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Biomedical subjects

B Reichart

Publications and source records attributed to B Reichart.

At least 253 records · Page 14Linked to original sources
PubMed1994

New morphologic aspects of explanted Hancock Extracorporeal pericardial bioprostheses.

Between 1981 and 1987 a total of 479 Hancock Extracorporeal bovine pericardial bioprostheses were implanted in 458 patients. During the time period from 1990 to 1993, 21 valves, 15 in the aortic and six in the mitral position, had to be removed 72 to 109 months after implantation. The mean age of these patients at the time of implantation was 49.7 +/- 10.5 years. All 21 removed as well as one unimplanted bioprosthesis were morphologically investigated. Visual examination, radiography, histology and ultrastructural observations were performed using scanning and transmission electron microscopy. In addition, clinical data were correlated to morphological findings. All valves failed due to cusp tears originating at the stent posts. Calcification was minimal in five valves, moderate in 10, and severe in five valves. Only one valve showed no mineralization at all. The late morphologic changes were associated with thickening of valve leaflets, tissue delamination, calcification, degeneration of collageneous network, and extensive insudation of plasma proteins and lipids. The present findings suggest that denatured collagen molecules may be capable of inducing immune response.

Adult↗
PubMed1993

Force-frequency-relation in human atrial and ventricular myocardium.

In human heart failure, an increase in frequency of stimulation is followed by a reduced force of contraction in vivo and in vitro. The present study aimed to investigate whether a different origin of the myocardial sample or pretreatment with the cardioprotective agent 2,3-butanedione-monoxime (BDM) influences the force-frequency-relationship in electrically driven muscle strips taken from failing and nonfailing human myocardium. With as well as without pretreatment with BDM, the altered force-frequency-relationship in failing compared to nonfailing human ventricular myocardium can be observed. The effectiveness and the potency to increase force of contraction following an increase in frequency of stimulation was significantly higher in atrial than in ventricular myocardium in nonfailing and failing tissue. The different observations in atrial and ventricular myocardium provide evidence for functionally relevant differences in the electromechanical coupling between the human atrial and ventricular myocardium.

Adult↗
PubMed1993

Percutaneous transluminal coronary angioplasty of focal coronary lesions after cardiac transplantation.

Transplant coronary artery disease is the greatest impediment to long-term survival beyond the first year after cardiac transplantation. Transplant coronary artery disease shows a heterogeneous angiographic appearance, but focal stenoses can occur alone or at least predominate. Based on an angiographic indication 35 critical focal lesions causing narrowing by 75% or more were treated by PTCA during 23 procedures in seven patients 18-84 months after cardiac transplantation. Three patients each underwent only one procedure and four underwent repeated procedures [2, 3, 4 and 11, respectively). Primary success was achieved without any complication in 35 of 35 lesions (100%). The mean degree of stenosis was reduced from 86 +/- 9% to 28 +/- 17% (P < 0.001). The rate of restenosis was 18/29 (62%) at a mean of 4 months after angioplasty. Four patients are alive and free of adverse effects (symptoms, myocardial infarction, repeated percutaneous transluminal coronary angioplasty, retransplantation) 16 +/- 10 months after their last angioplasty. One patient underwent a successful second heart transplantation 26 months after the first angioplasty. Two patients died, 1 and 31 months after the last angioplasty. In conclusion, percutaneous transluminal coronary angioplasty can be performed safely with an excellent primary success rate in critical focal transplant coronary artery disease. The rate of restenosis is higher than in native coronary artery disease. Long-term follow-up depends on the individually variable accelerated nature of graft atherosclerosis.

Adult↗
PubMed1993

Extended cardiopulmonary preservation: University of Wisconsin solution versus Bretschneider's cardioplegic solution.

Application of the University of Wisconsin cold storage solution has rapidly expanded to include medium-term to long-term preservation of virtually all intraabdominal organs. Its use in intrathoracic organ transplantation has also been suggested. We therefore examined the efficacy of the University of Wisconsin solution in a primate allotransplantation model for preservation of hearts, and as a simple single-solution system for static preservation of heart-lung blocks, for periods of ischemia ranging from 6 to 24 hours. For comparison, we employed the histidine-tryptophane-ketoglutarate cardioplegic solution of Bretschneider. University of Wisconsin solution provided superior results with regard to clinical outcome and hemodynamic recovery of hearts after ischemic periods of up to 16 hours. This was in contrast to Bretschneider's solution, which allowed storage of hearts for periods of only up to 10 hours. Heart-lung blocks were equally well preserved with either University of Wisconsin or Bretschneider's solution after 6 to 12 hours, although the University of Wisconsin solution group exhibited a more notable increase in pulmonary water content. This was in accordance with histological data, which suggested that, although hemodynamic recovery of hearts stored for periods longer than 10 hours was poor, preservation of pulmonary ultrastructure was far superior using Bretschneider's solution as compared with University of Wisconsin solution after an ischemic period of up to 16 hours.

