A methodological study of arterial wall function using ultrasound technique

We aimed to establish reference values for three important properties of the arterial wall using a conventional ultrasound scanner. We measured: (1) intima–media thickness (IMT) of the carotid arteries with the internal trace function of the ultrasound system; (2) wall stiffness by pulsatile diameter changes in the right common carotid artery assessed by M-mode; and (3) endothelial function expressed as flow-mediated dilatation (FMD) of the brachial artery. IMT and wall stiffness measurements and reproducibility were compared with those obtained by external analysing systems. All variables were obtained in healthy subjects (n = 20), 29–53 years old. IMT increased with age (P<0·01). There was no difference in IMT between men and women. The inter-operator variability for measuring IMT was 6–9%. The same order of reproducibility was obtained with an external PC-based analysing system. Regarding wall stiffness, no correlation was found with age, nor any difference between men and women. A low intra-operator variability (CV < 10%) was found for measurements of wall stiffness with both M-mode and an external wall tracking system. FMD of the brachial artery diminished with age (P<0·01). There was a relation between FMD and brachial artery size (P<0·01) and, therefore, as men have larger arterial diameters (P<0·01), smaller FMD in men. We conclude that it is possible to characterize arterial wall function non-invasively in an adequately reproducible manner using a conventional ultrasound system in healthy middle-aged men and women.     

Evaluation of intima-media thickness and vascular elasticity of the common carotid artery in patients with isolated systolic hypertension using ultrasound radiofrequency-data technology

Background: Radiofrequency (RF) data technology is a newly developed method to evaluate vascular disease, especially subclinical atherosclerotic change. Data regarding predictors of intima‐media thickness (IMT) and vascular elasticity of the common carotid artery (CCA) in subjects with isolated systolic hypertension (ISH) using ultrasound RF‐data technology are scarce. Aims: We evaluated the change in IMT and vascular elasticity of the CCA in patients with ISH at an early phase using US RF‐data technology. Methods: Thirty‐nine patients with ISH and 41 age‐matched control subjects were the study population. The common carotid arterial systolic diameter (Ds), diastolic diameter (Dd), IMT, carotid distensibility (CD), local pulse wave velocity (PWVβ) and stiffness (β) were compared between the two groups, as were correlations between pulse pressure (PP) and parameters of vascular stiffness. Results: Common carotid arterial Ds, Dd, IMT, PWVβ and β increased whereas CD decreased more significantly in the ISH group than in age‐matched controls. The level of PP in the ISH group had significant positive correlations with PWVβ (r = 0·298, P<0·05) and β (r = 0·291, P<0·05), whereas significant correlations with CD were not observed. Conclusions: US RF‐data technology could be used to accurately and quantitatively evaluate increased IMT and decreased arterial elasticity of the CCA in patients with ISH compared with normal subjects.     

Influence of arterial wave reflection on carotid blood pressure and intima‐media thickness in older endurance trained men and women with pre‐hypertension

Increased carotid intima‐media thickness (IMT) with aging is a significant predictor of mortality. Older endurance trained (ET) individuals have lower carotid artery stiffness but similar carotid IMT when compared to sedentary (SED) age‐matched peers. The purpose of this study was to examine the contribution of arterial wave reflections to carotid hemodynamics and IMT in older ET and SED with pre‐hypertension. Subjects consisted of endurance‐trained master athletes and age‐matched sedentary controls (mean age 67 years). Carotid artery Beta‐stiffness index and IMT was assessed with ultrasonography. Carotid pressure and augmented pressure from wave reflections (obtained from pulse contour analysis) was measured with applanation tonometry. Carotid systolic blood pressure (SBP) and IMT were not different between groups (P>0·05). Carotid stiffness was significantly lower in ET versus SED (7·3 ± 0·8 versus 9·9 ± 0·6, P<0·05). Augmented pressure was significantly greater in ET versus SED (17·7 ± 1·6 versus 13·3 ± 1·5 mmHg, P<0·05). When adjusting for differences in resting heart rate, there were no group differences in augmented pressure. In conclusion, older ET persons with pre‐hypertension have reduced carotid artery stiffness, but similar carotid SBP and carotid IMT when compared to SED. The lack of change in carotid SBP and IMT in older ET may be related to the inability of chronic exercise training to reduce bradycardia‐related augmented pressure from wave reflections with aging.     

