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Biomedical subjects

H Greve

Publications and source records attributed to H Greve.

At least 19 recordsLinked to original sources
PubMed2001

[Coronary bypass surgery in May-Hegglin anomaly].

HISTORY: Twelve years prior to hospitalization because of a severe bleeding, a 70 year old patient was diagnosed with a May-Hegglin anomaly, which is a rare autosomal dominant inherited form of thrombocytopenia. INVESTIGATIONS: The blood smear contained signs of the May-Hegglin anomaly: Döhle's inclusion bodies and giant platelets. Platelet counts were around 30 G/l. Coronary angiography revealed a highly severe left main stenosis. TREATMENT AND COURSE: Even using maximum drug therapy, angina pectoris could not be stabilized. Therefore emergency coronary artery bypass grafting had to be performed. Before skin incision 3 micrograms/kg DDAVP (Desmopressin) were administered and after extracorporeal circulation 8 units of platelets were transfused. In addition, perioperative coagulation management was performed according to usual standards. There were no bleeding complications. The patient could leave the clinic after 11 days in stable condition. CONCLUSION: Patients showing May-Hegglin anomaly, even with serious thrombocytopenia, can be operated using extracorporal circulation without a high risk of bleeding.

Adult↗
PubMed2001

Analysis of calcium imaging signals from the honeybee brain by nonlinear models.

Recent Ca(2+)-imaging studies on the antennal lobe of the honeybee (Apis mellifera) have shown that olfactory stimuli evoke complex spatiotemporal changes of the intracellular Ca(2+) concentration, in which stimulus-dependent subsets of glomeruli are highlighted. In this work we use nonlinear models for the quantitative identification of the spatial and temporal properties of the Ca(2+)-dependent fluorescence signal. This technique describes time series of the Ca(2+) signal as a superposition of biophysically motivated model functions for photobleaching and Ca(2+) dynamics and provides optimal estimates of their amplitudes (signal strengths) and time constants together with error measures. Using this method, we can reliably identify two different stimulus-dependent signal components. Their delays and rise times, delta(c1) = (0.4 +/- 0.3) s, tau(c1) = (3.8 +/- 1.2) s for the fast component and delta(c2) = (2.4 +/- 0.6) s, tau(c2) = (10.3 +/- 3.2) s for the slow component, are constant over space and across different odors and animals. In chronological experiments, the amplitude of the fast (slow) component often decreases (increases) with time. The pattern of the Ca(2+) dynamics in space and time can be reliably described as a superposition of only two spatiotemporally separable patterns based on the fast and slow components. However, the distributions of both components over space turn out to differ from each other, and more work has to be done in order to specify their relationship with neuronal activity.

Algorithms↗
PubMed2001

Early clinical experience with the On-X prosthetic heart valve.

BACKGROUND AND AIM OF THE STUDY: The study was designed to investigate the clinical performance of the On-X prosthetic heart valve in a multicenter experience. METHODS: Between September 1996 and September 1999, 301 patients (56% males) underwent isolated On-X valve replacement (184 isolated aortic (AVR), 117 isolated mitral (MVR)) at 11 European centers under a standardized protocol. Average age at implant was 60.2 years. Office or hospital follow up was required by the protocol; average follow up on all patients was 11 months. RESULTS: Thirty-day mortality in the study was 2.2% for AVR and 6.0% for MVR, with valve-related mortality of 0.5% for AVR. There were eight late deaths (0.7%/pt-yr AVR and 2.3%/pt-yr MVR). Two of these deaths were sudden, and thus possibly valve-related (one AVR, one MVR). Early total valve-related morbidity was 3.5% for AVR and 2.6% for MVR. In total, 13 thromboembolic events occurred; one early event in AVR resulted in death (0.5%), and one transient early event occurred in MVR (0.9%). There were 11 late events (seven AVR (1.7%/pt-yr) and four MVR (1.8%/pt-yr)), for a two-year freedom from thromboembolism of 96.6% after AVR and 97.1% after MVR. Three late bleeding events occurred, all after AVR (0.7%/pt-yr and 98.9% free at two years). Major paravalvular leaks requiring reoperation occurred on two occasions early (one AVR (0.5%), one MVR (0.8%)) and once late in MVR (0.5%/pt-yr). Late minor, untreated paravalvular leaks occurred in three AVR patients (0.7%/pt-yr) and in one MVR patient (0.5%/pt-yr). Prosthetic endocarditis occurred four times (two AVR (0.5%/pt-yr), two MVR (0.9%/pt-yr)), all within the first 12 months of surgery. Actuarial freedom from all valve-related events at two years was 88.7% for AVR and 88.1% for MVR. NYHA class was improved in 75.8% of AVR patients and 70.6% of MVR patients at two years after surgery. CONCLUSION: These early results indicate that the On-X valve provides satisfactory clinical outcome in the immediate postoperative period, and that the valve is both safe and effective.