Adenosine↗
PubMed1993

Regulation of acute phase response after cardiopulmonary bypass by immunomodulation.

The object of this prospective, randomized trial was to study the dysregulation effects of cardiopulmonary bypass on the synthesis pattern of interleukin-1, tumor necrosis factor, and interleukin-6, which have been identified as the key mediators of acute phase response. In addition, the counterregulation achieved by administration of indomethacin, which blocks the downregulating mediator prostaglandin E2, or indomethacin combined with thymopentin, which enhances T-lymphocytic reactivity, was investigated. Sixty patients who had undergone open heart operations were included in the study. These patients were divided into three groups: group A (n = 20) received both indomethacin and thymopentin, and group C (n = 20) served as control. In control patients interleukin-1 and tumor necrosis factor synthesis were suppressed postoperatively. This effect was significantly counteracted by indomethacin with no further improvement by adding thymopentin. Interleukin-6 synthesis increased in all groups. Although indomethacin treatment alone had little effect on this phenomenon, additional administration of thymopentin significantly reduced elevated interleukin-6 synthesis. Corresponding differences in clinical outcome could not be detected due to small patient numbers. This study was, however, able to demonstrate that an immunomodulatory therapy can influence alterations in immune mechanisms after cardiopulmonary bypass.

Acute-Phase Reaction↗
PubMed1993

Myocardial preservation using HTK solution for heart transplantation. A multicenter study.

Bretschneider HTK solution is commonly used for myocardial preservation. In order to evaluate its protective effect for heart transplantation, a retrospective study was initiated in cooperation with Eurotransplant and five heart transplant centers. Seventy-six female and 524 male patients who underwent cardiac transplantations between 1981 and 1991 were included in this study. Using standardized questionnaires, donor and recipient laboratory data, immunosuppressive therapy and the preoperative, intraoperative and postoperative organ function were documented. The average ischemic time of the donor hearts was 160 min, ranging from 75 min-304 min. Immediate postoperative graft failure was observed in 25 transplantations (4.2%). Within the first 30 days 71 organs (11.8%) failed. Using the chi2-test, a statistically significant increase of acute graft failure and early mortality was evident when they were correlated with the length of ischemic time (P = 0.01). In addition, a higher incidence of early graft failure was observed when the perfusion volume was less than 1500 ml. The 1- and 5-year survival rates were 72% and 63%, respectively. Organ preservation with HTK shows good results as long as the ischemic time does not exceed 4 h. The possibility that an increased perfusion volume allows longer ischemic times cannot be excluded with this study.

Cardioplegic Solutions↗
PubMed1993

Alterations of cell-mediated immune response following cardiac surgery.

Nosocomial infections in patients following cardiac surgery are frequently associated with opportunistic microorganisms indicating a dysregulation of cell-mediated immune response. The objective of this prospective randomized trial, therefore, was to investigate the mechanisms of dysregulation and the counterregulatory effects of immunomodulation. Twenty patients underwent conventional postoperative therapy, another 20 patients received indomethacin, which inhibits synthesis of the down-regulating mediator prostaglandin E2, and a further 20 patients were given thymopentin in addition to indomethacin, thereby augmenting activation and differentiation of the T-lymphocytes. The immunologic parameters studied included T-lymphocytes and monocytes as well as interleucin (IL)-1 and IL-6 synthesis by monocytes, and IL-2 and IL-6 synthesis by T-lymphocytes. Following cardiac surgery a significant, persistent reduction of T-lymphocytes and IL-2 synthesis as well as significant monocytosis could be observed. Indomethacin treatment resulted in a normalization of the cellular imbalance at the end of the first postoperative week, but IL-2 synthesis remained significantly reduced during the entire observation period. Conversely, with combined indomethacin and thymopentin treatment restoration of cellular distribution as well as protection of IL-2 synthesis could be achieved. These results indicate a quantitative and functional impairment of the forward regulation of cell-mediated immunity. It was shown for the first time that combined indomethacin and thymopentin treatment could successfully counteract these immunomechanistic alterations.

