Biomedical subjects

W Urbaszek

Publications and source records attributed to W Urbaszek.

At least 37 records · Page 2Linked to original sources

PubMed1990

Relationship between design and control of artificial heart for protection of the right/left balance.

Right/left matching in the total artificial heart (TAH) is essential to prevent fatal volume displacement into the pulmonary circuit. Measurements were made with three different sized Rostock pneumatic artificial ventricles incorporated in the Donovan mock circulatory system together with the heart driver AKT 86. First for each ventricle we determined the dependence of the maximum effective stroke volume on the systolic driving pressure and the afterload. The right ventricle (RV) is about 10% more effective than the left ventricle (LV). Control of the TAH permits different or equal frequencies for the RV and LV. For control with equal frequencies and full-to-empty regimen of one ventricle (RV-Master or LV-Master) the ratio of designed stroke volumes between RV and LV is important. This follows from the smaller efficiency of the LV and the left-to-left shunt. Otherwise a control mode with different heart rates must be used.

Heart, Artificial↗

PubMed1989

[Current status of the use of the artificial heart and ventricular assist systems].

The state of the technical development of the mechanical assist systems and the artificial heart, respectively, guarantees a sufficient support of the circulatory system up to the improvement of the own heart function or to the possible heart transplantation. There is the necessity for the temporarily limited support of the heart, but also for the long-term one. Independent of the underlying etiology in acute conditions of cardiac failure in many cases the external supporting system may be sufficiently helpful. The antithrombotic therapy and the prophylaxis of infections demands particular carefulness. There is still no representable release for the long-term use of the hitherto available cardiovascular supporting systems. The question is controversial, whether then an experiment on patients or an already accepted therapeutic intervention is still taken into consideration. Essential prerequisites for the long-term use would be a full implantability of the systems in transcutaneous energy transmission, a further biologization of the blood-contacting materials, a clarification of the immune phenomena, a possibly automatic mode of action adapted to the need as well as a reliable strategy of antithrombotic therapy. The increased risk of infection should be taken into consideration.

Animals↗

PubMed1988

[The status of prazosin in therapy of chronic heart failure].

Cardiac dysfunction and neurohumoral dysregulation show that the administration of vasodilators is reasonable in a cardiac insufficiency which is therapy-refractory against glycosides and saluretics. The alpha 1-blocker prazosin is a potent substance. On the basis of haemodynamic investigations of 55 patients the acute effects are demonstrated. Depending upon the degree of the cardiac insufficiency and the sympathetic dysregulation--measured at the behaviour of the resistance--the acute effects are convincing in more than 60% of the patients. For the long-term course patients with unequivocal initial improvement are suitable. This group can undergo a satisfactory therapy for a longer time by means of a carefully increased dosage, by corrections of the application of saluretics and by short interruptions of therapy and by the change of the dilator, respectively, or by an additional administration of another vasodilator. In the total spectre of the vasodilators which are administered in cardiac insufficiency prazosin occupies one of the first places.

Cardiomyopathy, Dilated↗

PubMed1988

[Kineto- and displacement cardiography in heart valve diseases and possible diagnostic values].

With the help of the method of the kinetocardiography (KKG) inaugurated by Eddleman and the displacement cardiography (DKG) using a high fidelity changer, apart from a control group of 12 test persons with healthy heart 8 different groups of cardiac abnormalities consisting of altogether 88 patients were examined. Displacement cardiography and kinetocardiography did not significantly differ in the course of the curves. The courses of the curves for the cardiac abnormalities proved reproducible. There were significant differences in at least 6 parameters of the curves (p less than 0.05 to p less than 0.001) between the control group and each group with cardiac abnormalities. Linear correlations between the parameters of the curves and invasively gained cardial parameters confirm relations relevant to cardiac abnormalities. In future in possible computer assisted analyses of curves a better rational evaluation in controls of the curves will be the result. The value of this methodology lies in the character of the parameters confirming the cardiac abnormalities. The disadvantage consists in the absent exact quantification of the degree of severity.

