Aortic distensibility in patients with isolated hypercholesterolaemia, coronary artery disease, or cardiac transplant

Resource efficient aortic distensibility calculation by end to end spatiotemporal learning of aortic lumen from multicentre multivendor multidisease CMR images

Aortic distensibility (AD) is important for the prognosis of multiple cardiovascular diseases. We propose a novel resource-efficient deep learning (DL) model, inspired by the bi-directional ConvLSTM U-Net with densely connected convolutions, to perform end-to-end hierarchical learning of the aorta from cine cardiovascular MRI towards streamlining AD quantification. Unlike current DL aortic segmentation approaches, our pipeline: (i) performs simultaneous spatio-temporal learning of the video input, (ii) combines the feature maps from the encoder and decoder using non-linear functions, and (iii) takes into account the high class imbalance. By using multi-centre multi-vendor data from a highly heterogeneous patient cohort, we demonstrate that the proposed method outperforms the state-of-the-art method in terms of accuracy and at the same time it consumes [Formula: see text] 3.9 times less fuel and generates [Formula: see text] 2.8 less carbon emissions. Our model could provide a valuable tool for exploring genome-wide associations of the AD with the cognitive performance in large-scale biomedical databases. By making energy usage and carbon emissions explicit, the presented work aligns with efforts to keep DL's energy requirements and carbon cost in check. The improved resource efficiency of our pipeline might open up the more systematic DL-powered evaluation of the MRI-derived aortic stiffness.

Early diagnosis of aortic calcification through dental X-ray examination for dental pulp stones

Vascular calcification, an ectopic calcification exacerbated by aging and renal dysfunction, is closely associated with cardiovascular disease. However, early detection indicators are limited. This study focused on dental pulp stones, ectopic calcifications found in oral tissues that are easily identifiable on dental radiographs. Our investigation explored the frequency and timing of these calcifications in different locations and their relationship to aortic calcification. In cadavers, we examined the association between the frequency of dental pulp stones and aortic calcification, revealing a significant association. Notably, dental pulp stones appeared prior to aortic calcification. Using a rat model of hyperphosphatemia, we confirmed that dental pulp stones formed earlier than calcification in the aortic arch. Interestingly, there were very few instances of aortic calcification without dental pulp stones. Additionally, we conducted cell culture experiments with vascular smooth muscle cells (SMCs) and dental pulp cells (DPCs) to explore the regulatory mechanism underlying high phosphate-mediated calcification. We found that DPCs produced calcification deposits more rapidly and exhibited a stronger augmentation of osteoblast differentiation markers compared with SMCs. In conclusion, the observation of dental pulp stones through X-ray examination during dental checkups could be a valuable method for early diagnosis of aortic calcification risk.

Computation of Vascular Parameters: Implementing Methodology and Performance Analysis

This paper presents the feasibility of automated and accurate in vivo measurements of vascular parameters using an ultrasound sensor. The continuous and non-invasive monitoring of certain parameters, such as pulse wave velocity (PWV), blood pressure (BP), arterial compliance (AC), and stiffness index (SI), is crucial for assessing cardiovascular disorders during surgeries and follow-up procedures. Traditional methods, including cuff-based or invasive catheter techniques, serve as the gold standard for measuring BP, which is then manually used to calculate AC and SI through imaging algorithms. In this context, the Continuous and Non-Invasive Vascular Stiffness and Arterial Compliance Screener (CaNVAS) is developed to provide continuous and non-invasive measurements of these parameters using an ultrasound sensor. By driving 5 MHz (ranging from 2.2 to 10 MHz) acoustic waves through the arterial walls, capturing the reflected echoes, and employing pre-processing techniques, the frequency shift is utilized to calculate PWV. It is observed that PWV measured by CaNVAS correlates exponentially with BP values obtained from the sphygmomanometer (BPMR-120), enabling the computation of instantaneous BP values. The proposed device is validated through measurements conducted on 250 subjects under pre- and post-exercise conditions, demonstrating an accuracy of 95% and an average coefficient of variation of 12.5%. This validates the reliability and precision of CaNVAS in assessing vascular parameters.

The Importance of Arterial Stiffness Assessment in Patients with Familial Hypercholesterolemia

Cardiovascular diseases are still the leading cause of mortality due to increased atherosclerosis worldwide. In the background of accelerated atherosclerosis, the most important risk factors include hypertension, age, male gender, hereditary predisposition, diabetes, obesity, smoking and lipid metabolism disorder. Arterial stiffness is a firmly established, independent predictor of cardiovascular risk. Patients with familial hypercholesterolemia are at very high cardiovascular risk. Non-invasive measurement of arterial stiffness is suitable for screening vascular dysfunction at subclinical stage in this severe inherited disorder. Some former studies found stiffer arteries in patients with familial hypercholesterolemia compared to healthy controls, while statin treatment has a beneficial effect on it. If conventional drug therapy fails in patients with severe familial hypercholesterolemia, PCSK9 inhibitor therapy should be administered; if these agents are not available, performing selective LDL apheresis could be considered. The impact of recent therapeutic approaches on vascular stiffness is not widely studied yet, even though the degree of accelerated athero and arteriosclerosis correlates with cardiovascular risk. The authors provide an overview of the diagnosis of familial hypercholesterolemia and the findings of studies on arterial dysfunction in patients with familial hypercholesterolemia, in addition to presenting the latest therapeutic options and their effects on arterial elasticity parameters.

Towards the non-invasive determination of arterial wall distensible properties: New approach using old formulae

Arterial function and wall mechanical properties are important determinants of hemodynamics in the circulation. However, their non-invasive determination is not widely available. Therefore, the aim of this work is to present a novel approach for the non-invasive determination of vessel's distensibility and elastic modulus. Simultaneous measurements of vessel's Diameter (D) and flow velocity (U) were recorded to determine local wave speed (_nC) in flexible tubes and calf aortas non-invasively using the lnDU-loop method, which was used to calculate the Distensibility (_nD_s) and Elastic Modulus (_nE), also non-invasively. To validate the new approach, the non-invasive results were compared to traditionally invasive measurements of Dynamic Distensibility (D_sd) and Tangential Elastic Modulus (E_m). In flexible tubes, the average _nD_s was higher and _nE was lower than D_sd and E_m by 1.6% and 6.9%, respectively. In calf aortas, the results of _nD_s and _nE agreed well with those of D_sd and E_m, as demonstrated by Bland-Altman technique. The results of _nD_s and _nE are comparable to those determined using traditional techniques. Our results suggest that _nD_s and _nE could be measured in-vivo non-invasively, given the possibility of measuring D and U to obtain _nC. Further studies are warranted to establish the clinical usefulness of the new approach.

Aortic Distensibility Can Predict Events in Patients With Premature Coronary Artery Disease: A Cardiac Magnetic Resonance Study

Noninvasive assessment of aortic distensibility (AD) is feasible with cardiac magnetic resonance (CMR). We investigated the relationship between AD (assessed by CMR) and coronary artery disease (CAD) severity (assessed by the SYNTAX score) in patients with premature CAD. We recruited 125 patients with CAD confirmed by coronary angiography (males were <55 years old and females <65 years old). We excluded patients with significant aortic disease or contraindications to CMR. We also recruited 25 age- and sex-matched healthy patients as controls. One-year follow-up was also carried out. Aortic distensibility at the aortic root (AR) and descending aorta (DA) was significantly (P < .001 for both) lower in the patient group. There was a significant negative correlation between SYNTAX score and AD at the AR (r = -0.56; P < .001) and DA (r = -0.34; P < .001), but insignificant correlation with distensibility at the ascending aorta (AA; r = -0.03; P = .81). AR, AA, and DA distensibility, as well as left ventricular ejection fraction were predictors of adverse events. The severity of CAD in young patients is associated with decreased AD, especially at the level of the AR. Aortic distensibility can predict adverse events in these patients.

