PubMed Health⌕ Search

Biomedical subjects

A Moritz

Publications and source records attributed to A Moritz.

At least 145 records · Page 8Linked to original sources
PubMed1992

Noninvasive monitoring of rotary blood pumps: necessity, possibilities, and limitations.

Although rotary blood pumps do not contain an inherent mechanism for adaptation to physiological flow necessities, hitherto only a few efforts have been made to obtain robust monitoring and control methods. This paper discusses the necessity of noninvasive monitoring of such pumps and the crucial points of sensor selection and development. A strategy of monitoring atrial pressure out of the data obtained by the collapse of the atrial wall around the inflow cannula and initial results on animal tests and computer simulation of this method are discussed. This approach might lead to reliable and demand-responsive controllers, if some basic criteria are fulfilled.

Atrial Function↗
PubMed1992

Doppler sonographic evaluation of the CarboMedics bileaflet valve prosthesis: one-year experience.

Between April 1989 and March 1991, 237 CarboMedics bileaflet valve prosthesis carriers (165 aortic and 72 mitral valves, mean age 54.4 years) were studied prospectively with pulsed- and continuous-wave Doppler at a mean interval of 11.4 months following surgery in order to establish ranges of normal flow velocities and pressure gradients. Physical examination revealed no signs of prosthetic dysfunction or heart failure. Postoperative left ventricular function as measured by fractional shortening was 37% for aortic valve carriers and 30% for mitral valve carriers (p = NS). Mean peak velocity (+/- SD) across the aortic valve was 2.6 m/sec (+/- 0.4) and calculated instantaneous peak pressure gradient ranged from 11 to 58 mmHg (mean 28.1 +/- 10.3). It has to be emphasized that occasional patients with normally functioning valve prostheses can show unusual high gradients. Ring diameters between 21 and 27 mm showed no significant difference with regard to flow velocities and pressure gradients, whereas in 19-mm valves, significantly higher values could be demonstrated. The 123 aortic valve carriers with normal left ventricular function (fractional shortening greater than 25%) showed significantly higher pressure gradients than the 19 patients with reduced left ventricular function (28.6 +/- 11.6 mmHg vs 16.2 +/- 5.1 mmHg, p less than 0.05). In the mitral position, the mean of peak velocity (+/- SD) was 1.7 +/- 0.4 m/sec and pressure half-time was 108 +/- 26 msec, representing a calculated valve area between 1.4 to 3.1 cm2 (mean orifice size 2.1 +/- 0.5 cm2). No significant difference between valves of different sizes was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1992

Improved biocompatibility of bioprosthetic heart valves by L-glutamic acid treatment.

Treatment of glutaraldehyde-fixed pericardium with L-glutamic acid and storage in bacteriostatic preservatives (paraben) stably antagonizes free, reactive aldehyde groups within the fixed bioprosthetic heart valve tissue. In 63-day subcutaneous implants in rats, the calcification rate of this treatment (13.3 +/- 2 mg calcium/g wt tissue) was markedly reduced as compared to conventionally treated tissue (169 +/- 24 mg/g; p less than 0.05). To test the influence of tissue-released toxic aldehydes on spontaneous endothelial cell ingrowth in vivo, vascular grafts (8-cm long, 6-mm diameter) from fixed pericardium treated with L-glutamic acid were interposed into the carotid arteries in ten sheep. They were compared to grafts from conventionally treated pericardium implanted at the contralateral side. Following 3 months of implantation, planimetry revealed 49% +/- 20% of the surface of conventionally preserved pericardium to be covered with red thrombus, but only 12% +/- 5% in L-glutamic acid treated pericardium (p less than 0.05). The ultrastructural findings of a closed endothelial cell layer on the graft surface reveals the new technique to be a promising approach towards increased biocompatibility of aldehyde-fixed bioprosthetic heart valves.

Animals↗
PubMed1992

Endothelial cell lining of bioprosthetic heart valve material.

In this in vitro study, the growth properties of cultured endothelial cells on conventionally treated pericardial valve material were measured. These data were compared to endothelial cell proliferation on an alternatively treated valve material. This alternative preservation procedure was developed in order to bind free, residual glutaraldehyde in the valve tissue by reaction with L-glutamic acid. In order to optimize endothelial cell attachment and proliferation, fibronectin and fibrillar collagen type I were tested as surface precoating substances. Cell viability of the seeded cells was evaluated by means of proliferation kinetics, antithrombotic activity, and morphological appearance. Endothelial cell death occurred within the first 2 days after seeding on conventionally treated valve tissue, independent of the type of precoating. On alternatively treated tissue, regular endothelial cell proliferation was observed. Precoating with fibrillar collagen markedly increased endothelial cell attachment and proliferation as compared to fibronectin. Maintenance of antithrombotic activity of the seeded cells was proven by regular release of prostacyclin.