Actuarial Analysis↗
PubMed2000

Examination of hemolytic potential with the On-X(R) prosthetic heart valve.

BACKGROUND AND AIM OF THE STUDY: Mechanical valves are known to produce chronic, subclinical hemolysis in most patients. Generally, haptoglobin is reduced to below normal in most patients, while lactate dehydrogenase (LDH) is increased to as much as 200% above the upper normal, sometimes resulting in anemia. The study was designed to investigate the clinical hemolysis of the On-X(R) prosthetic heart valve in a multicenter experience with a standard protocol and a single clinical laboratory. METHODS: Between September 1996 and August 1998, 248 patients underwent isolated valve replacement at 10 European centers. Blood samples were collected from these preoperatively and at 3-6 months and one year postoperatively. All samples were analyzed at a central laboratory, thus assuring poolability of the data. In total, 151 patients were tested at 3-6 months, and 62 at one year. Blood parameters measured were LDH, haptoglobin, hematocrit, total hemoglobin, red cell count and reticulocyte count. Paired analysis was used to compare preoperative baseline values with 3-6-month and one-year values. Data were analyzed with regard to both valve position and size. RESULTS: At 3-6 months and one year after surgery, average values for hematocrit, hemoglobin, red cell count and reticulocyte count were all near the center of the normal range, regardless of valve position or size. Statistically significant increases in red cell count and decreases in reticulocyte count occurred after both aortic valve replacement (AVR) and mitral valve replacement (MVR). These changes were of no clinical importance, but indicate that anemia has not occurred in these patients. At 3-6 months, haptoglobin was reduced to below normal in 86% of both AVR and MVR patients; this also occurred after one year and was statistically significant. Postoperatively, the mean LDH value in AVR was 228 U/l (91% of upper normal, 250 U/l) at 3-6 months, and 246 U/l (98% of upper normal) at one year. In MVR, these LDH values were 271 U/l (108% of upper normal) and 265 U/l (106% of upper normal). CONCLUSIONS: These results indicate that the On-X valve causes lower levels of chronic hemolysis in the immediate postoperative period and up to one year after surgery, especially when compared with reports of LDH elevations up to 200% of upper normal. Hemolytic anemia has not occurred in this patient population.

Aortic Valve↗
PubMed1996

Pathomorphological characteristics of resected mitral valves after unsuccessful valvuloplasty.

OBJECTIVE: Percutaneous mitral valvuloplasty has been shown to be an acceptable alternative to surgery as treatment for selected patients with severe mitral stenosis. We examined hemodynamic, echocardiographic, and pathomorphologic findings in a series of 308 patients undergoing balloon valvuloplasty, 41 of whom underwent subsequent surgery, in search of possible predictors of an unsuccessful outcome. INTERVENTION AND RESULTS: Patients with severe mitral stenosis underwent Inoue single ballon valvuloplasty over a 48-month period and had follow-up for a mean of 14.5+/-16.8 months (range 1 to 64 months). Of the 308 patients, 267 (Group I) were clinically improved and stable throughout follow-up, while subsequent surgery was required in 41 (Group II) after 38.2+/-143.5 days (range 1 to 1212). Significant differences between the groups were observed for NYHA class (2.7+/-0.6 vs 2.9+/-0.6, p<0.05), mitral valve area (1.0+/-0.3 vs 0.9+/-0.2 cm2, p<0.01) and left atrial endsystolic dimension by echo (51.3+/-8.0 vs 55.4+/-10.2 mm, p<0.01). Two of the 41 Group II patients underwent surgery for left to right shunting, 1 for tamponade and 2 were lost to follow-up. The excised mitral valves of the remaining 36 patients all showed calcification and/or fibrosis: 9 homogenous, 5 non-homogenous; 19 were classified as having a funnel-shaped deformity, and 3 did not fit into a discrete category. Among the funnel-shaped valves, 13 had a tear versus 6 where dilation was primarily accomplished by stretching. Only one of 9 valves with homogenous calcification was torn, whereas a tear was noted in 3 of the 5 with non-homogenous calcification. CONCLUSION: Funnel-shaped valves and those with non-homogenous distribution of calcification and/or fibrosis appear to be least suitable for balloon valvuloplasty.

