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Biomedical subjects

A Moritz

Publications and source records attributed to A Moritz.

At least 163 records · Page 9Linked to original sources
PubMed1991

[Complicated course of a compression syndrome of the popliteal artery in a 36-year-old patient].

The popliteal entrapment syndrome is an entity increasingly reported over the past few years. Anatomical variations should be considered if a localized stenosis or occlusion of the popliteal artery is diagnosed in a young, otherwise healthy individual. This case report documents a complicated course of the disease in a young man in whom diagnosis was made only after futile attempts of intraarterial lysis and dilatation at the time of a second operation. A complex crural reconstruction was necessary in order to revascularize the treatment limb.

Adult↗
PubMed1991

Closing click of St Jude Medical and Duromedics Edwards bileaflet valves: complaints created by valve noise and their relation to sound pressure and hearing level.

The metallic clicking sound created by mechanical heart valve prostheses frequently bothers patients. To test whether sounds generated by different bileaflet valves correlate to complaints related to the prosthetic clicking 73 patients were investigated after valve replacement with Duromedics Edwards (DE) (n = 38) and St Jude Medical (SJM) (n = 35) valves. The patients were asked about their complaints, sound pressure levels were recorded and audiometry was performed. Sixty-five percent of patients could hear their valve, 18% had sleeping disturbances, 5% felt bothered during daytime and 12% would prefer a less noisy valve. In symptomatic patients, sound pressure levels were higher than in asymptomatic patients (valve audible 45 +/- 8 db(A) vs not audible 39.9 +/- 10 db(A) at 10 cm; P = 0.016). These differences were most apparent in the high frequency bands, corresponding to the metallic click. Symptomatic patients had better hearing and were younger than patients without complaints. Fifty-one percent could hear their valve by conduction through the body, after eliminating air conduction by the use of headsets. The DE prostheses were louder than the SJM valves in general (47.4 +/- 7 vs 39.8 +/- 5 db (A) at 10 cm; P = 0.001) and in each valve position. Patients with DE prostheses had significantly more complaints. The intensity of the closing click of mechanical valves correlates to the complaints caused by prosthetic clicking and thus sound emission should be considered when a mechanical heart valve prosthesis is selected.

Adult↗
PubMed1991

Timing for implantation and transplantation in mechanical bridge to transplantation.

The implantation of a mechanical blood pump in a deteriorating candidate for heart transplantation is indicated in general if the cardiac index is less than 1.9 L/min/m2 despite maximal inotropic support. Deterioration of end organ function may be taken as a second factor indicating the need for mechanical support as patients with acute onset of shock may react differently from patients with chronic deterioration. Preoperative need for dialysis largely reduces the chances of long-term survival. The time on support should be long enough to normalize or at least improve secondarily damaged organ systems, but with time infectious and thromboembolic complications will increase. So optimal periods for artificial heart support range between two days and four weeks. Age less than 40 years is a positive predictor for outcome in TAH bridging. The general guidelines, however, do not preclude a favourable outcome in complicated cases, as we show in our own series.

Adult↗
PubMed1991

[Noise origin and noise-induced complaints after heart valve replacement with mechanical prostheses].

143 patients were investigated in order to determine whether there is a difference in the intensity of the closing click between different mechanical heart valve prostheses. 35 had St. Jude Medical (SJM), 38 Duromedics Edwards (DE), 36 Björk Shiley Monostrut (BSM) and 34 had Carbomedics prostheses implanted. Sound pressure level determined at 1 meter distance was significantly higher for the DE 33.5 +/- 6 dB(A) and BSM 31 +/- 4 dB(A) than for the SJM 24 +/- 4 dB(A) and CM 25 +/- 6 dB(A) prostheses (p = 0.0001). Valves developing higher sound pressures were more frequently audible for the patients (p = 0.0012), caused more sleep disturbances (p = 0.024) and more complaints during daytime (p = 0.07). Significantly more patients carrying such valves wished to have a less noisy valve implanted (0.0047). Symptomatic patients wear louder valves, were younger, had better hearing and were more frequently in sinus rhythm. Valve diameter correlated with the developed sound pressure level. 349 patients answered a questionnaire after valve replacement with DE (256) or BSM (93) prostheses. 5% registered their noise-related complaints as being severe, but more than one third wished to have a less noisy valve implanted. The noise created by the closing click of mechanical prostheses causes significant complaints and this factor should be considered when a mechanical valve is selected.

Adult↗
PubMed1991

[Stented dilated or varicose veins as arterial bypass transplants: experimental and initial clinical results].