Animals↗
PubMed1992

Closing sounds and related complaints after heart valve replacement with St Jude Medical, Duromedics Edwards, Björk-Shiley Monostrut, and Carbomedics prostheses.

OBJECTIVE: To measure the noise produced and related subjective complaints after implantation of four different mechanical heart valve prostheses and to identify further factors related to the patient and prosthesis that influence noise generation and complaints. DESIGN: Sound pressure was measured 5 and 10 cm and 1 m from the point of maximal impulse on the body surface by a calibrated meter in quiet rooms with either a decibel(A) filter or octave filters. The patients were asked about their complaints and examined physically. SETTING: The measurements were conducted in silent rooms of ear, nose, and throat departments. The patients had been operated on either in a university hospital or a community hospital. MAIN OUTCOME MEASURES: Sound pressures of frequency bands and sound pressures measured in dB(A) at various distances. Complaints registerd were: sleep disturbance, disturbance during daytime, "wants a less noisy prosthesis," and "can hear the closing click". PATIENTS: 143 patients after heart valve replacement with St Jude Medical (n = 35), Duromedics Edwards (n = 38), Carbomedics (n = 34) and Björk-Shiley Monostrut (n = 36) prostheses operated on between 1984 and 1988 were matched for valve position, ring size, and body surface area. RESULTS: Duromedics Edwards (33.5 (6) dB(A)) and Björk-Shiley Monostrut valves (31 (4) dB(A)) were significantly louder than St Jude Medical (24 (4) dB(A)) and Carbomedics (25 (6) dB(A)) prostheses (p = 0.0001) (mean (SD)). The louder valves were significantly more often heard by the patients (p = 0.0012) and caused more complaints both during sleep (p = 0.024) and during the daytime (p = 0.07). Patients with these valves were more likely to want a less noisy valve (p = 0.0047). Patients with symptoms were younger, had better hearing, and were more likely to be in sinus rhythm. As well as the type of prostheses, the valve diameter and body height also had an effect on sound emission. CONCLUSIONS: The intensity of the closing click of mechanical valve prostheses was significantly different for various designs. Patient complaints were related to the objectively measured sound pressure. Noise production should be considered when a mechanical valve is selected.

Adult↗
PubMed1992

A low affinity vasopressin V2-receptor in inherited nephrogenic diabetes insipidus.

Congenital nephrogenic diabetes insipidus (NDI) is an X-linked inherited disorder characterized by renal resistance to the antidiuretic hormonal action of vasopressin. This study describes the molecular basis of nephrogenic diabetes insipidus in a dog family. Kidney membranes prepared from NDI-affected male huskies were examined for vasopressin binding and response. Compared to membranes from unaffected canines, those from the kidney inner medulla of NDI-dogs possessed normal V2-receptor numbers, but with 10-fold lower affinity for [Arg8] vasopressin (AVP). Adenylate cyclase stimulation by AVP in contrast to that by forskolin or GTP-analogues was similarly reduced in a dose responsive manner. The NDI-affected dogs showed antidiuretic responses to very high doses of V2-specific agonists, consistent with their possessing V2-receptors of lower affinity. Prolonged treatment with V2-agonists, 1-deamino [D-Arg8] VP (dDAVP) and 1-deamino [Val4, Sar7] AVP (dVSAVP), rendered the NDI-affected dogs near normal in terms of water intake and urine osmolality.

Adenylyl Cyclases↗
PubMed1992

Mechanical bridge to transplantation with the Vienna heart in TAH and LVAD configuration.

