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G Wieselthaler

Publications and source records attributed to G Wieselthaler.

34 records · Page 2Linked to original sources
PubMed1995

Anemia and erythropoietin levels in lung transplant recipients.

An evaluation of 26 surviving outpatient lung transplant recipients at one center showed that 65% (17/26) had significant anemia (hemoglobin < 11 g/L for women, < 14 g/dl for men) at a median follow-up of 13.5 months after transplantation (range, 1-41 months). There were 14 men and 12 women with a mean age of 45.1 years (range, 23.1-66.7 years). Fifteen had a double allograft and 11 had a single allograft. Anemia was normochromic and normocytic/macrocytic with a tendency to anisocytosis, with normal reticulocyte counts. Iron deficiency (transferrin saturation < 20%) was found in 35% (6/17) of anemic patients, and two of them also had ferritin levels < 15 micrograms/L. In addition, vitamin B12 was decreased in 1 patient. Folate levels were all normal. Erythropoietin levels were significantly decreased in anemic lung transplant recipients as compared with nontransplanted iron-deficient anemic patients (median, 1 mU/ml, range 1-41 mU/ml, vs. 53 mU/ml, 15-88 mU/ml; P < 0.05). In nonanemic lung transplant recipients, erythropoietin levels were decreased too, as compared with normal controls (median, 2 mU/ml, range 1-21 mU/ml, vs. 5 mU/ml, 3-32 mU/ml; P < 0.05). Investigation of peripheral stem cells in 9 patients showed normal stimulation of erythroids (burst-forming unit, erythroid; median, 573 cells/ml; range, 128-1898 cells/ml) independent of erythropoietin concentrations. Analysis of putative prognostic factors, such as age, surgical procedure (double vs. single lung allograft), indication for transplantation, time after transplantation, infection status, presence of bronchiolitis obliterans, immunosuppression (+/- azathioprine), serum creatinine, creatinine clearance, hypertension, and arterial partial pressure of oxygen, did not demonstrate any difference in erythropoietin concentrations. Only the sex variable revealed a trend to higher levels in women than in men (median, 4 mU/ml, range 1-41 mU/ml, vs. 1 mU/ml, 1-16 mU/ml; P > 0.05). The causes for low erythropoietin levels are not quite understood yet; however, they offer a rationale for the treatment of chronic anemia with recombinant human erythropoietin.

Adult↗
PubMed1995

ICD therapy in survivors of sudden cardiac death awaiting heart transplantation.

The impact of implantable cardioverter defibrillator (ICD) therapy on survival of heart transplant candidates is of major socioeconomic and ethical interest. However, efficacy is even uncertain for patients at highest risk of tachyarrhythmic death on the waiting list. We studied 60 selected heart transplant candidates (mean age, 55.8 years; mean left ventricular ejection fraction, 0.15; functional class III and IV) with a history of successful resuscitation by external electric defibrillation for spontaneous, syncopal ventricular tachyarrhythmia during the study period from March 1992 through September 1994. At the time of registration for transplantation, 30 patients had ICD devices implanted, whereas 30 patients lacked ICD therapy for various nonmedical reasons. Both therapy groups were comparable in clinical and hemodynamic characteristics as well as in intention to transplant (median waiting time to transplantation, 5.7 and 6 months, respectively; not significant by log-rank method). Survival on the waiting list was significantly improved by ICD therapy; only 1 of the 30 ICD patients (19 transplanted) but 7 of the 30 non-ICD patients (14 transplanted) died on the waiting list (p < 0.05 by log-rank method). Implantable cardioverter defibrillator therapy did not affect survival after transplantation as compared with non-ICD patients (not significant by log-rank method). During the waiting time, 26 of the ICD patients (87%) experienced adequate ICD discharges, and 12 of the non-ICD patients were treated successfully by external electric defibrillation (40%).(ABSTRACT TRUNCATED AT 250 WORDS)

Death, Sudden, Cardiac↗
PubMed1995

The impact of implantable cardioverter-defibrillators on mortality among patients on the waiting list for heart transplantation.

