Clinical Hemorheology and Microcirculation - Volume 2, issue 1-2
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Clinical Hemorheology and Microcirculation, a peer-reviewed international scientific journal, serves as an aid to understanding the flow properties of blood and the relationship to normal and abnormal physiology. The rapidly expanding science of hemorheology concerns blood, its components and the blood vessels with which blood interacts. It includes perihemorheology, i.e., the rheology of fluid and structures in the perivascular and interstitial spaces as well as the lymphatic system. The clinical aspects include pathogenesis, symptomatology and diagnostic methods, and the fields of prophylaxis and therapy in all branches of medicine and surgery, pharmacology and drug research.
The endeavour of the Editors-in-Chief and publishers of
Clinical Hemorheology and Microcirculation is to bring together contributions from those working in various fields related to blood flow all over the world. The editors of
Clinical Hemorheology and Microcirculation are from those countries in Europe, Asia, Australia and America where appreciable work in clinical hemorheology and microcirculation is being carried out. Each editor takes responsibility to decide on the acceptance of a manuscript. He is required to have the manuscript appraised by two referees and may be one of them himself. The executive editorial office, to which the manuscripts have been submitted, is responsible for rapid handling of the reviewing process.
Clinical Hemorheology and Microcirculation accepts original papers, brief communications, mini-reports and letters to the Editors-in-Chief. Review articles, providing general views and new insights into related subjects, are regularly invited by the Editors-in-Chief. Proceedings of international and national conferences on clinical hemorheology (in original form or as abstracts) complete the range of editorial features.
The following professionals and institutions will benefit most from subscribing to
Clinical Hemorheology and Microcirculation: medical practitioners in all fields including hematology, cardiology, geriatrics, angiology, surgery, obstetrics and gynecology, ophthalmology, otology, and neurology. Pharmacologists, clinical laboratories, blood transfusion centres, manufacturing firms producing diagnostic instruments, and the pharmaceutical industry will also benefit.
Important new topics will increasingly claim more pages of
Clinical Hemorheology and Microcirculation: the role of hemorheological and microcirculatory disturbances for epidemiology and prognosis, in particular regarding cardiovascular disorders, as well as its significance in the field of geriatrics. Authors and readers are invited to contact the editors for specific information or to make suggestions.
Abstract: Out of the various problems in relation to clinical hemorheology, three items have been chosen to give a brief review together with the author’s own work and idea. The first item is the Copley–Scott Blair phenomenon, i.e. the remarkable decrease of apparent viscosity of blood in a fibrin-coated capillary tube as compared with that in a glass tube. A new explanation of this phenomenon is given based on an electric double layer formed at the interface between the wall and blood. The second item is the wall surface effect on clotting of blood. Kaibara and Fukada observed a remarkable difference…between the clotting curves of blood in a glass test tube and that in a siliconized polyethylene tube. They attributed this effect to the difference of disruption of platelets between the glass surface and the siliconized surface. Our idea is that the collision frequency of a platelet with the wall surface will be explained by the total potential energy curve due to the presence of electric double layers. The third item refers to the electrical aspect of intravascular thrombus formation. The author’s idea is that the sticking of platelets to the endothelium and the aggregation of platelets may be explained by the intermembrane potential curve. The role of turbulence in thrombus formation may also be explained along this line of thought.
Abstract: The dynamic rigidity modulus G′ and loss modulus G″ of horse and bovine bloods were determined over a wide range of hematocrit at 1 Hz after imposing the steady shear of 66 sec−1 for 1 min. At hematocrits below about 80% the value of G′ for horse blood gradually decreased with time after the initial increase. The rate of decrease of G′ showed maxima at hematocrits around 25 and 55% respectively. At high hematocrits above 80% no time variation of G’ was observed. The values of G′ and G″ for bovine blood were much smaller than those for…horse blood. No time variation of G′ and G″ for bovine blood was observed at any hematocrits. These observations indicate that changes in G′ with time at hematocrits below 50% are mainly due to the formation of rouleaux network in blood and the subsequent formation of the nonhomogeneous assembly of rouleaux like a pattern of islands in sea. At hematocrits between 50 and 80%, the time variation of G′ reflect the change of the aggregation structure of closely packed red blood cells from nonequilibrium state to equilibrium one. At high homatocrits above 80%, G′ mainly reflect the deformability or stiffness of packed red blood cells rather than the interaction between red blood cells.
