Arterial compliance: a diagnostic marker for atherosclerotic plaque burden?

Evaluation of local changes in radio-frequency signal waveform and brightness caused by vessel dilatation for ascertaining reliability of elasticity estimation inside heterogeneous plaque: a preliminary study

PURPOSE

To diagnose plaque characteristics, we previously developed an ultrasonic method to estimate the local elastic modulus from the ratio of the pulse pressure to the strain of the arterial wall due to dilatation in systole by transcutaneously measuring the minute thinning in thickness during one cardiac cycle. For plaques, however, some target regions became thicker as the vessel dilates, resulting in false elasticity. Therefore, a method to identify a reliable target for the elastic modulus estimation is indispensable. As a candidate for an identification index of plaques that become thicker during one cardiac cycle, the correlation of the radio-frequency (RF) signals remains high and it is not sufficient to obtain the elasticity. In this study, we thoroughly observed the target with a high correlation but positive strain in the plaque and characterized it by the property of the surrounding area.

METHODS

For the plaque formed in the right carotid sinus of a patient with hyperlipidemia and the wall of the right common carotid artery of a young healthy male, (1) the correlation value as the similarity between the RF signals, (2) change in brightness obtained from the log-compressed envelope signals, and (3) strain obtained between the time of the R-wave and that of the maximum vessel dilatation were observed to characterize the region in the plaque.

RESULTS

In the plaque, it was found that the region with high correlation and positive strain and its surrounding area could be classified into one of the three typical patterns.

CONCLUSION

As a preliminary study, this study provides a clue to assert the reliability of elasticity estimates for a region with high correlation and positive strain in the plaque based on measurable properties.

The relationship between arterial stiffness index and coronary heart disease and its severity

BACKGROUND

Arterial stiffness index (ASI) is closely related to coronary atherosclerosis. This study aims to explore whether ASI can predict coronary heart disease (CHD) and its severity.

METHODS

In this study, a total of 726 patients with suspected CHD were recruited. Based on coronary angiography results, the subjects were assigned into three groups: the control group (without obvious coronary artery disease), single-vessel disease group, and multi-vessel disease group (the number of vessels diseased ≥ 2). At the same time, according to the results of angiography, myocardial enzyme spectrum, electrocardiogram, color Doppler echocardiography and clinical manifestations, these patients were divided into four groups: the control group, stable angina (SA) Group, unstable angina (UA) group, and acute myocardial infarction (AMI) group. We have compared whether there were differences in ASI and related baseline data between groups. Receiver operating curve (ROC) analysis was conducted to determine whether ASI could predict CHD and evaluate the severity.

RESULTS

ASI was positively correlated with the number of diseased branches of coronary artery. The value of ASI was increased as the number of the diseased branches increased. The ASI value in the SA group was significantly higher compared with the control group. Furthermore, the ASI value in the UA and AMI groups was remarkably increased compared with the control and SA groups. The results of ROC analysis indicated that the sensitivity and specificity of ASI was 71.0% and 85.4% in diagnosing CHD, respectively. While ASI was used in predicting the severity of CHD, the sensitivity was 72.1% and specificity 57.9%.

CONCLUSION

ASI is of great value in the diagnosis of coronary heart disease and the prediction of its severity.

The Hippocampal Neuro-Glio-Vascular Network: Metabolic Vulnerability and Potential Neurogenic Regeneration in Disease

Brain metabolism is a fragile balance between nutrient/oxygen supply provided by the blood and neuronal/glial demand. Small perturbations in these parameters are necessary for proper homeostatic functioning and information processing, but can also cause significant damage and cell death if dysregulated. During embryonic and early post-natal development, massive neurogenesis occurs, a process that continues at a limited rate in adulthood in two neurogenic niches, one in the lateral ventricle and the other in the hippocampal dentate gyrus. When metabolic demand does not correspond with supply, which can occur dramatically in the case of hypoxia or ischemia, or more subtly in the case of neuropsychiatric or neurodegenerative disorders, both of these neurogenic niches can respond—either in a beneficial manner, to regenerate damaged or lost tissue, or in a detrimental fashion—creating aberrant synaptic connections. In this review, we focus on the complex relationship that exists between the cerebral vasculature and neurogenesis across development and in disease states including hypoxic-ischemic injury, hypertension, diabetes mellitus, and Alzheimer’s disease. Although there is still much to be elucidated, we are beginning to appreciate how neurogenesis may help or harm the metabolically-injured brain, in the hopes that these insights can be used to tailor novel therapeutics to regenerate damaged tissue after injury.

Effects of Transient Exposure to High Shear on Neutrophil Rolling Behavior

Introduction

Neutrophils display an array of behaviors ranging from rolling and migration to phagocytosis and granule secretion. Several of these behaviors are modulated by the local shear conditions. In the normal circulation, neutrophils experience shear rates from approximately 10-2,000 s^-1. However, neutrophils are also exposed to pathological shear levels in natural conditions such as severe stenosis and arteriosclerosis, as well as in blood-contacting devices such as ventricular assist devices (VADs) and hemodialysis machines. The effects of transiently (< 1 sec) exposing neutrophils to abnormally high shear rates (>3,000 s^-1) are not well understood.

