Carotid Stiffness Indicates Risk of Ischemic Stroke and TIA in Patients With Internal Carotid Artery Stenosis

Carotid artery stiffness and risk of vascular events and mortality: the REGICOR study

INTRODUCTION AND OBJECTIVES

The aims of this study were to determine the dose-response association of carotid arterial stiffness with vascular outcomes and overall mortality, and to assess their added predictive capacity.

METHODS

Population-based cohort study including 6468 individuals, with a median follow-up of 6.5 years. Six carotid artery stiffness indices were assessed: strain, stiffness, Peterson elasticity coefficient, compliance coefficient, distensibility coefficient, and pulse wave velocity (PWV). Incident coronary, cerebrovascular, global vascular, and total fatal events were identified.

RESULTS

Carotid compliance and distensibility coefficients were not associated with any of the outcomes. Carotid stiffness, Peterson elasticity coefficient, and PWV showed a direct linear relationship to cerebrovascular disease: the risk increased by 8% (95%CI, 1-16) per stiffness unit increase, by 7% (95%CI, 2-13) per 10-unit Peterson elasticity coefficient increase, and by 26% (95%CI, 8-48) per PWV unit increase. Carotid strain showed a nonlinear association with ischemic heart disease. When strain was ≤ 0.09 units, each 0.01-unit increase was associated with a 15% lower risk of coronary events (95%CI,-33 to 6); above 0.09 units, each 0.01 increase in strain was associated with a 16% higher risk of coronary events (95%CI, 6-27). The addition of the stiffness indices did not improve the predictive capacity of validated risk functions.

CONCLUSIONS

Carotid stiffness, Peterson elasticity coefficient, and PWV have a direct linear association with cerebrovascular disease risk. Carotid strain is not linearly related to U-shaped ischemic heart disease risk. The inclusion of these indexes does not improve the predictive capacity of risk functions.

What are the benefits and drawbacks of statins in carotid artery disease? A perspective review

INTRODUCTION

The prevalence of carotid artery stenosis in the general population is approximately 3%, but approximately 20% among people with acute ischemic stroke. Statins are recommended by multiple international guidelines as the drug of choice for lipid control in people with asymptomatic or symptomatic carotid artery stenosis due to their lipid-lowering and other pleiotropic effects.

AREAS COVERED

This review discusses the guidelines for statin usage as a cornerstone in the prevention and management of atherosclerotic carotid artery disease and the impact of statins on stroke incidence and mortality. Statin side effects, alternative therapy, and genetic polymorphisms are reviewed.

EXPERT OPINION

Statin therapy is associated with a decreased incidence of stroke and mortality as well as improved outcomes for patients treated with carotid revascularization. Statins are a safe and effective class of medications, but the initiation of therapy warrants close monitoring to avoid rare and potentially serious side effects. Lack of clinical efficacy or the presence of side effects suggests a need for treatment with an alternative therapy such as PCSK9 inhibitors. Understanding the interplay between the mechanisms of statins and PCSK9 inhibition therapies will allow optimal benefits while minimizing risks. Future research into genetic polymorphisms may improve patient selection for personalized therapy.

Relative Contribution of Blood Pressure in Childhood, Young- and Mid-Adulthood to Large Artery Stiffness in Mid-Adulthood

Background Blood pressure associates with arterial stiffness, but the contribution of blood pressure at different life stages is unclear. We examined the relative contribution of childhood, young- and mid-adulthood blood pressure to mid-adulthood large artery stiffness. Methods and Results The sample comprised 1869 participants from the Cardiovascular Risk in Young Finns Study who had blood pressure measured in childhood (6-18 years), young-adulthood (21-30 years), and mid-adulthood (33-45 years). Markers of large artery stiffness were pulse wave velocity and carotid distensibility recorded in mid-adulthood. Bayesian relevant life course exposure models were used. For each 10-mm Hg higher cumulative systolic blood pressure across the life stages, pulse wave velocity was 0.56 m/s higher (95% credible interval: 0.49 to 0.63) and carotid distensibility was 0.13%/10 mm Hg lower (95% credible interval: -0.16 to -0.10). Of these total contributions, the highest contribution was attributed to mid-adulthood systolic blood pressure (relative weights: pulse wave velocity, childhood: 2.6%, young-adulthood: 5.4%, mid-adulthood: 92.0%; carotid distensibility, childhood: 5.6%; young-adulthood: 10.1%; mid-adulthood: 84.3%), with the greatest individual contribution coming from systolic blood pressure at the time point when pulse wave velocity and carotid distensibility were measured. The results were consistent for diastolic blood pressure, mean arterial pressure, and pulse pressure. Conclusions Although mid-adulthood blood pressure contributed most to mid-adulthood large artery stiffness, we observed small contributions from childhood and young-adulthood blood pressure. These findings suggest that the burden posed by arterial stiffness might be reduced by maintaining normal blood pressure levels at each life stage, with mid-adulthood a critical period for controlling blood pressure.