Interrelationships between indices of longitudinal movement of the common carotid artery wall and the conventional measures of subclinical arteriosclerosis

Our objective was to study the interrelationships between longitudinal movement of the wall of the common carotid artery and the conventional measures of arteriosclerosis in a large and well-characterized study population. Successful longitudinal movement analyses were performed on 292 subjects. The peak-to-peak and retrograde amplitudes of the longitudinal movement were directly correlated with carotid artery distensibility (r = 0·21, P<0·001 and r = 0·23, P<0·001, respectively) and inversely correlated with pulse wave velocity (r = −0·14, P<0·05 and r = −0·17, P<0·01, respectively). All longitudinal motion parameters were independent of brachial flow-mediated dilatation and intima-media thickness. Our findings indicate that arterial stiffening modulates longitudinal movement and, therefore, measurement of longitudinal movement can be of value in the assessment of vascular health.     

Conventional treatment after myocardial infarction in routine clinical practice results in regression of left common carotid intima‐media thickness

This study aimed to evaluate the effect of standard medical treatment on the progression of atherosclerosis after a myocardial infarction, in an ordinary clinical setting, by measuring the right and left common carotid intima‐media thickness (IMT). The first investigation took place 3–12 months after the index event; the second took place 3·3–8·2 years after the first. In both investigations, the right and left carotid arteries of 102 patients were examined with an ultrasound duplex scanner. Common carotid IMT and calculated cross‐sectional intima‐media area (cIMa) were measured on both sides. More than 90% of the patients were treated with aspirin, beta‐blockers and statins. In the first investigation, IMT and cIMa were significantly greater on the left side compared to the right (IMT: 0·83 ± 0·22 and 0·74 ± 0·18 mm, P<0·001; cIMa: 18·2 ± 5·2 and 16·3 ± 5·1 mm², P<0·001). In the second investigation, IMT on the left side was significantly reduced compared to the first investigation (0·79 ± 0·22 and 0·83 ± 0·22 mm, P<0·05) with a corresponding tendency towards a decrease in cIMa on the same side. In our study, conventional medical treatment after a myocardial infarction in ordinary clinical routines resulted in regression of the common carotid IMT on the left side. The significant side difference in IMT emphasizes the importance of where and how the carotid IMT is measured in studies using this surrogate end point.     

Effects of adrenaline on longitudinal arterial wall movements and resulting intramural shear strain: a first report

Using ultrasound we recently demonstrated that in central elastic arteries as well as in large muscular arteries in humans there is a distinct longitudinal displacement of the arterial wall during the cardiac cycle. Further, for the first time, we also demonstrated that the inner parts of the vessel wall, the intima‐media complex, in these vessels exhibit a larger longitudinal displacement than the outer part of the vessel wall, the adventitial region, introducing the presence of substantial shear strain, and thus shear stress within the vessel wall. The role of these unexplored phenomena is unknown. Here, in a first study on the longitudinal movements of the porcine common carotid artery, we show that administration of adrenaline (epinephrine) might have pronounced effects on the longitudinal displacement of the intima‐media complex. In this experiment the longitudinal displacement of the intima‐media complex increased >200% at the highest blood pressure levels as compared to baseline. Further, shear strain within the wall increased >250%; the longitudinal displacement of the adventitial region being smaller than that of the intima‐media complex. Thus, our results indicate that adrenaline can markedly influence the longitudinal displacement of the arterial wall and the resulting shear strain, and thus shear stress, within the arterial wall. This opens up a new field within cardiovascular research, revealing a previously unknown mechanism in the circulatory system. Further studies on larger materials are needed to confirm our findings and to elucidate the underlying mechanisms and the physiological, pathophysiological and clinical implications of this phenomenon.     