The Vienna heart uses a vacuum formed, pellethane pulsatile ventricle and is available in left ventricular assist (LVAD) and total artificial heart (TAH) configurations. This device was used as mechanical support of the failing heart in nine patients intended for heart transplantation. In two patients with cardiomyopathy an orthotopic TAH was implanted; one survived despite severe preoperative ischemic liver damage, and the other died of sepsis. In seven patients an atrio-aortic LVAD was implanted; six had suffered an acute myocardial infarction with cardiogenic shock, and one could not be weaned off bypass. Three patients survived. These included one 65-year-old with incipient ARDS at operation, and a 40-year-old with preoperative liver and kidney insufficiency who was transplanted in septicemia. In this patient the septic focus, natural and artificial heart, were removed at transplantation. Four patients died. In one we were unable to establish satisfactory circulation, one died after failure of the transplanted heart, one suffered a lethal cerebral embolism and one developed multi-organ failure after repeated attacks of ventricular fibrillation. With the Vienna heart sufficient circulatory support could be established with cardiac outputs between 6 and 8 l/min for the TAH and 3.5 to 4.5 l/min for the LVAD. With this type of support an overall survival rate of 44% could be achieved. Mechanical hemolysis was not a clinical problem and no device failure occurred.

Cardiomyopathies↗
PubMed1992

[Direct diagnosis of the atherosclerotic vascular wall: possibilities and limits of intravascular ultrasound].

The clinical application of intravascular ultrasound still awaits established criteria for the interpretation of normal and diseased arterial wall structures. The aim of this preclinical study was to evaluate sonographic features of normal and atherosclerotic human arteries in vitro and to correlate these findings with histological cross-sections. Seventy-four segments from 33 human postmortem arteries of various anatomic locations were studied in saline solution using a mechanical 20-MHz transducer in a 6F catheter. In normal arteries, close correlations were found between sonographic and morphometric measurements of total wall thickness (r = 0.89), lumen circumference (r = 0.99), and of lumen area (r = 0.89, all p less than 0.001). Of 29 histologically verified atherosclerotic lesions, 19 were calcified, and all of them were correctly diagnosed with IVUS; however, acoustic shadowing prevented quantitative plaque evaluation. Of 10 fibromuscular lesions, six (60%) were correctly diagnosed with IVUS, using either direct morphologic criteria (n = 4) or indirect signs of vessel wall irregularity (n = 2), while the remainder (n = 4) were missed by IVUS due to a similar echodensity compared with the surrounding tissue. Thus, there was an overall sensitivity of 86% for the detection of atherosclerotic lesions by IVUS. In animal experiments in vivo, the feasibility of high-quality-imaging in pulsatile arteries was confirmed and pathologic changes in vein grafts were visualized. We conclude that IVUS carries the potential to directly assess arterial wall changes in vivo. The method appears very sensitive in the detection of calcified plaque, whereas fibromuscular lesions may often not be readily distinguished from normal surrounding tissue. This may limit the clinical usefulness of IVUS at the present time.

Adult↗
PubMed1992

Improved endothelialization of postfixation treated biological vascular grafts.

Preliminary in vitro and in vivo studies have shown that endothelialization is improved by a detoxifying postfixation treatment of glutaraldehyde (GA) fixed bovine pericardial patches and grafts. To test whether this is also true for GA tanned human vein (HUV) grafts, patches of commercially available HUV grafts (MHUV), postfixation treated HUV grafts (PTHUV) and GA fixed HUV granfts (GAHUV) were endothelialized in vitro. Eight pairs of MHUV and PTHUV grafts were implanted as femoropopliteal grafts in eight sheep. Endothelial cell adherence was significantly better on PTHUV (11910 +/- 4413 cells/cm2) than on MHUV (6545 +/- 2835 cells/mm2; p = 0.0007) and on GAHUV (3563 +/- 1638; p = 0.0001) one day after cell seeding. After eight days of culture significantly more cells spread on PTHUV material than on MHUV (p = 0.0002), but none of the cultures on GAHUV remained viable. Four PTHUV grafts occluded in the femoropopliteal position, mostly because of kinking, so that only in four pairs of grafts could the thrombus-free surface be compared by planimetry. Again PTHUV material was covered more by endothelial cells than was MHUV material. On PTHUV endothelial cells spread directly on the graft material while on MHUV these cells spread on a layer of fibrin and macrophages. Postfixation treatment of GA-fixed biological graft material by amino-acid solutions improves the biocompatibility of the material and enhances in vitro as well as spontaneous in vivo endothelialization.

Animals↗
PubMed1991

Isolation of Legionella maceachernii from an immunocompromised patient with severe underlying lung disease.