Evaluation of Intima-Media Thickness and Arterial Stiffness as Early Ultrasound Biomarkers of Carotid Artery Atherosclerosis

Carotid atherosclerosis is a major and potentially preventable cause of ischemic stroke. It begins early in life and progresses silently over the years. Identification of individuals with subclinical atherosclerosis is needed to initiate early aggressive vascular prevention. Although carotid plaque appears to be a powerful predictor of cardiovascular risk, carotid intima-media thickness (CIMT) and arterial stiffness can be detected at the initial phases and, therefore, they are considered important new biomarkers of carotid atherosclerosis. There is a well-documented association between CIMT and cerebrovascular events. CIMT provides a reliable marker in young people, in whom plaque formation or calcification is not established. However, the usefulness of CIMT measurement in the improvement of risk cardiovascular models is still controversial. Carotid stiffness is also significantly associated with ischemic stroke. Carotid stiffness adds value to the existing risk prediction based on Framingham risk factors, particularly individuals at intermediate cardiovascular risk. Carotid ultrasound is used to assess carotid atherosclerosis. During the last decade, automated techniques for sophisticated analysis of vascular mechanics have evolved, such as speckle tracking, and new methods based on deep learning have been proposed with promising outcomes. Additional research is needed to investigate the imaging-based cardiovascular risk prediction of CIMT and stiffness.

Carotid Artery Stiffness: Imaging Techniques and Impact on Cerebrovascular Disease

Arterial stiffness is an important measure of vascular aging and atherosclerosis. Though it is measured in many well-known epidemiologic cohort studies, arterial stiffness is often overlooked in routine clinical practice for a number of reasons including difficulties in measurement, variations in definition, and uncertainties surrounding treatment. Central arterial stiffness, a surrogate for aortic stiffness, is the most commonly measured marker of arterial stiffness. In addition to central stiffness, there are also a number of ultrasound based techniques to measure local vascular stiffness, including carotid stiffness. There is evidence that both local carotid stiffness and central arterial stiffness measures are associated with multiple cerebrovascular processes, including stroke and cognitive dysfunction. Mechanistic explanations supporting this association include increased flow load experienced by the cerebral microvasculature leading to cerebral parenchymal damage. In this article, we review definitions of carotid artery stiffness measures and pathophysiologic mechanisms underpinning its association with plaque development and downstream cerebral pathology. We will review the evidence surrounding the association of carotid stiffness measures with downstream manifestations including stroke, cerebral small vessel disease detected on brain MR such as white matter hyperintensities and covert brain infarctions, brain atrophy, and cognitive dysfunction. With consistent definitions, measurement methods, and further scientific support, carotid stiffness may have potential as an imaging-based risk factor for stroke and cognitive decline.

Carotid Compliance and Parahippocampal and Hippocampal Volume over a 20-Year Period

INTRODUCTION

We evaluated the association between carotid compliance, a measure of arterial stiffness, to parahippocampal volume (PHV) and hippocampal volume (HV) over 20 years later in the Atherosclerosis Risk in the Community study.

METHODS

We included participants with common carotid compliance measurements at visit 1 (1987-1989) and volumetric brain MRI at visit 5 (2011-2013). The primary outcomes are pooled bilateral PHV and HV. We performed linear regression models adjusting for age, sex, vascular risk factors, and total brain volume.

RESULTS

Of the 614 participants, higher compliance was correlated with higher PHV (R = 0.218[0.144-0.291], p < 0.001) and HV (R = 0.181 [0.105-0.255, p < 0.001]). The association was linear and significant after adjusting for confounders. At follow-up MRI, 30 patients with dementia had lower PHV and HV than patients without dementia (p < 0.001 and p < 0.001, respectively).

CONCLUSION

Carotid compliance is associated with higher PHV and HV when measured 20 years later, further supporting the link between arterial stiffness and cognitive decline.