Abstract: The circulation is designed for oxygen and carbon dioxide transport by the blood. Red cells collect oxygen in the lungs and carry it to the capillaries of the heart, brain and other tissues where it is metabolised. Physiological studies show that oxygen supply may be blood flow limited, but the role of blood rheology is ill-defined. This report outlines a simple cardiovascular model in which available hemodynamic and rheological data are embodied. Steady state transport optimisation data are calculated for the poorly compensated circulation assuming various ratios between capillary and systemic blood hematocrit. Limitations are defined and capillary perfusion velocity…calculated for cardiac output-modulated flow through a typical bed at constant perfusion pressure. Oxygen tension profiles are predicted using the Krogh cylinder model. Tissue PO2 becomes a function of the systemic hematocrit and the capillary-systemic hematocrit ratio, being almost constant for hematocrits from 10–40% with a potentially lethal fall-off above about 50%.
Abstract: By means of transillumination (light pipe and microtransillumination) comparative analyses were carried out in geometry, topography and morphometry of microcirculation between the left atrial muscle and cerebral cortex of the cats using computer analysis. In addition, specific types of capillary distribution (symmetric parallel, symmetric antiparallel and asymmetric distribution) in these two organs was ascertained from images visualized on films. It was found that capillary diameter, intercapillary distance, total capillary length per tissue volume, total capillary surface area per tissue volume, total capillary volume fraction and capillary tortuosity differed significantly between the two organs. The left atrial muscle had a low…degree of capillary tortuosity and both symmetric and asymmetric distributions. The cerebral cortex had a high tortuosity and mostly asymmetric distribution. These parameters were organotypic and related to their roles in tissue oxygen supply.
Abstract: Pulsatile flow in arterial models with an axisymmetric or nonsymmetric stenosis was visualized to investigate the pattern of streamlines and the mode of vortex formation. In a model with an axisymmetric constriction, a decrease in the constriction ratio or a rise in the Reynolds number decreased the magnitude of the acceleration number, which was an index to the unsteadiness of the flow, and facilitated the repetitive shedding of vortex rings which in turn led to the generation of turbulence. The presence of an oscillatory component in flow velocity altered the pattern of steady flow around a non symmetric constriction, which…was characterized by a pair of standing vortices behind and a stationary horseshoe vortex in front of the obstacle. In pulsatile flow, nonsymmetric vortex rings were generated periodically behind the obstacle and shed down-stream in succession, and periodical changes also were observed in the position and width of the horseshoe vortex.
Abstract: In order to elucidate performance characteristics of a few prosthetic heart valves, the present in vitro study was carried out to investigate disturbances of flow past the prostheses. Measurements of pressure and velocity around, and visualization of flow across, the valves were made with three kinds of the valves attached to the entrance of a metacrylate model of the aorta. Comparison of the pressure drops caused by these valves with those by plate orifices revealed that the prostheses corresponded to the orifices, the opening area of which was approximately 45% of the cross-sectional area of the inlet section. The pressure…drop by the Björk-Shiley valve was smaller than the drops by the Kay-Suzuki and the SAM-MT valves. Highly turbulent flow taking place downstream of the valves seemed to be responsible for the energy loss induced by the valves. The structure of the turbulence was studied in association with the formation of thrombi and focal vascular lesions.