Central Versus Peripheral Artery Stiffening and Cardiovascular Risk

The large elastic arteries fulfill an important role in buffering the cyclical changes in blood pressure, which result from intermittent ventricular ejection. With aging and accrual of cardiovascular risk factors, the elastic arteries stiffen, and this process holds a number of deleterious consequences for the cardiovascular system and major organs. Indeed, arterial stiffness is now recognized as an important, independent determinant of cardiovascular disease risk. Additional, important information concerning the mechanisms underlying arterial stiffening has come from longitudinal studies of arterial stiffness. More recently, attention has focused on the role of peripheral, muscular arteries in cardiovascular disease risk prediction and, in particular, the clinical consequences of reversal of the normal gradient of arterial stiffness between central and peripheral arteries, with aging and disease.

Establishing the interchangeability of arterial stiffness but not endothelial function parameters in healthy individuals

Background

Development of instruments capable of detecting early stage vascular disease has increased interest in employing arterial stiffness (e.g. pulse wave velocity (PWV), augmentation index (AIx)) and endothelial dysfunction (e.g. reactive hyperemia index (RHI)) to diagnose atherosclerotic disease before occurrence of a cardiovascular event. However, amongst the equipment designed for this purpose, there is insufficient information regarding each of these parameters to establish appropriate cutoffs to distinguish between healthy and unhealthy blood vessels. To address these limitations, the study was designed to establish the upper arterial stiffness and endothelial function thresholds in a healthy population, by comparing the outputs from different instruments capable of measuring PWV, AIx and RHI.

Methods

A systematic comparison of PWV, AIx and RHI was conducted to determine the inter-relationships between these parameters of vascular functionality. Outputs were obtained non-invasively using three instruments, the VP-1000 (VP), SphygmoCor (SC), and EndoPAT (EP), in 40 apparently healthy males and females.

Results

Correlations were found between the brachial-ankle PWV and radial-ankle PWV (by VP and SC), and PWV (VP) with AIx (SC). The interchangeability of these outputs was demonstrated by the Bland Altman test, making it feasible to extrapolate cut-offs for radial-ankle PWV and AIx equivalent to brachial-ankle PWV that signify healthy vessels. In contrast, RHI showed no association with AIx, suggesting these endothelial and arterial parameters are functionally distinct.

Conclusions

It was concluded that it is possible to compare the vascular function outputs of different instruments and identify healthy from unhealthy vessels, even though the approaches for quantifying the underlying physiological processes may differ. In this way, non-invasive determination of arterial function could be a new paradigm for detecting existing early stage asymptomatic atherosclerotic disease in individuals using techniques that are amenable to the clinical setting.

Electronic supplementary material

The online version of this article (10.1186/s12872-019-1167-3) contains supplementary material, which is available to authorized users.

LDL cholesterol is associated with systemic vascular resistance and wave reflection in subjects naive to cardiovascular drugs

BACKGROUND AND AIM

Low density lipoprotein cholesterol (LDL-C) is a primary risk factor for atherosclerosis, but it is also associated with elevated blood pressure (BP) and future development of hypertension. We examined the relationship between LDL-C and haemodynamic variables in normotensive and never-treated hypertensive subjects.

METHODS

We recruited 615 volunteers (19-72 years) without lipid-lowering and BP-lowering medication. Supine haemodynamics were recorded using continuous radial pulse wave analysis, whole-body impedance cardiography, and single channel electrocardiogram. The haemodynamic relations of LDL-C were examined using linear regression analyses with age, sex, body mass index (BMI) (or height and weight as appropriate), smoking status, alcohol use, and plasma C-reactive protein, sodium, uric acid, high density lipoprotein cholesterol (HDL-C), triglycerides, estimated glomerular filtration rate, and quantitative insulin sensitivity check index as the other included variables.

RESULTS

The mean (SD) characteristics of the subjects were: age 45 (12) years, BMI 27 (4) kg/m², office BP 141/89 (21/13) mmHg, creatinine 74 (14) µmol/l, total cholesterol 5.2 (1.0), LDL-C 3.1 (0.6), triglycerides 1.2 (0.8), and HDL-C 1.6 (0.4) mmol/l. LDL-C was an independent explanatory factor for aortic systolic and diastolic BP, augmentation index, pulse wave velocity (PWV), and systemic vascular resistance index (p < 0.05 for all). When central BP was included in the model for PWV, LDL-C was no longer an explanatory factor for PWV.

CONCLUSIONS

LDL-C is independently associated with BP via systemic vascular resistance and wave reflection. These results suggest that LDL-C may play a role in the pathogenesis of primary hypertension.

Arterial stiffness and stroke: de-stiffening strategy, a therapeutic target for stroke

Stroke is the second leading cause of mortality and morbidity worldwide. Early intervention is of great importance in reducing disease burden. Since the conventional risk factors cannot fully account for the pathogenesis of stroke, it is extremely important to detect useful biomarkers of the vascular disorder for appropriate intervention. Arterial stiffness, a newly recognised reliable feature of arterial structure and function, is demonstrated to be associated with stroke onset and serve as an independent predictor of stroke incidence and poststroke functional outcomes. In this review article, different measurements of arterial stiffness, especially pressure wave velocity, were discussed. We explained the association between arterial stiffness and stroke occurrence by discussing the secondary haemodynamic changes. We reviewed clinical data that support the prediction role of arterial stiffness on stroke. Despite the lack of long-term randomised double-blind controlled therapeutic trials, it is high potential to reduce stroke prevalence through a significant reduction of arterial stiffness (which is called de-stiffening therapy). Pharmacological interventions or lifestyle modification that can influence blood pressure, arterial function or structure in either the short or long term are promising de-stiffening therapies. Here, we summarised different de-stiffening strategies including antihypertension drugs, antihyperlipidaemic agents, chemicals that target arterial remodelling and exercise training. Large and well-designed clinical trials on de-stiffening strategy are needed to testify the prevention effect for stroke. Novel techniques such as modern microscopic imaging and reliable animal models would facilitate the mechanistic analyses in pathophysiology, pharmacology and therapeutics.

Thyroid hormones and cardiovascular disease

Myocardial and vascular endothelial tissues have receptors for thyroid hormones and are sensitive to changes in the concentrations of circulating thyroid hormones. The importance of thyroid hormones in maintaining cardiovascular homeostasis can be deduced from clinical and experimental data showing that even subtle changes in thyroid hormone concentrations - such as those observed in subclinical hypothyroidism or hyperthyroidism, and low triiodothyronine syndrome - adversely influence the cardiovascular system. Some potential mechanisms linking the two conditions are dyslipidaemia, endothelial dysfunction, blood pressure changes, and direct effects of thyroid hormones on the myocardium. Several interventional trials showed that treatment of subclinical thyroid diseases improves cardiovascular risk factors, which implies potential benefits for reducing cardiovascular events. Over the past 2 decades, accumulating evidence supports the association between abnormal thyroid function at the time of an acute myocardial infarction (MI) and subsequent adverse cardiovascular outcomes. Furthermore, experimental studies showed that thyroid hormones can have an important therapeutic role in reducing infarct size and improving myocardial function after acute MI. In this Review, we summarize the literature on thyroid function in cardiovascular diseases, both as a risk factor as well as in the setting of cardiovascular diseases such as heart failure or acute MI, and outline the effect of thyroid hormone replacement therapy for reducing the risk of cardiovascular disease.