Using Ultrasound and Inflammation to Improve Prediction of Ischemic Stroke: A Secondary Analysis of the Multi-Ethnic Study of Atherosclerosis

INTRODUCTION

Current ischemic stroke risk prediction is primarily based on clinical factors, rather than imaging or laboratory markers. We examined the relationship between baseline ultrasound and inflammation measurements and subsequent primary ischemic stroke risk.

METHODS

In this secondary analysis of the Multi-Ethnic Study of Atherosclerosis (MESA), the primary outcome is the incident ischemic stroke during follow-up. The predictor variables are 9 carotid ultrasound-derived measurements and 6 serum inflammation measurements from the baseline study visit. We fit Cox regression models to the outcome of ischemic stroke. The baseline model included patient age, hypertension, diabetes, total cholesterol, smoking, and systolic blood pressure. Goodness-of-fit statistics were assessed to compare the baseline model to a model with ultrasound and inflammation predictor variables that remained significant when added to the baseline model.

RESULTS

We included 5,918 participants. The primary outcome of ischemic stroke was seen in 105 patients with a mean follow-up time of 7.7 years. In the Cox models, we found that carotid distensibility (CD), carotid stenosis (CS), and serum interleukin-6 (IL-6) were associated with incident stroke. Adding tertiles of CD, IL-6, and categories of CS to a baseline model that included traditional clinical vascular risk factors resulted in a better model fit than traditional risk factors alone as indicated by goodness-of-fit statistics.

CONCLUSIONS

In a multiethnic cohort of patients without cerebrovascular disease at baseline, we found that CD, CS, and IL-6 helped predict the occurrence of primary ischemic stroke. Future research could evaluate if these basic ultrasound and serum measurements have implications for primary prevention efforts or clinical trial inclusion criteria.

Matrix stiffening induces endothelial dysfunction via the TRPV4/microRNA-6740/endothelin-1 mechanotransduction pathway

Vascular stiffening is associated with the prognosis of cardiovascular disease (CVD). Endothelial dysfunction, as shown by reduced vasodilation and increased vasoconstriction, not only affects vascular tone, but also accelerates the progression of CVD. However, the precise effect of vascular stiffening on endothelial function and its mechanism is unclear and a possible underlying has not been determined. In this study, we found that increasing substrate stiffness promoted endothelin-1 (ET-1) expression and inhibited endothelial nitric oxide synthase expression in human umbilical vein endothelial cells. Additionally, miR-6740-5p was identified as a stiffness-sensitive microRNA, which was downregulated by a stiff substrate, resulting in increased ET-1 expression. Furthermore, we found that substrate stiffening reduced the expression and activity of the calcium channel TRPV4, which subsequently enhanced ET-1 expression by inhibiting miR-6740-5p. Finally, analysis of clinical plasma samples showed that plasma miR-6740-5p levels in patients with carotid atherosclerosis were significantly lower than those in healthy people. Taken together, our findings show a novel mechanically regulated TRPV4/miR-6740/ET-1 signaling axis by which substrate stiffness affects endothelial function. Our findings indicate that vascular stiffening induces endothelial dysfunction, thereby accelerating progression of CVD. Furthermore, this study indicates that endothelial dysfunction induced by improper biophysical cues from cardiovascular implants may be an important reason for complications arising from the use of cardiovascular implants. STATEMENT OF SIGNIFICANCE: Cardiovascular disease is the leading cause of morbidity and mortality worldwide. The incidence of cardiovascular disease is accompanied by increased vascular stiffness. Our work indicated that increased vascular stiffness accelerates the development of cardiovascular disease by inducing endothelial dysfunction, which is a key contributor to the pathogenesis of cardiovascular disease. In addition, we identified a novel underlying molecular pathophysiological mechanism by which increased stiffness induce endothelial dysfunction. Our work could help determine the pathogenesis of cardiovascular disease induced by biomechanical factors.