OBJECTIVE: To present the first case in Australia in which Legionella maceachernii has been documented as a cause of infection. CLINICAL FEATURES: A 71-year-old retired carpenter with underlying autoimmune disease and pulmonary fibrosis was admitted to hospital with increasing shortness of breath and fever, and pneumonia was diagnosed. INTERVENTION AND OUTCOME: He was treated with ampicillin then gentamicin and flucloxacillin and later imipenem but his condition deteriorated with progression of the pneumonia and abscess formation and he died 25 days after admission. Subsequently, L. maceachernii was isolated from three sputum samples collected before the patient died. CONCLUSION: There is a need for clinical awareness of the value of sputum culture in the diagnosis of infection due to Legionella spp. other than L. pneumophila.

Aged↗
PubMed1991

Blood rheology after cardiac valve replacement with mechanical prostheses or bioprostheses.

Arterial thromboembolism is a serious complication in patients after heart valve replacement. Abnormalities in blood rheology may contribute to this complication. Therefore, the aim of this study was to compare various determinants of blood rheology in patients with substitute heart valves with those in healthy controls; furthermore, differences between patients with mechanical valves and those with bioprostheses should be investigated. The hemorrheologic determinants--fibrinogen, plasma viscosity, red cell aggregation, hematocrit and platelet aggregation--were studied in 92 patients with mechanical bileaflet valves, in 28 patients with bioprostheses and in 29 control subjects; the time since valve replacement was greater than or equal to 9 months. Fibrinogen, plasma viscosity, red cell and spontaneous platelet aggregation were found to be increased in all patients after heart valve replacement compared with normal subjects (fibrinogen: 348 +/- 87 vs 267 +/- 66 mg/dl, p less than 0.01; plasma viscosity: 1.71 +/- 0.1 vs 1.66 +/- 0.1 mPas, p less than 0.05; red cell aggregation: 9.9 +/- 2 vs 7.8 +/- 2 U, p less than 0.01; platelet aggregation: 22 +/- 15 vs 13 +/- 13%, p less than 0.01); among patients, fibrinogen, plasma viscosity and spontaneous platelet aggregation were higher in mechanical valves than in bioprostheses (fibrinogen: 359 +/- 95 vs 314 +/- 41 mg/dl, p less than 0.01; plasma viscosity: 1.72 +/- 0.1 vs 1.68 +/- 0.1 mPas, p less than 0.1; platelet aggregation: 23 +/- 15 vs 16 +/- 11%; p less than 0.05), whereas no difference could be found for red cell aggregation (9.7 +/- 2 vs 10.5 +/- 2%, p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Bioprosthesis↗
PubMed1991

Transesophageal echocardiographic evaluation in mechanically assisted circulation.

Transesophageal echocardiography (TEE) has assumed an increasing importance in cardiothoracic surgery, but its use in patients with mechanically assisted circulation is unclear. We performed TEE in 11 patients: total artificial heart (TAH) 2, right ventricular assist device (RVAD) 2, left ventricular assist device (LVAD) 6, biventricular assist device (BVAD) 1. TEE was helpful in three areas. (1) selection of the assist device (AD): evaluation of left and right ventricular function allows differentiation of left, right or biventricular failure. (2) management of patient and optimization of pump performance: in all patients, correct cannula position and pump flow could be identified. Right ventricular failure in the presence of LVAD was found to cause hemodynamic instability in 4 patients. In 1 patient with repeated RV dilation and hypotension despite RVAD, TEE allowed optimal pump settings to be determined. (3) weaning from AD: Recovery of ventricular function can be assessed prior to weaning and repeatedly monitored during weaning. TEE in TAH is limited to problems such as identification of atrial thrombus or inflow valve dysfunction. We conclude that TEE is useful in the setting of mechanically assisted circulation for AD selection, improvement of patient management, optimization of pump performance and during weaning from AD.

Assisted Circulation↗
PubMed1991

Improved spontaneous endothelialization by postfixation treatment of bovine pericardium.