Methods

We developed a set of microfluidic devices capable of exposing neutrophils to high shear rates for short durations (100-400 msec). Suspensions of isolated neutrophils were perfused through the devices and their rolling velocities on P-selectin were analyzed before and after shear exposure.

Results

We observed a significant increase in neutrophil rolling velocities on P-selectin coated regions following transient high shear exposure. The magnitude of the rolling velocity increase was dependent upon the duration of high shear exposure and became statistically significant for exposure times of 310 msec or longer. When polystyrene beads coated with a glycosulfopeptide that mimics the binding region of P-selectin glycoprotein ligand-1 (PSGL-1) were perfused through the devices, no change between the pre-shear and post-shear rolling velocities was observed.

Conclusions

These results suggest that high shear levels alter normal neutrophil rolling behavior and are important for understanding neutrophil biology in high shear conditions, as well as for improving medical device performance.

The Carotid Intima-Media Thickness and Arterial Stiffness of Pediatric Mucopolysaccharidosis Patients Are Increased Compared to Both Pediatric and Adult Controls

Treatments for mucopolysaccharidoses (MPSs) have increased longevity, but cardiovascular disease causes mortality in a significant percentage of survivors. Markers must be developed to predict MPS cardiac risk and monitor efficacy of investigational therapies.MPS patients underwent carotid artery ultrasonography from which carotid intima-media thickness (cIMT) and three measures of arterial stiffness were calculated: carotid artery distensibility (cCSD), compliance (cCSC), and incremental elastic modulus (cIEM). MPS carotid measurements were compared to corresponding data from pediatric and adult healthy cohorts. 33 MPS patients (17 MPS I, 9 MPS II, 4 MPS IIIA, and 3 MPS VI; mean age 12.5 ± 4.7 years), 560 pediatric controls (age 13.1 ± 4.0 years), and 554 adult controls (age 39.2 ± 2.2 years) were studied. Age and sex-adjusted aggregate MPS cIMT (0.56 ± 0.05 mm) was significantly greater than both pediatric (+0.12 mm; 95% CI +0.10 to +0.14 mm) and adult (+0.10 mm; 95% CI +0.06 to +0.14 mm) control cohorts; similar findings were observed for all MPS subtypes. Mean MPS cIMT approximated the 80th percentile of the adult cohort cIMT. MPS patients also demonstrated significantly increased adjusted arterial stiffness measurements, evidenced by reduced cCSD, cCSC, and increased cIEM, compared to pediatric and adult control cohorts. Regardless of treatment, MPS patients demonstrate increased cIMT and arterial stiffness compared to healthy pediatric and adult controls. These data suggest that relatively young MPS patients demonstrate a “structural vascular age” of at least 40 years old.

Plasma CTGF is independently related to an increased risk of cardiovascular events and mortality in patients with atherosclerotic disease: the SMART study

AIMS

Connective tissue growth factor (CTGF) plays a key role in tissue fibrogenesis and growing evidence indicates a pathogenic role in cardiovascular disease. Aim of this study is to investigate the association of connective tissue growth factor (CTGF/CCN2) with cardiovascular risk and mortality in patients with manifest vascular disease.

METHODS AND RESULTS

Plasma CTGF was measured by ELISA in a prospective cohort study of 1227 patients with manifest vascular disease (mean age 59.0 ± 9.9 years). Linear regression analysis was performed to quantify the association between CTGF and cardiovascular risk factors. Results are expressed as beta (β) regression coefficients with 95% confidence intervals (CI). The relation between CTGF and the occurrence of new cardiovascular events and mortality was assessed with Cox proportional hazard analysis. Adjustments were made for potential confounding factors. Plasma CTGF was positively related to total cholesterol (β 0.040;95%CI 0.013-0.067) and LDL cholesterol (β 0.031;95%CI 0.000-0.062) and inversely to glomerular filtration rate (β -0.004;95%CI -0.005 to -0.002). CTGF was significantly lower in patients with cerebrovascular disease. During a median follow-up of 6.5 years (IQR 5.3-7.4) 131 subjects died, 92 experienced an ischemic cardiac complication and 45 an ischemic stroke. CTGF was associated with an increased risk of new vascular events (HR 1.21;95%CI 1.04-1.42), ischemic cardiac events (HR 1.41;95%CI 1.18-1.67) and all-cause mortality (HR 1.18;95%CI 1.00-1.38) for every 1 nmol/L increase in CTGF. No relation was observed between CTGF and the occurrence of ischemic stroke.

CONCLUSIONS

In patients with manifest vascular disease, elevated plasma CTGF confers an increased risk of new cardiovascular events and all-cause mortality.

The ARTICO study: identification of patients at high risk of vascular recurrence after a first non-cardioembolic stroke

BACKGROUND

About 20% of patients with a first ischaemic stroke will experience a new vascular event within the first year. The atherosclerotic burden, an indicator of the extension of atherosclerosis in a patient, has been associated with the risk of new cardiovascular events in the general population. However, no predictive models reliably identify groups at a high risk of recurrence. The ARTICO study prospectively analysed the predictive value for the risk of recurrence of specific atherosclerotic markers.

METHODS

The multicentre ARTICO study included 620 consecutive independent patients older than 60 years suffering from a first non-cardioembolic stroke. We analysed classical stroke risk factors; duplex study of supraaortic trunk including intima-media thickness (IMT) measurement; quantification of internal carotid (ICA) stenosis; number, morphology and surface characteristics of carotid plaques; ankle brachial index (ABI); and the presence of microalbuminuria. Patients were followed up at 6 and 12 months after inclusion. The primary end-point was death or major cardiovascular events.

