Effects of the collateral circulation of the heart

Collateral circulation minimizes the myocardial injury which results from narrowing of a coronary artery. A large collateral circulation has disadvantages, however. It may divert so much of the limited blood flow through the adjacent nonarteriosclerotic coronary artery that the blood supply of the normal muscle supplied by that artery may be inadequate during heavy exercise. In the presence of a large collateral circulation, both the normal and ischemic regions of the heart may be extremely vulnerable to small arteriosclerotic changes narrowing the patent artery near the aorta. The effective increase in flow which results from arteriolar vasodilatation produced by drugs may be much greater in the presence of a small collateral circulation than a large one.     

Dependence of a drop in blood pressure in pulmonary circulation and in the right heart on dosage of isosorbide dinitrate]

An effect of isosorbide dinitrate on blood pressure values in the pulmonary circulation and the right heart has been investigated in 25 patients with a history of the first transmural myocardial infarction. Group I including 12 patients has been given 5 mg isosorbide nitrate in a 60-minute intravenous infusion while group II of 13 patients has been given 10 mg of the drug in the same way. Both groups have been matched in clinical data and blood pressure value in the pulmonary circulation which has been normal. Pulmonary blood pressure has been measured with Swan-Ganz catheter prior to the administration of drug, and 15, 30, 45 and 60 minutes following an infusion. Isosorbide dinitrate in a dose of 5 mg did not decrease blood pressure in the pulmonary circulation statistically significantly. The differences in blood pressure falls did exceed 9%. Filling pressure in the right ventricle did not change either while systolic blood pressure decrease by 16.6%. A double dose of isosorbide dinitrate reduced blood pressure in the pulmonary artery by about 1/3 of the baseline value, and blood pressure in the right ventricle (mean right atrial pressure) by 57.2%. Both systolic and diastolic arterial pressures were reduced. Isosorbide dinitrate reduced blood pressure in the pulmonary circulation in patients who underwent myocardial infarction, and hypotensive effect has been dose-related. A reduction in the right ventricular filling pressure has been a one of important mechanisms decreasing pulmonary pressures.     

Development of medical control of man in conditions of +Gz accelerations at short-arm centrifuge

To develop a program of on-line medical monitoring of human subjects during rotation on a short-arm centrifuge (SAC), which is viewed as a promising method of providing artificial gravity, 153 runs were performed with participation of 17 subjects exposed to +Gz at 0.8, 1.2 and 1.6 G up to 40 minutes 3 times a day over a 3-d cycle. It was found that the on-line medical monitoring program for humans exposed to SAC +Gz loads should include recording of the system blood circulation and local circulation in head and leg vessels.     

Diabetogenic action of alloxan in short-term termination of the blood supply to the pancreas and spleen

It has been shown that the development of alloxan diabetes in rats and the appearance of diabetogenic factor in blood is caused by the direct alloxan action on pancreas and spleen--the organs supplying by blood through the spleen artery. The stopping of blood circulation in that artery preserves rat's organism from the development of general toxic effect of alloxan. The inactivation of alloxan as a diabetogenic agent has been shown after its 5-minute at 37 degrees C incubation with blood. It has been established that the half activity of intravenous injected alloxan disappears in rat's organism during 50 s. and does not depend on alloxan sensitivity of animals.     

Pulmonary haemodynamics during nasal apnoea in rabbits.

Changes in pulmonary haemodynamics, produced during stimulation of the nasal mucosa with xylol fumes, were found in experiments on anaesthetized rabbits. In spontaneously breathing animals, a decrease in the mean blood pressure in the pulmonary artery and an increase in the mean blood pressure in the left atrium occurred in addition to apnoea and bradycardia. Pulmonary vascular resistance fell significantly, whereas systemic vascular resistance rose. Changes in the pulmonary circulation during nasal stimulation in spontaneously breathing rabbits did not differ significantly from changes in artifically ventilated animals.     

Experimental analysis of pulsatile flow through elastic collapsible tubes: application to cardiac assist device

This study presents a simulated analysis of Phased Compression Cardiac Assist Device (PCCAD) and evaluation of its applicability as a non-invasive temporary assist for a failing heart. The new technique is based on the chest pump mechanism for blood flow augmentation during external massage by phased compression of the abdominal and thoracic cavities. A semi-closed hydraulic system to simulate the systemic circulation was constructed; the system includes a left ventricle which functions according to the Starling principle and a pneumatic system which controls the pressures applied to the thoracic and abdominal cavities, in complete synchronization with the beating normal or failing heart. The possibility of manipulating the three pumps in series (venous, heart, and arterial) has been checked, and the principal parameters which effect the efficiency of the PCCAD were evaluated. This in vitro analysis shows the high potential of a non-invasive temporary cardiac assist device. It points to the necessary measures one has to take in order to achieve good synchronization and to interfere externally with the augmentation of cardiac output or with the augmentation of root aortic pressure.     

