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Biomedical subjects

A Haverich

Publications and source records attributed to A Haverich.

At least 271 records · Page 15Linked to original sources
PubMed1995

Radiographic assessment of structural defects in Björk-Shiley convexo-concave prostheses.

Following the implantation of Björk Shiley 60 degrees convexo-concave (BS-CC) prostheses, outlet strut fracture rates up to 2.5% per year have been reported. According to experimental results and clinical observations, single leg separations are regarded as the primary mechanisms leading to complete outlet strut fracture after a certain interval. In an experimental study the question was addressed, whether single leg separation can be identified by especially developed radiographic means, before outlet strut fracture occurs. Five BS-CC mitral prostheses (29-31 mm) with intentionally made single leg separations of defined gas sizes (0-75 microns) and one intact mitral prostheses were implanted in sheep in a double-blind study design. Repeat non-invasive investigations were then performed applying a recently developed fluoroscopy imaging technique with direct radiographic magnification (DIMA COR C22). Single leg separations with gap sizes of more than 25 microns were properly detected using DIMA COR C22. Separations 25 microns or less could not be detected with certainty but were evaluated as probable or possible as a result of multiple investigations. The intact prosthesis was correctly identified, but was investigated on only one occasion. Non-invasive control of Björk-Shiley CC mitral prostheses applying especially developed direct radiographic magnification may allow for a reliable assessment of single leg separation with gap sizes of more than 25 microns in sheep. Using this technique of non-invasive serial investigations on particular patients with high probability of outlet strut fracture appears feasible, anticipating single leg separation detectability in humans. This has to be assessed in a second step.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Endothelial dysfunction in heart transplanted patients with graft vasculopathy.

The pathological mechanism of cardiac transplant vasculopathy (TVP) is uncertain. We tested the hypothesis that the endothelial function, in terms of the release of endothelium-derived relaxing factor, is impaired in patients with angiographic evidence of transplant vasculopathy. In a pilot study, the effects of the substances used (substance P, acetylcholine, nitroglycerin) were assessed as regards tone of pre-contracted human coronary arteries in vitro, obtained from recipient hearts during cardiac transplantation. The study shows that substance P is a "pure' endothelium-dependent dilator of epicardial human coronary arteries, whereas acetylcholine has a more complex effect on vascular tone involving both a direct effect on the endothelium and the smooth muscle cells. In a second pilot study, the effects of intracoronary infusions of substance P (5-100 pmol.min-1) and acetylcholine (2-50 nmol.min-1) on flow velocity were compared in 10 patients undergoing cardiac catherization after heart transplantation. Flow velocity was determined by a 3F Doppler catheter placed into the proximal segment of the left anterior descending artery (LAD). Both drugs increased concentration-dependent flow velocity; substance P and acetylcholine maximally increased flow velocity by about 85 +/- 24% and 143 +/- 15%, respectively (P < 0.05). In a third study, 23 patients undergoing diagnostic cardiac catheterization were included approximately 40 months after heart transplantation. Patients were classified into those with (n = 8) and those without (n = 15) angiographic evidence of TVP. Coronary flow velocity (by Doppler) and epicardial coronary diameter (by quantitative angiography) were determined after intracoronary injections of substance P (20 pmol), nitroglycerin (0.1 mg), and papaverine (8 mg). Substances were injected through the central lumen which was placed into the LAD. Increases in flow velocity in response to substance P were significantly less in patients with TVP than in patients without evidence of TVP. Moreover, flow-mediated vasodilation in response to papaverine was almost abolished in patients with TVP. Vasodilation in response to nitroglycerin and maximal increase in flow velocity in response to papaverine was similar in both groups. These results suggest that TVP is associated with endothelial dysfunction, which may contribute to the pathogenesis of TVP and its vascular complications.

Acetylcholine↗
PubMed1995

[Prevention and therapy of prosthesis infections in the thoracic area].

Infections of vascular prostheses following replacement of the thoracic aorta remain a rare complication, fortunately. The incidence of prosthetic infection amounts to approximately 1.6%, however, there is only limited information from single center studies, and linearized actuarial data for more exact estimations are not available. Experience with prophylaxis and treatment of bacterial endocarditis as well as data available from peripheral vascular reconstruction nevertheless allow the development of treatment strategies concerning this complication. Experimentally, there is clear evidence that pretreatment of Dacron-grafts using the fibrin sealant-antibiotic compound results in a significant protection from infection, created by artificial contamination with staphylococcus aureus. This concept could clearly be confirmed in clinical series involving treatment of prosthetic valve endocarditis. Currently, the concept of implantation of cryopreserved human vascular allografts is studied clinically. Its efficiency in infected areas and following prosthetic replacement of the thoracic aorta has not been proven. Some preliminary results as well as studies on treatment for bacterial endocarditis would suggest a clear advantage of this strategy, however statistically significant improvements have not been published. Currently available data, however, appear to be sufficient to advocate potentially successful techniques as a prophylaxis in routine thoracic aortic replacement as well as for treatment in case of a vascular prosthetic infection following such procedures.