Computerized analysing system using the active contour in ultrasound measurement of carotid artery intima‐media thickness

Background and purpose B‐mode measurement of the carotid intima‐media (IM) thickness (T) based on manual tracing (MT) procedures are dependent on the subjectivity of the reader and the existing automatic tracing procedures often fail to detect the IM boundaries accurately. The purpose of this study was to compare the tracing results of the IM boundaries of the carotid wall with a new automatic identification (AI) procedure, based on an active contour model, and computer‐assisted manual tracing (MT). Methods The detection of the IM boundaries was performed with both procedures in 126 ultrasound images [63 each of the common carotid artery (CCA) and carotid bulb] along the far wall of the distal CCA and the carotid bulb. Intra‐ and inter‐reader variability for mean and maximum IMT with AI and MT and accuracy of identification of both IM boundaries were evaluated. Results Using MT the intra‐ and inter‐reader variability amounted to 0·01–0·03 and 0·03–0·07 mm, respectively. The variability was slightly higher in the carotid bulb than in the CCA. Using AI the variability was almost eliminated. Mean and maximum IMT were measured systematically lower by AI compared with MT in all regions by 0·01 mm. The accuracy of identification was similar for both IM boundaries, but lower in the carotid bulb region than in the CCA. Conclusions The new AI procedure identifies both IM boundaries in the region of the far wall of the CCA and carotid bulb with high precision, and eliminates most of the intra‐ and inter‐reader variability of the IMT measurement using MT.     

A Fully-Automatic Method to Segment the Carotid Artery Layers in Ultrasound Imaging: Application to Quantify the Compression-Decompression Pattern of the Intima-Media Complex During the Cardiac Cycle

The aim of this study was to introduce and evaluate a contour segmentation method to extract the interfaces of the intima–media complex in carotid B-mode ultrasound images. The method was applied to assess the temporal variation of intima–media thickness during the cardiac cycle. The main methodological contribution of the proposed approach is the introduction of an augmented dimension to process 2-D images in a 3-D space. The third dimension, which is added to the two spatial dimensions of the image, corresponds to the tentative local thickness of the intima–media complex. The method is based on a dynamic programming scheme that runs in a 3-D space generated with a shape-adapted filter bank. The optimal solution corresponds to a single medial axis representation that fully describes the two anatomical interfaces of the arterial wall. The method is fully automatic and does not require any input from the user. The method was trained on 60 subjects and validated on 184 other subjects from six different cohorts and four different medical centers. The arterial wall was successfully segmented in all analyzed images (average pixel size = 57 ± 20 μm), with average segmentation errors of 47 ± 70 μm for the lumen–intima interface, 55 ± 68 μm for the media–adventitia interface and 66 ± 90 μm for the intima–media thickness. The amplitude of the temporal variations in IMT during the cardiac cycle was significantly higher in the diseased population than in healthy volunteers (106 ± 48 vs. 86 ± 34 μm, p = 0.001). The introduced framework is a promising approach to investigate an emerging functional parameter of the arterial wall by assessing the cyclic compression–decompression pattern of the tissues.     

Predictors of the intima‐media thickness of carotid artery in asymptomatic newly detected severe hypercholesterolemic patients

Background: Data about predictors of intima‐media thickness (IMT) of common carotid artery (CCA) in asymptomatic subjects with newly detected severe hypercholesterolemia is scarce. Aim: This research is aimed at studying the predictors of the IMT of CCA among basic atherogenic risk biomarkers – lipid [total cholesterol (TC), triglycerides, high‐density lipoprotein cholesterol, low‐density lipoprotein (LDL) cholesterol, Apolipoprotein‐B, Apolipoprotein‐Ai, Apolipoprotein‐B/A₁ index] and non‐lipid, [asymmetric dimethylarginine (ADMA), total homocysteine, cell adhesion molecules] in asymptomatic subjects with newly detected severe hypercholesterolemia. Methods: Two hundred and fifty asymptomatic patients with severe, newly hypercholesterolemia and 200 controls were evaluated. Hypercholesterolemia was defined as TC > 7·5 mm and LDL cholesterol > 4·9 mm . The ADMA and cell adhesion molecules were determined by ELISA and total homocysteine by high‐performance liquid chromatography. Results: There was significant difference between the two groups in respect to all lipid biomarkers (P<0·001). Hypercholesterolemic patients had significantly higher level of ADMA, sVCAM‐1, sICAM‐1, IMT (P<0·001), whereas no significant difference was found between two groups with respect to total homocysteine, P‐selectin and E‐selectin (P>0·05). A strong positive correlation between IMT mean and age (r_xy = 0·714; P<0·001), Apolipoprotein‐B (r_xy = 0·706; r_xy < 0·001), Apolipoprotein‐B/A₁ (r_xy = 0·324; P<0·001), ADMA (r_xy = 0·603; P<0·001) was found. The subsequent linear and multiple regression analysis selected age and Apolipoprotein‐B as most significant factors in relation to IMT mean. Apolipoprotein‐B is a better factor for assessment of risk, as LDL cholesterol underestimates the risk in asymptomatic subjects with newly detected severe hypercholesterolemia, until more rapid and feasible methods for measurement of small and dense LDL are available.     