Predictive Performance of Echocardiographic Parameters for Cardiovascular Events Among Elderly Treated Hypertensive Patients

BACKGROUND

Hypertension leads to cardiac structural and functional changes, commonly assessed by echocardiography. In this study, we assessed the predictive performance of different echocardiographic parameters including left ventricular hypertrophy (LVH) on future cardiovascular outcomes in elderly hypertensive patients without heart failure.

METHODS

Data from LVH substudy of the Second Australian National Blood Pressure trial were used. Echocardiograms were performed at entry into the study. Cardiovascular outcomes were identified over short term (median 4.2 years) and long term (median 10.9 years). LVH was defined using threshold values of LV mass (LVM) indexed to either body surface area (BSA) or height(2.7): >115/95g/m(2) (LVH-BSA(115/95)) or ≥49/45g/m(2.7) (LVH-ht(49/45)) in males/females, respectively, and ≥125g/m(2) (LVH-BSA(125)) or ≥51g/m(2.7) (LVH-ht(51)) for both sexes.

RESULTS

In the 666 participants aged ≥65 years in this analysis, LVH prevalence at baseline was 33%-70% depending on definition; and after adjusting for potential risk factors, only LVH-BSA(115/95) predicted both short- and long-term cardiovascular outcomes. Participants having LVH-BSA(115/95) (69%) at baseline had twice the risk of having any first cardiovascular event over the short term (hazard ratio, 95% confidence interval: 2.00, 1.12-3.57, P = 0.02) and any fatal cardiovascular events (2.11, 1.21-3.68, P = 0.01) over the longer term. Among other echocardiographic parameters, LVM and LVM indexed to either BSA or height(2.7) predicted cardiovascular events over both short and longer term.

CONCLUSIONS

In elderly treated hypertensive patients without heart failure, determining LVH by echocardiography is highly dependent on the methodology adopted. LVH-BSA(115/95) is a reliable predictor of future cardiovascular outcomes in the elderly.

Vascular Adventitia Calcification and Its Underlying Mechanism

Previous research on vascular calcification has mainly focused on the vascular intima and media. However, we show here that vascular calcification may also occur in the adventitia. The purpose of this work is to help elucidate the pathogenic mechanisms underlying vascular calcification. The calcified lesions were examined by Von Kossa staining in ApoE−/− mice which were fed high fat diets (HFD) for 48 weeks and human subjects aged 60 years and older that had died of coronary heart disease, heart failure or acute renal failure. Explant cultured fibroblasts and smooth muscle cells (SMCs)were obtained from rat adventitia and media, respectively. After calcification induction, cells were collected for Alizarin Red S staining. Calcified lesions were observed in the aorta adventitia and coronary artery adventitia of ApoE-/-mice, as well as in the aorta adventitia of human subjects examined. Explant culture of fibroblasts, the primary cell type comprising the adventitia, was successfully induced for calcification after incubation with TGF-β1 (20 ng/ml) + mineralization media for 4 days, and the phenotype conversion vascular adventitia fibroblasts into myofibroblasts was identified. Culture of SMCs, which comprise only a small percentage of all cells in the adventitia, in calcifying medium for 14 days resulted in significant calcification.Vascular calcification can occur in the adventitia. Adventitia calcification may arise from the fibroblasts which were transformed into myofibroblasts or smooth muscle cells.

Comparison of inflammation, arterial stiffness and traditional cardiovascular risk factors between rheumatoid arthritis and inflammatory bowel disease

Background

Inflammation plays an important role in the pathogenesis of atherosclerosis. The link between rheumatoid arthritis (RA) and an increased risk of cardiovascular disease and mortality is well established; however, the association between inflammatory bowel disease (IBD) and cardiovascular risk is controversial. Arterial stiffness is both a marker and risk factor for atherosclerosis. Here we aimed to 1) compare circulating markers of inflammation and endothelial dysfunction, traditional cardiovascular risk factors, and arterial stiffness between RA and IBD to help to understand their different associations with cardiovascular disease; 2) assess the impacts of circulating markers of inflammation and endothelial dysfunction, and traditional risk factors on arterial stiffness.

Methods

Patients with RA (n = 43) and IBD (n = 42), and control subjects (n = 73) were recruited. Plasma inflammatory markers and von Willebrand factor (vWF) were measured by Multiplex assays or ELISA. Arterial stiffness was determined by brachial-ankle pulse wave velocity (baPWV) and ankle-brachial index (ABI) was measured. Framingham Risk Score (FRS) was calculated, and other traditional risk factors were also documented.

Results

Plasma levels of several inflammatory markers and vWF were significantly but comparably elevated in RA and IBD compared with controls, except for a higher level of C-reactive protein (CRP) in RA than IBD. Compared to controls, FRS, body mass index, waist circumference, and triglycerides were increased in RA, but not in IBD. baPWV did not significantly differ among 3 groups, while ABI was modestly but significantly lower in IBD than controls. Circulating markers (macrophage migration inhibitory factor, tumour necrosis factor-α, CRP, and vWF) were significantly associated with baPWV. However, traditional risk factors (age, systolic blood pressure, body mass index, diabetes and triglycerides) were the parameters associated with baPWV in multiple regression analyses (overall r = 0.866, p < 0.001).

Conclusions

RA has a higher level of CRP and more pronounced traditional cardiovascular risk factors than IBD, which may contribute to the difference in their associations with cardiovascular disease and mortality. Traditional risk factors, rather than inflammation markers, are major predictors of arterial stiffness even in subjects with inflammatory disorders. Our results point to the importance of modifying traditional risk factors in patients with inflammatory disorders.

Validation of a method for quantifying carotid artery calcification from panoramic radiographs

OBJECTIVE

Carotid artery calcification can be visualized on panoramic radiographs. Incidental observation of these calcifications could identify patients in need of further screening. The purpose of this study was to validate the assessment and quantification of calcification on panoramic radiographs with the stenosis and the calculated resistive index (RI) from Doppler ultrasonography.

STUDY DESIGN

Digital panoramic radiographs were used to assess the area of carotid artery calcification using tools available in NIH's ImageJ. Inpatient and outpatient discharge records were reviewed to identify subjects with a completed carotid Doppler ultrasound exam (n = 122).

RESULTS

The quantification of carotid artery calcification was found to correlate well with the degree of stenosis (area under the curve [AUC] 0.81 [95% confidence interval [CI] 0.64, 0.98]) and the RI of the common carotid artery (AUC 0.79 [95% CI 0.59, 0.98]).

CONCLUSION

This method for quantification of carotid artery calcification could identify patients in need of further evaluation.

Aortic Stiffness and Plasma Brain Natriuretic Peptide Predicts Mortality in Acute Ischemic Stroke

Background

The study aimed to evaluate the prognostic role and discriminative power of aortic stiffness and plasma brain natriuretic peptide levels in a cohort of patients hospitalized for acute ischemic stroke.

Methods and Results

Three hundred and ten consecutive patients aged 50 years and older with a first episode of acute ischemic stroke were prospectively evaluated. All patients were admitted to the hospital within 24 h of the onset of stroke symptoms. The type of acute ischemic stroke was classified according to the Trial of Org 10172 in Acute Stroke Treatment classification. Blood samples were taken for measurement of brain natriuretic peptide levels at admission. Aortic stiffness indices, aortic strain and distensibility, were calculated from the aortic diameters measured by transthoracic echocardiography. The patients were followed for one-year or until death, whichever came first. Death occurred in 51 (16·5%) patients. On multivariate logistic regression analysis, National Institutes of Health Stroke Scale score >13, diabetes, brain natriuretic peptide >235 pg/mL, aortic distensibility, and aortic strain were associated with all-cause mortality. The optimal cutoff level of brain natriuretic peptide to distinguish the deceased group from the survival group was 235 pg/mL (sensitivity 71·0% and specificity 63·0%) and to distinguish cardioembolic stroke from noncardioembolic stroke was 155 pg/mL (sensitivity 81% and specificity 63%).

