Feasibility of longitudinal monitoring of atherosclerosis with pulse wave imaging in a swine model

Objective.Atherosclerosis is a vascular disease characterized by compositional and mechanical changes in the arterial walls that lead to a plaque buildup. Depending on its geometry and composition, a plaque can ruptured and cause stroke, ischemia or infarction. Pulse wave imaging (PWI) is an ultrasound-based technique developed to locally quantify the stiffness of arteries. This technique has shown promising results when applied to patients. The objective of this study is to assess the capability of PWI to monitor the disease progression in a swine model that mimics human pathology.Approach.The left common carotid of three hypercholesterolemic Wisconsin miniature swines, fed an atherogenic diet, was ligated. Ligated and contralateral carotids were imaged once a month over 9 months, at a high-frame-rate, with a 5-plane wave compounding sequence and a 5 MHz linear array. Each acquisition was repeated after probe repositioning to evaluate the reproducibility. Wall displacements were estimated from the beamformed RF-data and were arranged as spatiotemporal maps depicting the wave propagation. The pulse wave velocity (PWV) estimated by tracking the 50% upstroke of the wave was converted in compliance using the Bramwell-Hill model. At the termination of the experiment, the carotids were extracted for histology analysis.Main results.PWI was able to monitor the evolution of compliance in both carotids of the animals. Reproducibility was demonstrated as the difference of PWV between cardiac cycles was similar to the difference between acquisitions (9.04% versus 9.91%). The plaque components were similar to the ones usually observed in patients. Each animal presented a unique pattern of compliance progression, which was confirmed by the plaque composition observed histologically.Significance.This study provides important insights on the vascular wall stiffness progression in an atherosclerotic swine model. It therefore paves the way for a thorough longitudinal study that examines the role of stiffness in both the plaque formation and plaque progression.

Pulse Wave Imaging Coupled With Vector Flow Mapping: A Phantom, Simulation, and In Vivo Study

Pulse wave imaging (PWI) is an ultrasound imaging modality that estimates the wall stiffness of an imaged arterial segment by tracking the pulse wave propagation. The aim of the present study is to integrate PWI with vector flow imaging, enabling simultaneous and co-localized mapping of vessel wall mechanical properties and 2-D flow patterns. Two vector flow imaging techniques were implemented using the PWI acquisition sequence: 1) multiangle vector Doppler and 2) a cross-correlation-based vector flow imaging (CC VFI) method. The two vector flow imaging techniques were evaluated in vitro using a vessel phantom with an embedded plaque, along with spatially registered fluid structure interaction (FSI) simulations with the same geometry and inlet flow as the phantom setup. The flow magnitude and vector direction obtained through simulations and phantom experiments were compared in a prestenotic and stenotic segment of the phantom and at five different time frames. In most comparisons, CC VFI provided significantly lower bias or precision than the vector Doppler method ( ) indicating better performance. In addition, the proposed technique was applied to the carotid arteries of nonatherosclerotic subjects of different ages to investigate the relationship between PWI-derived compliance of the arterial wall and flow velocity in vivo. Spearman's rank-order test revealed positive correlation between compliance and peak flow velocity magnitude ( rs = 0.90 and ), while significantly lower compliance ( ) and lower peak flow velocity magnitude ( ) were determined in older (54-73 y.o.) compared with young (24-32 y.o.) subjects. Finally, initial feasibility was shown in an atherosclerotic common carotid artery in vivo. The proposed imaging modality successfully provided information on blood flow patterns and arterial wall stiffness and is expected to provide additional insight in studying carotid artery biomechanics, as well as aid in carotid artery disease diagnosis and monitoring.

Correlation between serum low-density lipoprotein cholesterol concentration and arterial wall stiffness

BACKGROUND

Elevated serum low-density lipoprotein cholesterol (LDL-C) concentration is a risk factor for atherosclerosis, which involves remodelling of the arterial walls with their subsequent stiffening.

AIM

We sought to evaluate the relationship between serum lipid levels and the elastic properties of the arterial wall.