Abstract: Coagulation of blood is comparable to building a house. The plasmatic (fluid) phase of coagulation in the example of building includes any preparation until laying the foundation stone. Thereafter the proper phase of coagulation is the erection of the building itself. Thrombelastography and Resonance-Thrombography are the methods to measure the start and progress in raising a clot structure with elastic fibrin molecules and their condensation by platelets. Their parameter of measurement is clot elasticity, which in a wide range allows to differentiate the course of blood coagulation for diagnosis of hemorrhagic diseases as well as for the effect of clot-controlling…therapeutical and experimental measures. In the Thrombelastogram (TEG) fibrin elasticity and condensating effect of platelets cannot be differentiated, a fact which in a clinical laboratory for screening of hemorrhagic disorders represents some methodical limitation. Therefore the Resonace-Thrombography was developed, which with a simulation of flow. with a permanent “natural” strain on the growing fibrin structure by minimal orbital movement and with the utilization of a resonance effect for high sensitivity in measuring elasticity module is able to give additional informations. Especially platelet dysfunctions, dysfibrinogenemias as in liver diseases and in disseminated intravascular clotting as well as combined defects of the coagulation system including fibrinolysis may in the sense of screening by differentiation early and simply be diagnosed in the Resonance-Thrombogram (RTG).
Abstract: Role of antithrombin III (ATIII) and blood viscosity in development of thrombosis are investigated. A moderate decrease in levels of plasma ATIII before and after the development of acute myocardial infarction was observed. In cases of acute myocardial infarction, in whom concentrations of ATIII in plasma decreased markedly, thromboembolic episodes frequently developed. Levels of ATIII in plasma occasionally increased following oral anticoagulant therapy. From these results, it is suggested that ATIII in blood may be consumed in hypercoagulable states by reacting activated procoagulants formed in circulating blood. In observations in 437 autopsied cases with mean age of 77, acute myocardial…infarction seldom developed when sclerotic changes of coronary arteries remained mild. Incidence of myocardial infarction in cases with severe coronary sclerosis increased with elevation of hematocrits, measured on admission. It is suggested that, in cases of myocardial infarction with slight arteriosclerotic changes or very low hematocrit values, possibility of complication of DIC (disseminated intravascular coagulation) should be considered. Most remarkable decrease in levels of ATIII was observed in cases of DIC. Necessity of replacement therapy of ATIII is suggested, because of inefficacy of heparin therapy in patients with DIC, in whom levels of ATIII markedly decreased. Concentrations of ATIII in plasma were lower in younger females but higher in elderly ones than males with corresponding ages. Blood viscosity and hematocrit values were lower in women than in men in all decades of life over age 20. In elderly women, these may act beneficially for protecting them from thrombosis.
Abstract: Effects of artificially augmented membrane cholesterol on red cell functions (rheology and oxygen transport) were studied. As increasing the cholesterol content of human red cells by incubation with phospholipid vesicles containing cholesterol, the following dysfunctions were observed. 1) The decreased membrane fluidity as monitored by spin label motion. 2) The decreased deformability, due to hardening of lipid membrane. 3) The increased suspension viscosity, due to decreasing of deformability. 4) The retardation of oxygen release from red cells, inspite of constant oxygen affinity, due to the augmented oxygen diffusion barrier. In addition, the influence of cross-linked membrane proteins on membrane lipids…was de- scribed. The degrees of dysfunctions induced by excess membrane cholesterol were roughly quantified, and the phenomena were explained on the basis of molecular interaction of cholesterol in membrane.
Keywords: Cholesterol, red cell deformability, red cell functions, membrane fluidity, suspension viscosity, xygen release
Abstract: Intracardiac blood flow dynamics was visualized by a newly developed pulsed Doppler flowmeter combined with an electronic phased-array echocardiograph, which allowed to locate sample sites precisely in the heart and great vessels. Intracardiac blood flow revealed a specific flow pattern to each sample portion and particularly a laminar mode in outflow and inflow tract of the left ventiricle in healthy subjects. In the mitral regurgitations observed was the systolic regurgitant flow into the left atrium, while the diastolic regurgitant flow in the left ve.ntricular outflow tract was observed in the aortic regurgitation. The present study indicates that the pulsed Doppler…technique is effective in noninvasively analyzing the intracardiac flow dynamics in human hearts.