Aged↗
PubMed1993

Long-term myocardial function after heart transplantation.

With an increasing number of heart transplantations and an improved survival rate a characterization of the long-term hemodynamic profile of the transplanted heart is necessary. 222 cardiac catheterizations were performed in 71 heart recipients under cyclosporine A immunosuppression during a 7-year follow-up after transplantation. Hemodynamic evaluation revealed a non-progressive arterial hypertension due to an increased systemic vascular resistance, leading to a mild increase of left-ventricular chamber stiffness. Parameters of systolic myocardial function were found to be normal and did not deteriorate during the 7 year period. The prevalence of allograft coronary angiopathy increased from 13% one year to 54% five years after transplantation. Myocardial function was neither adversely influenced by the presence of coronary angiopathy nor by the number or severity of former rejection episodes. Unchanged annual pressure-volume loops excluded the development of a dilated or restrictive posttransplantation cardiomyopathy. Thus, not the myocardial function, but the coronary angiopathy represents the most critical cardiac long-term problem after transplantation.

Adolescent↗
PubMed1993

Effects of recombinant human erythropoietin on autologous blood donation before open heart surgery.

We studied the effects of four different doses of recombinant human erythropoietin (rhEPO) on the amount of preoperative autologous blood donation. 43 patients prior to open heart surgery were randomized into 5 groups (100, 200, 400, 800 U/kg rhEPO i.v. or placebo) and treated twice weekly over a period of 4 weeks. Autologous blood was taken at a hemoglobin of 13 g/dl and a hematocrit of 34% respectively. Application of low-dose rhEPO (100 and 200 U/kg) did not increase the amount of autologous blood donated, only 400 and 800 U/kg produced a significant increase by 27% and 39% respectively (p < 0.01) In addition RBC showed a reduced decline of hemoglobin level (p < 0.01). Reticulocytes increased by 2.5 times the baseline in the placebo and treatment groups up to 200 U/kg. Again, only 400 and 800 U/kg produced a significantly higher increase of 3.2 and 3.6 times respectively (p < 0.05 and p < 0.01). Although iron was supplied orally, ferritin levels declined in all groups whereas serum iron and transferrin levels remained unchanged. No influence could be detected on WBC, thrombocyte count, or arterial blood pressure. Mild and reversible side effects were observed in 8 patients (19%). Perioperatively 34 patients (81%) received exclusively autologous blood, only 8 patients (19%) needed additional homologous blood transfusions. Administration of high-dosed rhEPO (400-800 U/kg) seems to be an effective treatment with only slight side effects for increasing erythropoiesis during autologous blood donation.

Adolescent↗
PubMed1993

Heart transplantation after Senning operation for transposition of the great arteries.

In a 17.5-year-old boy and a 21-month-old girl orthotopic heart transplantation was performed after intractable right-heart failure had developed 14.5 years and 15 months respectively after Senning operation for TGA. Before the atrial repair, combined with closure of the VSD in each case, initial operation had involved a banding of the pulmonary artery in the boy and a modified Blalock-Taussig shunt in the girl. A coarctation of the first patient remained untreated. After resection of the diseased organ a new intraatrial septum of glutaraldehyde-fixed bovine pericardium was created. 15 and 3 months respectively after orthotopic heart transplantation both patients belong to NYHA classification I.

Adolescent↗
PubMed1993

Evidence for an interaction of halothane with the L-type Ca2+ channel in human myocardium.

BACKGROUND: The present study was aimed at investigating the underlying mechanisms for the cardiac depressant effect of halothane. To test the hypothesis, whether there is an interaction of halothane with the L-type Ca2+ channels in human myocardium and whether this interaction has functional consequences for force generation in the human myocardium, effects of halothane were studied in human myocardial membranes and isolated cardiac preparations. METHODS: The experiments were performed on isolated, electrically driven ventricular preparations (1 Hz, 37 degrees C) and cardiac membranes with radioligand binding experiments using 3H-PN 200-110. Myocardium from human failing and non-failing hearts was obtained at cardiac surgery. RESULTS: Halothane produced a negative inotropic effect, which was similar in nonfailing and failing myocardium. Halothane shifted the concentration-response curve for the positive inotropic effect of the L-type Ca2+ channel agonist BayK 8644 to the right. The density of dihydropyridine receptors as judged from 3H-PN 200-110 radioligand binding experiments was similar in nonfailing and failing myocardium, whereas the density of beta-adrenoceptors was reduced. Halothane concentration dependently reduced the binding of 3H-PN 200-110, an antagonist at the 1,4 dihydropyridine receptor site of the Ca2+ channel, to myocardial membranes. Furthermore, halothane produced a rightward shift of the competition curve of BayK 8644 for binding of 3H-PN 200-110 to cardiac membranes. CONCLUSIONS: In human ventricular myocardium, halothane exhibits an interaction with the L-type Ca2+ channel by interfering with its dihydropyridine binding sites. This may explain, at least in part, the observed negative inotropic effect of this agent and could hypothetically play a general role in its anesthetic effects.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1993