The echogenicity of the intima–media complex in the common carotid artery is related to insulin resistance measured by the hyperinsulinemic clamp in elderly men

The echogenicity of the intima–media complex (IM‐GSM) has recently been shown to be related to the echogenicity in carotid artery plaque and to predict cardiovascular (CV) mortality. The present study aims to evaluate the relationship between metabolic CV risk factors, with special emphasis on insulin resistance, and IM‐GSM in the carotid artery. Carotid artery ultrasound with grey‐scale median analysis of the intima–media complex, IM‐GSM, was performed in a population sample of 480 men aged 75 years. In these subjects, a euglycemic hyperinsulinemic clamp to investigate insulin resistance was performed together with measurements of conventional CV risk factors at the age of 70. The metabolic syndrome (MetS) was defined by the NCEP/ATPIII‐criteria. In univariate analysis, IM‐GSM in the common carotid artery was inversely correlated with the intima–media thickness (IMT), body mass index (BMI), waist/hip ratio, fasting glucose, serum triglycerides, low HDL cholesterol and insulin resistance at the clamp (r = ?0·24, P<0·001). In multiple regression analysis, only insulin resistance at the clamp and BMI were independently related to IM‐GSM. Subjects with the MetS (22%) showed a reduced IM‐GSM when compared to those without (64 ± 20 SD versus 68 ± 19, P<0·05). Because the echogenicity of the intima–media complex in the carotid artery is related to obesity and insulin resistance at clamp independently of IMT, this new vascular characteristic would serve as a marker of vascular alterations induced by insulin resistance and the MetS and has the advantage to be obtainable in almost all subjects.     

An Integrated Approach to Computer‐Based Automated Tracing and Its Validation for 200 Common Carotid Arterial Wall Ultrasound Images

Objective. Most of the algorithms for the segmentation of the common carotid artery (CCA) wall require human interaction to locate the vessel in the ultrasound image. The aim of this article is to show an accurate algorithm for the computer‐based automated tracing of the CCA in longitudinal B‐mode ultrasound images. Methods. Two hundred images (100 normal CCAs, 50 CCAs with an increased intima‐media thickness, 30 with fibrous plaques, and 20 with anechoic plaques) were processed to delineate the region of interest containing the CCA. The strategy is an integrated approach (carotid artery layer extraction using an integrated approach [CALEXia]) consisting of geometric feature extraction, line fitting, and classification. The output of the algorithm is the tracings of the proximal and distal adventitia layers. Performance of the algorithm was validated against human tracings considered the ground truth. Results. The mean distance errors ± SD using this integrated approach were 1.05 ± 1.04 pixels (0.07 ± 0.07 mm) for proximal or near adventitia and 2.68 ± 3.94 pixels (0.17 ± 0.24 mm) for distal or far adventitia. Sixteen of 200 images were not perfectly traced because of the presence of both plaques and blood backscattering. The computational cost ensures the possibility for near real‐time detection. Conclusions . Although the CALEXia algorithm automatically detects the CCA, it is also robust and validated over a large database. This can constitute a general basis for a completely automated segmentation procedure widely applicable to other anatomies.     