RESULTS

Any vascular event or death at 12 months occurred in 78 (13.8%) patients. In 40 (7.1%) of these the vascular event was a stroke recurrence. Weight, history of diabetes mellitus, history of symptomatic PAD, ABI <0.9 and significant ICA stenosis (>50%) were associated with a higher risk of vascular events on follow-up in the bivariate analysis. In the final Cox regression analysis, body mass index (BMI), systolic blood pressure, history of diabetes mellitus, symptomatic PAD (HR, 2.76; 95% CI, 1.10-6.95; p=0.03), and particularly patients with both ICA stenosis >50% and PAD (HR 4.52; 95% CI, 2.14-9.53; p<0.001) were independently associated with an increased risk of vascular events. Neither isolated ICA stenosis >50% nor isolated abnormal ABI remained associated with an increased risk of recurrence in comparison with the whole population.

CONCLUSIONS

Symptomatic PAD identifies a high risk group of vascular recurrence after a first non-cardioembolic stroke. The associated increased risk was particularly high in patients with both ICA stenosis and either symptomatic or asymptomatic PAD. Neither asymptomatic PAD alone nor isolated ICA stenosis >50% were associated with an increased risk of recurrence in this particularly high-risk group of non-cardioembolic stroke.

Relative impact of neuromuscular and cardiovascular factors on bone strength index of the hemiparetic distal radius epiphysis among individuals with chronic stroke

The objective of this study was to examine the associations of neuromuscular and cardiovascular impairments with the bone strength index of the hemiparetic distal radius epiphysis in chronic stroke survivors. The results showed that grip strength is the most predominant predictor of the bone strength index.

INTRODUCTION

The purpose of the study was to examine the associations of neuromuscular and cardiovascular impairments with the bone strength index of the hemiparetic distal radius epiphysis in chronic stroke survivors.

METHODS

Sixty-five chronic stroke survivors and 34 healthy control subjects underwent scanning of the distal radius epiphyseal site on both sides using peripheral quantitative computed tomography to measure trabecular volumetric bone mineral density (vBMD) (mg/cm(3)), total vBMD (mg/cm(3)), total area (mm(2)), and compressive bone strength index (cBSI) (g(2)/cm(4)). Various indicators of neuromuscular (grip strength, spasticity) and cardiovascular function (vascular elasticity, oxygen consumption during 6-min walk test) were evaluated.

RESULTS

Analysis of variance revealed a significant main effect of side (p < 0.001) and group × side interaction (p < 0.05) for total BMC, total vBMD, trabecular vBMD, and cBSI (p < 0.05), with the stroke group showing greater side-to-side difference in these variables. However, no significant side-to-side difference in total area was detected in either group (p > 0.05). Sex-specific analysis yielded similar results. Multiple regression analyses revealed that the cBSI of the hemiparetic distal radius epiphysis had a stronger association with neuromuscular factors than cardiovascular factors. Overall, grip strength was the strongest determinant of the cBSI of the hemiparetic distal radius epiphysis (p < 0.01).

CONCLUSIONS

Muscle weakness is the most predominant determinant of cBSI in the hemiparetic distal radius epiphysis among chronic stroke patients. Future studies should investigate the efficacy of different muscle-strengthening strategies in enhancing bone strength of this skeletal site in the chronic stroke population.

Oxidative stress markers are associated to vascular recurrence in non-cardioembolic stroke patients non-treated with statins

Background

Since atherogenesis is related to oxidative stress, our objective was to study the association of oxidative stress markers with the vascular recurrence in non-cardioembolic stroke.

Methods

Atherosclerotic and oxidative stress markers were evaluated on admission, in 477 patients suffering from a first non-cardioembolic stroke. Patients were followed at 6 and 12 months after inclusion, recording cardiovascular events. As markers of endothelial oxidative stress we used oxidized LDL, Cu/Zn superoxide dismutase and 8-OH deoxiguanosine. 136 patients were being treated with statins at the moment of serum samples acquisition.

Results

Patients who suffered vascular recurrence or vascular-origin death had higher levels of 8-OHDG (40.06±24.70vs33.11±15.18;p=0.003). We also found associations between vascular recurrence or vascular origin death and Cu/ZnSOD (OR,1.02; 95%CI,1.00-1.03;p=0.0001) and 8-OHDG (OR,1.12;95%CI,1.08-1.16;p<0.0001) in a subgroup of 333 patients that were not in treatment with statins on admission. We also found associations between 8-OHDG and intima media thickness (IMT) (OR,1.13;95%CI,1.09-1.16;p<0.0001), presence of ipsilatieral stenosis≥50% (OR,1.03;95%CI1.00-1.05;p=0.007) and other atherosclerotic plaque characteristics.

Conclusions

Specific oxidative stress markers were found to be markers of atherosclerosis plaque types and vascular recurrence in non-statins treated patients at admission.

Lifestyle in patients with chronic kidney disease is associated with less arterial stiffness

Cardiovascular disease is the major cause of mortality in chronic kidney disease (CKD). Arterial stiffening is recognised as a critical precursor of cardiovascular disease. Available evidence indicates that lifestyle modifications are therapeutic interventions for preventing and treating arterial stiffening.