Conclusions

Aortic stiffness and brain natriuretic peptide predict mortality in patients with first-ever acute ischemic stroke. Brain natriuretic peptide also differentiates cardioembolic stroke from noncardioembolic stroke.

Aortic Compliance and Stiffness Among Severe Longstanding Hypertensive and Non-hypertensive

Introduction

Abnormal aortic function in hypertension is generally attributed to accelerated breakdown of elastin in the aorta, leading to dilatation of the lumen and stiffening of the wall as elastin is replaced with stiffer collagen. Aortic stiffness is an independent predictor of cardiovascular risk and all-cause and cardiovascular mortality. Vascular stiffening can activate endothelium which in turn may promote atherogenesis. Modulation of arterial stiffness has been shown to be successfully managed via changes in lifestyle and put under control of hypertension pharmacologically with antihypertensive drugs and statins.

Methods

Hundred and forty four patients have been enrolled in this study. They have been divided in two groups, with hypertension and group of control. Groups were with no age difference.

Results

Group with hypertension were with reduced aortic strain, distensibility (compliance) and have higher stiffness than control group; GrHTA =9.3 compared to GC=5.4. After successful treatment of hypertension with antihypertensives and statins, for two years, these parameters showed improvement, but still remain out of normal range compared to control group; 7.6 vs. 5.38.

Conclusions

Hypertensive patients have reduced aortic elasticity and increased stiffness which can be stopped and improved after treatment with antihypertensive and statin.

Impact of ADMA, endothelial progenitor cells and traditional cardiovascular risk factors on pulse wave velocity among prediabetic individuals

Background

Central arterial stiffness represents a well-established predictor of cardiovascular disease. Decreased circulating endothelial progenitor cells (EPCs), increased asymmetric dimethyl-arginine (ADMA) levels, traditional cardiovascular risk factors and insulin resistance have all been associated with increased arterial stiffness. The correlations of novel and traditional cardiovascular risk factors with central arterial stiffness in prediabetic individuals were investigated in the present study.

Methods

The study population consisted of 53 prediabetic individuals. Individuals were divided into groups of isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT) and combined IGT-IFG. Age, sex, family history of diabetes, smoking history, body mass index (BMI), waist to hip ratio (WHR), waist circumference (WC), blood pressure, lipid profile, levels of high sensitive C-reactive protein (hsCRP), glomerular filtration rate (GFR), and history of antihypertensive or statin therapy were obtained from all participants. Insulin resistance was evaluated using the Homeostatic Model Assessment (HOMA-IR). Carotid -femoral pulse wave velocity was used as an index of arterial stiffness. Circulating EPC count and ADMA serum levels were also determined.

Results

Among studied individuals 30 (56.6%) subjects were diagnosed with isolated IFG, 9 (17%) with isolated IGT (17%) and 14 with combined IFG-IGT (26.4%). In univariate analysis age, mean blood pressure, fasting glucose, total cholesterol, LDL cholesterol, and ADMA levels positively correlated with pulse-wave velocity while exercise and GFR correlated negatively. EPC count did not correlate with PWV. In multivariate stepwise regression analysis PWV correlated independently and positively with LDL-Cholesterol (low density lipoprotein) and ADMA levels and negatively with exercise.

Conclusions

Elevated ADMA and LDL-C levels are strongly associated with increased arterial stiffness among pre-diabetic subjects. In contrast exercise inversely correlated with arterial stiffness.

A knowledge-based approach to arterial stiffness estimation using the digital volume pulse

We have developed a knowledge based approach for arterial stiffness estimation. The proposed new approach reliably estimates arterial stiffness based on the analysis of age and heart rate normalized reflected wave arrival time. The proposed new approach reduces cost, space, technical expertise, specialized equipment, complexity, and increases the usability compared to recently researched noninvasive arterial stiffness estimators. The proposed method consists of two main stages: pulse feature extraction and linear regression analysis. The new approach extracts the pulse features and establishes a linear prediction equation. On evaluating proposed methodology with pulse wave velocity (PWV) based arterial stiffness estimators, the proposed methodology offered the error rate of 8.36% for men and 9.52% for women, respectively. With such low error rates and increased benefits, the proposed approach could be usefully applied as low cost and effective solution for ubiquitous and home healthcare environments.

Impaired distensibility of ascending aorta in patients with HIV infection

Background

Our aim was to investigate the aortic distensibility (AD) of the ascending aorta and carotid artery intima-media thickness (c-IMT) in HIV-infected patients compared to healthy controls.

Methods

One hundred and five HIV-infected patients (86 males [82%], mean age 41 ± 0.92 years), and 124 age and sex matched HIV-1 uninfected controls (104 males [84%], mean age 39.2 ± 1.03 years) were evaluated by high-resolution ultrasonography to determine AD and c-IMT. For all patients and controls clinical and laboratory factors associated with atherosclerosis were recorded.

Results

HIV- infected patients had reduced AD compared to controls: 2.2 ± 0.01 vs. 2.62 ± 0.01 10^-6 cm² dyn^-1, respectively (p < 0.001). No difference was found in c-IMT between the two groups. In multiadjusted analysis, HIV infection was independently associated with decreased distensibility (beta –0.45, p < 0.001). Analysis among HIV-infected patients showed that patients exposed to HAART had decreased AD compared to HAART-naïve patients [mean (SD): 2.18(0.02) vs. 2.28(0.03) 10^-6 cm² dyn^-1, p = 0.01]. In multiadjusted analysis, increasing age and exposure to HAART were independently associated with decreased AD.

Conclusion

HIV infection is independently associated with decreased distensibility of the ascending aorta, a marker of subclinical atherosclerosis. Increasing age and duration of exposure to HAART are factors further contributing to decreased AD.

Increased aortic stiffness can predict perioperative cardiovascular outcomes in patients undergoing noncardiac, nonvascular surgery

BACKGROUND

Aortic stiffness is an early marker of arteriosclerosis and associated with cardiovascular mortality. However, the impact of aortic stiffness on perioperative cardiovascular outcomes in patients undergoing noncardiac surgery is unknown.

METHODS

The study population was composed of 660 consecutive adults aged 18 years and over (mean age = 65.3 ± 14 years) who underwent intermediate-risk (nonvascular), noncardiac surgery between January 2010 and February 2011. Nonemergency, non-day-case, open surgical procedures were enrolled. Aortic stiffness indices were calculated from the aortic diameters measured by echocardiography. Electrocardiography and cardiac biomarkers were evaluated 1 day before surgery, and on days 1, 3, and 7 after surgery.

RESULTS

Eighty patients (12.1%) experienced perioperative cardiovascular events (PCE). Preoperative aortic distensibility (AD) (2 ± 1.3 vs. 2.9 ± 1.1 cm2/dyn/10(3), P < 0.001) and aortic strain (AS) (4.4 ± 2.4 vs. 6.4 ± 1.9, P < 0.001) of the patients with PCE were significantly lower than in patients without PCE. Univariate analysis showed a significant association between age, diabetes mellitus (DM), coronary artery disease, preoperative atrial fibrillation, American Society of Anesthesiologists (ASA) status, Revised Cardiac Risk Index, left ventricle ejection fraction (LVEF), AD, aortic strain, and in-hospital PCE. However, on multivariate logistic regression analysis, only AD (OR: 1.94, 95% CI: 1.1-3.4; P = 0.02), AS (OR: 0.45, 95% CI: 0.3-0.6; P < 0.001), DM (OR: 2.28, 95% CI: 1.08-4.82; P = 0.03), and LVEF (OR: 0.96, 95% CI: 0.93-0.99; P = 0.03) remained as significant variables associated with PCE.