Fully Automated Dual‐Snake Formulation for Carotid Intima‐Media Thickness Measurement

Automated computer‐aided detection systems for measurement of the carotid intima‐media thickness (IMT) are becoming popular. These systems yield lumen‐intima (LI) and media‐adventitia (MA) borders. In this work, we developed and validated a novel and patented completely automated IMT measurement system called carotid measurement using dual snakes (CMUDS): a class of AtheroEdge system (Global Biomedical Technologies, Inc, Roseville, CA). CMUDS is modeled as a dual parametric system corresponding to LI and MA borders with initialization from the far adventitia layer. The novelty of CMUDS is the first‐order absolute moment–based external energy, which provides stable deformation. The dual snakes evolve simultaneously and are forced to maintain a regularized distance to prevent collapsing or bleeding. Two independent readers manually traced the LI/MA boundaries of a multi‐institutional, multi‐ethnic, and multi‐scanner database of 665 longitudinal images for performance evaluation. CMUDS was also benchmarked against a previously developed automated technique. CMUDS correctly processed 660 images (99.2% success). The differences between the CMUDS and two manual IMT measurements (mean ± SD) were 0.013 ± 0.216 and ?0.021 ± 0.197 mm, respectively. The corresponding figures of merit for CMUDS compared to reader tracings were 98.4% and 97.5%. Compared to the previous technique (IMT differences, 0.022 ± 0.276 and ?0.012 ± 0.266 mm), CMUDS improved accuracy (Wilcoxon P < 0.009) and variability (Fisher P < 10^?8). Among different resolution images from original equipment manufacturer ultrasound scanners, CMUDS performed best with high‐resolution images corresponding to 0.0789 mm/pixel. Accuracy in IMT measurement with the proposed automated CMUDS technique makes this system adaptable to large multi‐center studies, in which such an IMT measurement system would be very useful tool.     

Wall composition analysis of the human hepatic artery by intravascular ultrasound

Purpose  The purpose of this study was to elucidate the wall layer appearance of the human hepatic artery shown by intravascular ultrasound (IVUS). Methods  We evaluated the wall layer appearance of 57 human hepatic arteries from 36 cadavers. The thickness of the inner high-echoic layer and the second low-echoic layer of the arteries was measured by IVUS, and it was compared with that of the arterial intima and media, respectively. Results  The thickness of the inner high-echoic layer was 0.2 ± 0.1 mm and that of the second low-echoic layer was 0.4 ± 0.1 mm, on IVUS. However, the histological thickness of the intima was 120 ± 45 μm and that of the media was 258 ± 71 μm. The media of the hepatic artery correlated significantly with the second low-echoic layer on IVUS (r = 0.62, P < 0.01). The diameter of the vessels measured on IVUS correlated significantly with that of the histological specimens (r = 0.89, P < 0.01). Conclusion  From our results, the three layers of the hepatic artery detected with IVUS may correspond to the intima, media, and adventitia, respectively.     