Animals↗
PubMed1995

[Intramural hemorrhage of the thoracic aorta as a precursor of dissection].

Aortic dissection without entry and blood-flow in a false lumen was recently identified at necropsy and in vivo as intramural hemorrhage in the aortic wall (IMH). It was the purpose of the study to elucidate clinical signs and prognosis in this rare and poorly understood condition. Among 360 prospectively evaluated patients with clinical suspicion of aortic dissection, 195 patients presented with evidence of aortic disease. Of these, 25 patients (13.2%) had IMH of the thoracic aorta with no primary intimal tear, flap or overt dissection as shown by MRI (n = 12), contrast enhanced CT (n = 14) and TEE (n = 3). IMH was confirmed intraoperatively or at necropsy. There were 16 men and 9 women of ages 56 +/- 13 years; arterial hypertension was associated in 84% and Marfan's syndrome in 12%. IMH involved the ascending aorta in 12 (48%), the arch in 2 (8%), and the descending aorta in 11 cases (44%). IMH occupied 8.5 +/- 5 cm in length and 2.0 +/- 1.2 cm in aortic wall thickness. Both aortic regurgitation and pericardial/mediastinal effusion was present in 42% of type A and in 18% of type B IMH. IMH progression to overt dissection, rupture and/or acute tamponade occurred in 8/25 cases (32%) within 24 to 72 h, indicating the need for urgent surgical repair. The 30-day mortality of IMH inflicting the ascending aorta was 80% (4 of 5) with medical treatment in contrast to none (of 7) with early surgical treatment (p < 0.01). One-year survival was 71% in surgically treated patients and 20% with medical treatment (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Induction of endothelial adhesion molecules by rat cytomegalovirus in allogeneic lung transplantation in the rat.

Cytomegalovirus (CMV) infection is known to be a major risk factor for the development of chronic transplant rejection in heart and lung transplantation. A possible mechanism for the induction of lung transplant rejection by CMV infection is the inflammatory upregulation of adhesion ligand molecules by the viral infection leading to an increased endothelial-leucocyte interaction. To study this question, an experimental model was established in the rat using a rat cytomegalovirus (RCMV) infection and acute lung transplant rejection in left single lung transplantation. The distribution of RCMV, intercellular adhesion molecule-1 (ICAM-1) and its leucocyte receptor CD11a (LFA-1) were investigated by immunohistochemistry. The viral infection was observed in transplant lungs of infected hosts as early as day 11. The expression of ICAM-1 on endothelial cells was induced and enhanced by RCMV infection, and infiltration of CD11a-positive leucocytes found to be increased in infected recipients. An acceleration of the rejection of the allografts by the hosts was found.

Animals↗
PubMed1994

Effects of saterinone and its enantiomers R(+)-saterinone and S(-)-saterinone on the phosphodiesterase isoenzymes from ventricular tissue of failing human hearts and porcine hearts.

Stereoisomers often exhibit differences in their pharmacological activities. Therefore, the phosphodiesterase inhibitory effects of the cardiotonic agent saterinone in form of the racemate were investigated in comparison with the inhibitory properties of its enantiomers R(+)- and S(-)-saterinone. For this purpose the phosphodiesterase isoenzymes from ventricular tissue of failing human hearts and porcine hearts were separated by DEAE-sepharose anion exchange chromatography. Four different phosphodiesterase isoenzymes were isolated from failing human myocardium and designated phosphodiesterase I-IV. Three phosphodiesterase isoenzymes could be separated from ventricular tissue of porcine hearts. A Ca2+/calmodulin stimulated phosphodiesterase I was not detectable in porcine myocardium. In failing human hearts racemic saterinone was a potent inhibitor of phosphodiesterase III (IC50 0.02 mumol/l) and IV (IC50 0.03 mumol/l) as compared to the inhibition of phosphodiesterase I (IC50 37.3 mumol/l) and II (IC50 51.4 mumol/l). In comparison with the racemate, R(+)- and S(-)-saterinone showed only slight differences in their phosphodiesterase inhibitory effects. R(+)-saterinone inhibited phosphodiesterase III slightly but significantly more potently and selectively than did S(-)-saterinone. Compared to the inhibition of phosphodiesterase I and II both enantiomers were similarly potent and selective inhibitors of phosphodiesterase III and IV. Similar results were obtained in porcine hearts. It is concluded that the racemate saterinone and its enantiomers (R(+)- and S(-)-saterinone are virtually equipotent concerning the inhibition of phosphodiesterase isoenzymes isolated from failing human hearts or porcine ventricular tissue. The enantiomers of saterinone did not exhibit distinct stereoselectivity in their phosphodiesterase inhibitory effects.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Nosocomial hepatitis B virus infections in cardiac transplant recipients transmitted during transvenous endomyocardial biopsy.