Adult↗
PubMed1995

[Percutaneous mitral valvulotomy with the Inoue balloon in over 65-year-old patients--acute results and short-term follow-up in comparison with younger patients].

Percutaneous balloon mitral valvulotomy (PBMV) with the Inoue-balloon is a proven therapy in young patients with mitral stenosis. In this study, we investigated primary results in PBMV of elderly patients. In 383 patients with mitral stenosis PBMV was done with the Inoue-balloon. We compared primary success rates and short-term follow-up of 287 (74.9%) < 65-year-old patients and 96 (26.1%) > or = 65-year-old patients. Elderly patients were more likely to have atrial fibrillation (58% vs. 45%; p < 0.05), tricuspid regurgitation < or = II degrees (58% vs. 45%; p < 0.05), coronary artery disease (16% vs. 6%; p < 0.01), and previous pulmonary edema (42% vs. 30%; p < 0.05). PBMV was successful in 73.9% of the elderly and 84.7% of the younger patients (p < 0.05). Mitral valve gradients could be reduced from 12.5 +/- 11.6 mm Hg to 6.2 +/- 6.8 mmHg (p < 0.001) in elderly patients and from 15.5 +/- 6.9 mm Hg to 7.0 +/- 3.2 mm Hg (p < 0.001) in younger patients. Mitral valve areas increased from 1.0 +/- 0.3 cm2 to 1.6 +/- 0.5 cm2 (p < 0.001) in elderly patients and from 1.0 +/- 0.3 cm2 to 1.7 +/- 0.4 cm2 (p < 0.001) in younger patients. No patient died during the procedure. Two younger patients had emergency surgery because of pericardial tamponade following transseptal puncture. After PBMV elderly patients had more often an increase of mitral regurgitation (47% vs. 35%; p < 0.05) without need of an emergency mitral valve replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Evaluation of the bioequivalence of two fast-releasing iron(II) sulfate formulations].

Bioequivalence of a new oral iron formulation (A: FE(II)SO4.H2O, capsule with 100 mg Fe++, Eryfer 100, CAS 7782-63-0) with the standard formulation (B: Fe(II)SO4.H2O, capsule with 50 mg Fe++, Eryfer) was demonstrated after administration of 100 mg Fe++ in a single-dose two-way cross-over design to 16 normal female volunteers. Iron concentrations were monitored from 24 h before (basal) to 24 h post application. The area under concentration difference curve AUC(diff) and the maximal concentration difference Cmax(diff) were calculated subtracting the basal from the time-corresponding postabsorptive concentrations. AUC(diff) (A: 170 nmol/ml. h, B: 168 nmol/ml.h) and Cmax(diff) (A: 23.3 nmol/ml, B: 21.8 nmol/ml) showed but minor differences between formulations. The AUC(diff) and Cmax ratio (A/B) and the corresponding 90% confidence intervals, 102% (74-129%) and 107% (91-123%), were included by the acceptance range of 70-130% as stated in the study protocol. Hence, both formulations were bioequivalent with respect to rate and extent. The ANOVA coefficient of variation of Cmax(diff) was considerably smaller than that of AUC(diff) (26% versus 44%). The characteristics based on the postabsorptive iron increase (post-absorptive concentrations minus concentration preceding immediately application) AUC(pad) (ratio 99% (83-114%) and Cmax(pad) (ratio 104% (95-112%) exhibited smaller ANOVA-CVs (25% and 14%, respectively) as compared with AUC(diff) and Cmax(diff). All these characteristics appeared to be rather normal than log-normal distributed. It was concluded that the study design was selective to demonstrate an adequate bioavailability of iron formulations.

Adult↗
PubMed1992

[Priority of interventions: myocardial revascularization--heart valve replacement--carotid endarterectomy--tumor surgery].

The simultaneous treatment of heart and concomitant disease is now possible in many cases, and is usual in heart-valve disease with coexistent coronary artery disease. If in addition to the heart disease, a carotid artery stenosis exists, a simultaneous operation is preferred in our clinic using the aid of extracorporeal circulation (with hypothermia, hemodilution, and full heparinization). When both heart disease that is in need of operation and a malignant tumor are present, the clinical strategy can be dependent only on the prognosis of the malignant illness.

Aged↗
PubMed1990

Influence of collagen lattice on the metabolism of small proteoglycan II by cultured fibroblasts.

