In recent years, great emphasis has been placed on the role of arterial stiffness in the development of cardiovascular diseases. Indeed, the assessment of arterial stiffness is increasingly used in the clinical assessment of patients. Although several papers have previously addressed the methodological issues concerning the various indices of arterial stiffness currently available, and their clinical applications, clinicians and researchers still report difficulties in selecting the most appropriate methodology for their specific use. This paper summarizes the proceedings of several meetings of the European Network for Non-invasive Investigation of Large Arteries and is aimed at providing an updated and practical overview of the most relevant methodological aspects and clinical applications in this area.

Expert consensus document on arterial stiffness: methodological issues and clinical applications

Expert consensus document on arterial stiffness : methodological issues and clinical applications. Commentary

The Rotterdam study

http://yael-nissan.weebly.com/uploads/5/2/9/2/5292348/the_introduction_to_pain_an_integrative_review_-_millan.pdf

The induction of pain: an integrative review

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating, and categorizing indications for the evidence-based use of therapeutic apheresis in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the Committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Seventh Edition of the JCA Special Issue continues to maintain this methodology and rigor to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Seventh Edition, like its predecessor, has consistently applied the category and grading system definitions in the fact sheets. The general layout and concept of a fact sheet that was used since the fourth edition has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. The Seventh Edition discusses 87 fact sheets (14 new fact sheets since the Sixth Edition) for therapeutic apheresis diseases and medical conditions, with 179 indications, which are separately graded and categorized within the listed fact sheets. Several diseases that are Category IV which have been described in detail in previous editions and do not have significant new evidence since the last publication are summarized in a separate table. The Seventh Edition of the JCA Special Issue serves as a key resource that guides the utilization of therapeutic apheresis in the treatment of human disease. J. Clin. Apheresis 31:149-162, 2016. © 2016 Wiley Periodicals, Inc.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice—Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Sixth Special Issue

Objectives: It has been postulated that in the arterial system mean wall shear stress is maintained at a constant value. The present study was performed to investigate the level of wall shear stress in the common carotid artery (CCA) as function of age and possible interactions between diameter and storage capacity, defined as the absolute area change per heart beat, with mean wall shear stress. Methods : Wall shear stress (wall shear rate multiplied by whole blood viscosity) was assessed in the right CCA of 111 presumed healthy male ( n =56) and female ( n =55) volunteers, varying in age between 10 and 60 years. Wall shear rate was measured with a high resolution ultrasound system. Simultaneously, arterial diameter and storage capacity were determined. Whole blood viscosity was calculated from haematocrit, plasma viscosity and shear rate. Results : From the second to the sixth age decade peak wall shear stress was significantly higher in males than in females and decreased from 4.3 Pa to 2.6 Pa ( r =−0.56, p <0.001) in males and from 3.3 Pa to 2.5 Pa ( r =−0.54, p <0.001) in females. Mean wall shear stress tended to decrease from 1.5 Pa to 1.2 Pa ( r =−0.26, p =0.057) in males and decreased significantly from 1.3 Pa to 1.1 Pa ( r =−0.30, p =0.021) in females. No significant difference in mean wall shear stress was found between males and females in any age decade. The diameter of the CCA increased significantly in both males ( r =0.26, p <0.05) and females ( r =0.40, p <0.003). Storage capacity decreased significantly in both sexes (males: r =−0.63, p <0.001; females: r =−0.68, p <0.001). Conclusions : These observations suggest that the reduction in mean wall shear stress with age results from the concomitant increase in diameter in an attempt of the arterial system to limit the reduction in storage capacity of the arterial system with increasing age.

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Wall shear stress in the human common carotid artery as function of age and gender

Objective: Arterial distensibility (DC) and compliance (CC) are vessel wall properties of large arteries that can be measured non-invasively with a custom made vessel wall movement detector system (VWMDS). This study investigated the reproducibility of this device in 10 volunteers. Methods: To investigate intraobserver intrasession and intraobserver intersession variability, arterial diameter (D) and relative change in diameter during the heart cycle (ΔD/D) were measured in the elastic common carotid artery, and in the muscular femoral and brachial arteries. Interobserver intrasession variability was examined in common carotid artery by two observers, while interobserver variability on the same image was assessed for common carotid and femoral arteries. Variability was expressed as the coefficient of variation. Results: For common carotid artery, intraobserver intrasession variability was 7.9(SEM 1.6)% (ΔD/D), 4.5(1.1)% (D), 8.3(1.3)% (DC), and 9.1(2.6)% (CC), respectively. In femoral artery it was 12.4(2.2)% (ΔD/D), 2.7(0.6)% (D), 13.4(2.2)% (DC), and 12.5(2.1)% (CC). For brachial artery it was 13.4(2.8)% (ΔD/D). 2.5(0.5)% (D), 16.1(2.5)% (DC), and 15.6(2.6)% (CC). Intraobserver intersession variability was comparable to intraobserver intrasession variability for all vessels. Interobserver intrasession variability for common carotid artery was 11.3(2.6)% (ΔD/D) and 8.6(1.9)% (D), but was larger for DC and CC. Interobserver variability on the same image was <5% for common carotid and femoral arteries. Conclusions: In conclusion, the vessel wall movement detector system has a good technical reproducibility. Intraobserver intrasession and intersession variability are comparable, and are larger in muscular arteries. This might be due to a larger variation in tone of these arteries, which are under permanent neurohumoral control. Interobserver intrasession variability was larger than intraobserver variability and might be influenced by differences in observers' skill and spontaneous variation in vessel wall properties.

