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Biomedical subjects

R Körfer

Publications and source records attributed to R Körfer.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Prevention and management of dysfunction of prosthetic heart valves].

The ideal heart valve prosthesis has not been developed. The today available mechanical and biological prostheses are far from perfect concerning thrombogenesis, mechanical durability and hemodynamic performance. Failure of an implanted valve is possible due to inadequate indication, inadequate surgical technique and inadequate medical follow-up. The patient with a heart valve prosthesis must be seen as a life-long challenge for the cooperation between cardiologists and cardiac surgeons. This article describes the main causes of prosthetic heart valve dysfunction and the surgical treatment, including structural dysfunction, thrombosis, paravalvular leakage, tissue ingrowth and prosthetic valve endocarditis.

Heart Valve Prosthesis Implantation↗
PubMed1998

[Acute aortic dissection (Stanford A) with pericardial tamponade--extension of the dissection after emergency pericardial puncture].

The hemodynamic deterioration associated with acute aortic dissection (Stanford A) is caused by an acute loss of volume, acute aortic valve insufficiency, or possibly by hemopericardium with tamponade. In the latter case, a pericardiocentesis may restore hemodynamic stability. However, it is only indicated in the case of reduced perfusion of vital organs. The relief of the pericardial effusion can produce a pressure gradient between dissection and pericardial space, which again might cause hemodynamic deterioration by the blood flow into the pericardial space as well as extension of the aortic dissection. Following pericardiocentesis immediate surgery is indicated. In the present case, after a primarily effect hemodynamic stabilization by pericardiocentesis, this mechanism has very probably led to a repeated tamponade and extension of aortic dissection, which was successfully repaired by the implantation of a vascular prosthesis immediately following invasive diagnosis.

Aortic Dissection↗
PubMed1998

Cardiopulmonary resuscitation after cardiac surgery: a two-year study.

OBJECTIVE: The aim of this study was to investigate the incidence of cardiopulmonary resuscitation (CPR) after cardiac surgery and to find predictors of survival. DESIGN: A retrospective study with data obtained by chart review. SETTING: A university hospital 24-bed cardiac surgical intensive care unit (ICU). PARTICIPANTS: Between 1993 and 1994, 4,968 consecutive adult patients who underwent cardiac surgery at the authors' hospital were studied. INTERVENTIONS: None. MAIN RESULTS: One hundred thirteen of these patients (2.3%) were resuscitated. Seventy-nine patients (70%) survived to be discharged from the hospital. Significant predictors of survival were the time between admission to the ICU and initiation of CPR, CPR time, and creatine kinase (CK) and CK-MB values. CONCLUSIONS: The incidence of CPR after cardiac surgery was 2.3% with no difference between valve surgery and CABG. Best results were achieved when arrhythmias or bleeding were the predisposing causes. Further studies have to be undertaken concerning long-term results and quality of life of the discharged patients.

Adult↗
PubMed1998

Microanalysis and distribution of cardiac troponin I phospho species in heart areas.

Sequential phosphorylation and dephosphorylation of cTnI by the cAMP dependent protein kinase and by protein phosphatase 2A, respectively, produce the non-, mono- and bisphosphorylated species (Jaquet et al., 1995, Eur. J. Biochem. 231, 486-490). The aim of this study was to determine these forms even in small tissue samples, e.g. in biopsy probes of approximately 30 mg which would allow to define the phosphorylation state of cTnI in heart areas. In order to do so a micro isolation procedure for cTnI had to be established. cTnI is extracted from small bovine, rabbit and human heart tissue samples (30-100 mg) under special conditions avoiding dephosphorylation and is isolated by affinity chromatography on cTnC Sepharose. All three species, the bis-, mono- and dephospho cTnI, are precipitated quantitatively by acetone, then they are separated by non-equilibrium isoelectric focusing and quantified by scanning densitometry. The method presented here allows to quantify the three cTnI species reproducibly. No other phosphorylated species are detected. Truncated cTnI forms of each phospho species are found in human biopsy samples due to removal of a approximately 36 amino acid peptide from the C-terminus. In bovine, human and rabbit heart the pattern of the three cTnI phospho species is characteristic for left and right atrium, left and right ventricle and septum.

Animals↗
PubMed1998

Development and initial in vivo testing of a new hydraulic drive system (Paedipump) for circulatory support in infants.

