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At least 19 recordsLinked to original sources
PubMed1990

[A realistic cardiovascular model for evaluating clinical applicability of duplex and color-Doppler equipment].

To evaluate the accuracy and reliability of colour-coded Doppler devices (CCDD) for practical use, a circulatory phantom with in vivo characteristics was developed. The experimental design consists of a piston-diaphragm metering pump with an adjustable piston volume and frequency of stroke as well as silicone tubings with different elasticity and diameters comparable with cadaver arteries. Depending on physiological conditions, blood as a circulating fluid and the surrounding soft tissues of the artery near the Doppler probe should be employed. The transducer should be manually guided. Thus, comparable to physiological frequency spectral displays, different types of wave forms (e.g. monophasic, triphasic) were initiated to analyze the reliability of CCDDs for practical use.

Blood Flow Velocity↗
PubMed1991

[CO2 angiography: studies of gas filling of vessels and assessing the factors of influence on the injection process with a cardiovascular model].

Following the advent of digital subtraction angiography (DSA), carbon dioxide gas has become a useful contrast agent for arterial angiography. Former manual injection methods had precluded accurate dosing and reproducibility. An original gas injector was therefore developed and tested in a circulatory system model. This permitted an accurate evaluation of vascular gas-filling. it also proved possible to measure the injection parameters taking different influencing factors into account. It was shown that vessels up to 10 mm in diameter are virtually completely filled with gas. In vessels larger than 10 mm in diameter, a residual fluid level remains, which in turn reduces the possibility for complete vessel imaging. The injection flow is dependent primarily on the vascular circulation rate, vessel diameter and the inclination of the vessel. With respect to other factors examined, neither catheter size, number of holes nor the direction of the injection have any relevant influence.

Angiography, Digital Subtraction↗
PubMed1991

A model of cardiovascular activation components for studies using autonomic receptor antagonists.

Alpha-adrenergic, beta-adrenergic, and cholinergic responses are often considered important activation components when conceptual and empirical analyses are made of single physiological variables and of patterns of cardiovascular reactivity; these autonomic distinctions are also of particular significance in autonomic blockade studies. A Model of Cardiovascular Activation Components is introduced that relates these components to both the measured cardiovascular variables and the protocol of autonomic blockade studies. It is pointed out that a restricted form of the complete model is often implicitly used in cardiovascular psychophysiology. The differential consequences of an erroneous employment of the restricted model are discussed for single and dual blockade protocols. Critical evaluations of autonomic blockade as a tool in cardiovascular psychophysiology are examined and are proposed to be often the consequence of the restricted model assumptions. Lastly, the utility of the Activation Components Model for a componential description of tasks and for componential intertask relationships is illustrated with data from the literature.

Arousal↗
PubMed1992

A modular mock circulation for hydromechanical studies on valves, stenoses, vascular grafts and cardiac assist devices.

P6vices for hydrodynamic simulation are required in a variety of studies such as device evaluation, cardiovascular modeling and for student training. Most studies today use different, incompatible circuits, which must be redesigned for every new application. To obtain a universal apparatus, a unitized system with standard connectors was developed. Three types of connectors were selected: 1" flange connectors, 1/2" tubing connectors and Luer-connectors with a 2 mm lumen. The complete system consists of reservoirs, throttles, valve holders, adapters for Doppler ultrasound probes, and converters to link these basic diameters. The apparatus can be driven by membrane, centrifugal and geared pumps. The system has successfully been used in echocardiographic studies of stenosis and valvular insufficiency, for pulse propagation in vascular grafts, and to test the hydraulic performance of cardiac assist devices. Flow rates between 0.1 and 30 l/min and pressure gradients up to 250 mmHg were achieved. In practical use, the system can be adapted to suit various investigations, with minimal expense. Standardization of the parts and connectors results in simple documentation and good reproducibility.

Blood Circulation↗
PubMed1979

Further observations on modelling of the cardiovascular function in the electrical model.

