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Biomedical subjects

J Vasků

Publications and source records attributed to J Vasků.

At least 19 recordsLinked to original sources
PubMed1992

Biochemical and immunological studies in calves living over three months with a total artificial heart.

Changes in serum proteins, enzymes and isoenzymes of lactate dehydrogenase (LDH) were compared in long-term surviving calves with a total artificial heart without influencing their central venous pressure (CVP) and calves in which CVP was lowered by antihypertensive drugs administered from day 60 to the end of the experiment. Antihypertensive drugs helped keep CVP within physiological levels for longer and aided liver function as well as evidenced by the different values for the parameters studied in the two groups.

Animals↗
PubMed1992

The applicability of experimental experience with the total artificial heart to its clinical use.

Long-term experiments with the total artificial heart (TAH) are a source of valuable knowledge for later clinical application. Our observations result from 66 long-term experiments on calves and one goat ranging from 30 to 314 days, which have shown the main possible complications in the early period (one month) and later in the experiment. Problems until the second month of pumping concern the clinical pendant of the TAH as a bridge for transplantation, i.e. surgical problems, blood coagulation disorders, infection etc. Later problems are high venous pressure or arterial hypertension, infection with septic thromboembolization, mineralization of the driving diaphragm, etc., and are more closely comparable to the conditions of permanent clinical use of the TAH. Faultless surgery, device function and the regimen of pumping are essential factors in every long-term experiment, just as in clinical application. Infection is a threat throughout any experiment, as in clinical cases. The TNS-BRNO-VII/clin/80 TAH has been implanted in six patients.

Adult↗
PubMed1990

Mineralization of polyurethane membranes in the total artificial heart (TAH): a retrospective study from long-term animal experiments.

The degree of mineralization of TAH membranes in animals is directly related to the survival time of animals with a TAH. Large differences in mineralization of the membranes among individual animals have been observed. These differences can be explained by the simultaneous presence of infection on biomaterials (polyurethane) as well as by different levels of natural inhibitors of mineralization. No positive influence of applying sodium warfarin for the inhibition of the mineralization was observed.

Animals↗
PubMed1990

Development of the adrenergic innervation in the myocardium and coronary arteries of the dog.

The development of the adrenergic cardiac innervation was studied in premature dog fetuses, puppies and adult dogs by means of the formalin-induced fluorescence technique. A point-counting technique was used to evaluate the density of innervation. Two types of fluorescent profiles can be observed in the heart during development: (1) sprouting axons, and (2) beaded terminals. The axonal fluorescence disappears in adult neurons. A different morphology and a different time course of development enable to study separately the innervation of the myocardium (cardiomotor innervation) and that of the vessels (vasomotor innervation). The late prenatal innervation is very poor (0.1 hit). The first but very scant cardiomotor terminals appear in this period. A mature cardiomotor innervation is found in 4-month-old puppies [1.5 +/- 0.3 (SD) hits]. The vasomotor innervation is shifted to the right. The development of beaded vascular terminals begins and matures 1-2 weeks later. The growing fluorescent axons reveal that the myocardium is supplied by axons of the cardiac plexus and of the perivascular nerves; the vascular wall, on the other hand, is supplied by the perivascular nerves only. The developmental, spatial and morphological differences in innervation suggest that two different types of neurons exist in the sympathetic ganglia: (1) neurons innervating the vessels (coronaromotor neurons), and (2) neurons innervating the myocardium (cardiomotor neurons).

Adrenergic Fibers↗
PubMed1990

Evaluation study of calves with total artificial heart (TAH) surviving for 218-293 days of pumping.

Evaluation of five longest surviving calves among a total of 54 longterm survivors, at the Brno Research Centre was performed. These calves were treated by administration of antihypertensives and partially by electrical stimulation of the right atrium to reduce central venous pressure (CVP). Treatment for CVP was effective, as compared with two groups of 5 calves each not treated in this way, and it is assumed to be an important factor for prolongation of survival. Mineralization of driving diaphragms was present in all these calves. No preventive measures of this pathologic change were performed in this group. Another complication is hemolysis, which is partly caused by immune mechanisms initiated by administration of alpha-methyl dopa and partly by mechanical destruction due to a heavily mineralized driving diaphragm. The prevention of mineralization is another important problem for future research. Other problems, concerning the survival of TAH recipients are discussed.

