicated that lipids may be associated with abdominal aortic aneurysm (AAA); however the molecular mechanism involved is unclear. Our study aimed to investigate the expression pattern of cholesterol efflux related proteins in AAA. Liver X receptors (LXRα and LXRβ), ATP-binding-cassette transporter A1 (ABCA1), Apolipoprotein AI (ApoAI), smooth muscle α-actin (α-SM) and vimentin expression levels were evaluated in human AAA, atherosclerotic (ATH) and normal abdominal aortic tissues. We found significant differences in LXRα, LXRβ and ABCA1 mRNA expression levels between AAA, ATH and normal whole aortic tissues and also within the AAA, ATH and normal "intima-media" layers. Specifically, LXRα, LXRβ and ABCA1 mRNA levels were decreased in AAA compared to ATH-whole tissues, as well as in AAA "intima-media" compared to ATH and normal "intima-media" layers. Moreover, immunohistochemical evaluation revealed that LXRα and ABCA1 immunoreactivities (IR) were reduced in the AAA media compared to the normal and ATH media layers and that they were also reduced in the intima layer of AAA and ATH tissues, whereas ApoAI-IR was increased in the AAA and ATH aortic walls compared to normal pointing to possible deregulation of the cholesterol efflux mechanism in AAA. Furthermore, double staining for vimentin and α-SM showed vimentin expression in the intima and inner media layer of AAA with sparse vimentin positive SMCs designating possible SMCs phenotype switch from contractile to synthetic form. In addition, histochemical analysis showed excessive lipid accumulation in the AAA wall, while co-staining using Oil Red O with α-SM or CD68 revealed lipid accumulation in SMCs and macrophages, respectively. Our study provides novel evidence for impaired cholesterol efflux in AAA associated with lipid accumulation in SMCs and macrophages, as well as switch of SMCs phenotype from contractile to synthetic form.

Aortic aneurysm association with SLE - a case-control study

OBJECTIVES

Aortic aneurysm is a life threatening cardiovascular complication in patients with systemic lupus erythematosus (SLE).The purpose of this study was to investigate the association between SLE and occurrence of aortic aneurysms.

METHODS

Patients with SLE were compared with age- and sex-matched controls regarding the proportion of aortic aneurysm in a case-control study. Chi-square and t-tests were used for univariate analysis and a logistic regression model was used for multivariate analysis. The study was performed utilizing the medical database of Clalit Health Services.

RESULTS

The study included 5018 patients with SLE and 25,090 age- and sex-matched controls. The proportion of aortic aneurysm in patients with SLE was increased compared with the proportion in controls (0.6% and 0.1%, respectively, p < 0.001). In a multivariate analysis SLE was associated with the coexistence of aortic aneurysms (odds ratio 2.06, 95% confidence interval 1.21-3.51).

CONCLUSIONS

Patients with SLE have a higher proportion of aortic aneurysms as compared with matched controls. Therefore, physicians treating patients with SLE should be aware of this life threatening association.

A comparative review of the hemodynamics and pathogenesis of cerebral and abdominal aortic aneurysms: lessons to learn from each other

OBJECTIVE

Cerebral aneurysms (CAs) and abdominal aortic aneurysms (AAAs) are degenerative vascular pathologies that manifest as abnormal dilations of the arterial wall. They arise with different morphologies in different types of blood vessels under different hemodynamic conditions. Although treated as different pathologies, we examine common pathways in their hemodynamic pathogenesis in order to elucidate mechanisms of formation.

MATERIALS AND METHODS

A systematic review of the literature was performed. Current concepts on pathogenesis and hemodynamics were collected and compared.

RESULTS

CAs arise as saccular dilations on the cerebral arteries of the circle of Willis under high blood flow, high wall shear stress (WSS), and high wall shear stress gradient (WSSG) conditions. AAAs arise as fusiform dilations on the infrarenal aorta under low blood flow, low, oscillating WSS, and high WSSG conditions. While at opposite ends of the WSS spectrum, they share high WSSG, a critical factor in arterial remodeling. This alone may not be enough to initiate aneurysm formation, but may ignite a cascade of downstream events that leads to aneurysm development. Despite differences in morphology and the structure, CAs and AAAs share many histopathological and biomechanical characteristics. Endothelial cell damage, loss of elastin, and smooth muscle cell loss are universal findings in CAs and AAAs. Increased matrix metalloproteinases and other proteinases, reactive oxygen species, and inflammation also contribute to the pathogenesis of both aneurysms.

