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Biomedical subjects

C Wolter

Publications and source records attributed to C Wolter.

10 recordsLinked to original sources
PubMed2000

Permanent pacemaker therapy before and after the reunification of Germany: 16 years of experience at an East German regional pacing center.

The reunification of Germany had a significant influence on the management of patients with bradyarrhythmias. The current study was performed in a regional pacing center located in the former German Democratic Republic. It compares the situation of patients with critical bradyarrhythmias before and after the reunification of Germany in 1990 focusing on (1) indication for pacemaker implantation, (2) pacemaker modalities and function, (3) type of leads, (4) frequency of reintervention, and (5) early and late complications. The study covers 9 years before and 7 years after the reunification. A total of 1,125 patients were included, and the database was formed by the patients' files and the protocols of implantation. The situation before reunification was characterized by a nonavailability of modern physiological pacing devices and insufficient diagnostic equipment. Between 1981 and 1990, 384 patients underwent pacemaker implantation solely receiving single chamber devices with no or only minimal feasibility of programming. Between 1990 and 1996, 741 patients were treated, and they all received modern pacemakers having the capability of multiprogramming and telemetry. Regarding complications of pacemaker therapy, lead related problems significantly decreased after the reunification (dislocation, 5.3% vs 1.7%, P < 0.05; exit block, 6.7% vs 1.4%, P < 0.05) opposite to pacemaker infections, which significantly increasing after dual chamber pacemakers were implanted (2.2% vs 6.0%, P < 0.05). The reunification of Germany dramatically improved the situation of patients with critical bradyarrhythmias leading to free access to high-tech pacing equipment within a few months. However, the abrupt change from antiquated to modern pacemaker therapy created some new problems, especially regarding application and handling of modern physiological pacing devices.

Equipment Design↗
PubMed2000

Value of free prostate-specific antigen (Hybritech Tandem-R) in symptomatic patients consulting the urologist.

INTRODUCTION: Prostate-specific antigen (PSA) is a widely used tumor marker in the detection and follow-up of adenocarcinoma of the prostate. Selection of candidates for prostate biopsies is hampered by the lack of specificity resulting in a large number of unnecessary biopsies. The intention of our study was to compare the percent free PSA (f-PSA; Hybritech Tandem-R) with total PSA and age-specific PSA reference values to evaluate the clinical benefit in detecting patients with prostate cancer (PC) in a selected group of patients consulting the urologist. The question was whether cutoff points are influenced by this selection of patients. METHODS: A total of 188 patients, 114 with benign prostate hyperplasia (BPH) and 74 with PC were selected. It is a selected group of patients consulting the urologist. Diagnosis was confirmed in the BPH and PC groups by either ultrasound-guided biopsy or transurethral resection of the prostate or suprapubic adenomectomy or cystoprostatectomy. Total PSA (t-PSA) and f-PSA of all patients were measured before any manipulation by Tandem-R assay for f-PSA and Tandem-E assay for t-PSA (Hybritech). Mean values of age, prostate volume, t-PSA, f-PSA, percent f-PSA were compared in patients with BPH and PC by Mann-Whitney U test. The sensitivity and specificity of t-PSA and age-specific PSA were compared to the sensitivities and specificities of different cutoff points of percent f-PSA. RESULTS: The mean value of t-PSA, f-PSA and percent f-PSA in patients with BPH (n = 114) and PC (n = 74) were statistically significantly different. At PSA levels between 4 and 10 ng/ml 19% of negative biopsies could be avoided by the use of percent f-PSA (cutoff point 25%). There was no additional benefit of age-specific PSA. At a PSA of <4 ng/ml 6 of 7 PCs could be diagnosed by percent f-PSA (cutoff point 25%), whereas only 1 patient would be diagnosed by age-specific PSA. CONCLUSION: Percent f-PSA seems to decrease the biopsy rate at PSA levels from 4 to 10 ng/ml without missing a relevant number of cancers and to increase the detection rate at PSA <4 ng/ml. Our data indicate that it might be necessary to choose high cutoff points (25%; Tandem-E and R assay, Hybritech) in a selected study population consulting the urologist with large glands and a high prevalence of disease. However, this situation is not comparable to testing of screening populations. No benefit of age-specific PSA could be observed in this study.

Aged↗
PubMed1999

Local drug delivery: impact of pressure, substance characteristics, and stenting on drug transfer into the arterial wall.