Implantable cardioverter-defibrillators were investigated for their impact on mortality in 228 consecutive heart transplant candidates on the waiting list for transplantation (207 patients without and 21 with implantable cardioverter-defibrillator therapy). The mortality rate in 207 patients without implantable cardioverter-defibrillator therapy was 23.2% and in 21 patients with implantable cardioverter-defibrillator therapy was 4.7%. In a Cox proportional hazards model for all 228 study patients (mortality while on the waiting list: 21.5%; transplantation rate: 54.8%), the absence of an implantable cardioverter-defibrillator was only a marginally significant predictor of mortality (p = 0.079). However, the absence of an implantable cardioverter-defibrillator was a powerful predictor of mortality for a subgroup of 134 patients with high-grade ventricular arrhythmias on Holter electrocardiography (mortality while on the waiting list: 26.1%; transplantation rate: 54.5%; p = 0.022) and for a subgroup of 58 survivors of sudden cardiac death (mortality while on the waiting list: 22.4%; transplantation rate: 56.9%; p = 0.018). Implantable cardioverter-defibrillator therapy can be strongly recommended in transplant candidates with a history of sudden cardiac death. Recommendations for an expanded, prophylactic use of implantable cardioverter-defibrillator therapy in heart transplant candidates cannot be given.

Arrhythmias, Cardiac↗
PubMed1995

An implantable seal-less centrifugal pump with integrated double-disk motor.

Thrombus formation and sealing problems at the shaft as well as the compact and efficient design of the driving unit have been major difficulties in the construction of a long-term implantable centrifugal pump. To eliminate the problems of the seal, motor size, and efficiency, two major steps were taken by modifying the Vienna implantable centrifugal pump. First, a special driving unit was developed, in which the permanent magnets of the motor themselves are used for coupling the force into the rotor. Second, the rotor shaft in the pumping chamber was eliminated by adopting a concept recently presented by Ohara. The rotor is supported by 3 pins, which run on a carbon disk, whose concave shape leads to stabilization. The device has the following specifications: size: 65 mm (diameter) by 35 mm (height), 101 cm3; priming volume 30 cm3, 240 g; and a 6-pole brushless double disk DC motor. The required input power of the described prototype is 15 W at 150 mm Hg, 5 L/min (overall eta = 11%), and has an in vitro index of hemolysis (IH) of 0.0046 g/100 L. The test for in vitro thrombus growth exhibited far less thrombus formation in the new design than in designs with axles. In conclusion, the design of a special driving unit and the elimination of the axle led to the construction of a small pump with very low blood traumatization.

Biomechanical Phenomena↗
PubMed1995

A clinical monitoring system for centrifugal blood pumps.

In clinical application of rotary blood pumps, flow obstruction as a result of suction of the inflow cannula, kinking of tubing, or thrombus formation occurs quite frequently. Early detection of such problems is essential to avoid hemolysis, tissue degradation, or release of thrombi to the patient. A program was developed for automatic observation of pump performance, tubing resistance, and suction effects, which requires only the measurement of already available parameters (i.e., pump speed, pump flow, aortic pressure). The software is based on Visual-C and provides a user surface formatted in Windows. Pump flow, its time derivate, and the relationship between the pulsatile component and the mean graft flow are observed to detect suction in the left atrium. Furthermore, the generated pressure head is predicted from pump speed, graft flow, and the resistance of tubing/cannula and compared with the actually measured aortic pressure. An alarm sounds if a given limit between prediction and measurement is exceeded. In a mock circulation, suction events were detected in more than 95% with a mean deviation of actual aortic pressure from its predicted value of less than 5%. For in vivo application, even incomplete suction could be detected reliably in more than 90% of events. This system improves and standardizes monitoring of pump performance; it should therefore lead to greater safety during application of such devices.

Algorithms↗
PubMed1995

[Strategies in management of heart transplantation candidates with tachycardic ventricular arrhythmia anamnesis].