OBJECTIVE

To evaluate the influence of lifestyle modifications on the arterial vessel compliance in CKD patients not receiving renal replacement therapy (RRT). We measured the arterial vessel compliance in 50 CKD patients not receiving RRT (30 post-transplant, 20 pre-RRT). Noninvasive pulse wave analysis of radial artery was used to estimate large artery (C1) and small artery elasticity (C2) and was corrected for patients age. Renal transplant (RT) patients were younger than CKD patients. RT patients C1 normal in 13%. C2 lower than normal in 77% of cases and not associated with evaluated variables, but worse large artery compliance was observed. In CKD patients, C1 was normal in 55%. C1 was strongly associated with aerobic exercise. For CKD patients, exercise normalises large artery compliance. C2 was lower than normal in 90%. Small artery compliance was affected in majority of patients.

Association between human immunodeficiency virus infection and stiffness of the common carotid artery

BACKGROUND AND PURPOSE

Individuals with human immunodeficiency virus (HIV) who use highly active antiretroviral therapy (HAART) may have an increased risk for cardiovascular-related events, although the underlying mechanism remains unclear. We tested the hypothesis that carotid arterial stiffness was higher among persons using HAART compared to HAART-naïve and HIV-uninfected persons.

METHODS

Between 2004 and 2006, we performed high-resolution B-mode ultrasound on 2789 HIV-infected and HIV-uninfected participants of the Women's Interagency HIV Study (1865 women) and the Multicenter AIDS Cohort Study (924 men) and determined carotid arterial distensibility, which is a direct measure of carotid arterial stiffness. We used generalized estimating equations to evaluate the association between distensibility and HIV infection, CD4(+) cell count, and exposure to HAART adjusted for demographic, behavioral, and clinical characteristics.

RESULTS

In multivariable analysis, distensibility was 4.3% lower (95% confidence interval, -7.4% to -1.1%) among HIV-infected vs uninfected participants. Among HIV-infected participants with <200 CD4(+) cells, distensibility was 10.5% lower (95% confidence interval, -14.5% to -6.2%) than that among HIV-uninfected participants, and this effect did not differ significantly by cohort or race. Concurrent HAART use was independently associated with lower distensibility among Multicenter AIDS Cohort Study participants but not among Women's Interagency HIV Study participants.

CONCLUSIONS

Our finding that advanced HIV-related immunosuppression was associated with increased carotid arterial stiffness independent from the effects of traditional atherosclerosis risk factors suggests that the etiologic mechanism underlying reports of an increased cardiovascular disease risk among HIV-infected individuals might involve HIV-related immunosuppression leading to vascular dysfunction and arterial stiffening.

Impaired aortic stiffness and pulse wave velocity in patients with branch retinal vein occlusion

BACKGROUND

Aortic distensibility (AD) and pulse wave velocity (PWV) reflect arterial stiffness, which is linked to increased cardiovascular morbidity and mortality in different diseases such as atherosclerosis, hypertension, and diabetes mellitus, all of which are also common risk factors in patients with branch retinal vein occlusion (BRVO). In the present study, we aimed to determine whether arterial stiffness in different segments of the arterial tree is increased in patients with BRVO.

METHODS

The study group consisted of 35 patients with BRVO (20 female, 15 male, mean age: 55.9+/-6.8) and the age-matched control groups consisted of 19 patients with hypertension (9 female, 10 male, mean age: 55.2+/7.6) and 17 healthy subjects (9 female, 8 male, mean age: 53.4+/-9.6). Radial artery PWV was measured using a Pulse Wave Sensor HDI system, which measures non-invasively the radial pulse-wave recording with computer analysis of the diastolic decay, and provides separate assessment of the large arterial elasticity index (LAEI) and small artery elasticity index (SAEI). Aortic strain and AD was determined echocardiographically based on the relationship between changes in aortic diameter and pressure with each cardiac pulse. Patients with diabetes mellitus or inflammatory BRVO, and control patients with any occlusive vascular eye disease, were excluded. The results of the three groups were compared.

RESULTS

Compared to the subjects of the healthy control group, those with BRVO had lower LAEI (p<0.05). Both AD and aortic strain were significantly lower in the BRVO group than in both control groups (p<0.05 for both) and in the hypertensive control group than the healthy controls (p<0.05). The AD, LAEI and SAEI were positively correlated (p=0.021, r=0.307 and p=0.041, r=0.269 respectively).

CONCLUSIONS

The results of this study show that the arterial stiffness indices (large arterial elasticity index and aortic distensibility) are abnormal in patients with BRVO compared to the healthy and hypertensive controls. Arterial stiffness may play a role in the onset or progression of BRVO. Further studies are needed to determine the exact role of AS in the pathogenesis of BRVO, and to reveal its value in predicting systemic morbidity and mortality in patients with BRVO.