CONCLUSION

Impaired elastic properties of the aorta are associated with increased PCE rates in patients undergoing noncardiac, nonvascular surgery.

Effects of hunter-gatherer subsistence mode on arterial distensibility in Cameroonian pygmies

We aimed to assess whether arterial distensibility estimated by pulse wave velocity (PWV) and augmentation index (AI) differs between Cameroon traditional pygmies (TPs) on hunter-gather subsistence mode, contemporary pygmies who migrated to semiurban area, and the Bantou farmers (BFs) sharing the same environment. For that purpose, we recorded carotid-femoral PWV (ComplioR) in age and sex carefully matched 20 TPs, 20 contemporary pygmies, and 22 BFs. Aortic AI corrected for heart rate and blood pressures were generated from pressure wave analysis (SphygmoCor). Lipid profile was determined in TP and BF participants. TPs were shorter (P=0.02) with lower body weight (P<0.01) in comparison with contemporary pygmies and BFs. TPs had lower low-density lipoprotein cholesterol but higher high-density lipoprotein cholesterol than BFs (P<0.01). Their PWV (5.81±0.21 m/s) was slower (P=0.006) than that of contemporary pygmies (6.82±0.36 m/s) or BFs (6.93±0.29 m/s); however, after its adjustment for age, mean arterial pressure, and heart rate, the difference was slightly attenuated (P=0.051). PWV adjusted for weight did not differ between groups (P=0.10). In the whole study population but not in TPs taken separately, multivariate regression analysis revealed that PWV was independently associated with mean arterial pressure, age, and TP status (P<0.001), whereas age, mean arterial pressure, and height emerged as independent determinants of aortic AI corrected for heart rate (P<0.001). Aortic AI corrected for heart rate did not differ in the 3 groups. In conclusion, hunter-gather lifestyle is associated with low atherosclerosis risk translated by lower aortic stiffness attributed at least partly to low weight and blunted effects of aging and blood pressures on TP arterial structure and function.

Diameter-dependent axial prestretch of porcine coronary arteries and veins

The pressure-diameter relation (PDR) and the wall strain of coronary blood vessels have important implications for coronary blood flow and arthrosclerosis, respectively. Previous studies have shown that these mechanical quantities are significantly affected by the axial stretch of the vessels. The objective of this study was to measure the physiological axial stretch in the coronary vasculature; i.e., from left anterior descending (LAD) artery tree to coronary sinus vein and to determine its effect on the PDR and hence wall stiffness. Silicone elastomer was perfused through the LAD artery and coronary sinus trees to cast the vessels at the physiologic pressure. The results show that the physiological axial stretch exists for orders 4 to 11 (> 24 μm in diameter) arteries and orders -4 to -12 (>38 μm in diameter) veins but vanishes for the smaller vessels. Statistically, the axial stretch is higher for larger vessels and is higher for arteries than veins. The axial stretch λ(z) shows a linear variation with the order number (n) as: λ(z) = 0.062n + 0.75 (R(2) = 0.99) for artery and λ(z) = -0.029n + 0.89 (R(2) = 0.99) for vein. The mechanical analysis shows that the axial stretch significantly affects the PDR of the larger vessels. The circumferential stretch/strain was found to be significantly higher for the epicardial arteries (orders 9-11), which are free of myocardium constraint, than the intramyocardial arteries (orders 4-8). These findings have fundamental implications for coronary blood vessel mechanics.

Coronary artery distensibility assessed by 3.0 Tesla coronary magnetic resonance imaging in subjects with and without coronary artery disease

Coronary vessel distensibility is reduced with atherosclerosis and normal aging, but direct measurements have historically required invasive measurements at cardiac catheterization. Therefore, we sought to assess coronary artery distensibility noninvasively using 3.0 Telsa coronary magnetic resonance imaging (MRI) and to test the hypothesis that this noninvasive technique can detect differences in coronary distensibility between healthy subjects and those with coronary artery disease (CAD). A total of 38 healthy, adult subjects (23 men, mean age 31 ± 10 years) and 21 patients with CAD, diagnosed using x-ray angiography (11 men, mean age 57 ± 6 years) were studied using a commercial whole-body MRI system. In each subject, the proximal segment of a coronary artery was imaged for the cross-sectional area measurements using cine spiral MRI. The distensibility (mm Hg(-1) × 10(3)) was determined as (end-systolic lumen area - end-diastolic lumen area)/(pulse pressure × end-diastolic lumen area). The pulse pressure was calculated as the difference between the systolic and diastolic brachial blood pressure. A total of 34 healthy subjects and 19 patients had adequate image quality for coronary area measurements. Coronary artery distensibility was significantly greater in the healthy subjects than in those with CAD (mean ± SD 2.4 ± 1.7 mm Hg(-1) × 10(3) vs 1.1 ± 1.1 mm Hg(-1) × 10(3), respectively, p = 0.007; median 2.2 vs 0.9 mm Hg(-1) × 10(3)). In a subgroup of 10 patients with CAD, we found a significant correlation between the coronary artery distensibility measurements assessed using MRI and x-ray coronary angiography (R = 0.65, p = 0.003). In a group of 10 healthy subjects, the repeated distensibility measurements demonstrated a significant correlation (R = 0.80, p = 0.006). In conclusion, 3.0-Tesla MRI, a reproducible noninvasive method to assess human coronary artery vessel wall distensibility, is able to detect significant differences in distensibility between healthy subjects and those with CAD.

The relationship between arterial elasticity and lipid profile in people with type 1 diabetes mellitus

A cross-sectional study was carried out to assess small (SAEI) and large (LAEI) arterial elasticity indexes of individuals with T1DM, and its relationship with their lipid profile. There were associations between SAEI and total cholesterol and waist-hip ratio (R(2)=0.29). Most of the individuals investigated showed low measures of SAEI.

Impaired aortic distensibility measured by computed tomography is associated with the severity of coronary artery disease

Impaired aortic distensibility index (ADI) is associated with cardiovascular risk factors. This study evaluates the relation of ADI measured by computed tomographic angiography (CTA) with the severity of coronary atherosclerosis in subjects with suspected coronary artery disease (CAD). Two hundred and twenty-nine subjects,age 63 ± 9 years, 42% female, underwent coronary artery calcium (CAC) scanning and CTA, and their ADI and Framingham risk score (FRS) were measured. End-systolic and end-diastolic (ED) cross-sectional-area(CSA) of ascending-aorta (AAo) was measured 15-mm above the left-main coronary ostium. ADI was defined as: [(Δlumen-CSA)/(lumen-CSA in ED × systemic-pulse-pressure) × 10³]. ADI measured by 2D-trans-thoracic echocardiography (TTE) was compared with CTA-measured ADI in 26 subjects without CAC. CAC was defined as 0, 1–100, 101–400 and 400+. CAD was defined as luminal stenosis 0, 1–49% and 50%+. There was an excellent correlation between CTA- and TTE-measured ADI (r² = 0.94, P = 0.0001). ADI decreased from CAC 0 to CAC 400+; similarly from FRS 1–9% to FRS 20% + (P < 0.05). After adjustment for risk factors, the relative risk for each standard deviation decrease in ADI was 1.66 for CAC 1–100, 2.26 for CAC 101–400 and 2.32 for CAC 400+ as compared to CAC 0; similarly, 2.36 for non-obstructive CAD and 2.67 for obstructive CAD as compared to normal coronaries. The area under the ROC-curve to predict significant CAD was 0.68 for FRS, 0.75 for ADI, 0.81 for CAC and 0.86 for the combination (P < 0.05). Impaired aortic distensibility strongly correlates with the severity of coronary atherosclerosis. Addition of ADI to CAC and traditional risk factors provides incremental value to predict at-risk individuals.