离体血流循环切应力水平控制方法的研究

本文应用流体力学及血流动力学理论和分析方法,建立了离体心血管循环系统的切应力水平控制方法。并采用该方法研制可精确控制切应变水平的模拟在体血流动力学环境的层流流动装置,用于研究动力学因素对人工培养的内皮细胞生物学特性影响。     

Mathematical model of flow through the patent ductus arteriosus

The ductus arteriosus is one of several shunts in the cardiovascular system. It is a small vessel connecting the aortic arch and pulmonary artery that allows blood to bypass the pulmonary circulation. It is open during foetal development because the foetal lungs cannot function and oxygenation of the blood occurs by exchange with the maternal blood in the placenta. Normally it closes a few days after birth; however, in a small number of people closure does not occur, leading to a condition known as patent ductus arteriosus. In this paper our aim is to investigate the resulting cardiovascular effects. We develop a mathematical model of the haemodynamics in three different idealised geometries by assuming that the entry flow is irrotational and remains so in the core until at least the shunt position. We argue that separation or diffusion of vorticity into the core flow is delayed due to the high frequency associated with the pulsatile component of the flow profile. The analysis uses complex potential theory, Schwarz–Christoffel transformations, conformal mappings and Fourier series. The main results are based on the assumption that the flow in patients with patent ductus arteriosus is similar to the flow in healthy adults, and we apply this assumption using boundary conditions that are representative of physiological values in healthy adults. The model suggests that the pressures in the aorta and pulmonary artery are likely to equalise, that the shear stress increases near the edges of the shunt and that backflow of large volumes may occur from the pulmonary artery into the aorta or towards the ventricles due to the presence of the patent shunt. Our results strongly suggest that an abnormal compensatory physiology develops in patients with patent ductus arteriosus.     

The erythrocyte: aging of the cell and aging of the body

The factor analysis of the osmotic erythrocyte resistance involved 380 human subjects of both sexes aged from 20 to 106 years. It has been found that body aging is accompanied by a more marked aging of the blood cells during their circulation in the blood.     

CRIMSON: An open-source software framework for cardiovascular integrated modelling and simulation

In this work, we describe the CRIMSON (CardiovasculaR Integrated Modelling and SimulatiON) software environment. CRIMSON provides a powerful, customizable and user-friendly system for performing three-dimensional and reduced-order computational haemodynamics studies via a pipeline which involves: 1) segmenting vascular structures from medical images; 2) constructing analytic arterial and venous geometric models; 3) performing finite element mesh generation; 4) designing, and 5) applying boundary conditions; 6) running incompressible Navier-Stokes simulations of blood flow with fluid-structure interaction capabilities; and 7) post-processing and visualizing the results, including velocity, pressure and wall shear stress fields. A key aim of CRIMSON is to create a software environment that makes powerful computational haemodynamics tools accessible to a wide audience, including clinicians and students, both within our research laboratories and throughout the community. The overall philosophy is to leverage best-in-class open source standards for medical image processing, parallel flow computation, geometric solid modelling, data assimilation, and mesh generation. It is actively used by researchers in Europe, North and South America, Asia, and Australia. It has been applied to numerous clinical problems; we illustrate applications of CRIMSON to real-world problems using examples ranging from pre-operative surgical planning to medical device design optimization.     

The study of cerebral venous blood flow disturbance peculiarity in the norm and under the extravasal compression of brachiocephalic veins with the use of magnetic resonance venography and ultrasound duplex scanning

The MR-venography of the veins and brain venous sinuses, brachiocephalic veins an internal jugular veins duplex scanning have been performed in order to study the distinctions of cerebral venous hemodynamics of healthy people and the patients with venous encephalopathy caused by the extravasal compression of the brachiocephalic veins at the neck level and the superior sections of mediastinum. It has been revealed that the blood flow reducing in transverse brain sinuses occurs not only in the case of outflow disorder in the distal sections of the venous system, but also in norm. This reducing depends on anatomic constitution of confluens sinuum and the venous angle type of brachiocephalic veins. The three venous angle types of brachiocephalic veins have been distinguished: y-type, mu-type and Y-type. It has been registered that in case of the mu-type angle the blood flow can be reduced in norm due to peripheral resistance increase at the physiological bends of nearly a right angle type. The distinctions of hemodynamics in case of venous obstruction in contrast to arterial obstruction have been described. It has been registered that in case of outflow trouble in one of the internal jugular veins the speed and the volume of the blood flow in it are progressively reduced depending on the duration and the manifestation of compression. All this results in narrowing of the vein diameter from the affected side, and in compensatory distention of the diameter and increase of blood flow volume in the contralateral internal jugular vein, vertebral and external jugular veins, in succession.     