METHODS

The study group comprised 315 men and women aged 55.84 ± 9.44 years. Serum glucose and lipid concentrations were determited. All subjects underwent blood pressure (BP) measurement, transthoracic echocardiography, and assessment of vascular compliance of large (C1) and small arteries (C2) using the HDI/Pulse Wave™ CR-2000 Research CardioVascular Profiling System (Hypertension Diagnostics Inc., Eagan, MN, USA). The subjects were divided into three groups: group I - LDL-C < 2.6 mmol/L, group II - LDL-C ≥ 2.6 mmol/L and < 4.0 mmol/L, and group III - LDL-C ≥ 4.0 mmol/L.

RESULTS

There were no intergroup differences with regard to smoking status (p = 0.56), serum glucose concentration (p = 0.13), body mass index (p = 0.96), systolic (p = 0.17) and diastolic BP (p = 0.29), or C1 (p = 0.09). However, C2 was higher in groups I and II than in group III (5.12 ± 2.57 vs. 5.18 ± 2.75 vs. 4.20 ± 1.58 mL/mmHg × 100, respectively, p < 0.01). Multivariate regression analysis negated the independent associations between C1 and serum lipid levels. In contrast, C2 was independently inversely associated with serum LDL-C concentration (r = -0.15, p < 0.01).

CONCLUSIONS

Higher serum LDL-C concentration seems to contribute independently to stiffening of small arterial vasculature in otherwise healthy adults. Screening for dyslipidaemia in the general population and its prompt treatment are highly recom-mended.

[Early Markers of Cardiovascular Risk in Women With Hereditary Burdening by Cardiovascular Diseases]

PURPOSE

to identify early markers of development of cardiovascular diseases (CVD) in women.

MATERIALS AND METHODS

Female firstdegree relatives from 39 families formed 2 groups: families (n=19) containing mothers with arterial hypertension (AH) (group 1) and healthy daughters (group 1a); families (n=20) containing practically heathy mothers (group 2) and healthy daughters (group 2a). We assessed data of anamnesis, including registration of cardiovascular risk factors, and family history of CVD. Examination included registration of anthropometric parameters, automatic and manual measurement of intima-media thickness (IMT) and resistance indexes of brachiocephalic arteries (BCA). We also determined cardio-ankle vascular index (CAVI), ankle-brachial index (ABI), and measured magnitude of β-adrenoreception of membranes (β-ARM) of erythrocytes in micro-quantities of venous blood.

RESULTS

Mothers in both groups of families had excessive body mass or obesity. Mothers of group 1 had more pronounced signs of abdominal obesity (AO). They also had abnormalities of IMT and sings of subclinical atherosclerosis of BCA. CAVI in this group was significantly higher than in group 2. In group 1a median BMI (25.5 kg/m2) and waist/hip ratio were significantly higher than in group 2a. Daughters of group 1a contrary to group 2a had abnormalities of vascular wall: increased automatically measured IMT of carotid arteries and elevated CAVI. Arterial pressure and heart rate (HR) in group 1a were within limits of physiological norm but significantly higher than in group 2a. All included women had elevated β-ARM values but in group 1a this parameter was significantly higher than in group 2a and moderately correlated with HR.

CONCLUSIONS

Risk factors of CVD development in women are AH, AO, high activity of the sympathoadrenal system. These factors provoke changes of vascular wall (elevation of its stiffness and early subclinical atherosclerosis). In daughters of mothers with AH important prognostic components of CVD risk in addition to family history of CVD are AO, systolic blood pressure (BP) >120 mm Hg, diastolic BP >78 mm Hg, HR approaching upper limit of physiological norm, and high CAVI (indicator of vascular wall stiffness).

[Endothelial dysfunction and arterial wall stiffness: New targets in diabetic nephropathy]

In recent years, one of the promising areas in clinical medicine is the study of impaired ments in endothelial function and arterial wall stiffness, which can be referred to as one of the important predictors of cardiovascular events in patients with chronic kidney disease, including that of diabetic etiology. There is strong evidence that endothelial function and great artery stiffness may be used as reliable clinical and instrumental indicators to evaluate the efficiency of therapeutic measures and the rate of progression of cardiovascular disorders in type 2 diabetes mellitus. The article presents data on the role of endothelial dysfunction and arterial wall stiffness in the progression of chronic kidney disease in type 2 diabetes mellitus and discusses the possibility of their correction with pharmacological agents.