Visualizing Angle-Independent Principal Strains in the Longitudinal View of the Carotid Artery: Phantom and In Vivo Evaluation

Non-invasive vascular elastography can evaluate the stiffness of the carotid artery by visualizing the vascular strain distribution. Axial strain estimates of the longitudinal cross section of the carotid artery are sensitive to the angle between the artery and the transducer. Anatomical variations in branching and arching of the carotid artery can affect the assessment of arterial stiffness. In this study, we hypothesized that principal strain elastograms computed using compounded plane wave imaging can reliably visualize the strain distribution in the carotid artery, independent of the transducer angle. We corroborated this hypothesis by conducting phantom and in vivo studies using a commercial ultrasound scanner (Sonix RP, Ultrasonix Medical Corp., Richmond, BC, Canada). The phantom studies were conducted using a homogeneous cryogel vessel phantom. The goal of the phantom study was to assess the feasibility of visualizing the radial deformation in the longitudinal plane of the vessel phantom, independent of the transducer angle (±30°, ±20°, ±10° and 0°). The in vivo studies were conducted on 20 healthy human volunteers in the age group 50-60 y. All echo imaging was performed at a transmit frequency of 5 MHz and sampling frequency of 40 MHz. The elastograms obtained from the phantom study revealed that for straight vessels, which had their lumen parallel to the transducer, principal strains were similar to axial strains. At non-parallel configurations (angles ±30°, ±20° and ±10°), the magnitudes of the mean principal strains were within 2.5% of the parallel configuration (0° angle) estimates and, thus, were observed to be relatively unaffected by change in angle. However, in comparison, the magnitude of the axial strain decreased with increase in angle because of coordinate dependency. Further, the pilot in vivo study indicated that the principal and axial strain elastograms were similar for subjects with relatively straight arteries. However, for arteries with arched geometry, axial strains were significantly lower (p <0.01) than the corresponding principal vascular strains, which was consistent with the results obtained from the phantom study. In conclusion, the results of the phantom and in vivo studies revealed that principal strain elastograms computed using CPW imaging could reliably visualize angle-independent vascular strains in the longitudinal plane of the carotid artery.

Endothelial Dysfunction, Distensibility and Intima-media Thickness and Aetiology of Stroke

This study measured carotid artery distensibility, intima-media thickness (IMT) and flow-mediated dilatation (FMD) in patients with ischaemic stroke and evaluated if there was a relationship between these measurements and the presence of atrial fibrillation. Distensibility and IMT were measured in 89 patients with ischaemic stroke using ultrasonography; 44 patients had atrial fibrillation. Distensibility was determined using the Reneman equation. FMD was measured in a second group of 52 patients with ischaemic stroke; 20 patients had atrial fibrillation. Patients with atrial fibrillation had lower IMT values compared with patients without atrial fibrillation (0.67 versus 0.79 mm, respectively). Distensibility increased in patients with atrial fibrillation compared with patients without atrial fibrillation (0.19 versus 0.10 mm/100 mmHg, respectively). Patients with atrial fibrillation had significantly better FMD results than patients without atrial fibrillation (5.7% versus 3.2%, respectively). Measuring distensibility, IMT and FMD might be helpful in differentiating between stroke of embolic and thrombotic aetiology.

A systematic literature review of the effect of carotid atherosclerosis on local vessel stiffness and elasticity

OBJECTIVE

This systematic literature review sought to determine the effects of carotid atherosclerotic plaque on local arterial stiffness.

METHODS

MedLine, EMBASE, and grey literature were searched with the following term: ("atherosclerosis" or "carotid atherosclerosis" or "carotid artery disease" or "carotid plaque") AND ("distensibility" or "elasticity" or "stiffness" or "compliance") NOT ("pulse wave velocity" or "PWV" or "carotid-ankle" or "ankle-brachial" or "augmentation index" or "cardio-ankle" or "CAVI" or "flow mediated dilation" or "FMD"). Results were restricted to English language articles reporting local arterial stiffness in human subjects with carotid atherosclerosis.

RESULTS

Of the 1466 search results, 1085 abstracts were screened and 191 full-text articles were reviewed for relevance. The results of the 50 studies that assessed some measure of carotid arterial elasticity or stiffness in patients with carotid plaque were synthesized and reviewed.

DISCUSSION

A number of different measures of carotid elasticity were found in the literature. Regardless of which metric was used, the majority of studies found increased carotid stiffness (or decreased distensibility) to be associated with carotid plaque presence, the degree of atherosclerosis, and incident stroke.

CONCLUSION

Carotid artery mechanics are influenced by the presence of atherosclerotic plaque. The clinical applicability of carotid elasticity measures may be limited by the lack of reference values and standardized techniques.

The effect of diabetes self-management education on body weight, glycemic control, and other metabolic markers in patients with type 2 diabetes mellitus

AIMS

To comprehensively evaluate the effect of a short-term diabetes self-management education (DSME) on metabolic markers and atherosclerotic parameters in patients with type 2 diabetes.