速度向量成像技术评估吸烟大学生颈总动脉管壁运动的意义

目的探讨速度向量成像(VVI)技术评估吸烟大学生颈总动脉管壁运动的意义。方法选择在校吸烟大学生25名作为吸烟组,在校非吸烟大学生25名作为对照组,常规超声测量颈总动脉扩张期内径及内中膜厚度。应用VVI技术对这2组大学生颈总动脉前壁、前内侧壁、后内侧壁、后壁、后外侧壁、前外侧壁6个壁段的运动情况进行量化分析并进行比较。结果吸烟组与正常对照组颈总动脉内中膜厚度及内径比较差异均无统计学意义。吸烟组及对照组组内比较时,前壁、前内侧壁、后内侧壁、后壁、后外侧壁、前外侧壁6个壁段间的径向速度负向峰值(Pv)、切向应变正向峰值(Ps)、应变率正向峰值(Psr)、径向位移负向峰值(Pd)差异均无统计学意义。吸烟大学生颈总动脉前壁、前内侧壁、后内侧壁、后壁、后外侧壁、前外侧壁的Ps分别为(4.39±2.94)%、(4.64±3.06)%、(5.07±2.82)%、(4.62±2.58)%、(4.75±2.82)%、(4.49±2.64)%,Psr分别为(0.37±0.26)/s、(0.39±0.28)/s、(0.41±0.27)/s、(0.38±0.25)/s、(0.39±0.26)/s、(0.37±0.24)s,均低于对照组的(6.37±2.06)%、(6.20±1.85)%、(6.39±1.98)%、(6.71±3.54)%、(6.41±2.81)%、(6.35±2.16)%、(0.54±0.21)/s、(0.52±0.19)/s、(0.54±0.19)/s、(0.55±0.23)/s、(0.54±0.21)/s、(0.52±0.19)s,差异均有统计学意义(t=-3.687,P=0.000;t’=2.813,P=0.007;t’=2.499,P=0.015;t=3.098,P=0.003;t=2.749,P=0.007;t’=3.578,P=0.001;t=3.338,P=0.001;t’=2.493,P=0.015;t’=2.490,P=0.015;t=3.313,P=0.001;t=3.084,P=0.003;t’=3.230,P=0.002),而各壁段Pv、Pd与对照组比较差异无统计学意义。吸烟大学生颈总动脉前壁、前内侧壁、后内侧壁、后壁、前外侧壁的径向速度正向达峰时间标准差(Tv-SD)分别为(46±63)、(82±99)、(13±140)、(102±121)、(58±54)ms,切向应变负向达峰时间标准差(Ts-SD)分别为(25.8±47.4)、(29.6±61.5)、(9.2±14.7)、(1.1±22.8)、(10.2±16.6)ms,切向应变率负向达峰时间标准差(Tsr-SD)分别为(30.9±60.4)、(37.5±76.1)、(9.3±12.5)、(10.1±14.5)、(11.3±13.8)ms,均高于对照组的(18±23)、(30±42)、(54±77)、(48±64)、(34±42)、(8.3±29.8)、(4.0±7.7)、(2.6±4.8)、(1.9±2.8)、(10.2±19.2)、(8.3±28.6)、(4.1±8.2)、(2.8±4.8)、(2.2±3.0)、(3.9±4.9)ms,差异均有统计学意义(t’=-2.668,P=0.010;t’=-3.135,P=0.003;t’=-3.218,P=0.002;t’=-2.567,P=0.013;t’=-2.367,P=0.021;t’=-2.064,P=0.043;t’=-2.620,P=0.012;t’=-2.714,P=0.009;t’=-2.460,P=0.018;t’=-2.147,P=0.042;t’=-1.650,P=0.049;t’=-2.147,P=0.042;t’=-2.474,P=0.020;t’=-2.659,P=0.014;t’=-2.565,P=0.017),而各壁段径向位移正向达峰时间标准差(Td-SD)与对照组比较差异无统计学意义。结论在颈总动脉形态学指标发生改变之前,VVI技术可以通过对动脉管壁运动特性的分析更早地评价吸烟者颈总动脉病变情况。     

The effect of cholesterol lowering on carotid and femoral artery wall stiffness and thickness in patients with familial hypercholesterolaemia

BACKGROUND: Early in the process of atherosclerosis, changes in vessel wall stiffness and thickness may occur. The present study evaluates the effect of cholesterol reduction on artery wall stiffness and intima media thickness in patients with familial hypercholesterolaemia (FH). MATERIALS AND METHODS: Forty-five patients with familial hypercholesterolaemia (mean age 46+/-10 years) with untreated LDL cholesterol concentration > 9 mmol L(-1), were studied before and after one year of cholesterol lowering therapy with statins (simvastatin, atorvastatin 40-80 mg day(-1). The distensibility (DC in 10-3 kPa(-1) and compliance (CC in mm2. kPa(-1) of the common carotid artery (CCA) (right and left side) and common femoral artery (CFA) (right side) were determined by a wall track system (Pie Medical). The intima media thickness (IMT) (both right and left) of the CCA, bulb (BUL), internal carotid artery (ICA) and CFA were measured in mm by high-resolution ultrasound (Biosound). RESULTS: The mean concentration of total cholesterol (TC), LDL-cholesterol (LDL-C) and triglycerides (TG) were reduced significantly by 43%, 51% and 25%, respectively, whereas HDL-cholesterol (HDL-C) increased by 13% (P<0.001). In the CFA, the DC and CC increased significantly (DC from 7.9+/-3.0 to 9.1+/-3.7 in 10(-3) kPa(-1); CC 0.5+/-0.2-0.6+/-0.3 in mm2. kPa(-1), whereas the DC and CC did not change in the CCA. In contrast, the IMT of the CCA decreased significantly in both men and women whereas an IMT decrease was also seen in the BUL and ICA in premenopausal women. A LDL-cholesterol reduction of 44.8% and 45.4% was necessary to induce significant decreases in IMT and increases in DC and CC. CONCLUSIONS: One year of cholesterol lowering therapy in FH decreases the wall stiffness in the CFA and the arterial wall thickness in the CCA.     