CONCLUSION

Our review revealed similar pathways in seemingly different pathologies. We also highlight the need for cross-disciplinary studies to aid in finding similarities between pathologies.

Analysis of axial prestretch in the abdominal aorta with reference to post mortem interval and degree of atherosclerosis

It is a well-known fact that the length of an artery in situ and the length of an excised artery differs. Retraction of blood vessels is usually observed. This prestretch plays an important role in arterial physiology. We have recently determined that the decrease of axial prestretch in the human abdominal aorta is so closely correlated with age that it is suitable for forensic applications (estimation of the age at time of death for cadavers of unknown identity). Since post mortem autolysis may affect the reliability of an estimate based on axial prestretch, the present study aims to detail analysis of the effect of post mortem time. The abdominal aorta is a prominent site of atherosclerotic changes (ATH), which may potentially affect longitudinal prestretch. Thus ATH was also involved in the analysis. Axial prestretch in the human abdominal aorta, post mortem interval (PMI), and the degree of ATH were documented in 365 regular autopsies. The data was first age adjusted to remove any supposed correlation with age. After the age adjustment of the sample, the correlation analysis showed no significant PMI effects on the prestretch in non-putrefied bodies. Analysis of the prestretch variance with respect to ATH suggested that ATH is not a suitable factor to explain the prestretch variability remaining after the age adjustment. It was concluded that, although atherosclerotic plaques may certainly change the biomechanics of arteries, they do not significantly affect the longitudinal prestretch in the human abdominal aorta.

Long telomeres in blood leukocytes are associated with a high risk of ascending aortic aneurysm

Ascending aortic aneurysm is a connective tissue disorder. Even though multiple novel gene mutations have been identified, risk profiling and diagnosis before rupture still represent a challenge. There are studies demonstrating shorter telomere lengths in the blood leukocytes of abdominal aortic aneurysm patients. The aim of this study was to measure whether relative telomere lengths are changed in the blood leukocytes of ascending aortic aneurysm patients. We also studied the expression of telomerase in aortic tissue samples of ascending aortic aneurysms. Relative lengths of leukocyte telomeres were determined from blood samples of patients with ascending aortic aneurysms and compared with healthy controls. Telomerase expression, both at the level of mRNA and protein, was quantified from the aortic tissue samples. Mean relative telomere length was significantly longer in ascending aortic aneurysm blood samples compared with controls (T/S ratio 0.87 vs. 0.61, p<0.001). Expressions of telomerase mRNA and protein were elevated in the aortic aneurysm samples (p<0.05 and p<0.01). Our study reveals a significant difference in the mean length of blood leukocyte telomeres in ascending aortic aneurysm and controls. Furthermore, expression of telomerase, the main compensating factor for telomere loss, is elevated at both the mRNA and protein level in the samples of aneurysmal aorta. Further studies will be needed to confirm if this change in telomere length can serve as a tool for assessing the risk of ascending aortic aneurysm.

Mechanics, mechanobiology, and modeling of human abdominal aorta and aneurysms

Biomechanical factors play fundamental roles in the natural history of abdominal aortic aneurysms (AAAs) and their responses to treatment. Advances during the past two decades have increased our understanding of the mechanics and biology of the human abdominal aorta and AAAs, yet there remains a pressing need for considerable new data and resulting patient-specific computational models that can better describe the current status of a lesion and better predict the evolution of lesion geometry, composition, and material properties and thereby improve interventional planning. In this paper, we briefly review data on the structure and function of the human abdominal aorta and aneurysmal wall, past models of the mechanics, and recent growth and remodeling models. We conclude by identifying open problems that we hope will motivate studies to improve our computational modeling and thus general understanding of AAAs.