The longstanding release of locally cytotoxic glutaraldehyde concentrations from fixed biological materials is one reason for the lack of spontaneous endothelialization in vivo and in vitro of biological grafts (and valves). Preliminary studies have shown that bovine pericardium postfixation-treated with aminoacids may be endothelialized in vitro. To test whether such treatment improves spontaneous endothelialization in vivo 8 cm long segments grafts (6 mm I.D.) were interposed into the carotid arteries of 10 sheep. Ten grafts were sewn from postfixation treated pericardium (PTP), 4 from standard glutaraldehyde fixed pericardium (GAP) and 6 polytetrafluoroethylane (PTFE) grafts were implanted to study the degree of spontaneous endothelialization. In two pregnant animals, all grafts occluded (2 PTP, 1 GAP, 1 PTFE). In the remaining animals 1 additional PTFE graft occluded and 2 PTFE and 1 GA grafts showed significant thrombotic obstruction. The patent grafts were harvested at 3 months and the surface covered with red thrombus was determined by planimetry. PTP grafts had significantly less (12.2% +/- 15%) thrombotic appositions than glutaraldehyde treated grafts (49% +/- 20%; P = 0.01) and PTFE grafts (40.5% +/- 13%; P = 0.01). In the central areas of the PTP grafts, endothelial cells spread directly on the collagenous matrix and produced a basal lamina. In GAP, endothelial cells spread on amorphous material or macrophages and in PTFE grafts, only a neointima composed of myofibroblasts was endothelialized. Neutralization of glutaraldehyde concentrations by postfixation with aminoacids improves spontaneous endothelialization in vivo in biological materials.

Animals↗
PubMed1991

Relationship between clinical and milk isolates of Yersinia enterocolitica.

In the summer of 1987-1988, an outbreak of 11 cases of Yersinia enterocolitica enteritis caused by 2 serogroups (0:3, 0:6,30) occurred prompting an investigation into possible environmental sources. Symptoms were present for a mean of 9 days and occurred in 2 distinct age groups--toddlers (7) who presented with diarrhea, and young adults (4), 3 of whom presented clinically with appendicitis. In a survey of 39 randomly chosen pasteurized milk samples, 9 were positive for growth of Y. enterocolitica and 1 each for Y. fredericksenii and Y. intermedia. An association between clinical and milk isolates of Y. enterocolitica was thus sought by comparison of biogroups, serogroups, virulence markers and biochemical and outer membrane profiles. All milk isolates belonged to biogroup 1, serogroup 0:6,30. Pathogenicity studies on the 0:6,30 serogroup isolates from feces and milk were performed with 3 in-vitro tests (Ca2+ dependency, autoagglutination, & serum resistance). The human isolates were positive in most of the 3 tests whilst none of the milk isolates were positive. Outer membrane protein analysis of 0:6,30 from human and milk isolates showed similar profiles suggesting a possible association, however the environmental source of the majority of isolates (0:3) remains unknown.

Adolescent↗
PubMed1991

[The diagnosis of nephrogenic diabetes insipidus in the dog].

Nephrogenic diabetes insipidus is characterized by polyuria, hyposthenuria and compensatory polydipsia. With conventional clinical and laboratory examinations the diagnosis can be established and the differential diagnostic diseases excluded. In order to verify the diagnosis, differentiate the condition from central and nephrogenic diabetes insipidus and rule out psychogenic polydipsia, additional laboratory studies are required: of these, the concentration test, modified Carter-Robbins test and AVP stimulation test are described.

Animals↗
PubMed1991

Mesh-constricted varicose and dilated veins used as arterial bypass grafts.

To avoid non-autogenous vascular prostheses in coronary and peripheral vascular procedures, otherwise unusable dilated, varicose or thin-walled veins can be implanted as naturally endothelialized grafts after being calibrated by insertion into mesh tubes. In six sheep the 14 mm diameter jugular vein was inserted into a 12 cm long, 6 mm diameter Dacron mesh tube and implanted as a femoropopliteal graft. On the contralateral side the femoral vein with a maximal diameter of 7 to 8 mm was implanted. At control angiography after two months all grafts were patent, none of the wrapped grafts showed wrinkles or signs of anastomotic hyperplasia. Segments of wrapped veins were casted in paraffin under physiological pressure and cut transversely. In all cases the vein wall was pressed against the mesh tubes without forming folds. Mesh-wrapped varicose veins were used for three femorocrural and seven femoropopliteal reconstructions. All grafts showed a smooth flow surface at control angiography. Indentations occurred only at sites where thick-walled side branches had been ligated rather than oversewn. One popliteo-pedal reconstruction occluded after two months and one patient with a crural reconstruction died two months after surgery with a patent graft. The remaining grafts were patent after 11 (2-32) months. Oversized veins can be considerably constricted by tubes without forming wrinkles. By this technique varicose veins can be used as bypass grafts and in general vein grafts can be matched in size to the recipient vessel.

Aged↗