Between March 1986 and September 1990, 67 of 243 cardiac transplant recipients in outpatient care at our clinic became hepatitis B virus surface antigen (HBsAg) positive after operation. The HBsAg of 63 patients belonged to the subtype ay, suggesting a common source of infection. These 63 cases and 103 controls with negative hepatitis B virus (HBV) serology were studied in order to analyse the outbreak. The sources of infection were patients who were chronic HBsAg carriers. Infection was transmitted at the time of endomyocardial biopsy, if performed on the same day and in the same room after biopsy of an HBsAg positive patient. The most likely mode of HBV transmission was droplet contamination of instruments and/or medication vials used for subsequent patients. Performing biopsies on HBsAg positive and negative patients in separate rooms resulted in the termination of the outbreak.

Adult↗
PubMed1994

In vivo comparison of free coronary grafts using the inferior epigastric (IEA), the gastroepiploic (GEA) and the internal thoracic artery (ITA).

The validity of alternative arterial conduits for myocardial revascularization in comparison to internal thoracic artery (ITA) has not been sufficiently defined. Evaluation of the functional in vivo vascular properties of the different conduits may be appropriate to give a perspective on long-term graft qualities. The intraoperative function of single free grafts to the left anterior descending artery (LAD) was compared in inferior epigastric (IEA, n = 13), internal thoracic (ITA, n = 12) and gastroepiploic artery (GEA, n = 12) conduits. Graft flows were measured at four points of time, 1) in situ free flow after distal dissection (IEA: 42.2 ml/min, ITA: 68.8 ml/min, GEA: 61.1 ml/min), 2) free flow following proximal grafting to the aorta (IEA: 48.1 ml/min, ITA: 63.7 ml/min, GEA: 84.2 ml/min), 3) selective graft flow after distal attachment to the LAD (IEA: 52.6 ml/min, ITA: 77.5 ml/min, GEA: 102.8 ml/min), and 4) selective LAD graft flow following paraverine (Pap) stimulation (IEA: 98.4 ml/min, ITA: 128.0 ml/min, GEA: 142.9 ml/min). Endothelium-dependent and -independent relaxation was evaluated by examination of the intraluminal graft pressures at mechanically controlled constant flow rates. Following stimulation with substance P (SP), the change of intraluminal pressure (dp) was similar in IEA (dp: -20.0 mmHg) and GEA grafts (dp: -21.1 mmHg). Only ITA conduits were less reactive to SP (-9.7 mmHg). The response to acetylcholine (ACh) could only be assessed in ITA (dp: -16.0 mmHg) and IEA (dp: -10.7 mmHg) grafts. Gastroepiploic arteries did not react on ACh stimulation (dp: +0.4 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1994

Protection of the right ventricular myocardium during acute right heart failure from pulmonary hypertension.

Protection of the failing right ventricle (RV) in the surgical treatment of massive pulmonary embolism is a keystone for myocardial recovery. This study evaluated whether cardioplegia should be used or avoided. In a modified Langendorff rat heart model pulmonary embolism was simulated by afterload elevation (20 cm H2O) for 30 min. Hearts were arrested with cardioplegic solutions [St. Thomas Hospital (ST); University of Wisconsin (UW); oxygenated Krebs-Henseleit-Potassium (KHP)] and stored for 10 min or were allowed to beat empty (NoCP) for 15 min. After reestablishing of baseline conditions groups were measured for 60 min. Cardiac index (CI) decreased in all groups to 20% during afterload elevation. Group NoCP showed 68 and Group ST 65% recovery after 10 min and deteriorated after 30 min. After 60 min CI was 37 (ST) and 39% (NoCP). UW and KHP showed a significantly better recovery (KHP 100%; UW 88%). At 60 min CI decreased to 60 (KHP) and 64% (UW), but was still significantly higher than corresponding values of NoCP and ST. Following increased pulmonary afterload cardioplegia with UW or KHP solution is beneficial for RV recovery. The composition of the cardioplegia is obviously important and needs further study.

Acute Disease↗
PubMed1994

Scanning and transmission electron microscopy of human donor lungs: fine structure of the pulmonary parenchyma following preservation and ischemia.