Vascular compliance is reduced in geriatric people with angiographic coronary atherosclerosis

This study investigated the value of arterial elasticity measurement in the early diagnosis of angiographic coronary artery atherosclerosis in 105 consecutive elderly patients. They were divided into two groups according to the results of selective coronary angiography: 55 with coronary atherosclerosis and 50 with a normal coronary angiogram. The Gensini score of the coronary artery was acquired and capacitive arterial compliance (C1) and oscillatory arterial compliance (C2) were measured. An independent-sample t-test was used to evaluate the difference in C1 and C2 between the two groups. Bivariate analyses were performed to study the association between the Gensini score and C1 and C2. A significant difference between the two groups in C2 was found and the Gensini score of the coronary artery was significantly correlated with C2. Identification of early coronary atherosclerosis in geriatrics may be aided by the prognostic value of C2.

Effect of rosiglitazone, metformin and medical nutrition treatment on arterial stiffness, serum MMP-9 and MCP-1 levels in drug naive type 2 diabetic patients

The aim of the study was to evaluate the long-term effect of rosiglitazone and metformin monotherapy with medical nutrition treatment (MNT) and of MNT alone on arterial stiffness, serum monocyte chemoattractant protein (MCP)-1 and matrix metalloproteinase (MMP)-9 in drug naive patients with type 2 diabetes mellitus. Fifty type 2 diabetic patients were randomized to receive rosiglitazone 4 mg/day (n=19) or metformin 850 mg/day (n=16) with MNT or MNT alone (n=15), for 52 weeks. Arterial stiffness was assessed by using large and small artery elasticity index (SAEI and LAEI, respectively). SAEI, LAEI, serum MCP-1 and MMP-9 levels were measured at baseline and following 52 weeks of treatment. SAEI was improved only in the rosiglitazone group, and the difference was still statistically significant when the three groups were compared (p=0.024). There were no differences in LAEI in inter- and intragroup comparisons at the end of the study. Serum MMP-9 levels were decreased in the metformin (-13.5+/-34.8%, p=0.02) and rosiglitazone (-27.2+/-51.0%, p=0.023) groups compared with baseline values, whereas no significant change was seen in serum MCP-1 levels. These results suggest that rosiglitazone monotherapy has favorable effects on arterial stiffness compared with metformin monotherapy independent of glycemic control.

Arterial wave reflection in HIV-infected and HIV-uninfected Rwandan women

To assess differences in arterial wave reflection, a marker of atherosclerosis, in HIV-positive and HIV-negative Rwandan women, applanation tonometry was performed on 276 HIV(+) and 67 HIV(-) participants. Radial artery pressure waveforms were recorded and central aortic waveforms were derived by validated transfer function. Central augmentation index (C-AI), central pulse pressure (C-PP), and peripheral augmentation index (P-AI) were measured. HIV(+) participants were younger and had lower diastolic blood pressure (BP) and 41% of the HIV(+) women were taking antiretroviral therapy (ART). Mean C-AI and P-AI were significantly lower in HIV-infected than in uninfected participants (20.3 +/- 12.0 vs. 25.5 +/- 12.1, p = 0.002 and 74.6 +/- 18.8 vs. 83.7 +/- 20.0, p < 0.001). After age matching, C-AI, C-PP, and P-AI were similar among the groups. On multivariate analysis, age, heart rate, weight, and mean arterial pressure were independently associated with C-AI (R(2) = 0.33, p < 0.0001). Among HIV-infected women, current CD4 count did not correlate with C-AI (Rho = -0.01, p = 0.84), C-PP (Rho = 0.09, p = 0.16), or P-AI (Rho = -0.01, p = 0.83). In conclusion, HIV infection was not associated with increased arterial wave reflection in women with little exposure to antiretroviral therapy and without CV risk factors. Whether long-term ART increases measures of arterial stiffness remains unknown.

Nonlinear optical microscopy reveals invading endothelial cells anisotropically alter three-dimensional collagen matrices

The interactions between endothelial cells (ECs) and the extracellular matrix (ECM) are fundamental in mediating various steps of angiogenesis, including cell adhesion, migration and sprout formation. Here, we used a noninvasive and non-destructive nonlinear optical microscopy (NLOM) technique to optically image endothelial sprouting morphogenesis in three-dimensional (3D) collagen matrices. We simultaneously captured signals from collagen fibers and endothelial cells using second harmonic generation (SHG) and two-photon excited fluorescence (TPF), respectively. Dynamic 3D imaging revealed EC interactions with collagen fibers along with quantifiable alterations in collagen matrix density elicited by EC movement through and morphogenesis within the matrix. Specifically, we observed increased collagen density in the area between bifurcation points of sprouting structures and anisotropic increases in collagen density around the perimeter of lumenal structures, but not advancing sprout tips. Proteinase inhibition studies revealed membrane-associated matrix metalloproteinase were utilized for sprout advancement and lumen expansion. Rho-associated kinase (p160ROCK) inhibition demonstrated that the generation of cell tension increased collagen matrix alterations. This study followed sprouting ECs within a 3D matrix and revealed that the advancing structures recognize and significantly alter their extracellular environment at the periphery of lumens as they progress.