We followed up 73 consecutive patients with a history of syncopal ventricular tachyarrhythmias on the waiting list for a heart transplant between 1st March 1992 and 15th September 1994 with the aim of evaluating the impact of implantable cardioverter defibrillator (ICD) on survival. On registration 60 patients were considered fit enough to be ambulant whilst awaiting transplantation. 30 were given ICD therapy (group 1) and 30 were not (group 2). 13 patients required inpatient supervision for ventricular arrhythmias whilst awaiting transplantation, but received no ICD therapy (group 3). The 13 in-patients were in a worse clinical state (NYHA) than the 30 out-patients not given ICD (p < 0.05). With respect to all other clinical and hemodynamic characteristics all groups were comparable. Waiting time for transplantation was also comparable in all groups (n.s., log-rank method). ICD therapy resulted in a significant improvement of survival in these high-risk patients prior to transplantation. Only 1 out of the 30 ICD patients (group 2) and 5 out of the 13 in-patients (group 3) (p < 0.05 log-rank method). During the waiting time group 3 patients were hospitalised longest (p < 0.05), but there was a clear trend that also ICD patients had to be hospitalised to an increased extent (n.s.). Cox multivariate regression analysis of this study population showed that the cardiac index (p = 0.001) and lack of ICD therapy (p = 0.035) were the only independent significant predictors of mortality on the waiting list. ICD therapy had no influence on mortality after transplantation (n.s. log-rank method).

Adult↗
PubMed1994

The Vienna implantable centrifugal blood pump.

Because of the inherent disadvantages of membrane pumps, rotary pumps have been increasingly investigated in recent years. As a result of improving biocompatibility, extended assistance with implantable devices is of special interest. Questions arise concerning shear stress, blood traumatization, design of seals, and specific control conditions. In their development of an implantable impeller pump, the Vienna group studied the minimization of hemolysis and thrombus formation by means of numerical simulation, visualization, and in vitro blood evaluation. The latter was revealed to be the most powerful tool for pump evaluation. With optimization of geometry, a hemolysis of in vitro: IH = 0.008; MIH = 0.58; and in vivo: 2.1 to 3 mg% plasma-free hemoglobin could be obtained. For proper control and physiological adaptation, a controller based on a nonlinear and a fuzzy strategy was developed. Furthermore, a method for evaluation of the contractility of the assisted heart during nonpulsatile support was tested by computer simulation. This paper summarizes the evaluation methods used and provide an overview of the results of pump and controller design.

Animals↗
PubMed1994

Effect of lung transplantation on diaphragmatic function in patients with chronic obstructive pulmonary disease.

BACKGROUND: To date there are no data on the effects of lung transplantation on diaphragmatic function in patients with end stage chronic obstructive pulmonary disease (COPD). It is not known whether the relation between the transdiaphragmatic pressure (PDI) and lung volume is altered in recipients after transplantation as a result of changes in diaphragmatic structure caused by chronic hyperinflation. The effect of lung transplantation on diaphragmatic strength was determined in patients with COPD and the relation between postoperative PDI and lung volume analysed. METHODS: Diaphragmatic strength was assessed in eight double lung transplant recipients, six single lung transplant recipients, and in 14 patients with COPD whose lung function was similar to those of the transplant recipients preoperatively. PDI obtained during unilateral and bilateral phrenic nerve stimulation at 1 Hz (twitch PDI) at functional residual capacity (FRC) and during maximal sniff manoeuvres (sniff PDI) at various levels of inspiratory vital capacity (VCin) served as parameters for diaphragmatic strength. Sniff PDI assessed at the various VCin levels were used to analyse the PDI/lung volume relation. RESULTS: Lung transplantation caused a reduction in lung volume, especially in the double lung transplant recipients. As a consequence sniff PDI was higher in the double lung transplant recipients than in the patients with COPD at all levels of VCin analysed. However, sniff PDI values analysed at comparable intrathoracic gas volumes were not reduced in the patients with COPD when compared with those who underwent lung transplantation. Bilateral twitch PDI values were similar in the patients with COPD and in the lung transplant recipients. In the single lung transplant recipients unilateral twitch PDI values were similar on the transplanted and the non-transplanted side. The relation between PDI and lung volume was similar in the patients with COPD and in the lung transplant recipients. CONCLUSIONS: In patients with COPD lung transplantation leads to an increase the maximal sniff induced PDI values by placing the diaphragm in a more favourable position for pressure generation. Since patients with COPD and postoperative lung transplant recipients showed similar PDI/lung volume relations, this suggests that chronic pulmonary hyperinflation does not cause major functional alterations of the diaphragm.

Adult↗
PubMed1993

[Cytomegalovirus infection following lung transplantation].