Animals↗
PubMed1990

Central nervous complications in subjects with artificial heart.

The artificial heart is a device for urgent solution of final heart failure. The systems used currently for this task are particularly pneumatic systems that allow only a limited life comfort for the patient. Therefore they have been used for short-term application as so-called bridge systems designed for periods preceding heart transplantation. Artificial hearts should be available for such situations. They are antithrombogenic owing to their construction and material properties and thus the patient's central nervous system is not threatened by thromboembolic complications. The Czechoslovak artificial heart TNS-Brno-VII is optimal in this respect. In experiments lasting for months, however, microembolism into the CNS from a calcified diaphragm often threatens the experimental animal. This danger can be limited both by optimal construction of the pump and by affecting the calcifying mechanism biologically, or by suitable processing of the diaphragm material that prevents calcifying nucleation. Perfect technology in the production of artificial hearts warrants complete elimination of potential air embolism into the central nervous system. Therefore the aim of further research is to design an absolutely defect-free system of the artificial heart which would eliminate any damage to the central nervous system during permanent long-lasting application, either on the basis of cerebral embolism of any origin, or on the basis of CNS hypoperfusion caused by limited pumping function of the artificial heart.

Animals↗
PubMed1989

[The artificial heart from the aspect of results thus far and from the aspect of further perspectives for research and clinical practice].

The author gives an account of the present position in the development of research of artificial hearts and mechanical support whereby special attention is paid to research in the CSSR which holds one of the foremost places in the world. When resolving some basic questions of long-term biological adaptation to the activity of the mechanical system, i.e. the artificial heart, this research becomes very important as a unique model for investigation of the isolated peripheral circulation the reactions of which are not affected by the action of the biological heart which has been eliminated. Moreover, specific conditions are created for the investigation of other general biologically important problems (hormonal regulation, metabolic factors, leading to calcification of biomaterials and its prevention, problems of dynamics of the coagulation system, thrombogenesis etc.) in the organism with an artificial heart. At present there are essentially two methods suitable for clinical application, i.e. mechanical support of the heart of the type of mono- or biventricular bypass with total replacement of the heart as a temporary operation before subsequent transplantation. Both these methods are promising. Further intensive research of the long-term survival of subjects with an artificial heart creates in addition to typical features of fundamental research the basis for permanent implantation of an artificial heart in clinical work which is another important stage of clinical applications.

Animals↗
PubMed1989

[Therapy of venous hypertension in animals with an artificial heart and long-term survival].

1. The authors elaborated an original concept for the interpretation of vasomotor disorders in subjects with an artificial heart. 2. This concept is based on the regeneration of nervous elements in the walls of the atria (in particular the right one) after implantation of the artificial heart and on comparison of their activity with the venous pressure which revealed the interrelationship of the two phenomena. 3. Both therapeutic methods based on this concept, the method of influencing the afferentation and efferentation of vasomotor nervous regulations leading to a reduction of the central venous pressure proved valid and effective. 4. Evaluation of the effectiveness of this therapy is based on regular assessment of the central venous pressure, on the laboratory assay of enzymes (AST, ALT, GMT and LDH), on the assessment of serum albumin and finally on the morphological and histological examination of the liver incl. assessment of the hepatic index. 5. The nervous pathogenesis is closely linked with hormonal factors. The latter are conceived as the participation of associated factors in the pathogenesis of venous hypertension in recipients with an artificial heart.

Animals↗
PubMed1989

Therapy of venous hypertension in calves with total artificial heart (TAH).

Vasomotor disregulation, preponderantly expressed by a pathological increase of central venous pressure (CVP) in calves with total artificial heart (TAH), starts to be evident from about the 50th day of pumping. The main cause of this state is an imbalance in cardiac receptor areas. Ventricular vasodepressor mechanisms are eliminated with the ventricular tissue, which is replaced by the artificial blood pump. In the stumps of both atria, which remain in situ, all neural elements disappear immediately after TAH implantation, but within two months they are fully regenerated. Regenerated atrial receptors are the starting points of afferent neural stimuli, which in the vasomotor center of the brainstem, increase the activity of the vasoconstricting functional component. A general tendency to vasoconstriction, now not well counterbalanced, increases, and the progressive venous hypertension causes loss of liver function and morphology. Two therapeutic approaches were tried: afferent therapy by atrial electrical stimulation, and efferent therapy by the administration of antihypertensives. Both kinds of this therapy were sufficiently effective in reducing CVP, protecting the liver, and prolonging average survival.