Arterial compliance in adolescents and young adults receiving chronic hemodialysis

Increased vascular stiffness is an established risk marker of cardiovascular diseases (CVD) in adults with end-stage renal disease, but its role in pediatric patients remains to be defined. We prospectively examined arterial compliances of adolescents and young adults on hemodialysis (HD) using diastolic pulse wave analysis (DPWA). Each of the ten HD patients (age 17.3 +/- 3.9 years; mean +/- SD) had two DPWA tests within a three-week time period. DPWA measurement was performed before and hourly until the end of three-hour HD. Pre-HD large artery elasticity index (LAEI) was reduced in one patient and small artery elasticity index (SAEI) was reduced in another. Neither patient was hypertensive. Eight other patients had a reduction in both LAEI and SAEI. Among them, six patients had systolic and/or diastolic hypertension, and the other two were normotensive. Serum phosphorus correlated positively with stroke volume and cardiac output indices and negatively with SAEI. The reduction in BP during HD correlated with the amount of fluid removal. LAEI and SAEI were unchanged during HD. In conclusion, the reduction in LAEI and/or SAEI was observed in four normotensive patients, suggesting hypertension was not the only contributing factor for the reduced arterial compliances in our patients. The association between SAEI and serum phosphorus suggests that SAEI derived from DPWA can potentially be an early non-invasive, operator-independent, and volume-independent marker of CVD in adolescents and young adults receiving HD. Longitudinal studies with a larger sample size are needed to confirm our observation and speculation.

Small arterial elasticity predicts the extent of coronary artery disease: Relationship with serum uric acid

BACKGROUND

Arterial elasticity has been previously linked to atherosclerotic vascular disease states. Serum uric acid level has been recently associated with increased arterial stiffness, but to what extent serum uric acid reflects angiographic coronary artery status and vessel compliance remains to be established. In this study we aimed to evaluate the association of arterial elasticity indexes, serum uric acid and the presence and extent of angiographic coronary artery disease (CAD) in patients with chronic stable angina.

METHODS

One hundred and eight consecutive patients attending for elective coronary angiography were investigated. The severity of CAD was expressed using the Gensini score. Quantitative analysis of the arterial elasticity was performed by applanation tonometry. Serum uric acid was measured in all participants. Stepwise multiple linear regression analysis was used to identify the independent correlates of the Gensini score.

RESULTS

After adjustment for age, gender, common cardiac risk factors and cardiovascular drugs, small artery elasticity index (SAEI) (p<0.001) and serum uric acid (p<0.001) were independently correlated with the severity of CAD. Stepwise multiple linear regression analysis was also used to identify independent correlates of the SAEI. Serum uric acid emerged as the only independent correlate of SAEI (p<0.001).

CONCLUSIONS

SAEI independently reflects the extent of CAD in patients with chronic stable angina. This relationship is chiefly mediated by serum uric acid. Our data add to the growing evidence that serum uric acid may be a marker of arterial stiffness and atherosclerotic burden.

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.

Relationship between arterial distensibility and coronary atherosclerosis in angina patients

OBJECTIVE

Arterial stiffening is associated with an increased risk of cardiovascular disease. However, limited evidence exists on whether it also relates to subclinical atherosclerosis, thereby providing a non-invasive marker of the overall cardiovascular status. The aim of the present study was to provide information on arterial stiffening in angina patients in whom angiographic evaluation allowed quantification of coronary atherosclerosis.

METHODS

We studied 101 patients with angina from a large number admitted to our hospital for coronary angiography. In each patient, radial (RA), subdiaphragmatic aorta (AO) and carotid (CA) distensibility (Dist) were measured by an ultrasonic device, following ultrasonic exclusion of atherosclerotic lesions at these specific sites. Patients were classified into three groups according to the angiographic findings: (i) no significant coronary lesions (lumen obstruction < 50%, group A); (ii) one (group B); and (iii) two or three (group C) coronary vessels with hemodynamic significant plaques (lumen obstruction > 50%).

RESULTS

Age, male prevalence, previous cardiovascular disease and interventions were progressively greater or more common from group A to C, whereas several other risk factors (plasma glucose, serum cholesterol, smoking, history of hypertension, etc.) did not differ between the three groups or between the group with single vessel (B) versus the group with multivessel disease (C). CA and AO Dist decreased progressively from group A to C with a significant relationship in the group as a whole between distensibility values and the number of diseased vessels. The progressive decrease in AO Dist from group A to C remained significant after adjustment for variables that showed between-group differences (such as gender, age and systolic blood pressure) and the ROC curve showed it to be a more sensitive and specific marker of coronary atherosclerosis than CA Dist. RA Dist was similar in the three groups and showed no relationship with the number of diseased vessels in the group as a whole.

CONCLUSION

In patients with angina, AO and CA Dist are related to the severity of coronary atherosclerosis, with the relationship being better for alterations in aortic than in carotid mechanical properties. Large elastic artery (and in particular aortic) stiffening can thus be considered as a marker of the severity of coronary atherosclerosis, providing non-invasive obtainable information on the need to proceed with further clinical examinations.

A new technique for assessing arterial pressure wave forms and central pressure with tissue Doppler

Background

Non-invasive assessment of arterial pressure wave forms using applanation tonometry of the radial or carotid arteries can be technically challenging and has not found wide clinical application. 2D imaging of the common carotid arteries is routinely used and we sought to determine whether arterial waveform measurements could be derived from tissue Doppler imaging (TDI) of the carotid artery.

Methods

We studied 91 subjects (52 men, age 52 ± 14 years) with and without cardiovascular disease. Tonometry was performed on the carotid artery simultaneously with pulsed wave Doppler of the LVOT and acquired digitally. Longitudinal 2D images of the common carotid artery with and without TDI were also acquired digitally and both TDI and tonometry were calibrated using mean and diastolic cuff pressure and analysed off line.