Arterial tension time reflects subclinical atherosclerosis, arterial stiffness and stroke volume

Objective: To introduce and evaluate a new haemodynamic parameter known as arterial tension time (ATT) and study whether ATT is associated with traditional cardiovascular risk factors as well as with indices of arterial stiffness, cardiac pump function and subclinical atherosclerosis. Methods: Arterial tension time was measured from the whole‐body impedance cardiography (ICG) signal and defined as the time difference between the onset of arterial distension induced by stroke volume (SV) and maximal integrated arterial distension. As measures of subclinical atherosclerosis and arterial stiffness, carotid artery intima‐media thickness (IMT), Young’s elastic modulus (YEM), arterial stiffness index (ASI) and carotid artery compliance (CAC) were assessed with ultrasound in 336 Finnish adults (aged 46–76 years, 43·2% men) participating in the Health 2000 Survey. In addition, pulse wave velocity (PWV) and stroke volume index (SI), as indices of arterial stiffness and cardiac pump function, were assessed with ICG. Results: Arterial tension time was associated inversely with PWV, IMT, YEM and ASI (P<0·002 for all) and directly with SI and CAC (P<0·001 for both). Age, systolic blood pressure, diastolic blood pressure and fasting glucose were independent determinants of decreased ATT (P<0·04 for all). Moreover, accumulation of cardiovascular risk factors was associated with the decrease in ATT (P for trend <0·001). Conclusion: Decreased ATT was associated with increased arterial stiffness, increased subclinical atherosclerosis and decreased SV. Current results suggest that ATT provides simultaneous information on several aspects of cardiovascular structure and function and could possibly serve as a new integrated parameter for cardiovascular risk stratification.     

Arterial stiffness in relation to subclinical atherosclerosis

Background Increased arterial stiffness or arteriosclerosis, represents a physiological part of ageing. Atherosclerosis is a process that does not affect the arterial bed uniformly but has a variable local distribution and is frequently superimposed on stiffened vessels. We therefore addressed the question of whether any correlation exists between the general characteristics of arterial stiffness or wave reflection and subclinical atherosclerosis as assessed by carotid intima‐media thickness (IMT) in a sample of healthy subjects. Methods A total of 116 healthy subjects (mean age 55 years, 43 female) were evaluated. Arterial stiffness and wave reflection was assessed with the use of digital volume pulse analysis (DVP) and pulse wave analysis (PWA). Subclinical atherosclerosis was assessed by measurement of IMT. Results Stiffness Index (SI_DVP), the measure of general arterial stiffness correlated significantly with IMT (r = 0·37, P < 0·01). IMT correlated significantly with age (r = 0·5, P < 0·0001), waist to hip ratio (WHR) (r = 0·39, P < 0·0001) and mean blood pressure (BPmean) (r = 0·4, P < 0·0001). IMT did not correlate with measures of wave reflection. SI_DVP correlated significantly with age (r = 0·32, P < 0·005), WHR (r = 0·36, P < 0·0001), BPmean (r = 0·36, P < 0·0001) and measurements of wave reflection. However analysis of a model which included variables that significantly influenced SI_DVP and IMT, such as age, WHR and mean BP showed that arterial stiffness is not independently associated with subclinical atherosclerosis. Conclusions The indices of subclinical atherosclerosis, arterial stiffness and wave reflection, indicate different aspects of vascular status in otherwise healthy subjects     