The main limitation in the use of circulatory support in children is the lack of an adequate system with regard to size and pumping capacity. Recently, two pneumatically driven ventricular support systems with low volume chambers for use in a pediatric population became available. We have developed a hydraulic drive system with an advantageous exact control of the stroke volume. The system enables two different modes of operation: the full-empty and the filled-empty modes. In both cases the ventricle is empty at the end of systole. This new system was tested in experimental animals (6 pigs, body weight 9.5-14.0 kg) with normal and reduced left ventricular function (MAP<45 mmHg). A 25 ml ventricle (HIA-Medos) was implanted. The full-empty and the filled-empty mode used led to a significant load reduction, both in animals with normal and impaired cardiac function. Plasma lactate levels, pH-values and total body O2-consumption were in the normal range during circulatory support indicating adequate organ perfusion. Results showed that sufficient ventricular support was achieved during all pumping modes due to the possibility of controlling and modifying the stroke volume of the hydraulically driven support system employed according to necessity. This is a promising feature for its future application in infants with congenital or acquired heart diseases.

Animals↗
PubMed1998

The Ultracor tilting disc heart valve prosthesis: a seven-year study.

BACKGROUND AND AIM OF THE STUDY: The Ultracor heart valve is a recent entry in the evolution of the tilting disc valve. This report summarizes the experience with the Ultracor valve from three European centers. METHODS: Between 1990 and 1996, 446 patients received 499 Ultracor heart valve prostheses in 450 procedures, including 225 (50.0%) aortic, 172 (38.2%) mitral and 49 (10.9%) double valve replacements. An additional four (1.0%) patients had mitral valve replacement (MVR) added to a previous aortic valve replacement (AVR) and were considered double valve replacement (DVR) patients. The total follow up was 751 patient-years (pt-yr) for AVR (mean 3.4), 440 pt-yr for MVR (mean 2.6) and 125 pt-yr for DVR (mean 2.4). Nine patients (one AVR, eight MVR) were lost to follow up, which was 98% complete. RESULTS: The actuarial survival rate, including operative mortality rate, at five years was 90% for AVR, 77% for MVR and 82% for DVR. The linearized complication rates (%/year) for AVR, MVR and DVR were: 2.1, 4.0 and 4.0 for late mortality; 0.1, 3.0 and 0.8 for thromboembolism; 0, 0.2 and 0 for thrombosis; 2.0, 1.6 and 1.6 for anticoagulant-related hemorrhage (ACH); 0.3, 0.5 and 1.6 for prosthetic valve endocarditis (PVE); and 0.5, 0.9 and 3.2 for reoperation, respectively. The actuarial rates of freedom from complications at five years were: thromboembolism, 99% for AVR and 88% for MVR; thrombosis, 100% for AVR and 99% for MVR; ACH, 91% for AVR and 94% for MVR; PVE, 99% for AVR and 97% for MVR; reoperation, 98% for AVR and 98% for MVR. No structural failure was observed. CONCLUSIONS: Seven years' experience showed the Ultracor heart valve prosthesis to be comparable with other currently used mechanical heart valves. Continued evaluation of this prosthesis is warranted in order to obtain a more extended clinical follow up.

Adult↗
PubMed1997

[Anatomic and functional hypoplastic left heart syndrome and its surgical Norwood and Fontan treatment].

UNLABELLED: The surgical therapy of newborns with hypoplastic left heart syndrome (HLHS) is still regarded with some distrust. The complete heart conserving palliation includes not only the Norwood operation during the newborn period but also the complete separation of both circuits by the Fontan operation some time later. Our experiences with each surgical step are presented. From 1989 to 1996, 43 infants with anatomical (n = 33) or functional (n = 10) HLHS underwent the Norwood operation. Functional HLHS were: Mitralatresia with double outlet right ventricle and subaortic stenosis (n = 2), atrioventricular septal defect with hypoplastic left ventricle, subaortic stenosis, and aortic coarctation (n = 1), hypoplastic, subaortic right ventricle with restrictive ventricular septal defect and aortic hypoplasia (n = 7). The median age at operation was 15 days (5 to 182 days), mean weight was 3.3 kg (3.0 to 4.9 kg). Total operative mortality was 32% (n = 14) with 16% since 1994 (3/19 patients). Five infants (12%) died 2 weeks to 6 months later, and 2 patients underwent cardiac transplantation. Up to now, 19 out of the 22 long term survivors underwent the bidirectional cavopulmonary anastomosis (Hemi-Fontan) at a median age of 7 months (2 to 14 months). Two infants died (10%). Up to now, 12 out of the remaining 17 survivors received the total cavopulmonary anastomosis after a mean period of 12 months. All children survived, and they are now completely palliated. The longest follow up after the complete Fontan operation is 6 years. CONCLUSION: With increasing experience the results of the Norwood operation improved. The following two-stage Fontan procedure bears only a low risk and leads to good quality of life.