Cardiovascular disease risk factors and blood pressure response during exercise in healthy children and adolescents: the European Youth Heart Study

Raised blood pressure (BP) response during exercise independently predicts future hypertension. Subjects with higher BP in childhood also have elevated BP later in life. Therefore, the factors related to the regulation of exercise BP in children needs to be well understood. We hypothesized that physiological cardiovascular disease (CVD) risk factors would influence BP response during exercise in children and adolescents. This is a cross-sectional study of 439 Danish third-grade children and 364 ninth-grade adolescents. Systolic blood pressure (SBP) was measured with sphygmomanometer during a maximal aerobic fitness test. Examined CVD risk factors were high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)-cholesterol, triglyceride, homeostasis model of assessment of insulin resistance (HOMA-IR) score, body mass index (BMI), waist circumference, and aerobic fitness. A random effect model was used to test the hypotheses. In boys, HOMA-IR score and BMI were positively related to SBP response during exercise (β = 1.03, P = 0.001, and β = 0.58, P = 0.017, respectively). The effects sizes of HOMA-IR score and BMI and the significance levels only changed slightly (β = 0.91, P = 0.004, and β = 0.43, P = 0.08, respectively) when the two variables were added in the same model. A significant positive association was observed between aerobic fitness and SBP response in girls (β = 3.13 and P = 0.002). HOMA-IR score and BMI were found to be positively related to the SBP response in male children and youth. At least partly, adiposity and insulin sensitivity seem to influence exercise SBP through different mechanisms. The positive relationship observed between aerobic fitness and SBP response in girls remains unexplainable for us, although post hoc analyses revealed that it was the case in the ninth graders only.

Comparison of short-time Fourier transform and Eigenvector MUSIC methods using discrete wavelet transform for diagnosis of atherosclerosis

In this paper, a more effective use of Doppler techniques is presented for the purpose of diagnosing atherosclerosis in its early stages using the carotid artery Doppler signals. The power spectral density (PSD) graphics are obtained by applying the short-time Fourier transform (STFT)-Welch and the Eigenvector MUSIC methods to the discrete wavelet transform (DWT) of Doppler signals. The PSDs for the fourth approximation component (A4) of both methods estimated that the patients with atherosclerosis in its early phase had lower maximum frequency components. On the other hand, the healthy subjects had higher maximum frequency components. The area under the curve (AUC), which belongs to the receiver operating characteristic (ROC) curve for the frequency level of the maximum PSDs of the A4 approximation obtained from the STFT modeling, is computed as 0.97. The AUC for the MUSIC modeling is computed as 0.996. The AUC belonging to the ROC curve for the higher maximum frequency component is computed as 0.87. The AUC belonging to the ROC curve for the test parameter of the frequency level of the maximum PSDs derived from the MUSIC modeling is determined to be 0.882. The results of this study clearly demonstrate that it is possible to distinguish between the healthy people and the patients with atherosclerosis by using the frequency level of the maximum PSDs for the A4 approximation. Furthermore, it is concluded that the power of Eigenvector-MUSIC method in terms of the resolution of the high frequencies is better than that of the STFT methods.

Associations between augmentation index and severity of atheroma or aortic stiffness of the descending thoracic aorta by transesophageal echocardiography

BACKGROUND

Although the aortic augmentation index (AI) is an attractive tool as an index of the vascular system, the association between radial AI or brachial-ankle pulse wave velocity (PWV) and severity of atheroma or arterial stiffness of the morphological central artery is unclear.

METHODS AND RESULTS

Severity of atheroma and aortic stiffness of the descending thoracic aorta (DTA) by transesophageal echography in 96 patients with paroxysmal atrial fibrillation was assessed. The relationship between radial AI or brachial-ankle PWV and atherosclerotic lesions was also investigated. The DTA was divided into 3 equal longitudinal portions, and the atheromatous lesions of each portion of the DTA were scored according to their character and extension. Instantaneous dimensional changes in the DTA was measured, and the aortic stiffness index beta was calculated. Radial AI was significantly correlated with age, plasma low-density lipoprotein-cholesterol concentrations, systolic blood pressure, pulse pressure, the mean atheromatous score and the mean aortic stiffness index. However, brachial-ankle PWV was not associated with central arterial stiffness. Multivariate logistic regression analysis showed that radial AI was most closely correlated with the mean atheromatous score.

CONCLUSIONS

Radial AI might be a novel tool for determining the severity of central aortic atheromatous lesions.

Pulse pressure and coronary atherosclerosis in asymptomatic type 2 diabetes mellitus: a 64 channel cardiac computed tomography analysis

BACKGROUND

Identification of high risk sub-groups for early initiation of preventive medical therapy requires widespread population screening using simple, inexpensive tests. High pulse pressure has been shown to predict adverse coronary events. We examined if this correlation was related to a greater coronary plaque burden in patients with high pulse pressure using 64 channel coronary computed tomographic angiography (CCTA) in patients with type 2 diabetes mellitus.

METHODS

The study included 427 consecutive asymptomatic diabetic patients with no history of coronary disease, (age 55-74 years, 58% women), undergoing CCTA as part of a prospective outcomes study.

RESULTS

Coronary atheroma was present in 76.6% of patients, multivessel coronary atheroma in 55.1% and luminal stenosis (>or=50% of diameter) in 22.9%. Pulse pressure (adjusted for age, gender, mean blood pressure and heart rate) correlated with number of coronary arteries with atheroma (p=0.005) and with multivessel coronary atheroma (odds ratio 1.24 95%CI 1.06-1.43 for each 10 mm Hg pulse pressure, p=0.009). The correlation was independent of Framingham and United Kingdom Prospective Diabetic Study risk scores (p=0.027 and p=0.036 respectively). Adjusted pulse pressure also correlated with quartiles of coronary artery calcium score (p=0.009).

CONCLUSION

Elevated pulse pressure was a useful independent marker of presence and extent of pre-clinical coronary artery disease in an asymptomatic diabetic population.

Right coronary artery becomes stiffer with increase in elastin and collagen in right ventricular hypertrophy

Changes in blood flow influence the structure, function, mechanical properties, and remodeling of arteries. The objective of the present study was to investigate the role of increased blood flow on the biaxial incremental elastic moduli of the porcine right coronary artery (RCA) and to determine the microstructural basis for the changes in moduli. We hypothesized that an increase in RCA flow will lead to increased stiffness in conjunction with remodeling of elastin and collagen in the vessel wall. The control and experimental groups consisted of five RCA vessels each. The RCA of the experimental group was exposed to 4 wk of flow-overload in right ventricular hypertrophy induced by pulmonary artery banding. Stress-strain relationships were determined and the incremental elastic moduli were derived in the circumferential, axial, and cross directions. The results show a significant increase in the elastic moduli in the circumferential (262.7 +/- 15.7 vs. 120.2 +/- 12.4 kPa; P < 0.001), axial (177.8 +/- 25.5 vs. 100.3 +/- 11.9 kPa; P = 0.025), and cross directions (104.8 +/- 8.2 vs. 68.2 +/- 8.6 kPa; P = 0.016) of the experimental RCA compared with controls. Multiphoton microscopy was used to assess the changes in elastin and collagen content in the media and adventitia of the vessel wall. We found a significant increase in elastin and collagen area fraction particularly in the adventitial layer. These data suggest stiffening of the vessel wall as a result of increased elastin and more predominantly collagen.