Abstract: The blood velocity field and sites of occurrence of early atheroma are considered in arterial bifurcations in man. Evidence is increasing that these lesions occur preferentially where wall shear stress is low. Mechanisms are examined which might account for this correlation and also the influence of wall shear stress on the permeability of the arterial intima to macromolecules. Hypertension seemingly favours the development of atheroma, but the focal occurrence of lesions is not readily explained in terms of the arterial blood pressure. A widely held view is that atheroma results from damage to the endothelium and increased influx of lipoprotein,…and interaction of platelets with the damaged wall leading to smooth muscle cell replication and migration. Exposed subendothelium is, however, rarely seen, except over advanced lesions and a theory appears necessary to account for the observed findings in the absence of endothelial damage. Recent studies suggest that the media may offer a barrier to the drainage of material from the subendothelial space to the adventitia and that the transport properties of the media may be influenced by arterial blood pressure and medial smooth muscle tone.
Keywords: Arterial fluid mechanics, atherogenesis, blood velocity field, early atheroma, wall shear stress, absence of endothelial damage
Abstract: Atherosclerotic lesions and thrombus formation occur preferentially around bifurcations, curved segments and stenoses where flow is likely disturbed and vortices may form. Hence we have studied the detailed flow patterns, and the effects of the associated fluid mechanical stresses existing at such sites on the aggregation and wall adhesion of corpuscles using microrheological techniques and a newly developed method for making large arteries and veins transparent. The annular vortex formed downstream of a model stenosis was found to provide favorable conditions for spontaneous aggregation and enhanced adhesion of platelets onto the vessel wall. Similar flow patterns were observed in the…pockets of venous valves where venous thrombi are suspected to originate. Formation of standing vortices was also found in dog aortas at each branching site and in the sinus of the human internal-external carotid artery bifurcation under physiological flow conditions.
Abstract: In order to understand blood circulation, knowledge of the rheological properties of blood is required. However, the characteristic parameters which must be considered differ according to the circulatory region investigated. A distinction must therefore be made between the macrorheological parameters (viscosity, viscoelasticity) and the microrheological parameters (aggregation, cell deform ability). As far as the microrheological parameters are concerned, red blood cell deformability is quite definitely the most important parameter in any physiophathological study of capillary circulation and the resulting exchanges. The main intrinsic parameters of R.B.C. deform ability are: – internal viscosity of the cell (concentration and physico-chemical…properties of hemoglobin) – surface/volume ratio. The surface of the membrane is 50% greater than that of a sphere with the same volume as the erythrocyte (90µm3 ); deformations at constant volume are therefore possible, – membrane properties related to the lipid bi-layer (changes in composition or structure) or to the cytoskeleton. Abnormal erythrocyte microrheology may result from alterations of anyone of these three parameters and would affect the ability of the cell to transit in capillaries. Disturbances of red blood cell deform ability are encountered in many clinical cases and mainly: – during anomalies relating to hemoglobin structure or its oxygen affinity – in constitutional deficiency of the memr.cane – during degenerative cardiovascular diseases or diseases which are considered to be atherosclerosis risk factors. The significance of the determinants of R. B.C. deformability in microcirculation and the clinical and pharmacological applications are discussed. internal viscosity of the cell (concentration and physico-chemical properties of hemoglobin) surface/volume ratio. The surface of the membrane is 50% greater than that of a sphere with the same volume as the erythrocyte (90µm3 ); deformations at constant volume are therefore possible, membrane properties related to the lipid bi-layer (changes in composition or structure) or to the cytoskeleton. during anomalies relating to hemoglobin structure or its oxygen affinity in constitutional deficiency of the memr.cane during degenerative cardiovascular diseases or diseases which are considered to be atherosclerosis risk factors.