Injection parameters for local drug delivery are frequently determined by studies with marker substances. However, the pharmacologic properties of the actual drug may influence delivery efficiency and lead to different results. Aim of this study was to assess the delivery capacities of two device-drug combinations in order to verify this approach for further in vivo studies. Tritiated (3H) preparations (5 ml) of the hydrophylic low-molecular-weight heparin reviparin and the lipophilic taxane paclitaxel were injected into the left anterior descending artery of freshly explanted porcine hearts with the Infusasleeve II catheter system. A balloon support pressure of 6 atm and infusion pressures of 40, 60, 80, or 100 psi were used. In three additional groups, reviparin was injected following stent implantation and paclitaxel was injected prior to or following stent implantation. Arteries along with surrounding myocardium were harvested. The artery was carefully dissected, and artery and myocardium were separately homogenized, and activity was measured. Of the totally delivered activity, 0.09%+/-0.03% (40 psi) to 0.17%+/-0.13% (100 psi) of reviparin and 2.03%+/-0.67% (60 psi) to 2.68%+/-1.57% (100 psi) of paclitaxel were found in the vessel wall. The results for different injection pressures were not significantly different for either drug. The percentage activity delivered to the vessel wall was substantially larger in the paclitaxel group as compared to reviparin delivery (P < 0.01 at 60, 80, and 100 psi). The mean concentration of reviparin in the artery was 20 to 33 times higher than in the myocardium. For paclitaxel the factors were 110 to 243. Stent implantation prior to or following local delivery did not result in a different delivery efficiency. The results demonstrate that the characteristics of the delivered drug contribute largely to the delivery efficiency. Using identical injection parameters, drug concentrations in the arterial wall were significantly higher for the lipophilic paclitaxel as compared to the hydrophilic reviparin. Stenting of the artery did not influence delivery efficiency.

Animals↗
PubMed1998

Optimizing frequency and number of controls for automatic multichannel analyzers.

Sampling strategy fundamentally influences the effectiveness of quality control with control charts. This study shows a simple approach for optimizing the control strategy for automatic multichannel analyzers that takes into account cost-efficiency considerations. Our main focus is on the frequency of controls necessary. The methods used are based on a field study (on a Hitachi/BM 747), the views of experts, and computer simulations of customary cost-models together with a survey of the literature. We found that industrial cost-models are applicable only with distinct limitations, but-unlike the test-yield model-they offer consistent solutions. On the basis of the field study and the opinions of experts, we adjusted the control strategy to account for inadequacies in the theoretical models. The combined result is that, for effective operation, the number of samples between controls may reach values up to 100 and should not require controls more often than every 30 samples on comparable multichannel analyzers. For adequate statistical performance, a simple 3-SD Shewhart chart usually requires not more than two controls of the same material at each time.

Autoanalysis↗
PubMed1981

[Examination of the effect of aorto-coronary revascularisation by means of exercise tests (author's transl)].

The purpose of this study was to determine the value of exercise tests in the examination of the effect of aorto-coronary revascularisation. 48 patients (mean age 52 +/- 6 years) were examined 5.0 +/- 1.9 months before and 4.9 +/- 3.0 months after coronary revascularisation by means of coronary and left ventricular angiography. Left ventricular function at rest was unchanged. 122 grafts were constructed, the patency rate was 86%. Preoperatively two exercise tests with a bicycle ergometer were performed, some days before angiography and some days before operation, respectively. A third test was performed postoperatively (again some days before angiography). During exercise at identical work load, heart rate and systolic blood pressure did not change significantly pre- and postoperatively. At the second preoperative examination, pulmonary artery pressure (31.6 +/- 11.3 mm Hg) was significantly lower than at the first examination (36.3 +/- 10.8 mm Hg). Postoperatively there was a further decrease of mean pulmonary artery pressure (27.6 +/- 6.5 mm Hg). At the highest work load, mean pulmonary artery pressure was significantly lower at the second preoperative and at the postoperative examination (34.4 +/- 11.6 and 31.3 +/- 8.1 mm Hg versus 39.6 +/- 9.8 mm Hg). The explanation of the preoperative reduction of pulmonary artery pressure is not clear. The pressure decrease must be considered in the examination of the effect of aorto-coronary revascularisation by means of exercise tests.

Coronary Angiography↗
PubMed1977

Hyperkalemia due to selective hypoaldosteronism.

Hyperkalemia secondary to hyporeninemic hypoaldosteronism with a normal glucocorticoid function was diagnosed in a 47-year-old man with moderate renal insufficiency. Mineralocorticoid administration corrected the hyperkalemia. A probable explanation for hyporeninemia and hypoaldosteronism in this syndrome is that the primary defect is an inability to release renin and the resultant angiotensin deficiency leads to an aldosterone deficiency.

Acidosis↗