Noninvasive pulse wave analysis for the determination of central artery stiffness

Central artery stiffness predicts cardiovascular structural damage and clinical outcome. It is controversial whether central artery stiffness can be determined by noninvasive measurements. We compared noninvasive determination of central artery stiffness obtained from applanation tonometry of the peripheral radial artery waveform with invasive measurements of the ratio of pulse-pressure-to-stroke-volume. A total of 112 invasive measurements of the ratio of pulse-pressure-to-stroke-volume and noninvasive determinations of central artery stiffness were performed in 49 patients on the intensive care unit. In 13 out of 112 attempts of noninvasive measurements (12%) radial pulse could not be obtained using applanation tonometry because of cardiac arrhythmia or radial pulse could not be detected. These 13 failing noninvasive measurements were attempted in 7 patients. In the remaining cases we found a significant correlation between noninvasively obtained central artery stiffness and invasive measurements of the ratio of pulse-pressure-to-stroke-volume (Spearman r=0.40; p<0.0001). The association between invasive and noninvasive measurements was confirmed using Bland-Altman plots. Furthermore, a norepinephrine-induced increase of arterial stiffness was detected both invasively and noninvasively. Noninvasive determination of central artery stiffness obtained from peripheral radial artery waveform should be useful in clinical practice although it cannot be performed in every patient.

Relationships Between Vascular Indexes and Atherosclerotic Risk Factors in Patients With Type 2 Diabetes Mellitus

The relationships of cardio-ankle vascular index, (a new indicator of arterial stiffness), common carotid artery intima-media thickness, and ankle-brachial pressure index with atherosclerotic risk factors were compared in patients with type 2 diabetes. There were significant correlations between each pair of the above vascular indexes. Both cardio-ankle vascular index and intima-media thickness showed significant correlations with age, systolic blood pressure, pulse pressure, and serum total cholesterol. Ankle-brachial pressure index showed a significant negative correlation with pulse pressure but not with systolic blood pressure and total cholesterol. Logistic regression analysis showed that cardio-ankle vascular index and intima-media thickness were associated with systolic blood pressure and pulse pressure independently of age. These results suggest that there are significant associations among the 3 vascular indexes and that systolic blood pressure and pulse pressure are major, age-independent determinants of cardio-ankle vascular index and common carotid artery intima-media thickness in patients with diabetes.

Abdominal aortic wall motion of healthy and hypertensive subjects: evaluation of tissue Doppler velocity imaging

PURPOSE

To investigate the potential clinical application of tissue Doppler imaging (TDI) for motion measurement of the aortic wall in healthy and hypertensive adults.

METHOD

We used TDI to examine 53 hypertensive and 29 sex-matched healthy adults. Maximum velocity of the first and second systolic wall expansion peaks (S1, S2), maximum velocity of early (D) and end (E) diastolic retraction velocity peaks, pulse wave transmit time (PWTT), and stiffness index (beta) of the abdominal aorta were measured and compared as for factors influencing vascular compliance, including age, sex, and blood pressure.

RESULTS

Compared with the healthy subjects, the wall motion waveform of hypertensive patients showed absent E, mixed S1 and S2 peaks, and blunted S1. S1 and D were lower in hypertensive than in healthy subjects. Shortened PWTT and increased indicated increased aortic stiffness in both male and female hypertensive subects when compared with controls. Age, diastolic blood pressure (DBP) and sex were the significant independent factors modulating S1, while DBP and age were the significant independent factors modulating D. PWTT was independently influenced by age and systolic blood pressure.

CONCLUSION

This study provides evidence that abdominal aortic wall motion measurement with TDI could demonstrate qualitative and quantitative wall motion features differentiating hypertensive from healthy adults. Wall motion velocity and PWTT could reflect abdominal aortic compliance changes related to age, sex, and blood pressure.

Uncomplicated obesity is associated with abnormal aortic function assessed by cardiovascular magnetic resonance

AIMS

Obese subjects with insulin resistance and hypertension have abnormal aortic elastic function, which may predispose them to the development of left ventricular dysfunction. We hypothesised that obesity, uncomplicated by other cardiovascular risk factors, is independently associated with aortic function.

METHODS AND RESULTS

We used magnetic resonance imaging to measure aortic compliance, distensibility and stiffness index in 27 obese subjects (BMI 33 kg/m2) without insulin resistance and with normal cholesterol and blood pressure, and 12 controls (BMI 23 kg/m2). Obesity was associated with reduced aortic compliance (0.9 +/- 0.1 vs. 1.5 +/- 0.2 mm2/mmHg in controls, p < 0.02) and distensibility (3.3 +/- 0.01 vs. 5.6 +/- 0.01 mmHg-1 x 10-3, p < 0.02), as well as higher stiffness index (3.4 +/- 0.3 vs. 2.1 +/- 0.1, p < 0.02). Body mass index and fat mass were negatively correlated with aortic function. Leptin was higher in obesity (8.9 +/- 0.6 vs. 4.7 +/- 0.6 ng/ml, p < 0.001) and also correlated with aortic measures. In multiple regression models, fat mass, leptin and body mass index were independent predictors of aortic function.

CONCLUSION

Aortic elastic function is abnormal in obese subjects without other cardiovascular risk factors. These findings highlight the independent importance of obesity in the development of cardiovascular disease.

Aortic distensibility and retinal arteriolar narrowing: the multi-ethnic study of atherosclerosis

Increased aortic stiffness and retinal arteriolar narrowing are subclinical vascular effects of chronic hypertension and predict future cardiovascular events. The relationship between these 2 vascular measures is uncertain and is examined in the Multi-Ethnic Study of Atherosclerosis. This cross-sectional analysis involves 3425 participants (aged 45 to 85 years) free of clinical cardiovascular disease. Retinal vascular caliber was quantified from digital retinal photographs using standardized protocols. Aortic distensibility was determined from chest MRI. After controlling for age, squared age, gender, race, study center, height, weight, heart rate, cigarette smoking, past and current systolic blood pressure, use of antihypertensive medications, diabetes, fasting glucose, lipid profile, and C-reactive protein, reduced aortic distensibility (first versus fourth distensibility quartile) was associated with increased odds of retinal arteriolar narrowing (odds ratio: 1.72; 95% CI: 1.15 to 2.58, comparing lowest to highest quartile of arteriolar caliber). Further adjustments for atherosclerotic measures (carotid intima-media thickness, coronary calcium score, and ankle brachial index) had minimal impact on this association (odds ratio: 1.70; 95% CI: 1.13 to 2.55). Reduced aortic distensibility was not associated with retinal venular caliber. We conclude that increased aortic stiffness is associated with retinal arteriolar narrowing, independent of measured blood pressure levels and vascular risk factors. These data suggest that changes in the microvasculature may play a role linking aortic stiffness with clinical cardiovascular events.

Medical diagnosis of atherosclerosis from Carotid Artery Doppler Signals using principal component analysis (PCA), k-NN based weighting pre-processing and Artificial Immune Recognition System (AIRS)

In this study, we proposed a new medical diagnosis system based on principal component analysis (PCA), k-NN based weighting pre-processing, and Artificial Immune Recognition System (AIRS) for diagnosis of atherosclerosis from Carotid Artery Doppler Signals. The suggested system consists of four stages. First, in the feature extraction stage, we have obtained the features related with atherosclerosis disease using Fast Fourier Transformation (FFT) modeling and by calculating of maximum frequency envelope of sonograms. Second, in the dimensionality reduction stage, the 61 features of atherosclerosis disease have been reduced to 4 features using PCA. Third, in the pre-processing stage, we have weighted these 4 features using different values of k in a new weighting scheme based on k-NN based weighting pre-processing. Finally, in the classification stage, AIRS classifier has been used to classify subjects as healthy or having atherosclerosis. Hundred percent of classification accuracy has been obtained by the proposed system using 10-fold cross validation. This success shows that the proposed system is a robust and effective system in diagnosis of atherosclerosis disease.