Adult↗

PubMed1988

[Therapeutic possibilities in terminal heart failure].

The severe and terminal cardiac insufficiency with myogenic failure and severe neurohumoral dysregulation means a problem situation in the chronically progressive or acute form of the course. The medicamentous treatment in form of the basis therapy with glycosides and saluretics may be improved by vasodilators or/and adrenergic agonists. In most cases we succeed in stabilizing the cardiovascular situation once to several times. As a rule the maximum stress only little increases. The neurohumoral dysregulation remains in different form apart from the basic disease which is no more to be corrected. Thus, in principle the vicious circle is closed. Whether the group of the so-called new inotropic and vasodilating pharmaca may essentially change the prognosis due to better influences on cardial and vascular and neurohumoral, respectively, dysfunctions, is not yet to be answered. A distinct alternative from the aspect of the cardiovascular function gives only the cardiac transplantation. The artificial heart and ventricular assist-systems, respectively, are accepted for the bridging-over up to the cardiac transplantation. The hitherto existing state of development does not yet correspond to the imaginations of a pump regulated according to the needs, disregarding material, coagulation and energy problems.

Adrenergic beta-Agonists↗

PubMed1987

[Noninvasive monitoring of pneumatically driven blood pumps based on measurements of air volume flow in the drive hose].

A computer-assisted measuring system for the noninvasive control of pneumatically driven blood pumps in the artificial total heart replacement and in assist-systems is described. Air volume current measurements with heat wire anemometer in the driving tube underlie as principle. The technique takes into consideration losses of valves, depending upon driving parameters and central circulatory parameters. The dependences established base on measurements at the circulation model. The methods demonstrated allow to qualitatively characterize the signals of the air volume current in the driving tube and approximatively to determine central circulatory parameters on the basis of comparative measurements at the circulation model. Animal-experimental experiences confirm the necessary application of such systems for the measurement of the cardiac output and for the control of the pumping function of pneumatically driven blood pumps. Analyses at the circulation model let expect a measuring error for the volume of output smaller than 20%. By increased measuring exactness of the heat wire anemometer this error can be diminished. For final evidence concerning the measuring exactness animal-experimental investigations and comparisons with reference techniques are provided.

Algorithms↗

PubMed1987

[Catheter problems in the use of ventricular cardiovascular assist systems].

The prerequisite for efficient assist-ventricles and impulses in the pulsatile pumping function are sufficiently dimensioned afflux and flowing off connections. In systematic investigations on the hydraulic circulation model the cannulas from an internal parameter of 12 mm with a total length of the connection distance to the inflow and outflow valve, respectively, at the bypass ventricle of 30 cm proved sufficient for performing a volume of output of 5-6 l/min in clinic-relevant filling pressures in a hypodynamic circulatory situation. Connection cannulas for the heart-lung machine used in routine work are not sufficient in periodic filling and ejection processes in the pulsatile pumping function for an effective decompression and effective increase of the cardiac output. In case of an ECG-triggered mode of action of the ventricular assist-system an increase of frequency up to 130/min in after that incomplete filling of the assist-ventricle does not remarkably restrict the effectiveness of the assist-system.

Assisted Circulation↗

PubMed1987

[Filling behavior of pneumatically driven artificial ventricles of the membrane type in vitro].

The filling behaviour of pneumatically driven artificial hearts is an essential determinant of its pumping function. The artificial ventricles developed in Rostock were investigated by means of a hydraulic circulation model for analysis of the influence of different parameters on the filling time. The filling rate is decided by the flow resistance of the inlet valve. Additional resistances are given by the rigidity of the membrane and the flow resistances of the drive line and the drive.

Heart, Artificial↗

PubMed1986

[Pressure measurements of pneumatically driven artificial ventricles].