METHODS

76 patients with type 2 diabetes were recruited in this study. They were divided into the intervention group (n = 36) and control group (n = 40). The patients in the intervention group received a 3-month intervention, including an 8-week education on self-management of diabetes mellitus and subsequent 4 weeks of practice of the self-management guidelines. The patients in the control group received standard advice on medical nutrition therapy. Metabolic markers, carotid intima-media thickness (CIMT), and carotid arterial stiffness (CAS) of the patients in both groups were assessed before and after the 3-month intervention.

RESULTS

There was a significant reduction in hemoglobin A1c (HbA1c, -0.2 ± 0.56% versus 0.08 ± 0.741%; P < 0.05) and body weight (-1.19 ± 1.39 kg versus -0.61 ± 2.04 kg; P < 0.05) in the intervention group as compared to the control group. However, no significant improvements were found in other metabolic markers, CIMT and CAS (P > 0.05).

CONCLUSIONS

DSME can improve HbA1c and body weight in patients with type 2 diabetes.

Cumulative effects of hypertension, dyslipidemia, and chronic kidney disease on carotid atherosclerosis in Chinese patients with type 2 diabetes mellitus

AIMS. The aim of this study is to determine the extent of carotid atherosclerosis in Chinese patients with type 2 diabetes in relation to the cumulative atherosclerosis risk factors using ultrasonography. METHODS. The presence of hypertension, dyslipidemia, and chronic kidney disease (CKD) was documented in 106 Chinese subjects with type 2 diabetes. Subjects with 0, 1, and ≥2 additional atherosclerosis risk factors were assigned into groups 1, 2, and 3, respectively (n = 17, 49, and 40, resp.). Using ultrasound, the carotid arteries were assessed for the presence of carotid plaque, plaque score, intima-media thickness (IMT), and carotid arterial stiffness. RESULTS. With the adjustment for age and gender, the presence of plaque and plaque score were significantly higher in groups with more atherosclerosis risk factors (P < 0.05). In addition, age > 60 years old (odds ratio = 2.75; 95% CI: 1.26-6.0) and the presence of hypertension (odds ratio = 2.48; 95% CI: 1.11-5.58), dyslipidemia (odds ratio = 2.41; 95% CI: 1.05-5.51), and CKD (odds ratio = 7.80; 95% CI: 1.46-41.72) could independently predict higher plaque score (P < 0.05). CONCLUSIONS. Hypertension, dyslipidemia, and CKD in Chinese patients with type 2 diabetes have cumulative effects on the burden of carotid plaque.

Differences of aortic stiffness and aortic intima-media thickness according to the type of initial presentation in patients with ischemic stroke

BACKGROUND

Aortic stiffness and intima-media thickness (IMT) are known to be associated with ischemic stroke. The aim of the present study was to investigate the differences of aortic stiffness and IMT between cerebral infarction (CI) and transient ischemic attack (TIA).

METHODS

A total of 500 patients with acute stroke were divided into 2 groups: the TIA group (n = 230, 62.4 ± 12 years, 144 males) versus CI group (n = 270, 63.4 ± 11 years, 181 males). Aortic stiffness index and IMT, as well as conventional cardiovascular risk factors, were compared.

RESULTS

The prevalence of hypertension, diabetes, and dyslipidemia were significantly higher, and left atrial volume and E/E' were significantly elevated in the CI group than in the TIA group. Carotid IMT was significantly thicker in the CI group than in the TIA group. Aortic stiffness index β was significantly higher (7.99 ± 2.70 vs. 7.02 ± 4.30, p = 0.043) and aortic IMT was significantly thicker (1.53 ± 0.41 vs. 1.45 ± 0.39 mm, p = 0.040) in the CI group than in the TIA group. Aortic stiffness index β was significantly correlated with the IMT of the aorta (r = 0.279, p = 0.014), right (r = 412, p < 0.001) and left carotid artery (r = 441, p < 0.001).

CONCLUSION

Aortic stiffness index β and IMT were significantly higher in patients with CI than TIA. The result of the present study suggested that CI is associated with more advanced degree of atherosclerotic and arteriosclerotic process than TIA.