体外循环长时间转流535例临床估价

目的：介绍长时间体外循环管理的方法和经验。方法：我院自1984年至1995年12月共施行体外循环时间超过120分钟的心脏直视手术535例,其中男性345例,女性190例;年龄3～71岁．体表面积0．55～2．2平方米。双瓣替换术151例．二尖瓣替换术113例,法乐氏四联症107例,冠状动脉旁路移植术62例,主动脉瓣替换术30例．复杂畸形25例．其它47例。全组病例均采用中深度低温及中深度血液稀释,心肌保护采用灌注含钾冷停跳液。复跳后．适当延长辅助循环时间。术中采用血液超滤法,并尽可能采用搏动性血流,以确保重要脏器有充沛的血供。结果：全组病例中．体外循环时间为70～214分钟,心脏停跳时间72～230分钟。术中自动复跳209例．自动复跳率占39％。结论：在长时间体外循环心脏直视手术中．综合应用上述措施．可显著提高体外循环质量．增加手术成功率。     

The effects of a new xanthine derivative, 3,7-dimethyl-1(5-oxohexyl)-xanthin (pentoxifylline) on the general and cardiac haemodynamics of the intact animal.

A study has been made of the effects of xanthine derivative (pentoxifylline) upon the general and cardiac haemodynamics of intact anaesthetised dogs. The drug increased heart-rate, respiration rate, cardiac output and systemic pressure. It reduced mean pulmonary arterial pressure. Coronary flow was increased for only a few minutes, but coronary sinus O2 content increased throughout the study. Lactate and pyruvate values increased in both artery and coronary sinus, as did the cardiac extraction of these substances. Cardiac extraction of non-esterified fatty acid increased.     

Oxidative stress during ex vivo hemodialysis of blood is decreased by a novel hemolipodialysis procedure utilizing antioxidants

The high cardiovascular mortality in patients receiving hemodialysis (HD) has been attributed, in part, to oxidative stress. Here we examined the effectiveness of antioxidants introduced by means of a novel hemolipodialysis (HLD) procedure in terms of reducing oxidative stress during ex vivo blood circulation. Oxidative stress was studied in a model HD system resembling the extracorporeal circulation of blood during clinical HD. Blood circulation produced an increase of up to 280% in free hemoglobin levels and an increase of 320% in electronegative LDL (LDL(-)) subfraction. A significant correlation between LDL(-) and free hemoglobin levels confirmed previous findings that LDL(-) formation during ex vivo circulation of blood can be mediated by the oxidative activity of free hemoglobin. These effects were significantly attenuated during HLD using a dialysis circuit containing vitamin E with or without vitamin C. By contrast, HLD with vitamin C alone had a marked pro-oxidant effect. TBARS, lipid hydroperoxides, vitamin E and beta-carotene content in LDL were not significantly altered by the HD procedure. These findings demonstrate the occurrence of oxidative stress in human plasma where lipoproteins are a target and indicate antioxidant-HLD treatment as a specific new approach to decreasing the adverse oxidative stress frequently associated with cardiovascular complications in high-risk populations of uremic patients.     

Dopamine-beta-hydroxylase activity in plasma obtained from the pulmonary artery and left ventricle of man

Dopamine-β-hydroxylase activity (DBH) has been measured in plasma obtained simultaneously from the pulmonary artery and left ventricle of fourteen patients who underwent diagnostic cardiac catheterisation. In the majority of these subjects the levels of enzyme activity in the arterial and venous blood were similar, indicating that inactivation of DBH had not occurred in its passage through the pulmonary circulation. One patient with pulmonary hypertension had a large a-v difference in enzyme activity that may have been caused by altered pulmonary haemodynamics. Three of the five subjects that undertook a standardised exercise test on a bicycle ergometer showed a significant increase in plasma DBH activity. There was no correlation between the increases in DBH activity and in cardiac index and heart rate.     