The significance of cytomegalovirus (CMV) infection after lung transplantation was investigated in 20 patients (ten women and ten men; mean age 46 [21-67] years). Indications for transplantation were emphysema (n = 6), cystic fibrosis (n = 2), primary pulmonary hypertension (n = 2), pulmonary fibrosis (n = 5), obliterating bronchiolitis (n = 2), cystic lung (n = 2) and bronchiectasis (n = 1). Incidence, diagnostic parameters (serology, virus isolation and histology) and efficacy of prophylactic and therapeutic measures were recorded. 16 of the 20 patients developed a CMV infection, which in 12 was clinically significant. CMV pneumonia developed in two patients, proving fatal in one. The infection occurred a median of 47 (17-200) days after the transplantation. Administration of Ganciclovir (5 mg/kg twice daily intravenously) brought about remission of symptoms in all but one of the patients and improved the clinical parameters.--This experience demonstrates that regular monitoring of the patients for possible CMV infection and its early therapy can achieve a low death rate.

Adult↗
PubMed1992

Noninvasive monitoring of rotary blood pumps: necessity, possibilities, and limitations.

Although rotary blood pumps do not contain an inherent mechanism for adaptation to physiological flow necessities, hitherto only a few efforts have been made to obtain robust monitoring and control methods. This paper discusses the necessity of noninvasive monitoring of such pumps and the crucial points of sensor selection and development. A strategy of monitoring atrial pressure out of the data obtained by the collapse of the atrial wall around the inflow cannula and initial results on animal tests and computer simulation of this method are discussed. This approach might lead to reliable and demand-responsive controllers, if some basic criteria are fulfilled.

Atrial Function↗
PubMed1992

Diminished release of atrial natriuretic factor in calves with a total artificial heart.

Venous hypertension after total artificial heart (TAH) replacement, a common problem in humans as well as experimental animals, is thought to be related to reduced release of atrial natriuretic factor (ANF) due to atrial damage. To verify this hypothesis, we stimulated the release of ANF in 6 calves before (-7 days) and after TAH replacement (+25, +50, +80, and +100 days) by the rapid (+ = 10 min) infusion of 2 L of Ringer's solution. In normal calves (-7 days) this procedure induced a rise in plasma concentration of ANF from 18.5 +/- 12 to 31.6 +/- 12 pmol/L (p < 0.05). After TAH the ANF release continuously decreased (analysis of variance, p < 0.02). Thus, ANF increased by 9.8 +/- 9.3, 6.8 +/- 17.5, 0.4 +/- 5.2, and 0.5 +/- 3.2 pmol/L at days 25, 50, 80, and 100, respectively. The central venous pressure increased by 3.4 +/- 1.5 mm Hg (before TAH) and by 6 +/- 2.9 mm Hg (after TAH) during this procedure. A decrease in plasma concentrations of aldosterone, most likely due to extracellular volume expansion and a decrease in total protein plasma concentrations and in hematocrit due to the dilution of blood, was seen in each experiment. Necropsy demonstrated massive atrial dilatation and myocardial dystrophy with atrial fibrosis. ANF granules were present to a small extent in every calf. We conclude that rapid intravenous infusion is an adequate stimulus to release ANF in normal calves. After TAH implantation the release of ANF by high venous pressure declines although ANF granules are still present in the damaged atrial stumps. Therefore, the loss of stimulated ANF could contribute to the observed increase in venous pressure in TAH calves although other pathophysiologic mechanisms cannot be excluded.

Aldosterone↗
PubMed1992

[A measuring device for calculating electrical impedance of the heart in clinical conditions].

Changes in the electrical impedance of tissue can indicate structural changes. This suggests a technique for the noninvasive detection of allograft rejection after heart transplantation. The direct electrical connection to the heart and the application of a measuring current to the myocardium requires a high standard of safety. A device was developed for measuring cardiac impedance using a sinusoidal current of 20 microA at a frequency of 15 kHz. The control logic ensures a slow current onset and also an immediate cessation in case of conductor fracture or excessive voltage. Initial results in patients with normal recovery after heart transplantation revealed a rapid drop in impedance to about 70% of the initial value in the 1st 48 hours and then a stable course. In the sole rejection episode observed so far, the impedance increased again to 85% of the initial value. This paper discusses the technical safety requirements and the design of the device, and presents initial results of clinical examinations.