Obstructive sleep apnea as a potential risk factor for aortic disease

Obstructive sleep apnea (OSA) is not only a cause of hypertension; it also possibly affects the pathogenesis and progression of aortic disease because an inspiratory effort-induced increase in negative intrathoracic pressure generates mechanical stress on the aortic wall. The objective of the present study was to examine the incidence by location of OSA as a complication in patients with aortic aneurysm and patients with aortic dissection (AD). An overnight sleep study was conducted in the following study groups: the aortic disease group (n = 95) consisting of patients with thoracic aortic aneurysm (TAA, n = 32), patients with abdominal aortic aneurysm (AAA, n = 36), and patients with AD (n = 27); and a control group (n = 32), consisting of patients with coronary risk factors who were matched with the aortic disease group for age, gender, and body mass index (BMI). The 3% oxygen desaturation index (ODI) was significantly higher in all the TAA, AAA, and AD groups (P = 0.045, P = 0.003, and P = 0.005, respectively) than in the control group. The incidence of moderate to severe OSA [apnea hypopnea index (AHI) ≥15 events/h] was significantly higher in the first three groups (P = 0.026, P = 0.001, P = 0.003, respectively) than in the control group, while no significant difference was found between the TAA group and the AAA group with respect to these variables. Furthermore, no significant differences were found between the thoracic AD subgroup and the abdominal AD subgroup with respect to AHI and 3% ODI, as well as with respect to the incidences of moderate to severe OSA. Patients with TAA, patients with AAA, and patients with AD showed high incidences of moderate to severe OSA. Although this result suggests that OSA may be one of risks for aortic disease, unelucidated mechanism(s) other than negative intrathoracic pressure may be involved in the pathogenesis of aortic disease.

In vitro and preliminary in vivo validation of echo particle image velocimetry in carotid vascular imaging

Noninvasive, easy-to-use and accurate measurements of wall shear stress (WSS) in human blood vessels have always been challenging in clinical applications. Echo particle image velocimetry (Echo PIV) has shown promise for clinical measurements of local hemodynamics and wall shear rate. Thus far, however, the method has only been validated under simple flow conditions. In this study, we validated Echo PIV under in vitro and in vivo conditions. For in vitro validation, we used an anatomically correct, compliant carotid bifurcation flow phantom with pulsatile flow conditions, using optical particle image velocimetry (optical PIV) as the reference standard. For in vivo validation, we compared Echo PIV-derived 2-D velocity fields obtained at the carotid bifurcation in five normal subjects against phase-contrast magnetic resonance imaging (PC-MRI)-derived velocity measurements obtained at the same locations. For both studies, time-dependent, 2-D, two-component velocity vectors; peak/centerline velocity, flow rate and wall shear rate (WSR) waveforms at the common carotid artery (CCA), carotid bifurcation and distal internal carotid artery (ICA) were examined. Linear regression, correlation analysis and Bland-Altman analysis were used to quantify the agreement of different waveforms measured by the two techniques. In vitro results showed that Echo PIV produced good images of time-dependent velocity vector maps over the cardiac cycle with excellent temporal (up to 0.7 ms) and spatial (∼0.5 mm) resolutions and quality, comparable with optical PIV results. Further, good agreement was found between Echo PIV and optical PIV results for velocity and WSR measurements. In vivo results also showed good agreement between Echo PIV velocities and phase contrast MRI velocities. We conclude that Echo PIV provides accurate velocity vector and WSR measurements in the carotid bifurcation and has significant potential as a clinical tool for cardiovascular hemodynamics evaluation.

Sex, race, and age distributions of mean aortic wall thickness in a multiethnic population-based sample

BACKGROUND

Reference values and age-related changes of the wall thickness of the abdominal aorta have not been described in the general population. We characterized age-, race-, and gender-specific distributions, and yearly rates of change of mean aortic wall thickness (MAWT), and associations between MAWT and cardiovascular risk factors in a multi-ethnic population-based probability sample.

METHODS

Magnetic resonance imaging measurements of MAWT were performed on 2466 free-living white, black, and Hispanic adult subjects. MAWT race/ethnicity- and gender-specific percentile values across age were estimated using regression analyses.