Results

Correlation between central pressure by TDI and tonometry was excellent for maximum pressure (r = 0.97, p < 0.0001). The mean differences between central pressures derived by TDI and tonometry were minimal (systolic 5.36 ± 5.5 mmHg; diastolic 1.2 ± 1.2 mmHg).

Conclusion

Imaging of the common carotid artery motion with tissue Doppler may permit acquisition of a waveform analogous to that from tonometry. This method may simplify estimation of central arterial pressure and calculation of total arterial compliance.

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.

Ageing and vascular ageing

There is an age related decline in various physiological processes. Vascular ageing is associated with changes in the mechanical and the structural properties of the vascular wall, which leads to the loss of arterial elasticity and reduced arterial compliance. Arterial compliance can be measured by different parameters like pulse wave velocity, augmentation index, and systemic arterial compliance. There is evidence that arterial compliance is reduced in disease states such as hypertension, diabetes, and end stage renal failure. Changes in arterial compliance can be present before the clinical manifestation of cardiovascular disease. Pharmacological and non-pharmacological measures have been shown to improve arterial compliance. Arterial compliance may constitute an early cardiovascular risk marker and may be useful in assessing the effects of drugs on the cardiovascular system. Pharmacogenetics and genetics of arterial compliance in the future will improve our knowledge and understanding about vascular ageing.

Arterial elasticity identified by pulse wave analysis and its relation to endothelial function in patients with coronary artery disease

Patients with coronary artery disease (CAD) have impaired endothelial function. Arterial elasticity is modulated by endothelial function. The association between arterial elasticity and endothelial function has not been reported in patients with CAD. The present study was designed to investigate whether endothelial dysfunction contributes to impaired arterial elasticity. Thirty patients with CAD and 30 control subjects were recruited. Large and small artery elasticity indices were non-invasively assessed using pulse wave analysis. Brachial artery endothelium-dependent and -independent function were assessed by vascular response to flow-mediated vasodilation (FMD) and sublingual nitroglyceride (NTG), respectively. C1 large artery elasticity index was not different in the CAD group compared with the control group. However, C2 small artery elasticity index was significantly reduced in the CAD group compared with the control group. Flow-mediated vasodilation (FMD) was also impaired in the CAD group compared with the control group. Flow-mediated vasodilation (FMD) in the brachial artery correlated with C2 small arterial elasticity index. But NTG-mediated brachial artery vasodilation was similar between the two groups. The present findings suggest that the patients with CAD have reduced C2 small arterial elasticity index and impaired FMD. Endothelial dysfunction is involved in diminished arterial elasticity, suggesting that C2 small arterial elasticity index is a novel surrogate measure for the clinical evaluation of endothelial function.

Assessment of vascular wall shear stress and implications for atherosclerotic disease

Mechanical characteristics of circulation and vasculature, such as blood flow in combination with geometrical features, participate in the generation of several pathophysiological processes, such as development of blood vessel structure, chronic vessel tone regulation, atherosclerosis and others. We aim to briefly describe the basic mechanical and haemodynamic phenomena related to the forces applied to arterial walls, especially shear stresses and the shear-induced physiologic and pathophysiologic processes focusing on those related to atherosclerotic disease.

Nitric oxide modulates the interaction of pressure-induced wall mechanics and myogenic response of rat intramural coronary arterioles

Interactions between the biomechanical characteristics and pressure-induced active response of coronary microvessels are still not well known. We tested the hypothesis that pressure-dependent biomechanical characteristics of the coronary vascular wall are modulated by the active myogenic response and local vasodilators. We have utilized data obtained previously in isolated rat intramural coronary arterioles (approximately 100 microm in diameter), in which the diameter was investigated as a function of intraluminal pressure (Szekeres et al.: J. Cardiovasc. Pharmacol., 43, 242-249, 2004). To characterize the magnitude of myogenic response, diameter was expressed as percent of passive diameter as a function of pressure (normalized diameter; ND). In addition, circumferential wall stress (WS) and incremental distensibility (ID) were calculated. In control conditions, after an initial increase between 0-30 mm Hg, ND decreased substantially as pressure increased from 30 to 150 mm Hg. Correspondingly, WS gradually increased as a function of pressure (from 0.3 +/- 0.03 to 34.7 +/- 4.4 kPa) exhibiting a plateau phase between 40-80 mm Hg. In contrast, ID decreased and reached negative values (min: -104.9 +/- 21.9 10(-6) m2/N at 50 mm Hg). Inhibition of nitric oxide (NO) synthase by L-NNA decreased basal diameter (approximately 35% at 2 mm Hg), eliminated pressure-induced changes in ND, reduced the slope of pressure-WS curve, and decreased ID at lower pressures. Simultaneous administration of L-NNA and adenosine (which restored initial diameter, i.e. length of smooth muscle) restored--in part--the pressure-induced reduction in ND, reversed the pressure-induced behavior of WS to control, but not that of ID. These results not only confirm that in coronary arterioles wall stress is regulated by the myogenic response, but also suggest that there is interplay between the mechanical behavior of the wall and the myogenic response. Furthermore, the presence of NO seems to be necessary for maintaining a higher distensibility of intramural coronary arterioles allowing increases in diameter to lower pressures, which then activate the myogenic mechanism resulting in constrictions and full development of myogenic tone, as indicated by the presence of negative slope of pressure-diameter curve in the presence of NO.