Small dermatan sulphate proteoglycan II from cultured human skin fibroblasts interacts with type I collagen in vitro and in vivo. When fibroblasts are maintained in a type I collagen lattice the proteoglycan remains exclusively within the lattice, and its association with fibrils can be demonstrated immunocytochemically. On the basis of [35S]sulphate incorporation, small proteoglycan II comprises about 80% of total proteoglycans secreted by cells in monolayer culture. In a collagen lattice, fibroblasts down-regulate its synthesis to the level of large chondroitin sulphate/dermatan sulphate and of heparan sulphate proteoglycans, the synthesis of which remains unaffected. Compared with the product from monolayer cultures, small proteoglycan II from collagen gels contained a longer polysaccharide chain which is characterized by a larger proportion of disulphated and a smaller proportion of monosulphated glucuronic acid-containing disaccharides. The half-life varied between 60 and 110 h. It is suggested that the compositional differences between the proteoglycan from monolayer cultures and from cells in a collagen lattice are related to the slower intracellular trafficking of the proteoglycan under the latter culture conditions.

Adult↗
PubMed1989

[Experimental studies of stabilization of refixation following median sternotomy].

So far several methods have been established for refixing the sternum halves after longitudinal sternotomy like steel wire or steel strap according to Parham. The use of twisted absorbable PDS-strings is new. During experimental investigations in corpse sterna during tension load the different refixing methods were compared. As a result we found an increased tension stability of the sternum refixation as well as the reversibility of suture dehiscences, if occurred, after employment of the elastic PDS-string. Polydioxanon is a suggestive alternative compared with the usual not absorbable materials for refixation of the sternum.

Biomechanical Phenomena↗
PubMed1989

Primary angiosarcoma of the heart.

A case report on a 27 year old woman with an inoperable angiosarcoma of the right atrium is presented. The tumor localization was established by echocardiography, computed tomography and cinecardiography. There was no evidence of distant metastases at diagnosis. After exploratory thoracotomy with surgical biopsy a radiotherapy was started covering the whole heart and the mediastinum. Superior Vena Cava Syndrome was improved quickly and reducing the target volume to the right atrium after 40 Gy radiotherapy was continued up to a total dose of 60 Gy. A complete remission was documented by echocardiography and computed tomography. Chemotherapy ("VAPAC") for distant metastases led to partial remission. The patient died 15 months after diagnosis from brain metastases. Autopsy revealed no macroscopic evidence of tumor in the right atrium. A combined modality approach with surgical tumor mass reduction followed by high dose locoregional radiotherapy (60 Gy) and combination chemotherapy (e.g. "VAPAC") is suggested.

Adult↗
PubMed1988

Influence of chlorate on proteoglycan biosynthesis by cultured human fibroblasts.

The influence of chlorate, an inhibitor of sulfate adenylyltransferase, on biosynthesis and secretion of proteoglycans was investigated in cultured human skin fibroblasts. At up to 10 mM concentrations, chlorate caused a reduction of [35S]sulfate incorporation into small chondroitin sulfate/dermatan sulfate proteoglycan by up to 96%. Incorporation of [3H]leucine and [3H] glucosamine was only slightly affected. No influence was seen on the polymerization degree of the polysaccharide chain as judged by gel filtration, and on the kinetics of secretion of the proteoglycan. Concomitant with reduced sulfation, however, was an increased sensitivity toward chondroitin AC lyase which suggests a diminished epimerization of D-glucuronic acid to L-iduronic acid residues. Agarose gel electrophoresis revealed that all polysaccharide chains of control chondroitin sulfate/dermatan sulfate proteoglycan exhibited a similar sulfation degree. Chlorate treatment led to the formation of polysaccharide chains of widely varying degree of sulfation, but fully sulfated chains were synthesized even in the presence of 3 mM chlorate, and sulfate-free chondroitin was not detected. Studying the effects of chlorate treatment on the synthesis of other proteoglycan types it was found that, in cell-associated galactosaminoglycans, 6-sulfation of N-acetylgalactosamine residues was less affected than was 4-sulfation. In case of heparan sulfate the synthesis of sulfamate groups was less impaired than sulfate ester formation. Nitrous acid degradation at pH 4.1 indicated the presence of unsubstituted amino groups. Chlorate treatment may be considered as a means for the production of proteoglycans with defined structural alterations.

Adult↗
PubMed1988

Substitution of the wall of the trachea by absorbable synthetic material.