In 1976 the fourth type of the electrical model of the cardiovascular function was constructed, showing formal and electronic changes: inverting system, hysteresis comparator (for the valve function), simulation of the insufficiency and the stenosis of the valves. The analog values were established but they are not yet definitive. The important values are: pressure 100 mm Hg = 100mV; flow 100 ml/sec = 137 microA. The action of the heart is given by changing capacity; the contractility is characterized by systolic capacity (CS). The diastolic capacity (CD) is not yet variable (CD = 4,000 microF) and consequently the diastolic pressure is always near to zero. The pressure curves of the left ventricle and of the aorta of cardiac patients with aortic valve disease were simulated. For comparison purposes only two clinical records and electrical model simulation records are given in this paper. In the patients (only aortic stenosis is given here) left heart catheterization was carried out. A case of coronary heart disease is also shown. The curves (simulated) are satisfactory and reflect the events in the compression chamber. The values of the parameters, which were used in the stimulation, represent the analysis of the clinical curves and a functional characterization of the situation. Besides these simulations the effect of valve changes on the pressure in the left ventricle, aorta and large arteries was also studied. With the aim of extending the integrative view of the use of the electrical model, an attempt of comparing the time course of capacity changes and the time course of inner surface changes of the left ventricle was made. The cinecardioangiographic data, obtained in an invasive way, were used for the purpose of obtaining the inner surface of the left ventricle. From pressure and surface data the cardiac forces (isometric, average and also total force per minute) were calculated and compared with the normal state, taken from the literature. The total force per minute includes the sum of systolic durations per minute and characterizes the energy expenses of the heart. Further data must be obtained by different cardiographic techniques in order to obtain a solid basis for the use of indirect methods, where the electrical model would be helpful as a noninvasive integrative tool in the assessment of the cardiovascular function.

Adult↗
PubMed1990

Swine as a model for cardiovascular research: improved cardiopulmonary bypass techniques.

A large-animal model is essential for the assessment of functional parameters in cardiovascular surgical research. To date the canine model has been used successfully because of its availability and tolerance to cardiopulmonary bypass. However, because of decreased availability and increased cost, an alternative animal model is now needed. The swine model has been used in experimental cardiac procedures, but complications during cardiopulmonary bypass have presented a formidable challenge. These complications include enormous fluid shifts from the vascular bed, increased metabolic acidosis, and marked hemoglobinuria. To eliminate these deleterious complications within the swine model, a number of technical alterations were achieved. The priming solution used for the extracorporeal circuit was altered to consist of 1000 mL lactated Ringer's solution. 500 mL 20% mannitol, 500 mL 6% dextran in 5% detrose solution. 50 mEq sodium bicarbonate, and 10,000 IU heparin. The extracorporeal circuit employed the use of membrane oxygenation. Three different blood flow rates (150, 175, and 200 mL/kg min-1) were studied. We conclude that the optimum blood flow rate for cardiopulmonary bypass in swine is in the range of 175-200 mL/kg min-1. Membrane oxygenation results in less damage to blood during cardiopulmonary bypass. The asanguinous hyperosmolar priming solution is beneficial for cardiopulmonary bypass in swine to greatly reduce fluid shifts, prevent metabolic acidosis, and eliminate hemoglobinuria.

Acidosis↗
PubMed1990

[The marmoset in biomedical research. Value of this primate model for cardiovascular studies].

Because of its small size, low cost of maintenance, breeding capabilities in captivity, the marmoset, a New World monkey, appears well suited for clinical and fundamental investigations. The contribution of this laboratory animal in the main areas of biomedical research is succinctly described: viral oncology, infections diseases, immunology, reproduction, toxicology and teratology, odontology, behaviour and neuro-psychopathology. Emphasis is put upon the exceptional interest of the use of marmoset as a biological model in cardiovascular studies.

Angiotensinogen↗
PubMed1992

Theoretical analysis of the relationship between the ratio of ventricular systolic elastance to diastolic stiffness and stroke volume.