Influence of arterial compliance on presence and extent of ischaemia during stress echocardiography

OBJECTIVE

To seek an association between total arterial compliance (TAC) and the extent of ischaemia at stress echocardiography.

DESIGN

Cohort study.

SETTING

Regional cardiac centre.

METHODS

255 consecutive patients (147 men; mean (SD) age 58 (8)) presenting for stress echocardiography for clinical indications were studied. Wall motion score index (WMSI) was calculated and ischaemia was defined by an inducible or worsening wall motion abnormality. Peak WMSI was used to reflect the extent of dysfunction (ischaemia or scar), and DeltaWMSI was indicative of extent of ischaemia. TAC was assessed at rest by simultaneous radial applanation tonometry and pulsed wave Doppler in all patients.

RESULTS

Ischaemia was identified by stress echocardiography in 65 patients (25%). TAC was similar in the groups with negative and positive echocardiograms (1.08 (0.41) v 1.17 (0.51) ml/mm Hg, not significant). However, the extent of dysfunction was associated with TAC independently of age, blood pressure, risk factors, and use of a beta blocker. Moreover, the extent of ischaemia was determined by TAC, risk factors, and use of a beta blocker.

CONCLUSION

While traditional cardiovascular risk factors are strong predictors of ischaemia on stress echocardiography, TAC is an independent predictor of the extent of ischaemia.

Higher small arterial elasticity in hypertensive patients treated with angiotensin II receptor blockers

Although evidence from basic research suggests the involvement of angiotensin II (Ang II) in the progression of arteriosclerosis, the clinical data are limited. In the present study, hypertensive outpatients who were well controlled with antihypertensive medication and had similar blood pressure levels were studied, and arterial elasticity was compared between those receiving Ang II receptor blockers (ARBs) and those treated with other antihypertensive agents. The effects of HMG-CoA reductase inhibitors (STs) on arterial elasticity were also evaluated. The study enrolled 298 outpatients who had been diagnosed with essential hypertension whose blood pressure was controlled to 150/95 or less by antihypertensive treatment (excluding angiotensin converting enzyme [ACE] inhibitors) for at least 2 months. The small artery elasticity index (SAEI) was determined for each patient from the radial artery pulse waves using a non-invasive pulse wave analysis system CR-2000. The mean of two blood pressure measurements taken from subjects lying in a recumbent position during SAEI analysis was used for the data analysis. The patients were grouped according to the use of ARBs and STs, and two-way analysis of variance (ANOVA) was used for statistical comparisons. A backward stepwise multiple regression analysis was carried out to identify factors contributing to the SAEI. Hypertensive patients receiving ARB treatment had a significantly higher SAEI compared to those not receiving ARBs, despite the similar blood pressure levels of both groups. No significant effects of ST treatment on the SAEI were observed (two-way ANOVA). A backward stepwise multiple regression analysis for the SAEI suggested that ARB treatment was an independent determinant of the SAEI after the adjusting of age, gender, total cholesterol, high density lipoprotein cholesterol, smoking and systolic blood pressure. Our results suggested that while providing blood pressure control similar to that of other antihypertensive agents, ARBs may also increase vascular elasticity and thereby delay the progression of arteriosclerosis.

Assessment of Arterial Stiffness Index as a Clinical Parameter for Atherosclerotic Coronary Artery Disease

BACKGROUND

The aim of the present study was to assess the feasibility and usefulness of the arterial stiffness index (ASI) measured non-invasively by computerized oscillometry and by comparing it with the pulse wave velocity (PWV).

METHODS AND RESULTS

The study group comprised 60 consutive patients who underwent coronary angiography and whose aorto-femoral PWV were obtained with a Judkins catheter. The ASI was obtained using Cardio Vision MS-2000 (IMDP, Las Vegas, NV, USA): (i) baseline (ASI-B); (ii) hyperemia induced by compression of the arm with cuff pressure for 5 min (ASI-H); and (iii) sublingual nitroglycerin (ASI-N). In total, 34 patients had significant coronary artery disease (CAD). The PWV and all ASI were higher in patients with CAD than in those without CAD (ASI-B, 85.9+/-57.8 vs 48.2+/-24.5, p=0.001; ASI-H, 98.1+/-49.8 vs 48.1+/-21.3, p<0.01; ASI-N, 66.7+/-55.7 vs 33.2+/-27.9, p=0.002). However, only ASI-B and ASI-H were positively correlated to the PWV (ASI-B, r=0.27, p=0.03; ASI-H, r=0.49, p=0.001; ASI-N, r=0.19, p=0.16). The ASI was increased after hyperemia in patients with CAD (ASI-H, 85.9+/-57.8 to 98.1+/-49.8, p=0.01), but not in patients without CAD (ASI-H, 48.2+/-24.5 to 48.1+/-21.3, p>0.01). After adjusting their age, only ASI-H was correlated to the presence of CAD (r=0.33, p<0.01).

CONCLUSIONS

It is feasible and useful to use the ASI for detection of atherosclerotic coronary disease. The findings of ASI-H suggests that in addition to stiffening of the arterial wall itself, the impairment of flow mediated vasodilation, because of endothelial dysfunction, further increases the arterial stiffness.