The relationship between aortic stiffness and changes in retinal microvessels among Asian ischemic stroke patients

Large-artery stiffness is a risk factor for stroke, including cerebral small-vessel disease. Retinal microvascular changes are thought to mirror those in cerebral microvessels. We investigated the relationship between aortic stiffness and retinal microvascular changes in Asian ischemic stroke patients. We studied 145 acute ischemic stroke patients in Singapore who had aortic stiffness measurements using carotid-femoral pulse wave velocity (cPWV). Retinal photographs were assessed for retinal microvessel caliber and qualitative signs of focal arteriolar narrowing, arteriovenous nicking and enhanced arteriolar light reflex. Aortic stiffening was associated with retinal arteriolar changes. Retinal arteriolar caliber decreased with increasing cPWV (r=-0.207, P=0.014). After adjusting for age, gender, hypertension, diabetes, mean arterial pressure and small-vessel stroke subtype, patients within the highest cPWV quartile were more likely to have generalized retinal arteriolar narrowing defined as lowest caliber tertile (odds ratio (OR) 6.84, 95% confidence interval (CI) 1.45-32.30), focal arteriolar narrowing (OR 13.85, CI 1.82-105.67), arteriovenous nicking (OR 5.08, CI 1.12-23.00) and enhanced arteriolar light reflex (OR 3.83, CI 0.89-16.48), compared with those within the lowest quartile. In ischemic stroke patients, aortic stiffening is associated with retinal arteriolar luminal narrowing as well as features of retinal arteriolosclerosis.

Effect of hyper- and hypocapnia on cerebral arterial compliance in normal subjects

BACKGROUND

Changes in partial pressure of carbon dioxide (PaCO2) are associated with a decrease in cerebral blood flow (CBF) during hypocapnia and an increase in CBF during hypercapnia. However, the effects of changes in PaCO2 on cerebral arterial compliance (Ca) are unknown.

METHODS

We assessed the changes in Ca in 20 normal subjects using monitoring of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). Cerebral arterial blood volume (CaBV) was extracted from CBFV. Ca was defined as the ratio between the pulse amplitudes of CaBV (AMPCaBV ) and ABP (AMPABP). All parameters were recorded during normo-, hyper-, and hypocapnia.

RESULTS

During hypocapnia, Ca was significantly lower than during normocapnia (.10±.04 vs. .17±.06; P<.001) secondary to a decrease in AMPCaBV (1.3±.4 vs. 1.9±.5; P<.001) and a concomitant increase in AMPABP (13.8±3.4 vs. 11.6±1.7 mmHg; P<.001). During hypercapnia, there was no change in Ca compared with normocapnia. Ca was inversely correlated with the cerebrovascular resistance during hypo- (R2=0.86; P<.001), and hypercapnia (R2=0.61; P<.001).

CONCLUSION

Using a new mathematical model, we have described a reduction of Ca during hypocapnia. Further studies are needed to determine whether Ca may be an independent predictor of outcome in pathological conditions.

A Virtual Instrument for Automated Measurement of Arterial Compliance

Measurement of arterial distensibility is very important in cardiovascular diagnosis for early detection of coronary heart disease and possible prediction of future cardiac events. Conventionally, B-mode ultrasound imaging systems have been used along with expensive vessel wall tracking systems for estimation of arterial distension and calculation of various estimates of compliance. We present a simple instrument for noninvasive in vivo evaluation of arterial compliance using a single element ultrasound transducer. The measurement methodology is initially validated using a proof of concept pilot experiment using a commercial ultrasound pulser-receiver. A prototype system is then developed around a PXI chassis using LABVIEW software. The virtual instrument employs a dynamic threshold algorithm to identify the artery walls and then utilizes a correlation based tracking technique to estimate arterial distension. The end-diastolic echo signals are averaged to reduce error in the automated diameter measurement process. The instrument allows automated measurement of the various measures of arterial compliance with minimal operator intervention. The performance of the virtual instrument was first analyzed using simulated data sets to establish the maximum measurement accuracy achievable under different input signal to noise ratio (SNR) levels. The system could measure distension with accuracy better than 10 μm for positive SNR. The measurement error in diameter was less than 1%. The system was then thoroughly evaluated by the experiments conducted on phantom models of the carotid artery and the accuracy and resolution were found to meet the requirements of the application. Measurements performed on human volunteers indicate that the instrument can measure arterial distension with a precision better than 5%. The end-diastolic arterial diameter can be measured with a precision better than 2% and an accuracy of 1%. The measurement system could lead to the development of small, portable, and inexpensive equipment for estimation of arterial compliance suitable in mass screening of “at risk” patients. The automated compliance measurement algorithm implemented in the instrument requires minimal operator input. The instrument could pave the way for dedicated systems for arterial compliance evaluation targeted at the general medical practitioner who has little or no expertise in vascular ultrasonography.