Female↗
PubMed1997

Strong crossreaction of human anti-aprotinin antibodies from heart transplant patient with [Arg15]aprotinin.

We detected anti-aprotinin antibodies by an enzyme immunoassay in serum of a 33 year old man who showed anaphylactic reactions during heart transplantation under aprotinin reexposition. The antibodies were isolated by affinity chromatography by aprotinin immobilized on CNBr activated Sepharose. The crossreactivity was tested by a competitive enzyme immunoassay (50% inhibition) against different aprotinin homologues and two human Kunitz-type protease inhibitors, bikunin and TFPI. In comparison with native aprotinin (immunoreactivity = 100%) the crossreaction of the homologue [Arg15]aprotinin was 76%, of [Val15]aprotinin 15% and of isoaprotinin 1, [Ala14,38]aprotinin and [seco15/16]aprotinin less than 10%. An immunoreactivity with bikunin and TFPI was not detected. Similar results were obtained with polyclonal anti-aprotinin antibodies from rabbit. Our results show that human anti-aprotinin antibodies are mainly directed against the reactive site of aprotinin. From this we conclude that the reactive site exposes the major epitope resulting in a major target site for antibodies in a species independent way, and therefore, it is obvious that the recombinant aprotinin homologue [Arg15]aprotinin, which is scheduled for therapy in open-heart surgery, will have similar immunogenic effects as native aprotinin.

Adult↗
PubMed1997

Ischemic cardiomyopathy--revascularization vs. transplantation.

Advanced coronary artery disease (CAD) and ischemic cardiomyopathy with elevated pulmonary artery pressures are criteria of a severe illness. In selected cases surgical revascularization has proved beneficial in terms of survival, reduction of morbidity and lowering the frequency of angina pectoris [6] in numerous studies over the past 25 years. But most of the earlier publications concentrated on patients with angina pectoris (AP) as a dominant symptom. Patients without AP but with predominant signs of congestive heart failure were largely excluded. This has changed recently [1-3,7,8,10,12,16,18] with the advent of the concept of hibernating myocardium. This term is defined as the presence of persistent myocardial and left ventricular dysfunction at rest due to reduced regional coronary blood flow that can be partially or completely restored to normal by myocardial revascularization [5,19]. Salvage of viable myocardium by successful revascularization improves left ventricular dysfunction. Diagnosis of hibernating myocardium is crucial because it does not leave the patient with chronic heart failure a candidate only for cardiac transplantation. Instead, these patients' left ventricular dysfunction is potentially reversible following revascularization by coronary bypass surgery. Furthermore we face a critical shortage of donor organs and extending waiting lists for possible transplant candidates. Following the start of the heart transplantation (HTX) program at our institution more than 690 operations were performed until September 1995. We screened more than 1600 patients for their eligibility as cardiac transplant recipients or for other forms of treatment. In this group of patients it has always been our policy to revascularize rather than transplant whenever possible.

Adult↗
PubMed1997

Out-of-hospital experience in patients with implantable mechanical circulatory support: present and future trends.

From March 1993 to August 1995, 33 patients received implantable VAD systems at our center. Nineteen patients received the wearable Novacor LVAS and 14 patients the TCI HeartMate device. Both systems enable the patients to be mobilized very quickly and some of them even do not require critical care after a few days. In our series 17 patients (eight Novacor, nine TCI) could be transferred to the normal floor. The wearable electrically driven Novacor system opens the opportunity of sending patients out of hospital. Since July 1994 we have referred five patients to a rehabilitation center, and six patients were sent home, three of them for more than 70 days. A number of factors are necessary to prepare the patient for being discharged. One of the most important things is to guarantee ambulatory patient care and to find an easy way for effective home monitoring. Our experience has shown that discharging these patients means giving them a maximum in quality of life and decreasing the costs by more than 50% in comparison to a stay in hospital for the whole time. Our results are encouraging to improve this strategy in the future.