In the mock circulation are investigated methods for pressure measurement developed especially for the application on artificial ventricles. They require the in-vivo-confirmation in the long-term experiment. An exact analysis of the pressure curves gives information about the absolute measuring values and also about the function of the pump itself, such as about the points of reaching the final positions of the pump membrane. Via a control related to this in the "full stroke" mode with ejection of the complete stroke volume, when the stand-still times of the membrane are minimized, in addition to this the atrial pressures and the cardiac output can be determined. Eventual non-linearities in the lower pressure region (less than or equal to 0.5 kPa) are not essential in the measurement of the ventricular pressure with amplitudes of 20-25 kPa on the left side and are not investigated in detail.

Assisted Circulation↗

PubMed1986

[Possibilities of using cardiovascular assist systems and the artificial heart].

The mechanical support of the cardiovascular circulation of the reversibly or irreversibly damaged natural heart is possible in a different way. Beginning with the balloon pulsation with limited haemodynamical efficacy the application of left-or right-ventricular assist-systems finally leads to the biventricular assistance, when there are signs of the global cardiac dysfunction and an ability of recovery the heart function is assumed. The trend to use assist-systems over longer periods is perceptible also in patients in terminal phases of chronic cardiac diseases. Thus the importance of artificial hearts is increasing which are to be regarded as biventricular assist-system in orthotopic position. For a short-time use the up to now developed blood pumps, drives and regulation units are suited in few centres of the world. The orthotopic implantation of artificial hearts permits as second step the transplantation of a suitable donor heart. The heart transplantation guarantees high success rates and a cardiac function adapted according need. The demands on the long-term implantation of artificial hearts are at present so high that the majority of the specialists at the present stage of the development has a sceptical attitude to the long-term use.

Assisted Circulation↗

PubMed1986

[Therapeutic principle of organ replacement--artificial organs].

The natural or artificial replacement of organs provides the aimed influence on terminal phases of organ diseases. The hitherto obtained solutions for the replacement in diseases of kidneys, the heart, the lungs, the pancreas and the liver are developed in a different way. For the natural replacement of organs ameliorations in the fields of recipient conditioning, immunotherapy, prophylaxis against infections in operative and technical prerequisites given are subject of further efforts. The complex of problems artificial replacement of organs in the sense of the influence on global and partial organ dysfunctions organ-related reveals different consideration and development. The most advanced perfectioning is existing for the artificial kidney. The elementary and relatively high need of replacement of organs is another challenge to medical and technological sciences.

Humans↗

PubMed1986

[Therapy of chronic heart failure with vasodilators].

The chronic heart insufficiency is essentially characterized by a disturbed regulative function of the peripheral circulation. These processes taking place within efforts for compensation close the chain of the vicious circle. The vasodilators with their different principles of effect affect in various places of the vegetative nervous system up to the smooth musculature of the vessels and modulate the peripheral part of the cardiovascular system. Via a changed behaviour of the impedance also with the arterial vasodilation the ejection behaviour of the insufficed hearts changes. With the increase of the ejection fraction the filling pressure can decrease, also when only the arterial branch of the periphery of the vessels is influenced. In case of an additional vasodilation of the capacity vessels greater influences of the preload are present. As a rule after the full use of the conventional therapy with digitalis and saluretics is resorted to the adjuvant therapy with vasodilators. Good experiences in the therapy of chronic heart insufficiency are present above all for hydralazine and prazosin as well as increasingly also for captopril, when vasodilating and at the same time positively inotropic medicaments are disregarded. In future, depending upon haemodynamic and neurohumoral (PNA, PRAA) findings in problematic cases and aimed additional adjuvant therapy will be aspired to.

Adrenergic beta-Agonists↗

PubMed1986

Surgical principle in total artificial heart--an experimental review.