Metabolic syndrome increases carotid artery stiffness: the Northern Manhattan Study

BACKGROUND

Arterial stiffness, an intermediate pre-clinical marker of atherosclerosis, has been associated with an increased risk of stroke and cardiovascular disease. The metabolic syndrome and its components are established cardiovascular disease risk factors and may also increase arterial stiffness; however, data regarding this are limited.

AIM

The goal of this study was to determine the association between the metabolic syndrome and carotid artery stiffness in an elderly multi-ethnic cohort.

METHODS

Carotid artery stiffness was assessed by carotid ultrasound as part of the Northern Manhattan Study, a prospective population-based cohort of stroke-free individuals. Carotid artery stiffness was calculated as [ln(systolic BP/diastolic BP)/strain], where strain was [(systolic diameter-diastolic diameter)/diastolic diameter]. Metabolic syndrome was defined by the National Cholesterol Education Program: Adult Treatment Panel III criteria. LogSTIFF was analysed as the dependent variable in linear regression models, adjusting for demographics, education, current smoking, presence of carotid plaque and intima-media thickness.

RESULTS

Carotid artery stiffness was analysed in 1133 Northern Manhattan Study subjects (mean age 65 +/- 9 years; 61% women; 58% Hispanic, 22% Black and 20% Caucasian). The prevalence of the metabolic syndrome was 49%. The mean LogSTIFF was 2.01 +/- 0.61 among those with the metabolic syndrome and 1.90 +/- 0.59 among those without the metabolic syndrome (P=0.003). The metabolic syndrome was significantly associated with increased logSTIFF in the final adjusted model (parameter estimate beta=0.100, P=0.01). Among individual metabolic syndrome components, waist circumference and elevated blood pressure were most significantly associated with a mean increase in logSTIFF (P<0.01).

CONCLUSION

The metabolic syndrome is significantly associated with increased carotid artery stiffness in a multiethnic population. Increased carotid artery stiffness may, in part, explain a high risk of stroke among individuals with the metabolic syndrome.

Relationship between carotid artery stiffness index, BNP and high-sensitivity CRP

Arterial stiffness is an independent predictor of cardiovascular morbidity and mortality. Brain natriuretic peptide (BNP) and high-sensitivity C-reactive protein (hs-CRP) are considered as novel biomarkers that are useful in the prediction of early cardiovascular risk. We studied the relationship between carotid artery stiffness index beta and the cardiovascular biomarkers BNP and hs-CRP in 55 consecutive subjects. Carotid artery stiffness was assessed using the stiffness index beta derived from brachial artery blood pressure measurement and carotid ultrasonography. Venous blood samples were obtained for BNP and hs-CRP. Pearson's correlation coefficient suggested a strong bivariate relationship between carotid stiffness index beta and age (r=0.56, P<0.0001), BNP (r=0.45, P<0.004) and hs-CRP (r=0.26, P=0.06), respectively. On multiple regression analysis, significant correlations were found between carotid stiffness index beta and age (P=0.004), BNP (P=0.027) and hs-CRP (P=0.029). These findings suggest that there is a relationship between intra-cardiac pressures (measured by BNP), vascular inflammation (measured by hs-CRP) and vascular stiffness. Cardiovascular biomarkers are thus associated with functional parameters of the vascular tree.

Carotid artery distensibility: a reliability study

OBJECTIVE

Carotid distensibility (CD) is a measure of carotid artery elasticity that has been introduced as a risk factor for cardiovascular disease. Information regarding reproducibility of sonographic CD measures is limited. The objective of this study was to evaluate the inter-reader reliability of sonographic measurements of common carotid artery (CCA) diameters and derived metrics of CD.

METHODS

Two independent readers (R1 and R2) measured the systolic diameter (SD) and diastolic diameter (DD) for the right CCA from the B/M-mode sonographic registrations among 118 subjects. The derived CD metrics (strain, elastic modulus [E], stiffness [beta], and CD) were calculated. The inter-reader type 3 intraclass correlation coefficients (ICC3,1) for carotid diameters were calculated.