Dilated and varicose veins are usually not used as arterial bypass-grafts despite they are lined with functional endothelium. External support by a constrictive mesh tube could conform these veins into evenly calibrated bypass-grafts. Ovine jugular veins could be constricted from 15 to 6 mm diameter without forming folds on the inner flow surface. 6 months after implantation of 5 cm long jugular vein segments into the carotid arteries of 7 sheep the inner diameter was 19.5 +/- 3.3 mm for native veins (n = 4) and 7.6 +/- 0.8 mm for constricted veins (n = 10). Intimal hyperplasia was reduced from 0.4 +/- 0.2 mm in native to 0.23 +/- 0.07 mm in reinforced veins (p = 0.03). Mesh tube constricted varicose veins were used as bypass material in 11 infrainguinal reconstructions. All grafts were well calibrated at control angiography. External constriction by mesh tubes is a means to convert varicose veins into suitable bypass grafts.

Aged↗
PubMed1991

[Successful bridge transplantation with the Vienna artificial heart].

The Vienna Heart, a pulsatile artificial ventricle, vacuum-formed from Pellethane has been used successfully as total artificial heart (TAH) and left ventricular assist device (LVAD) to bridge over patients in terminal heart failure. A 50 year-old patient with cardiomyopathy had to be resuscitated and was transferred in cardiogenic shock, with impaired renal and liver function. 6 days after orthotopic implantation of a Vienna TAH a suitable donor organ was found and the patient was transplanted. 7 weeks later he was discharged and is alive and well now. A 40-year-old patient was transferred in cardiogenic shock 22 days after recurrent anterior infarction. Due to renal failure he was on haemofiltration. Congestive liver failure caused a severe coagulation disorder so a Vienna LVAD was implanted without the use of extracorporeal circulation. Despite development of septicaemia he was transplanted 24 days later. It was thought that either the ventricular thrombus or the LVAD was the septic focus. All consecutive blood cultures have been negative and he was discharged 6 weeks later. To our knowledge, case 1 represents the first successful bridging with a non-Jarvic TAH. The second case shows that sepsis is not necessarily a contraindication to heart transplantation.

Adult↗
PubMed1990

[The patient following heart valve replacement].

Results of heart-valve-surgery based on a large group of patients of the University-hospitals in Vienna are given. Problems such as anticoagulant therapy and the prevention of prosthesis-endocarditis are shown.

Anticoagulants↗
PubMed1990

Enzymatic synthesis of pyrene-labeled polyphosphoinositides and their behavior in organic solvents and phosphatidylcholine bilayers.

A method is reported for the synthesis of pyrene-labeled analogues of phosphatidylinositol 4-phosphate (Pyr-PIP) and phosphatidylinositol 4,5-biphosphate (Pyr-PIP2) from sn-2-(pyrenyl-decanoyl)phosphatidylinositol (Pyr-PI) using partially purified PI and PIP kinase preparations. Phosphorylation of Pyr-PI and Pyr-PIP was extensive (more than 50%) provided that the ATP concentration was high and that stabilizing agents such as sucrose and polyethylene glycol were present in the incubation medium. Pyr-PIP and Pyr-PIP2 were isolated by chromatography on immobilized neomycin. The identity of the products was established by thin-layer chromatography, UV-absorption spectroscopy, and spectrofluorometry. The pyrene excimer/monomer fluorescence technique revealed that, in contrast to Pyr-PI, Pyr-PIP and Pyr-PIP2 formed clusters in organic solvents. By use of the same technique for model membranes, it was shown that in phosphatidylcholine bilayers the collision frequency of the three fluorescent phosphoinositides decreased in the order PI greater than PIP greater than PIP2. Addition of Ca2+ at concentrations above 0.1 mM increased the collision frequency of Pyr-PIP2 and, to a much lesser extent, Pyr-PIP; Ca2+ had no effect on Pyr-PI.

Animals↗
PubMed1990

Purification of a phosphatidylinositol 4-phosphate kinase from bovine brain membranes.

A phosphatidylinositol 4-phosphate (PIP) kinase (EC 2.7.1.68) was purified from bovine brain membranes in a six-step procedure involving solubilization of the enzyme with 170 mM NaCl followed by chromatography on diethylaminoethyl-cellulose, phosphocellulose, Ultrogel AcA44, hydroxylapatite, and ATP-agarose. The enzyme preparation was nearly homogeneous and was purified 5,600-fold with a final specific activity of 85 nmol/min/mg of protein and a yield of 20%. Its molecular mass was 110 kilodaltons, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was specific for PIP; phosphorylation of phosphatidylinositol and diacylglycerol was not observed.

Animals↗
PubMed1990

Noise level and perception of the closing click after heart valve replacement with St. Jude Medical and Björk Shiley Monostrut prostheses.