Cephazolin and cephapirin circulation in the blood of rabbits

Circulation of 2 semi-synthetic cephalosporins, i. e. cephazoline and cephapyrine in the blood of rabbits after their intramuscular administration in single doses of 5 and 20 mg/kg was studied. It was found that the antibiotics were well adsorbed into the blood. Their maximum blood levels were achieved 15--30 minutes after administration. Cephazoline provided a higher blood level persisting for longer periods of time as compared to cephapyrine. The value of the time of the two-fold decrease in the cephazoline blood level was higher. A four-fold increase in the dose of the cephalosporines resulted in an increase in their blood levels but did not induce any significant increase in the time of their circulation.     

Cerebral responses to exercise and the influence of heat stress in human fatigue

There are a number of mechanisms thought to be responsible for the onset of fatigue during exercise-induced hyperthermia. A greater understanding of the way in which fatigue develops during exercise could be gleaned from the studies which have examined the maintenance of cerebral blood flow through the process of cerebral autoregulation. Given that cerebral blood flow is a measure of the cerebral haemodynamics, and might reflect a level of brain activation, it is useful to understand the implications of this response during exercise and in the development of fatigue. It is known that cerebral blood flow is significantly altered under certain conditions such as altitude and exacerbated during exercise induced – hyperthermia. In this brief review we consider the processes of cerebral autoregulation predominantly through the measurement of cerebral blood flow and contrast these responses between exercise undertaken in normothermic versus heat stress conditions in order to draw some conclusions about the role cerebral blood flow might play in determining fatigue.     

Doppler ultrasound signal analysis based on the TMS320 signal processor

Doppler ultrasound is an established method for the study of haemodynamics. Considerable improvement in accuracy and resolution can be achieved by utilizing advanced data processing techniques. Such a system has been developed and used to assess the cardiac component of the Baroreceptor Reflex in adults and to examine cerebral blood flow in neonates.     

Interrelations of hypocapnia, hypoxia, cerebral blood flow and electrical activity of the brain under voluntary hyperventilation in humans

Changes of different physiological parameters in human caused by hyperventilation of 3-min and longer duration were investigated and correlated. It was found that during 3-min hyperventilation, resulting in 4.5-5 fold increase of the respiration velocity, similar phasing changes of the central and cerebral haemodynamics occurred. The blood flow velocity according to the rheographic data during the hyperventilation first increases, reaching maximum at 1st - 2nd min of the test, and then decreases, reaching minimum at 2nd - 3rd min after it's end, and then slowly increases. Cerebral blood flow velocity during all the 3 min of the hyperventilation in most of the subjects keeps being increased, and after the test - decreased. At the same time transcutaneous pressure of carbon dioxide changes differently - decreases to minimum (approximately 25 mmHg) at the end of the test and then increases, reaching approximately 90% of the background level, at 5th min after the end of the test. Oxygen saturation of the blood during the test is found to be 98-100% and decreases to 90% at 5th min after it's end, which in overall with cerebral blood flow decrease appears to be the factor of the brain's hypoxia. In different subjects "mirror" changes of the EEG spectral power of different EEG ranges in relation to transcutaneous pressure of carbon dioxide dynamics were revealed by the hyperventilation. Taking into account the factors of duration or recurrence of the hyperventilation is important for the understanding the interrelations of cerebral haemodynamics, hypocapnia, hypoxia and electrical activity of the brain. It was found that after the recurrent hyperventilation of increasing amount (several times in hour by 3 min) cerebral blood flow might decrease markedly against the background of relatively small changes of electrical activity of the brain. The discussing of the data presented in the paper is carried out from the point of view of important role of tissue oxygen utilization mechanisms of the brain in adaptation to hypoxia and hypocapnia.     

A methodology for numerically analysing the hepatic artery haemodynamics during B-TACE: a proof of concept

Balloon-occluded transarterial chemoembolisation (B-TACE) is an intraarterial transcatheter treatment for liver cancer. In B-TACE, an artery-occluding microballoon catheter occludes an artery and promotes collateral circulation for drug delivery to tumours. This paper presents a methodology for analysing the haemodynamics during B-TACE, by combining zero-dimensional and three-dimensional modelling tools. As a proof of concept, we apply the methodology to a patient-specific hepatic artery geometry and analyse two catheter locations. Results show that the blood flow redistribution can be predicted in this proof-of-concept study, suggesting that this approach could potentially be used to optimise catheter location.