Based on implantation experiments in calves resulted some experiences for the implantation technic of artificial hearts. After resection of the natural ventricles and of the valvular parts of the aorta and pulmonary artery the connectors should be adapted and implanted. The first connected left ventricle get a caudal-lateral traction especially under supervision of the pulmonary veins and optimal development of the aorta. During connection of the right ventricle it is necessary to check up the inflow - and outflow tract situation. May be, the left ventricle get with this maneuver an unfavourable caudal kinking. Careful preparation and splitting of the pericardium is necessary to avoid obstructions for the venous flow. The closing of the chest and initial changes in position of the animal may alternate good positions of the heart, if the resection as well as preparation, adaptation and bedding don't remarked the discussed principles. One of the most relevant aspects in achieving the consistent survival of an animal undergoing the experimental implantation of a total artificial heart is obviously related to the correct anatomic placement of prosthetic ventricles inside the chest. In this case, the skillful surgical procedures based on an established surgical principle are considered to be attributable in obtaining the optimal hemodynamic situation. Description of the surgical procedures has been made elsewhere. However, it has been difficult to find a well defined surgical principle although particular milestone has already been made by a clinical application of the total artificial heart in 1982. Although the presently available prosthetic ventricles generally fit better in the chest, the problems in design and size of the prosthesis still exist.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Surgical Procedures↗

PubMed1985

[Mono- or combination therapy with myocardial and coronary active drugs in ischemic heart disease].

The medicamentous treatment of the ischaemic heart disease with nitrates, beta-receptor blockers and calcium antagonists takes into account the in the ideal case evident pathomechanism and the essential principles of the effect of these groups of pharmaca. Apart from the influence on way of life and environmental factors at first the monotherapy is tried. As a rule, in individually possible full use of the dose a large part of the patients can sufficiently be improved. As to "conventional therapy", however, from the first the concerning the therapeutic mechanism favorable combination beta-receptor blocker and nitrates is understood. The increasing interest in calcium antagonists aprt from the increased application of these pharmaca in monotherapy led to the question of the combination with beta-receptor blockers and nitrates. Taking into consideration the different spectres of action of the calcium antagonists particularly in unstable angina pectoris, especially under haemodynamically controlled conditions a combination of three remedies is to be discussed. With regard to this there are no sufficient clinical experiences. At present there are no sufficient evidences for the superiority of this combination therapy.

Adrenergic beta-Antagonists↗

PubMed1985

[Pathophysiological investigations on the function of artificial hearts].

The mode of action of artificial hearts is in a wide range variable and to be adapted to different conditions of the circulatory systems. The direct regulative function of the peripheral circulation is restricted by the rigid ability of artificial hearts bound to motor drive parameters. Their great dependence on pre- and afterload already in normal calves presumes a harmonized functional capacity of the right and left ventricle. As to the situation in potential recipients of artificial hearts with considerably disturbed macro- and microhaemodynamics there are problems for the choice of suitable conditions of motor drive, in order to favour a right-left balance and an adequate volume. The substitution of the natural regulators by suitable sensors and the regulation of the artificial hearts according to haemodynamic controls and pump parameters, respectively, is necessary to achieve a balanced adequate ventricular function. This complex is subject of an intensive research.

Animals↗

PubMed1984

[The Rostock artificial heart--current status and perspectives].

The authors report on their experiences gained by animal experiments (calf) and their attempts (human corpses) concerning adaptation of the apparatus to the human thorax. At the present time they do not see a chance for its routine clinical use. The main reason why is the impossibility to install the extrathoracic driving system into the thoracic cage and last not least the wear of the material used for the heart chambers.

Animals↗

PubMed1984

[Animal experiments using the left-ventricular-assist system].

The left ventricular assist device (LVAD) was tested in 27 sternotomied dogs using hemodynamic parameters. The left ventricular failure was attained by the starvation of the coronary vessels. The use of cannulae and ventriculi fitting for the size of the animals, and a diastolic vacuum were an essential premise for an effective support of the left heart. By variation of the latent period, the systole duration, and the operating pressures were selected for optimal pumping conditions. The effectiveness of the LVAD was shown by the detected pressure and flow parameters.

Animals↗

PubMed1984

[An improved connecting system for artificial hearts].

The certain connection of the artificial ventricles to the vascular system has a decisive importance in the implantation of an artificial heart. Demands concerning tightness, reliability, easy attendance, and anatomic fit are to be considered especially in the construction of a suitable connecting system. A modified bayonet system came in use. The connection between the artificial heart and the vascular system is placed here by distortions of a tightening ring.

Animals↗