Adolescent↗
PubMed1997

Coronary artery and aortic valve disease as a long-term sequel of mediastinal and thoracic irradiation.

Mediastinal and thoracic irradiation has been identified as a risk factor for the development of among other things, coronary artery disease (CAD) and valvular disease. We screened all patients for a history of mediastinal or thoracic radiotherapy. Between 01.07.1989 and 31.12.1995 we identified 33/16,364 patients with such a history. In 19 cases (0.12%) the cardiac disease was considered radiation-induced, nine patients were female, ten were male. Mean age was 51.7 years (range 38-73). All 19 patients displayed proximal coronary artery stenoses. Mean age in the CAD group was significantly lower (48.5, range 38-63) than in the valvular group (mean age 64.0, range 55-73). The mean interval since radiotherapy in the valvular group was significantly longer (22.25 years, range 13-32) than the one in the CAD group (12.2 years, range 7-24). All patients were treated surgically and made an uneventful recovery. Some form of mediastinal fibrosis or pericardial adhesions was present in all patients. We conclude from these findings that radiation-induced cardiac disease is infrequently encountered in patients from a large surgical center. However, especially the radiation-induced coronary artery disease displays a specific pattern of stenosis location.

Adult↗
PubMed1997

Long-term mechanical circulatory support.

Against the background of an increasing number of patients waiting for heart transplantation but a stagnating number of transplant procedures, long-term mechanical circulatory support is gaining major importance. We investigated the outcome of 20 patients (15 men, and 5 women, aged between 15 and 66 years) each supported for more than 100 days between September 1987 and August 1996. The indications for implantation were bridging in 17 patients, myocarditis in 2 patients, and postcardiotomy cardiogenic shock in one patient. 12 patients received the Novacor IVAD, 4 patients the Thoratec system, 3 patients the HeartMate device and one patient both Novacor and Thoratec. Mean duration of support was 178.1 days, 15 patients were transplanted, 14 of them could be discharged, 2 patients died, 4 patients are still waiting. The most frequent complication was device-related infection in 11 patients. The results have shown that all three systems are safe and reliable devices for supporting patients for more than 100 days.

Adolescent↗
PubMed1997

Tuberculosis in heart transplant recipients.

STUDY OBJECTIVES: To clarify the prevalence and factors associated with tuberculosis, as well as patient survival in heart transplant recipients. DESIGN: A retrospective review of case records of all heart transplant recipients from March 1989 to February 1996 during a 7-year period. SETTING AND PATIENTS: During the period reviewed, 727 orthotopic heart transplantations were performed in 716 patients at the Heart Center Northrhine-Westphalia, Germany. RESULTS: Tuberculosis was proved in seven (1%) patients (four men/three women; age, 33 to 71 years; two miliary lesions, three pulmonary lesions, and two urogenital lesions). None of them had primary history of tuberculosis. Tuberculin skin tests were not performed before transplantation because there were no lesions indicating primary infection of turberculosis. The immunosuppressive regimen was based on double-drug (cyclosporine + azathioprine) therapy. Immunosuppression had been intensified by methylprednisolone pulses at least three times in those seven patients, and prednisone had been used orally in six of seven patients. Tuberculosis developed from 2.5 to 41 months after transplantation. Tuberculosis was found by routine examinations in four of seven patients. Diagnoses were made with both direct microscopy and cultures in six patients, and by histologic study in one. Treatment consisted of isoniazid, rifampicin, ethambutol, and pyrazinamide. Two patients with miliary lesions were treated with four drugs, and the others were treated with three drugs. Isoniazid was used in all patients. Rifampicin, which decreases cyclosporine serum levels, was not used from the beginning in one patient and treatment with it was stopped halfway in another patient because low cyclosporine level had induced rejection. Six of the seven patients are doing well while receiving antituberculous therapy. One patient died with miliary tuberculosis as a cause of death. CONCLUSIONS: The prevalence of tuberculosis in heart transplant recipients was higher than that in the general population. We recommend that a high degree of clinical suspicion is maintained for tuberculosis in heart transplant recipients with meticulous follow-up, and that the treatment of tuberculosis has to be with meticulous care, especially during the use of rifampicin.