Cardiac amyloidosis is associated with increased aortic stiffness

OBJECTIVE

Cardiac amyloidosis (CA) is as an infiltrative disorder primarily caused by extracellular tissue deposition of amyloid fibrils in the myocardial interstitium. The current study was designed to test whether alterations in ascending aortic elastic properties could be detected by echocardiography in CA patients, and to compare their results to controls.

PATIENTS AND METHODS

We included 19 CA patients from which CA proved to be AL amyloidosis in 17 cases and transthyretin (TTR) amyloidosis in 2 cases. Their results were compared to 20 age-, gender-, and risk factor-matched controls.

RESULTS

There was significantly greater interventricular septum and left ventricular (LV) posterior wall thickness, lower LV ejection fraction and greater E/A in CA patients than in controls, suggesting systolic, and diastolic dysfunction. CA patients also showed significantly reduced aortic strain and pulsatile change in aortic diameter, and increased aortic stiffness index.

CONCLUSION

These results suggest increased aortic stiffness in CA patients.

Premature atherosclerosis in systemic sclerosis patients: Its relation to disease parameters and to traditional risk factors

AIM

To detect premature atherosclerosis in systemic sclerosis (SSc) patients and its relation to disease parameters and traditional risk factors.

METHOD

This study included 40 SSc patients and 40 healthy age and sex matched controls. All patients were subjected to full history taking, clinical examination, relevant laboratory and radiological investigations. Doppler ultrasonography (US) of the common carotid was performed to measure intima-media thickness (ccIMT) and Doppler US of the brachial artery was performed to measure flow mediated dilatation (FMD).

RESULTS

The mean value of ccIMT was 0.59 ± 0.2 mm in SSc patients and 0.51 ± 0.09 mm in controls and the difference was significant (P = 0.03). A statistically significant difference was found in mean brachial artery diameter before and after hyperemia, in flow change and in FMD between SSc patients and controls. ccIMT showed significant positive correlation with age, C-reactive protein (CRP), cholesterol, triglycerides and low density lipoprotein (P < 0.05). FMD showed significant positive correlation with daily dose of steroids (P = 0.04). Brachial artery diameter after hyperemia showed significant negative correlation with erythrocyte sedimentation rate (ESR). Peak systolic velocity before ischemia showed significant positive correlation with body mass index (BMI) and significant negative correlation with insulin level.

CONCLUSION

Our findings confirm the presence of premature atherosclerosis in SSc patients assessed by significant impairment of FMD, flow change and ccIMT, and it is associated with traditional cardiovascular risk factors such as age, dyslipidemia and obesity (BMI) as well as with the use of steroids and markers of inflammation such as CRP and ESR.

Displacement and strain estimation for evaluation of arterial wall stiffness using a familial hypercholesterolemia swine model of atherosclerosis

PURPOSE

To track variations in the deformation of the arterial wall noninvasively by estimating the accumulated displacement and strain over a cardiac cycle may provide useful indicators of vascular health.

METHODS

In this paper, we propose an approach to track a region of interest (ROI) locally and estimate arterial stiffness variation in a familial hypercholesterolemic swine model of spontaneous atherosclerosis that allows for systematic and reproducible study of progression of the disease mechanism.

RESULTS

Strain and displacement indices may be derived from the variations of the accumulated displacement and accumulated strain (obtained from the gradient of the accumulated displacement) over a cardiac cycle to predict not only the likelihood of developing vascular diseases, but also the sites where they may occur. Currently, an ROI thickness value of less than one mm within the arterial wall is necessary for the axial accumulated displacement and strain to obtain reproducible estimates.

CONCLUSIONS

Accumulated axial displacement and strain estimation on the artery wall shown in this paper indicate the repeatability of these measurements over several cardiac cycles and over five familial hypercholesterolemic swine. Our results also demonstrate the need for a small region of interest within the arterial walls for accurate and robust estimates of arterial function.