In six cases of clinical single-lung transplantation, the contralateral donor lungs were studied by means of scanning (SEM) and transmission (TEM) electron microscopy. SEM and TEM revealed an overall good to excellent preservation of the pulmonary parenchyma. Since the donor double lung blocks, which were preserved by means of pulmonary arterial perfusion with modified Euro-Collins solution, were separated immediately prior to transplantation, transplanted and contralateral lungs had been subjected to identical influences. Comparing the arterial oxygenation achieved in the recipient 6 h after transplantation with the structural data of the corresponding contralateral donor lung, the degree of epithelial alterations appeared to be most important in determining postoperative lung function. Concerning the assessment of the quality of the alveolar epithelium, gradings performed independently by means of SEM and TEM yielded largely corresponding scores, while a significant shortcoming of SEM was the very limited access to the endothelial surface. Taking into account the relevance of epithelial injury in determining postoperative lung function, SEM can provide clinically relevant data more quickly than TEM. To quantify the fine structural alterations of human donor lungs, however, TEM-based morphometry is required.

Adolescent↗
PubMed1994

Heart transplantation under coumarin therapy: friend or foe?

Thirty-six patients were included in a retrospective study of the effect of pre-operative anticoagulant therapy on peri-operative blood loss and haemostatic changes after heart transplantation. Eleven patients (group H) had received intravenous heparin for at least 3 weeks before cardiac transplantation. Twelve patients (group P) had been transplanted when fully anticoagulated with phenprocoumon. A control group of 13 patients (group C) had undergone bypass grafting of their coronary arteries with no pre-operative anticoagulant therapy. Post-operative drainage from the chest drains was 700 ml (median) in group H, 425 ml in group P, and 360 ml in group C (group H vs. group C: P < 0.05). After heparinization for cardiopulmonary bypass, activated clotting time was 462 s (median) in group H, 1500 s in group P, and 727 s in group C (P < 0.003 vs. groups H and P). Post-operatively, patients in group P were given more units of fresh frozen plasma (median 2.5 units; P < 0.01), prothrombin complex concentrate (median 1000 I.U.; P < 0.05) and vitamin K (median 10 mg; P < 0.05) than groups H and C. Heart transplantation under full phenprocoumon therapy does not increase the likelihood of complications caused by peri-operative bleeding.

Adult↗
PubMed1994

[Lung transplantation in pulmonary hypertension].

Medical therapy for pulmonary hypertension is very limited and surgical interventions can only be performed in cases with acute or chronic pulmonary embolism. Secondary pulmonary hypertension of other origin (Eisenmengers' Syndrome) as well as primary pulmonary hypertension can only be treated with lung transplantation. In selected cases, three different techniques are available, heart-lung transplantation (HLTx), single, and double lung transplantation (SLTx; DLTx). The indication for any of these operations has to be made on an individual basis, and the degree of pulmonary hypertension and right ventricular failure have to be encountered. Also, correctability of the underlying congenital disorder in Eisenmenger Syndromes has to be taken into account. In principle, combined heart-lung transplantation will allow for the best results. Due to the restricted number of donor organs, SLTx and DLTx are performed in increasing numbers. SLTx for pulmonary hypertension, however, is characterized by a high number of early (reperfusion injury) and late complications (ventilation-perfusion-mismatch). Following lung transplantation in pulmonary hypertension, 1- and 5-year survival rates of 70 and 60% can be expected, respectively. Which type of transplantation will ultimately prove to be the best therapy for pulmonary hypertension has not yet been defined.

Follow-Up Studies↗
PubMed1994

[The value of myocardia protection in chronic hypoxic immature rat hearts].

This study examines the efficacy of three methods for myocardial protection during 8 hours of global ischema at 10 degrees C in immature (28 days) rat hearts subjected to lifelong hypoxia afforded by exposure to simulated high altitude. Hearts in group 1 were protected by rapid topical cooling alone, in group 2 by slow pre-arrest cooling with Krebs-Henseleit solution plus topical cooling and in group 3 by coronary perfusion with St. Thomas' Hospital cardioplegia No 2 (STS 2) plus topical cooling. Hearts in groups 4-6 served as controls without hypoxia and were protected accordingly. Parameters of myocardial function (left ventricular pressure, LVP), the metabolic status (myocardial concentration of ATP and creatine phosphate) and endothelial function (response to the vasodilator acetylcholine) were measured. Myocardial protection by rapid topical cooling alone resulted in equal--or significantly improved--postischemic recovery of LVP and endothelial function compared with slow pre-arrest cooling or additional protection with STS 2. The data advocate topical cooling for myocardial protection during surgical correction of cyanotic congenital cardiac disease in early infancy. In this age group, coronary perfusion with cold crystalloid solutions appears to aggravate ischemic endothelial injury.

Animals↗