Adult↗
PubMed1997

Effect of cyclosporine A on the release of tissue factor pathway inhibitor from endothelial cells in heart transplant patients and cell culture.

We investigated the influence of cyclosporine A on the concentration of tissue factor pathway inhibitor and von Willebrand factor antigen in plasma of heart transplant outpatients. Tissue factor pathway inhibitor was quantified in plasma of blood donors (n = 50) and heart transplant outpatients (n = 50) by a chromogenic substrate assay with a mean of 32.4 micrograms/l and 98.2 micrograms/l, respectively. Von Willebrand factor antigen was determined with an enzyme-linked immunoassay with a mean of 90.9% for blood donors and 184.5% in plasma of heart transplant recipients. In addition, we investigated the effect of cyclosporine A on endothelial cell cultures over an incubation period of four days. A dose-dependent effect of cyclosporine A on the release of endothelial tissue factor pathway inhibitor and von Willebrand factor antigen was determined in a concentration range from 100 to 200 micrograms/l cyclosporine A. The tissue factor pathway inhibitor and von Willebrand factor antigen concentrations in the cell culture supernatant increased during the incubation time according to the cyclosporine A concentration 2-3 fold and 2 fold, respectively. For a further elucidation of the cyclosporine A effect we investigated the influence of cremophor EL, the vehicle of cyclosporine A. Cremophor EL alone did not increase the tissue factor pathway inhibitor release. However, the release was enhanced 2-4 fold after co-stimulation with the calcium ionophore A 23187 (10(-4) mol/l) in a concentration-dependent mode. We conclude that a generalized endothelial damage or activation is most probably caused by cyclosporine A and its vehicle cremophor EL. This process probably depends upon the increase of cytosolic free calcium, as described for the liberation of von Willebrand factor by endothelial cells.

Adolescent↗
PubMed1997

Pulsatile and nonpulsatile extracorporeal circulation using Capiox E terumo oxygenator: a comparison study with Ultrox and Maxima membrane oxygenators.

An open randomised, prospective study was undertaken on 90 patients who underwent routine myocardial revascularization. The aim of the study was to demonstrate that the Capiox E polypropylene fiber membrane oxygenator with a conventional single pulsatile/nonpulsatile blood pump for cardiopulmonary bypass (CPB) was comparable in performance to that of the Maxima and the Ultrox membrane oxygenators using a double pump system. The patients were divided into six groups according to perfusion mode and oxygenator type. Laboratory parameters, fluid balance and oxygenation was examined at set times before during and after cardiopulmonary bypass. Net fluid input was lower in the Capiox E groups regardless of perfusion mode: 2932 +/- 562 ml (Capiox E), compared to 3646 +/- 531 ml (Ultrox) and 3593 +/- 582 ml (Maxima). Net fluid balance 1288 +/- 534 ml was lowest in the Capiox/NP group, compared to 1604 +/- 460 ml (Ultrox/NP) and 1881 +/- 594 ml (Maxima/NP), (p < 0.05). The higher net fluid balance in the Capiox E/PP group 1649 +/- 580 ml compared to 1592 +/- 583 ml (Ultrox E/PP) and 1494 +/- 542 ml (Maxima/PP) was attributed to a technicality whereby the recommended priming volume of the Capiox E oxygenator was exceeded for safety reasons. The values of plasma free Hb were slightly higher in the PP than NP groups: Maxima/PP 80 mg/dl, /NP 50 mg/dl; Ultrox/PP 62 mg/dl, /NP 48 mg/dl; Capiox E/PP 55 mg/dl, /NP 48 mg/dl. The FiO2 was higher in the Capiox E groups 0.77 (PP) and 0.88 (NP) compared to Maxima/PP (0.66), /NP (0.65) and Ultrox/PP (0.64), /NP (0.63). Reciprocally, the venous saturation was higher in the Ultrox and Maxima groups compared to Capiox E at end of CPB. The study demonstrated that the CapioxE oxygenator with a single blood pump system can compare to the Maxima and Ultrox oxygenators with a double blood pump for CPB with regard to blood handling, oxygenation and fluid balance in routine cardiac surgery.

Blood Gas Analysis↗