Long-term results of pacemaker therapy after orthotopic heart transplantation.

The objectives of this study were to identify: (1) the indications for pacemaker implantation; (2) the long-term survival; (3) the percentage of bradyarrhythmias below 50 beats/min persisting for more than 3 months; and (4) the variables predicting persistent bradyarrhythmias following orthotopic heart transplantations. During the recent decade (August 1, 1981 through December 31, 1991), 237 patients underwent orthotopic heart transplantation at our institution. Twenty-six recipients (11%) showed evidence of a symptomatic bradyarrhythmia due to sinus node dysfunction (n = 25) or complete heart block (n = 1), which required insertion of a permanent pacing device. During a mean follow-up period of 17.2 months (range 3 to 57 months), five patients (19%) died and one was lost to follow-up. Actuarial survival at 1 and 4 years were 81% and 65%, respectively, as compared to 79% and 69%, respectively, in patients without permanent pacemakers. Holter monitoring after 3 months (n = 25) and 1 year (n = 14) showed a spontaneous heart rate below 50 beats/min in six (24%) and three patients (18%), respectively. None of the tested variables predicted the necessity of initial pacemaker implantation. However, in patients requiring permanent pacing for a period longer than 3 months, ischemic time of the donor heart was found to be significantly longer as compared to the other patients (221 +/- 76 min vs 137 +/- 91 min, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effect of inotropic stimulation on the negative force-frequency relationship in the failing human heart.

BACKGROUND: In severe human heart failure, an increase in frequency of stimulation is accompanied by a reduced force of contraction in vivo and in vitro. The present study was aimed to investigate whether inotropic stimulation influences the inverse force-frequency relationship in failing human myocardium. METHODS AND RESULTS: The effects of the cAMP-independent positive inotropic agents ouabain (0.01 mumol/L) and BDF 9148 (0.1 mumol/L) as well as the beta-adrenoceptor agonist isoprenaline (0.01 mumol/L and 0.1 mumol/L) on the force-frequency relationship in electrically driven papillary muscle strips from nonfailing (brain death, n = 5) and terminally failing (NYHA class IV, heart transplants, dilated cardiomyopathy, n = 22) human myocardium were studied. For comparison, we examined the effect of elevation of the extracellular Ca2+ concentration (3.2 mmol/L and 6.2 mmol/L). In nonfailing myocardium, force of contraction, peak rate of tension rise, and peak rate of tension decay increased, whereas time to peak tension and time to half relaxation decreased following an increase of stimulation frequency. In NYHA class IV, force of contraction gradually declined followed by changes of other parameters of isometric contraction. Moderate stimulation of contractility by isoprenaline (0.01 mumol/L) partly reversed the negative force-frequency relationship in NYHA class IV and preserved the positive force-frequency relationship in nonfailing myocardium. The addition of ouabain and BDF 9148 together restored completely the force-frequency relationship in NYHA class IV. In contrast, high concentrations of isoprenaline (0.1 mumol/L) and an elevation of the extracellular Ca2+ concentration enhanced the decline in force of contraction in the presence of higher stimulation frequencies. CONCLUSIONS: It is concluded that functionally important changes occur in the intracellular Ca2+ handling, leading to the negative force-frequency relationship in terminally failing human myocardium. Interestingly, the negative force-frequency relationship can be restored by agents producing positive inotropic effects by elevation of the intracellular Na+ concentration. These findings suggest that hitherto unknown changes in the intracellular ionic homeostasis occur in the failing human heart. Even though increasing [Ca2+]i in failing heart cells may be detrimental, increasing [Na+bdi may be beneficial through a mechanism independent of an increase in [Ca2+]i.

Adult↗