Progressive Attenuation of the Longitudinal Kinetics in the Common Carotid Artery: Preliminary in Vivo Assessment

Longitudinal kinetics (LOKI) of the arterial wall consists of the shearing motion of the intima–media complex over the adventitia layer in the direction parallel to the blood flow during the cardiac cycle. The aim of this study was to investigate the local variability of LOKI amplitude along the length of the vessel. By use of a previously validated motion-estimation framework, 35 in vivo longitudinal B-mode ultrasound cine loops of healthy common carotid arteries were analyzed. Results indicated that LOKI amplitude is progressively attenuated along the length of the artery, as it is larger in regions located on the proximal side of the image (i.e., toward the heart) and smaller in regions located on the distal side of the image (i.e., toward the head), with an average attenuation coefficient of −2.5 ± 2.0%/mm. Reported for the first time in this study, this phenomenon is likely to be of great importance in improving understanding of atherosclerosis mechanisms, and has the potential to be a novel index of arterial stiffness.     

Reproducibility of contractile properties of the human paralysed and non‐paralysed quadriceps muscle

This study assessed the reproducibility of electrically evoked, isometric quadriceps contractile properties in eight people with spinal cord injury (SCI) and eight able‐bodied (AB) individuals. Over all, the pooled coefficients of variation (CV_ps) in the SCI group were significantly lower (ranging from 0·03 to 0·15) than in the AB group (ranging from 0·08 to 0·21) (P<0·05). Furthermore, in all subjects, the variability of force production increased as stimulation frequency decreased (P<0·01). In subjects with SCI, variables of contractile speed are clearly less reproducible than tetanic tension or resistance to fatigue. Contractile properties of quadriceps muscles of SCI subjects were significantly different from that of AB subjects. Muscles of people with SCI were less fatigue resistant (P<0·05) and produced force–frequency relationships that were shifted to the left, compared with AB controls (P<·01). In addition, fusion of force responses resulting from 10 Hz stimulation was reduced (P<·05) and speed of contraction (but not relaxation) was increased (P<0·05), indicating an increased contractile speed in paralysed muscles compared with non‐paralysed muscles. These results correspond with an expected predominance of fast glycolytic muscle fibres in paralysed muscles. It is concluded that quadriceps dynamometry is a useful technique to study muscle function in non‐paralysed as well as in paralysed muscles. Furthermore, these techniques can be reliably used, for example, to assess therapeutic interventions on paralysed muscles provided that expected differences in relative tetanic tension and fatigue resistance are larger than ～5% and differences in contractile speed are larger than ～15%.     

Intra-Observer Variability of Longitudinal Displacement and Intramural Shear Strain Measurements of the Arterial Wall Using Ultrasound Noninvasively in vivo

Using a recently developed high-resolution noninvasive ultrasonic method, we recently demonstrated that the intima-media complex of the common carotid artery show a bidirectional multiphasic longitudinal displacement of the same magnitude as the diameter change during the cardiac cycle. The longitudinal movement of the adventitial region was smaller, thus, we identified shear strain and, thus, shear stress, within the arterial wall. The aim of this study was to evaluate the intra-observer variability of measurement of the longitudinal displacement of the intima-media complex and the intramural shear strain of the common carotid artery in vivo using the new ultrasonic method. The evaluation was carried out by comparing two consecutive measurements on the common carotid artery of 20 healthy human subjects. According to the method of Bland Altman, we show that the systematic and random differences for the different phases of movement are acceptable in comparison to the measured displacement and no significant differences between the two measurements could be detected (p > 0.05 for all measured parameters). The coefficient of variation (CV) for measurement of the different phases of movement was ≤16%, including short-term physiologic variations. The higher variability in the measurement of the intramural shear strain (CV = 24%) has several explanations, which are discussed. In conclusion, this study shows that the present first ultrasonic method for high-resolution measurement of the longitudinal movement of the arterial wall is reliable and satisfactory for the further research of the longitudinal movement of the arterial wall in vivo. Further studies on the longitudinal movement of the arterial wall are important for developing an improved understanding of the physiology and the pathophysiology of the cardiovascular system. (E-mail: magnus.cinthio@elmat.lth.se)