Synthetic, absorbable tissue proved to supply a valuable "interim support" for an orderly reconstruction of the wall of the trachea during the first three months following surgery. This is in general the result of experiments in which the use of implanted Polyglactin 910 as a substitute material for the tracheal wall of rats and rabbits was tested. Additionally the possibilities for satisfactory stabilization of the tracheal wall by means of Polydioxanon, another synthetic substance, which is absorbed more slowly, were investigated. The experiments were performed in a total of 30 rats and 70 rabbits. Initial attempts to substitute the entire circumference of the tracheal wall in the area of the neck by synthetics resulted in excessive difficulties post-surgically. Frequently substantial stenoses, obstructing respiration, developed. Consequently, patches of substitute material, covering more than half of the circumference of the trachea, were applied. The periods of survival of the animals ranged from one to 23 weeks. Following autopsy and macroscopical inspection, selected specimens were examined histologically by means of light microscopes and scanning electron microscopes. Evaluation of the samples showed progressive lining of the inner surface of the prosthetic patches with connective tissue and subsequent covering with squamous cell epithelium. On the average, approximately six weeks after surgery, ciliated columnar epithelium resembling normal respiratory mucosa developed. Gradually the synthetic fabric was replaced by dense connective tissue, which finally contained newly generated hyaline cartilage also. The very slow rate of dissolution of the polydioxanone material provided sufficient time for the formation of a new, stratified wall of the trachea, maintaining sufficient clearance in the tracheal lumen.

Animals↗
PubMed1988

Clinical experience with the rate responsive pacemaker Sensolog 703.

Pacemaker therapy with rate responsive systems becomes increasingly more important. Numerous clinical and experimental trials have been conducted thus far to investigate different sensors of metabolic demands of the body, functioning independently of an atrial electrogram. To transform mechanical energy into electrical energy, activity-triggered systems utilize a piezo-quartz as their sensor. Thirty five patients suffering from pathological bradyarrhythmias and therefore from an inadequate increase of the heart rate during exercise were supplied with a Sensolog 703. Clinical follow-up was first performed with the help of treadmill ergometry, later on by walking on flat ground and climbing steps. The settings due to the first test caused inadequately high stimulation rates. A 24-h-Holter-ECG was necessary to control the programming and the rate profile in the patient's daily life. Using only the histogram and the rateread function, all rate adaptive parameters of the Sensolog 703 could be set by walking on flat ground and climbing steps. We defined a frequency of 75-85 min-1 to be appropriate during walking, respectively "low work." Individual programming ranged from 2-5/8-15/high-low/very fast-medium/fast-medium (slope, threshold, gain, reaction and recovery time). Reprogramming based on 24-h-Holter ECG was only necessary if the pacemaker was formerly adjusted with the help of treadmill ergometry. Besides, we observed an increase of the stimulation rate due to vibrations not related to exercise, e.g., by driving in a car.

Aged↗
PubMed1988

Termination of malignant ventricular tachycardias by use of an automatical defibrillator (AICD) in combination with an antitachycardial pacemaker.

We implanted an "Automatic Implantable Converter-Defibrillator" (AICD) and as far as useful an antitachycardial pacemaker (Intertach) in addition in 11 patients suffering from malignant ventricular tachycardias via a median sternotomy. In eight cases a coronary artery disease and in three cases a dilatative myopathy was the intrinsic disease. During surgery in all patients we attempted to trigger ventricular tachycardias and their termination by programmed stimulation. This procedure was successful in nine patients who received an antitachycardial pacemaker system. After the wounds healing, repeated induced ventricular tachycardias in all patients, who received a combination of the systems, could be terminated by the antitachycardial pacemaker prior to an intervention of the implanted defibrillator.

Cardiac Pacing, Artificial↗
PubMed1988

[Uni- and bipolar 2-chamber stimulation with a DDD system of programmable polarity].

In order to compare bi- (b) and unipolar (u) stimulation, sensing and electrical interference, twelve patients were followed over a period of ten months. The implanted device was the CPI Delta 925, programmable to the bi- and unipolar mode in the atrium (a) as well as in the ventricle (v). A CPI-4266 screw-in lead positioned in the atrium and a CPI-4260 hook lead placed in the ventricle were connected to the pacemaker. Intraoperatively determined were: (1) the threshold at pulse durations of 0.1 ms, of 0.5 ms and of 1.0 ms, (2) the P/QRS-amplitude, (3) the slew-rate and (4) the resistance in both the bi- and unipolar mode. Having programmed the atrial sensitivity to 0.25 mV or to 0.75 mV and the ventricular sensitivity to 0.5 mV or to 1.5 mV, we postoperatively examined and compared in the two modes of polarity the threshold (2.2 V and 5 V), the P/QRS-amplitude and finally the electrical interference triggered with the help of chest wall stimulation. All measurements were performed one day, four weeks and four months after implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