Cardiography, Impedance↗
PubMed1990

Action of endogenous atrial natriuretic peptide in calves with experimental acute central venous congestion and low cardiac output.

STUDY OBJECTIVE: The aim of the study was to investigate plasma concentrations of atrial natriuretic peptide, aldosterone, and renin during experimentally induced acute central venous congestion. DESIGN: Two experimental calf models were used: (1) right heart failure due to pulmonary artery obstruction; (2) inferior vena cava syndrome produced by inferior vena caval obstruction. Hormonal responses and haemodynamic variables were measured over 6 h. SUBJECTS: Experiments were performed on three female "Schwarzbund" calves, age 3 months, weight 92 +/- 8 kg. MEASUREMENTS AND MAIN RESULTS: In the pulmonary artery obstructed group there was an increase of plasma aldosterone from 6.5(SEM 1.6) to 22.1(3.2) ng.dl-1 (p less than 0.05), of renin from 0.7(0.1) to 2.5(0.3) Goldblatt units x 10(-4).ml-1 (p less than 0.05), and of atrial natriuretic peptide from 22.1(4.5) to 141.4(27.8) pmol.litre-1 (p less than 0.05). During inferior vena caval obstruction, aldosterone increased from 2.4(0.4) to 20.9(2.0) ng.dl-1 (p less than 0.05), and renin increased from 0.4(0.05) to 2.0(0.20) Goldblatt units x 10(-4).ml-1 (p less than 0.05). In this experiment, atrial natriuretic peptide remained unchanged. Cardiac output decreased in both groups. There was significant fluid and electrolyte retention during both experiments, with urine volume decreasing from 87.7(11.6) to 35.0(1.2) ml-h-1 in experiment (1), and from 185(14) to 95.7(8.6) ml.h-1 in experiment (2). CONCLUSIONS: The study suggests (1) that in an experimental acute state of reduced cardiac output due to pulmonary artery stenosis with constantly increased right heart pressures, raised endogenous atrial natriuretic peptide failed to induce diuresis and natriuresis; (2) that in acute right heart failure, renin and aldosterone secretion could not be suppressed by raised atrial natriuretic peptide concentrations; and (3) atrial natriuretic peptide secretion seemed to be exhausted after 6 h continuous atrial distension.

Acute Disease↗
PubMedDate not supplied

Atrial natriuretic factor production and secretion during clinical total artificial heart-bridge-to-transplantation.

In 5 total artificial heart (TAH)-bridge-to-transplant (BTT) patients production and secretion of atrial natriuretic factor (ANF)1 was studied before, during, and after TAH implantation. Bridging periods lasted between 9 and 28 days. Atrial biopsies were taken during implantation, and after TAH explantation for histologic and histochemical investigations to evaluate differences in morphology and ANF-content of the specific atrial granules. Plasma concentrations of ANF (pANF), aldosterone (PAC) and renin (PRC) were measured daily, as were hemodynamic parameters. In the preoperative state, pANF was always markedly elevated, while during TAH bridging, pANF remained moderately elevated with fluctuations. A positive correlation between pANF levels and right atrial pressure (RAP) was seen in all patients (p less than 0.05). Slight correlation was also observed between pANF and left atrial pressure (LAP), but no correlation was seen between pANF and systemic blood pressure, and no consistent pattern was seen in the plasma concentrations of either renin or aldosterone. After heart transplantation (HTX), which was performed in 3 patients, pANF levels were significantly higher than during TAH, and continued to show a positive correlation with RAP. From our data, we conclude that ANF production sites and secretory mechanisms remain intact during TAH-bridging, although upon implantation of a TAH, the remaining atria are deprived of all coronary blood supply and most autonomic innervation.

Adult↗
PubMedDate not supplied

Thromboembolism associated with junctional escape rhythm and atrial standstill after orthotopic heart transplantation.

We report on thromboembolism in a heart transplant recipient with mechanical atrial standstill and spontaneous echocardiographic contrast during intermittent periods of sinus arrest and junctional escape rhythm. The temporal relationship between the conversion of atrial flutter to junctional bradycardia and two episodes of thromboembolism strongly suggest a role of the lack of atrial contraction during junctional rhythm for the development of spontaneous echocardiographic contrast and thromboembolism.

Arrhythmias, Cardiac↗