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Biomedical subjects

W Urbaszek

Publications and source records attributed to W Urbaszek.

At least 19 recordsLinked to original sources
PubMed1995

[Imprints of coronary plaque particles in the PTCA balloon surface during the dilatation processing].

UNLABELLED: Seventy-six PTCA-balloons after coronary angioplasty were studied for superficial changes using scanning electron microscopy (SEM) after fixing in glutardialdehyde. Coronary plaque particles were identified on the balloon surface in 52 cases (68%). Twelve new and unused balloons were subjected to the same chemical treatment and SEM showed no imprints. The average length of the longest imprinted plaques was 128 +/- 201 microns and the average number of plaque particles per balloon was 4.9 +/- 2.7. The maximal dilatation pressure and the number of dilatations showed no influence on the impregnation of plaque particles. However, longer plaque imprints tended to occur under low dilatation pressure. Imprints of plaque particles were significantly higher in patients with low cholesterol (p = 0.0001) and low triglycerides (p = 0.0016). No correlation was seen between imprint length and lipid levels. Similarly, the different balloon materials (polyethylene, polyolefincopolymer) showed no significant differences with regard to plaque occurrence. The PTCA-balloons, plaque particles and six coronary plaques obtained after endatherectomy were subjected to energy dispersive x-ray analysis (EDX) under SEM as EDX reveals qualitative and quantitative information about the structural elements. Highly significant differences in calcium, sodium, phosphorus and silicon contents (p = 0.0000) between plaque particles and balloon surface were observed, owing to the absence of these in balloon material. Thus EDX offers additional advantages over SEM in that it clearly differentiates deformed balloon surface, plaque particle, and retained contrast medium. CONCLUSION: Plaque particles can be recovered from balloon surfaces after PTCA. Depending upon their size, they could lead to coronary spasm or microembolic phenomenon.

Adult↗
PubMed1992

[The incidence of silent myocardial ischemia].

Retrospectively evaluated was the patient population of the years 1982 to 1988 which underwent ergometric investigations concerning the appearance of silent myocardial ischaemias. In 256 reactions of exercise ischaemia of patients with definitive coronary disease in 47 cases angina pectoris appeared (18.4%). Reactions of ischaemia in a large area of the breast wall showed, compared with a small area of ischaemia, a significantly higher proportion of symptomatic episodes (34.3% vs 13.0%, P less than 0.05). Ergometric exercises lying below the norm of age were more frequently accompanied by symptomatic ischaemias than ischaemic reactions, which only appeared in a good area of performance (26.0% vs 11.4%, P less than 0.05). In addition to this more anginose complaints were found in patients, whose ischaemic reaction was accompanied by an insufficient frequency response (28.1% vs 9.8%, P less than 0.05).

Angina Pectoris↗
PubMed1991

[A measuring procedure for experimental determination of tensile strength of catheters and flexible probes].

In order to obtain a more objective description of the properties usually subsumed under such terms as the "handling" of catheters, it is necessary to measure the significant parameter bending stiffness. A contact-free method of recording the oscillations of rod-shaped elements is presented. The stiffness EI can be calculated from the measured characteristic frequency. The logarithmic decrement can be derived from the damped natural oscillation and the damping properties of the catheter thus characterised. In addition, a consideration of imposed oscillations can be employed to calculate resonance frequency. A computer-driven measuring set-up employing a CCD line camera for the non-contact recording of oscillations of rodshaped elements, together with the software required is presented. The measuring principle and possible errors are discussed and a measurement described by way of an example.

Biomechanical Phenomena↗
PubMed1991

[Definition and classification of heart failure].

The definition of the syndrome of heart failure is dependent upon clinical, pathophysiological and biochemical criteria. The interrelationship of the contributing factors in a given hemodynamic situation must be clarified by simple examination. "Heart failure" implies a condition with insufficient peripheral perfusion, despite a normal blood volume, a sufficient or increased filling pressure, and intact intrinsic and extrinsic compensatory mechanisms. The cardiac output varies with basic illness. The worsening vicious cycle between cardiac dysfunction and neuroendocrinal dysregulation in chronic heart failure has to be taken into consideration, especially while planning therapeutic strategy. The classification of the severity of the disease is based upon simple, clear history taking and clinical examination. The conclusions have to be supported by radiological and echocardiografic observations. It is difficult to categorize patients during early stages of the disease. Prognosis is based on preexisting hemodynamic, biochemical, neuroendocrinal, and clinical parameters, as well as therapeutic strategy. At the same time, prognosis is dependent on the efficacy of the therapeutic regimen in any given situation.

Heart↗
PubMed1991

[Effects of diltiazem in acute and long-term administration].

In 16 patients with unstable angina pectoris haemodynamic and clinical effects of diltiazem were investigated. In a second group patients (n = 11) with unstable or therapy-refractory course the long-term effect was tested. The acute intervention with injected and infused diltiazem via an improved oxygen balance due to decreased minute work and reduced product of cardiac frequency and pressure stabilized the clinical picture from the haemodynamic aspect. The decreases of the ST segment were significantly lower. In the long-term use a significant influence on the frequency of angina pectoris with increase of the range of efficacy by one NYHA-state was the result. Diltiazem can be regarded as alternative medicament in unstable phases and in therapy-refractory courses of the chronic coronary heart disease.

Angina, Unstable↗
PubMed1991

[Ventricle-vessels relationship in aspects of hypertension].

The diagnostics of the ventricle-vessel relations in arterial hypertension is significant in particular for advanced stages. Under the aspect to regard the cardiac contraction in form of a model as temporarily varying elastance of the volume invasively (P-measurement, V-measurement, preload alteration via balloon in the inferior vena cava) relations of the ventricular pressure volume (ESPVR, EDPVR) and system-arterial ones in form of the effective arterial elastance can be established. Additionally calculated functional curves give separated information concerning the influence of preload, afterload and contractility on the stroke work. Thus a comprehensive statement concerning the cardiovascular function and a basis for valuable therapeutic effects is worked out. Several references result for advanced stages of the arterial hypertension with hypertrophied heart. The systolic function remains normal for a long time. Diastolically the increasingly disturbed relaxation with pathological preload is found. The relation stroke work-afterload is no more in the optimum region and can further be deteriorated by vasodilation. Whether or not, however, this relation has the same relevance for all clinical questions, remains open. Is the stroke work really that parameter which shall be optimized therapeutically?

Blood Pressure↗
PubMed1990

[Treatment indications of hypertensive blood pressure dysregulation (a 7-year follow-up)].

The results of the present course investigations by means of bicycle ergometry over seven years on patients with vitality-limiting load hypertension in normotensive and initial situation of the borderline blood pressure, respectively, render necessary from the point of view of the authors an increase of the former indications to treatment. Situative measurement of blood pressure only at rest are hereby not sufficient and demand a bicycle-ergometric objectivation of the possible hypertensive dysregulation of blood pressure in patients with anamnestically restricted range of physical efficacy. In patients with exclusively under load increased vitality-limiting blood pressure values the ergometry represents the diagnostic method of choice.

Adult↗
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↗