Complex-valued wavelet artificial neural network for Doppler signals classifying

OBJECTIVE

In this paper, the new complex-valued wavelet artificial neural network (CVWANN) was proposed for classifying Doppler signals recorded from patients and healthy volunteers. CVWANN was implemented on four different structures (CVWANN-1, -2, -3 and -4).

MATERIALS AND METHODS

In this study, carotid arterial Doppler ultrasound signals were acquired from left carotid arteries of 38 patients and 40 healthy volunteers. The patient group had an established diagnosis of the early phase of atherosclerosis through coronary or aortofemoropopliteal angiographies. In implemented structures in this paper, Haar wavelet and Mexican hat wavelet functions were used as real and imaginary parts of activation function on different sequence in hidden layer nodes. CVWANN-1, -2 -3 and -4 were implemented by using Haar-Haar, Mexican hat-Mexican hat, Haar-Mexican hat, Mexican hat-Haar as real-imaginary parts of activation function in hidden layer nodes, respectively.

RESULTS AND CONCLUSION

In contrast to CVWANN-2, which reached classification rates of 24.5%, CVWANN-1, -3 and -4 classified 40 healthy and 38 unhealthy subjects for both training and test phases with 100% correct classification rate using leave-one-out cross-validation. These networks have 100% sensitivity, 100% specifity and average detection rate is calculated as 100%. In addition, positive predictive value and negative predictive value were obtained as 100% for these networks. These results shown that CVWANN-1, -3 and -4 succeeded to classify Doppler signals. Moreover, training time and processing complexity were decreased considerable amount by using CVWANN-3. As conclusion, using of Mexican hat wavelet function in real and imaginary parts of hidden layer activation function (CVWANN-2) is not suitable for classifying healthy and unhealthy subjects with high accuracy rate. The cause of unsuitability (obtaining the poor results in CVWANN-2) is lack of harmony between type of activation function in hidden layer and type of input signals in neural network.

Pattern Detection of Atherosclerosis from Carotid Artery Doppler Signals using Fuzzy Weighted Pre-Processing and Least Square Support Vector Machine (LSSVM)

Carotid Artery Doppler Signals were recorded from 114 subjects, 60 of whom had Atherosclerosis disease while the rest were healthy controls. Diagnosis of Atherosclerosis from Carotid Artery Doppler Signals was conducted using Fuzzy weighted pre-processing and Least Square Support Vector Machine (LSSVM). First, in order to determine the LSSVM inputs, spectral analysis of Carotid Artery Doppler Signals was performed via Autoregressive (AR) modeling. Then, fuzzy weighted pre-processing based is proposed expert system, applied to inputs obtained from spectral analysis of Carotid Artery Doppler Signals. LSSVM was used to detect Atherosclerosis from Carotid Artery Doppler Signals. All data set were obtained from Carotid Artery Doppler Signals of healthy subjects and subjects suffering from Atherosclerosis disease. The employed expert system has achieved 100% classification accuracy using a 10-fold Cross Validation (CV) method.

Noninvasive assessment of preclinical atherosclerosis

Initially considered as a semipermeable barrier separating lumen from vessel wall, the endothelium is now recognised as a complex endocrine organ responsible for a variety of physiological processes vital for vascular homeostasis. These include the regulation of vascular tone, luminal diameter, and blood flow; hemostasis and thrombolysis; platelet and leucocyte vessel-wall interactions; the regulation of vascular permeability; and tissue growth and remodelling. The endothelium modulates arterial stiffness, which precedes overt atherosclerosis and is an independent predictor of cardiovascular events. Unsurprisingly, dysfunction of the endothelium may be considered as an early and potentially reversible step in the process of atherogenesis and numerous methods have been developed to assess endothelial status and large artery stiffness. Methodology includes flow-mediated dilatation of the brachial artery, assessment of coronary flow reserve, carotid intimamedia thickness, pulse wave analysis, pulse wave velocity, and plethysmography. This review outlines the various modalities, indications, and limitations of available methods to assess arterial dysfunction and vascular risk.

Effects of window types on classification of carotid artery Doppler signals in the early phase of atherosclerosis using complex-valued artificial neural network

In this study, carotid artery Doppler ultrasound signals were acquired from left carotid arteries of 38 patients and 40 healthy volunteers. The patient group had an established diagnosis of the early phase of atherosclerosis through coronary or aortofemoropopliteal angiographies. Doppler signals were processed using fast Fourier transform (FFT) with different window types, Hilbert transform and Welch methods. After these processes, Doppler signals were classified using complex-valued artificial neural network (CVANN). Effects of window types in classification were interpreted. Results for three methods and five window types (Bartlett, Blackman, Boxcar, Hamming, Hanning) were presented as comparatively. CVANN is a new technique for solving classification problems in Doppler signals. Furthermore, examining the effects of window types in addition to CVANN in this classification problem is also the first study in literature related with this subject. Results showed that CVANN, whose input data were processed by Welch method for each window types stated above, had classified all training and test patterns, which consist of 36 healthy, 34 unhealthy and four healthy, four unhealthy subjects, respectively, with 100% classification accuracy for both training and test phases.

Role of osteoprotegerin and its ligands and competing receptors in atherosclerotic calcification

Vascular calcification significantly impairs cardiovascular physiology, and its mechanism is under investigation. Many of the same factors that modulate bone osteogenesis, including cytokines, hormones, and lipids, also modulate vascular calcification, acting through many of the same transcription factors. In some cases, such as for lipids and cytokines, the net effect on calcification is positive in the artery wall and negative in bone. The mechanism for this reciprocal relation is not established. A recent series of reports points to the possibility that two bone regulatory factors, receptor activator of NF-kappaB ligand (RANKL) and its soluble decoy receptor, osteoprotegerin (OPG), govern vascular calcification and may explain the phenomenon. Both RANKL and OPG are widely accepted as the final common pathway for most factors and processes affecting bone resorption. Binding of RANKL to its cognate receptor RANK induces NF-kappaB signaling, which stimulates osteoclastic differentiation in preosteoclasts and induces bone morphogenetic protein (BMP-2) expression in chondrocytes. A role for RANKL and its receptors in vascular calcification is spported by several findings: a vascular calcification phenotype in mice genetically deficient in OPG; an increase in expression of RANKL, and a decrease in expression of OPG, in calcified arteries; clinical associations between coronary disease and serum OPG and RANKL levels; and RANKL induction of calcification and osteoblastic differentiation in valvular myofibroblasts.

Classification of carotid artery Doppler signals in the early phase of atherosclerosis using complex-valued artificial neural network

In this study, carotid arterial Doppler ultrasound signals were acquired from left carotid arteries of 38 patients and 40 healthy volunteers. The patient group had an established diagnosis of the early phase of atherosclerosis through coronary or aortofemoropopliteal angiographies. Results were classified using complex-valued artificial neural network (CVANN). Principal component analysis (PCA) and fuzzy c-means clustering (FCM) algorithm were used to make a CVANN system more effective. For this aim, before classifying with CVANN, PCA method was used for feature extraction in PCA-CVANN architecture and FCM algorithm was used for data set reduction in FCM-CVANN architecture. Training and test data were selected randomly using 10-fold cross validation. PCA-CVANN and FCM-CVANN architectures classified healthy and unhealthy subjects for training and test data with about 100% correct classification rate. These results shown that PCA-CVANN and FCM-CVANN classified Doppler signals successfully.