RESULTS

MAWT was greater in men than in women and increased linearly with age in all the groups and across all the percentiles. Hispanic women had the thinnest and black men the thickest aortas. Black men had the highest and white women the lowest age-related MAWT increase. Age, gender, ethnicity, smoking status, systolic blood pressure, low-density lipoprotein-cholesterol levels, high-density lipoprotein-cholesterol levels, and fasting glucose levels were independent predictors of MAWT.

CONCLUSIONS

Age, gender, and racial/ethnic differences in MAWT distributions exist in the general population. Such differences should be considered in future investigations assessing aortic atherosclerosis and the effects of anti-atherosclerotic therapies.

Quantitative analysis of aortic atherosclerosis in Korean female: a necropsy study

To assess the regional difference and influence of the biological variables on atherosclerosis in female, we analyzed 7 segments of aorta (2 ascending, 3 thoracic, and 2 abdominal) from 90 superficially healthy Korean women (39+/-14 yr of age) who died from external causes. Tissue specimens were macroscopically examined and histopathologically divided into 7 grades for scoring (ATHERO, from 0=intact, to 6=thrombi formation). Lumen diameter (LD), wall thickness (WT), intima thickness (INT), and media thickness (MED) were obtained by computed morphometry. Atherosclerosis was common in the distal infrarenal (C2), proximal thoracic (B1), and proximal ascending (A1) segments. Total 95.6% of all subjects had atherosclerosis of variable degree in one or more segments, but an aneurysmal change was not found. The number of atherosclerotic segments and atherosclerosis score in the 7 segments increased with aging. However, the body size did not affect the aortic size and ATHERO. With aging, LD and INT of the A1, B1 and C2 increased (p<.00001); WT of the B1 and C2 increased (p<.01); and MED of C2 decreased (p<.01). LD and WT of the B1 and C2 (p<.05), INT of the A1, B1 and C2 (p<.00001) increased, and MED of C2 decreased (p<.01) with ATHERO. These data suggest that age is simple but a reliable parameter for estimating the progression of atherosclerosis.

Atherosclerotic carotid plaque segmentation

Atherosclerosis is the major cause of heart attack and stroke in the western world. In this paper we present a computerized method for segmenting the athrerosclerotic carotid plaque from ultrasound images. The method uses the blood flow image first to detect the initial contour of the plaque, and then despeckle filtering and snakes to deform the initial contour for best fit of plaque boundaries. The accuracy and reproducibility of this method was tested using 35 longitudinal ultrasound images of carotid arteries and the results were compared with the manual delineations of an expert. The comparison showed that the computerized method gives satisfactory results with no manual correction needed in most of the cases. The true positive fraction, TPF, true negative fraction, TNF, false negative fraction, FNF and false positive fraction, FPF, were 86.44%, 84.03%, 8.5%, and 7% respectively.

Carotid plaque 3D compound imaging and echo-morphology analysis: a Bayesian approach

This paper describes a method for volume reconstruction of the carotid plaque and presents a novel local characterization of its echo-morphology. The data is composed by a series of nearly parallel ultrasound images (3D Compound Imaging) and the acquisition is performed using traditional non-invasive ultrasound equipment available in most medical facilities, without need of a spatial locator device. The reconstruction algorithm uses the observed pixels inside the plaque, which were obtained in a pre-segmentation stage performed under medical guidance [1]. The paper proposes a Bayesian algorithm which estimates the underlying volume inside the plaque, by filtering and interpolating the data in order to remove speckle noise and fill non-observed regions, respectively. This volume is further used in plaque echo-morphology analysis. The observation model is based on the Rayleigh distribution, commonly used to model speckle noise in ultrasound images. A prior model based on the edge preserving Total Variation Gibbs distribution is also used to fill the gaps on non-evenly spaced observations. An energy function is derived from these models and an iterative algorithm computes its minimizer. The estimated function, defined in a given volume of interest, is used in global and local plaque characterization, namely to estimate its average levels of stenosis, echo-morphology and to identify vulnerable foci inside the plaque. The goal is to make atherosclerosis diagnosis more accurate and complete than using traditional 2D ultrasound analysis.