Cardiovascular Research 1994; 28 :610-614

Evaluation of reproducibility of a vessel wall movement detector system for assessment of large artery properties.

The distribution of blood platelets flowing in arterioles (21-35 microns) of the mesentery of anesthetized rabbits was studied using intravital fluorescence microscopy. Sites were selected without upstream branch points within at least 10 vessel diameters. The distribution was determined by counting in flashed video frames the number of platelets present in each of six equal segments across the vessel. Only platelets were counted that could be localized objectively within a thin optical section around the median plane of the vessel. It could be shown that differences in counting volume between the six segments were negligible. Because of the use of flashed pictures (flash duration less than 0.1 ms; interval 180 ms), the method is independent of differences in velocity over the cross-sectional area of the vessel. In all measurements (15 sites in 13 vessels in 10 animals) the distribution was nonuniform, the wall segments containing the highest platelet numbers. The general distribution as calculated from all measurements (total platelet number 6,571) and expressed in percentages was found to be 23.0, 14.6, 12.5, 12.1, 13.6, and 24.2.

Distribution of blood platelets flowing in arterioles

Reflex sympathetic dystrophy (RSD) is a pain syndrome that is characterised by autonomic, motor and sensory disturbances. The syndrome has often been associated with sympathetic dysfunction. Therefore, we investigated whether there are disturbances in the sympathetic function of skin microcirculation in the various clinical stages of RSD. Laser Doppler flowmetry (LDF) was used to obtain information about total (mainly thermoregulatory) skin blood flow (TSBF), since blood flow in arteriovenous anastomoses and subpapillary plexus, which are richly innervated by sympathetic nerve endings, contributes predominantly to the flow signal as obtained by LDF. Capillary microscopy was used to appraise whether the trophic changes, as observed in RSD, result from an impaired nutritive skin blood flow (NSBF). Transcutaneous oximetry (TCPO2) was employed as a measure of the oxygenation of superficial skin layers. Skin temperature (ST) was also determined. Patients were divided into 3 clinical stages: stage I in case of a chronic warmth sensation, stage II in case of an intermittent warmth and cold sensation, and stage III in case of a chronic cold sensation. As compared to controls: (1) TSBF was increased (P < 0.05) at stage I and decreased at stages II (P < 0.05) and III (P < 0.001), (2) NSBF was decreased at stages II (P < 0.05) and III (P < 0.001), (3) TCPO2 was not impaired at any stage, (4) ST was increased (P < 0.01) at stage I and decreased (P < 0.05) at stage III. The present study is the first to report an increase of TSBF at stage I of RSD, which may be caused by a decrease in efferent sympathetic nerve impulses. At stages II and III both TSBF and NSBF were decreased which may reflect increased sensitivity of skin microvessels to (circulating) catecholamines.

Reflex sympathetic dystrophy : evolution of microcirculatory disturbances in time

The axisymmetric model described represents myocardial tissue as a spongy anisotropic viscoelastic material. It includes torsion around the axis of symmetry of the ventricle, transmural variation of fiber angle, and redistribution of intracoronary blood in the myocardial wall. In simulations, end-systolic principal strains were equal to 0.45, -0.01, and -0.24 at two-thirds of the wall thickness from the epicardium and 0.26, 0.00, and -0.19 at one-third of the wall thickness from the epicardium. The direction of maximal shortening varied by less than 30 degrees from epicardium to endocardium, whereas fiber direction varied by greater than 100 degrees from epicardium to endocardium. During a normal cardiac cycle peak, equatorial intramyocardial pressure differed by less than 5% from peak intraventricular pressure. When redistribution of intracoronary blood in the ventricular wall was suppressed, peak equatorial intramyocardial pressure was found to exceed peak intraventricular pressure by greater than 30%. Simulated contraction of an unloaded left ventricle (left ventricular pressure = 0 kPa) produced similar magnitude for systolic intramyocardial pressures as the normal cardiac cycle. Transmural systolic fiber stress distribution was very sensitive to the chosen transmural fiber angle distribution.

R. S. Reneman

Papers

Wall shear stress in the human common carotid artery as function of age and gender

Evaluation of reproducibility of a vessel wall movement detector system for assessment of large artery properties.

Distribution of blood platelets flowing in arterioles

Reflex sympathetic dystrophy : evolution of microcirculatory disturbances in time

Porous medium finite element model of the beating left ventricle