Animals↗
PubMed1989

[The contribution of artificial heart research in Czechoslovakia to modern medical science].

A summary of the development of total artificial heart research in Czechoslovakia is presented. The experimental setting of this research was based mainly on experiments on calves and partially on goats. The original concept of the blood pump is represented by an asymmetrical type of pump with an asymmetrical diaphragm and undulating motion of the diaphragm allowing optimal washing of the blood chamber. This is the key factor of the antithrombogenic properties of the latest version of the Brno artificial heart. For the pneumatic drive of the artificial heart control and driving units of our own construction--Chirasist-TN-3--are used. In 50 completed long-term experiments the mean survival time was 117.4 days. In the group of 23 experiments with polyurethane total artificial heart (TAH) the mean survival time was 133.9 days. The longest survival was achieved in the calf "Artur", No. 121 with 293 days of pumping which is worldwide one of the three longest survival times with TAH using the calf as an experimental animal. The experiment with an intrathoracic TAH implantation in the goat with a survival time of 184 days represents a worldwide unique success. After solving a number of technical and biological problems, we focused our attention on two crucial complications, i.e. increased central venous pressure leading to severe liver damage and diaphragm calcification. The original Brno concept concerned with the pathomechanism of central venous pressure increase made efficient pathogenetic therapy feasible and resulted in a marked protection of liver functions, so that increased venous pressure is no longer a problem in our experiments that would limit the period of survival. However diaphragm calcification has remained a serious survival limiting complication and therefore prevention of calcification is in the focus od our intensive research activities. Parallelly with these activities we have been engaged in research aimed at the clinical application of the TAN to bridge the period in severely affected patients until a suitable heart transplant is available. So far we have performed four artificial heart implantations in patients in the final stage of heart failure. We could keep these four patients on the TAH from one to ten days without the slightest failure of the system, and the blood chambers of the TAH-TNS-BRNO--VII/Klin/80, removed from the patient's chest after pumping had been stopped, were completely free of thrombi.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Surgical aspects of the implantation of a left ventricle assist device.

The authors have summarised their experience with short-term use of a left ventricle assist device (LVAD). Nine experiments were carried out in healthy calves. A polyurethane pump of their own design, placed extracorporeally, was used. Its in-flow cannula was placed in the left atrium, the outflow one in the initial segment of the descending aorta. The LVAD was operated for a period of 5 days. Fourteen days after its disconnection, the animal was sacrificed and both the bypass system and parenchymal organs were examined. No surgical complications were observed during the experiments. Macro- and microscopical pictures showed minor infarctions in the renal tissue which, however, did not impair renal function. The findings in other organs were related to anaesthesia, the operative procedure and way of animal sacrificing. The experiments have proved the safety of the bypass system used over a short period and, consequently, its potential for future clinical application.

Animals↗
PubMed1988

Serum aldosterone studies in 10 calves living for 2-5 months with a total artificial heart (TAH).

A group of 10 experimental calves that lived for 61-147 days with a TAH was used to study serum aldosterone levels by RIA with ALDOCTK-125 CEA Kit (Sorin Biomedica, Italy). The aldosterone levels were plotted against the serum sodium and potassium, body weight, CVP, urinary sodium and potassium and with hematocrit levels. In these experiments, three types of TAH (TNS-BRNO II, VII, and Rostock) were used. The levels of aldosterone were already high before the surgery and during the entire pumping period, which indicates the development of secondary aldosteronism. The study deals with the mechanisms that participate in the development of aldosteronism in each phase of the experiment with the TAH.

Aldosterone↗
PubMed1987

Haemocompatibility of segmented polyurethanes investigated in vivo.

Samples of segmented polyurethanes differing in composition and in surface morphology were introduced into the left ventricles of hearts of goats for 72 h. After removal of the samples, their surface and the surface of the heart endothelium were evaluated visually with respect to the formation of thrombi. Differences in the interaction of the individual polyurethanes with blood were examined by XPS photoelectron spectroscopy, SEM, and by infrared (i.r.) reflexion spectroscopy. The results suggest ways for improving the haemocompatibility of the surfaces of polyurethanes used as parts of the total artificial heart.

Animals↗