RESULTS

The mean SDs +/- standard deviation were 7.15 +/- 1.43 mm for R1 and 7.24 +/- 1.43 mm for R2. The mean DDs were 6.71 +/- 1.36 mm for R1 and 6.68 +/- 1.41 mm for R2. The mean differences of SD and DD between R1 and R2 were 0.08 +/- 0.40 mm (paired t test, P = .04) and 0.03 +/- 0.43 mm (paired t test, P = .46), respectively. Inter-reader type 3 intraclass correlation coefficients were 0.96 for SD and 0.95 for DD. We observed a significant association of demographics with carotid diameters but not with derived CD metrics or risk factors.

CONCLUSIONS

Our results suggest good reproducibility of CCA diameters measured with B/M-mode sonography. However, very small changes in linear measurements of carotid diameters can have big effects on estimates of arterial mechanical properties such as strain and Young's modulus. The standard boundary identification methods may not be precise and reproducible enough for use in a clinical setting.

Arterial stiffness and cardiovascular outcome

1. Studies have reported an association between arterial function indices and cardiovascular risk factors, as well as the risk of incident cardiovascular events, including coronary heart disease and stroke. 2. The data are overwhelmingly in favour of an independent role for aortic pulse wave velocity in predicting fatal and non-fatal cardiovascular events in healthy and diseased populations and in the evaluation of cardiovascular risk. 3. Augmentation index may independently predict all-cause mortality and cardiovascular events in coronary and end-stage renal disease patients, but some outcome studies have questioned its usefulness in hypertensive subjects and dialysis patients. 4. Systemic arterial compliance, to this time, has not been shown to independently predict cardiovascular outcome. 5. Future cardiovascular risk is greatly modified by prior disease and risk factors; the greatest additional value in measuring arterial stiffness and compliance may be in those with little or no end-organ disease.

Carotid arterial stiffness is marginally higher in the metabolic syndrome and markedly higher in type 2 diabetes mellitus in patients with manifestations of arterial disease

INTRODUCTION

Insulin resistance is generally considered to be of major importance in the pathophysiology of the metabolic syndrome and type 2 diabetes mellitus, both high-risk conditions for cardiovascular complications. Carotid artery stiffness is increasingly recognized as an important predictor of cardiovascular morbidity and mortality. Therefore, in the present study we determined whether the metabolic syndrome (MetSyn) and type 2 diabetes mellitus (DM2) are associated with carotid artery stiffness in patients with already clinical manifestations of arterial disease.

METHODS AND RESULTS

A cross-sectional study in 2105 patients with manifest arterial disease (cerebral, coronary or peripheral artery disease, renal artery stenosis or an aneurysm of the abdominal aorta) was performed. The difference in carotid stiffness between patients with and without MetSyn and with and without DM2 was studied with linear regression analysis. Compared to patients without DM2 (N=1112), patients with DM2 (N=301) had significantly higher arterial stiffness (distension -18.5 (-35.1;-1.9) 95% CI/distensibility -1.8 (-2.2;-1.4) 95% CI). Generally, there was a trend of higher carotid stiffness in patients with MetSyn (N=922) compared to patients without (N=1112) MetSyn (distension -9.6 (-21.5;2.3) 95% CI/distensibility -2.0 (-2.6;-1.4) 95% CI). Excluding the patients with also DM2 (N=230) from the MetSyn-group diminished this relation (distension -5.7 (-18.8;7.4) 95% CI/distensibility -1.1 (-1.6;-0.6) 95% CI). Furthermore, in the population as a whole, carotid artery stiffness increased with increasing number of components of the metabolic syndrome (p=0.08 for distension/p< or =0.001 for distensibility). In addition, this association was not as clear after exclusion of the patients with DM2 from the MetSyn-group (p=0.24 for distension/p<0.001 for distensibility). From all the components of the MetSyn only high blood pressure and high fasting glucose influenced the carotid artery stiffness.

CONCLUSIONS

We concluded that (increasing number of components of) the metabolic syndrome were associated with marginally higher carotid artery stiffness, while type 2 diabetes was associated with a marked increase in carotid artery stiffness, in patients with already clinical manifestations of arterial disease.

Evolving concepts regarding transient ischemic attacks

Transient ischemic attack (TIA) represents one end of the spectrum of focal brain ischemia, the other being completed infarction or ischemic stroke. The evolving technologic advancements in neuroimaging continue to change and sharpen the definition, epidemiology, and management of TIA. As a powerful risk factor for ischemic stroke, TIA deserves widespread public and physician education, urgent attention and investigation, and rapid management. The recognition and treatment of TIA provides an excellent opportunity for stroke prevention that is often missed or poorly recognized among physicians.