The maintenance of adequate blood circulation requires a sufficient ventricular contractility; in addition, to eject blood, the ventricles must first receive a sufficient volume, requiring a low diastolic stiffness. A simplified cardiovascular model was used to derive formulae for stroke volume (SV) as a function of atrial pressure and the ratio of ventricular end-systolic elastance to end-diastolic stiffness. A more complex cardiovascular model was used to assess the ability of the expressions to predict stroke volume under various steady-state conditions. The predicted SV correlated linearly with the model SV over a wide range of diastolic stiffnesses and systolic elastance. The formulae predict that with fixed right atrial pressure the SV is proportional to the ratio of end-systolic elastance to end-diastolic stiffness (GR) for the right ventricle, but relatively insensitive to the ratio (GL) for the left ventricle provided that GL is greater than GR. Model simulations confirmed this. When the right atrial pressure was not fixed increases in GR with fixed GL reduced the right atrial pressure with little change in SV. Similarly, varying GL with fixed GR produced little change in SV. The ratios highlight the importance of diastole to cardiac function.

Diastole↗
PubMed1992

Transgenic animal models of cardiovascular disease.

Transgenic experimentation has become a crucial part of hypertension and atherosclerosis research, and is growing more important in several other areas of cardiovascular disease. It has recently made a particular contribution to understanding the role of the renin-angiotensin system in controlling hypertension. The study of blood pressure regulation, cardiac hypertrophy, atherogenesis and thrombosis are also benefiting from the transgenic approach.

Animals↗
PubMed1992

Haemodynamic effects of a new dihydropyridine calcium entry blocker, S-12968-(-), in a rat model of cardiovascular calcium overload.

1. The haemodynamic effects of S-12968-(-), a new dihydropyridine calcium entry blocker (enantiomer of S-11568), were compared with those of the stereoisomer, S-12967-(+), nifedipine, and sodium nitroprusside. 2. A first experiment was performed in conscious, young male rats chronically implanted with femoral artery and vein cannula and repeated in rats previously treated with vitamin D3 and nicotine. Such treatment produces marked vascular calcium overload, especially of the compliance arteries, with no overt sign of toxicity as far as can be judged from the plasma profile. 3. In conscious rats the hypotensive effects of S-12968-(-), nifedipine and sodium nitroprusside were of similar potency. The falls in blood pressure produced by nifedipine and sodium nitroprusside were accompanied by reflex tachycardia which was less marked in the vascular calcium overload model. S-12968-(-) did not induce reflex tachycardia. S-12967-(+) increased blood pressure in both models. 4. A second experiment was performed in open-chest pentobarbitone-anaesthetized rats with electromagnetic flowprobes on the ascending aorta. In controls the falls in blood pressure produced by low doses (0.1 and 0.3 mg kg-1, i.v.) of S-12968-(-) were accompanied by falls in total peripheral resistance. The higher dose (1 mg kg-1, i.v.) of S-12968-(-) produced no change in total peripheral resistance, and in rats pretreated with vitamin D3 and nicotine, cardiac output fell. 5. In conclusion, S-12968-(-) appears to have a dual action and to lower blood pressure at higher doses at least in part by a cardiac effect. This phenomenon is more pronounced in rats pretreated with vitamin D3 and nicotine.6. S-12967-(+) resembles a calcium channel activator in this model.

Animals↗
PubMed1992

Swine models for cardiovascular research: a low stress transport and restraint system for large swine.

A restraint and transport system was developed for handling large swine during cardiovascular research studies. The major design criteria provided for comfortable, low stress restraint of the swine, safety for laboratory personnel and ability to perform a wide variety of hemodynamic and echocardiographic measurements in the standing, supported standing and sedated, or in Panepinto sling positions. A head gate is provided for venipuncture procedures, and an auxiliary feeding and watering front panel can replace the head gate for use of the system as a post-operative "recovery room". Using this system animals weighing 22 to 150 kg can be easily managed.

Animals↗