The metallic click generated by the closure of mechanical heart valve prostheses may severely bother patients, but generated sound energy and the extent of complaints after implantation are not known. In 62 patients, after valve replacement with St. Jude Medical (SJM) (n = 35) and Björk Shiley Monostrut (BSM) (n = 27) prostheses, sound energy was recorded with a calibrated noise level analyzer at 5, 10, and 100 cm distance from patients and correlated with their complaints. At a distance of 100 cm, the BSM valves produced a significantly higher sound pressure level, 30.5 +/- 5 db(A), compared to the SJM valves, 24.1 +/- 4 db(A) (p = 0.0001). There was no significant difference at shorter distances. After splitting into frequency bands the highest sound pressure levels were observed in the high frequency ranges (8 to 16 kHz) representing the metallic click. BSM valves produced higher sound levels in all frequency ranges at 1 m distance. Seventy-three percent of all patients were aware of the noise generated by the valve; 20% had disturbed sleep; and 26% preferred a less noisy valve type. Twelve of 27 patients with BSM valves wanted less noisy valves, whereas only 4 of 35 patients with SJM valves wished to have a less noisy valve type (Chi-square p = 0.003). In patients who could hear their valve measured, sound level was higher than in patients who could not. In 9 of 27 patients with BSM (33%), versus 3 of 35 with SJM prostheses (9%), the clicking caused sleep disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustics↗
PubMed1990

A method for constricting large veins for use in arterial vascular reconstruction.

A satisfactory biologic graft can be created if dilated, but otherwise unusable veins are wrapped with a constrictive mesh tube. The purpose of this study was to determine whether a resorbable constrictive tube creates an appropriately sized vascular graft by induction of neoarterial wall growth. In 8 sheep a 5 cm segment of the carotid artery was resected and the external jugular vein inserted as a tubular graft. The vein was either wrapped with a polydioxanon (PDS) reinforced polyglactin (Vicryl) mesh (n = 4), a Vicryl mesh (n = 4), or a Dacron mesh tube (n = 3) to achieve a diameter reduction to 7 mm. Or the vein was used without reinforcement (n = 3). At angiography after 6 months the unreinforced veins had a diameter of 19 mm (range 15-22). The Vicryl reinforced veins measured 9.4 (8.5-10) mm, but 3 of 4 developed aneurysmatic dilatations at sites of valve sinuses with a mean diameter of 19 (15-21) mm. PDS reinforced veins measured 7.4 mm (7.1-7.9). Two of 4 had minor aneurysms of 13 and 16 mm. The two remaining PDS reinforced grafts were indistinguishable from the native artery. Dacron tubes reduced the vein size reliably to 7.6 (7.5-7.9) mm, but showed narrowing at the proximal anastomoses (PDS 7.2 +/- 0.4, Dacron 6.1 +/- 0.4, p = 0.016). PDS wrapping reduced maximal graft diameter to 10.9 +/- 4 mm as compared to that of the native vein, 18.7 +/- 3.5 (p less than 0.05). Resorbable meshes can reduce the diameter of a venous graft by strengthening the vessel wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Electrostimulation of ileum and jejunum reservoirs in an acute and chronic experiment].

Voluntary control of the motility of intestinal reservoirs may be used to improve evacuation and continence. In 4 dogs a U-shaped jejunum pouch and in another 4 an ileum pouch was constructed and instrumented with stimulating and EMG electrodes and pressure lines. In the acute experiments jejunum pouch stimulation with 200 microseconds 1.67 kHz 30 mA increased the intrapouch pressure by 38 +/- 4 mm Hg (n = 6) and 500 microseconds 910 Hz 25 mA by 60 +/- 5 mm Hg (n = 3). The pressure increase in the awake animals was consistently lower (200 microseconds 4 +/- 6 mm Hg, n = 9; 500 microseconds 25 +/- 17, n = 11). The ileum pouch responded with a 37 +/- 10 mm Hg pressure increase (n = 9) to 50 ms 6 Hz 20 mA pulse trains. Ileum pouches could not be stimulated in the awake animal due to contraction of the abdominal wall. Electrostimulation may be used to contract and evacuate intestinal reservoirs but additional drug therapy or autonomic nerve stimulation will be necessary to lower the thresholds especially for ileum stimulation in the awake animal.

Animals↗
PubMed1989

Contractile response to electrical stimulation of the small intestine in anesthetized and awake dogs.

To test whether small bowel contraction can be induced by electrostimulation similar to in vitro results in anesthetized and awake animals, five dogs had stainless steel electrodes implanted on the serosal surface of the jejunum and ileum. Fifty milliamperes of 500-microseconds 910-Hz currents induced a 50-80-mm Hg pressure increase in the jejunum with a threshold of 25 mA. Transverse stimulation was studied long-term in two dogs. The mean pressure change for 500-microseconds 910-Hz 25-mA stimulation in 10 studies was 26 mm Hg (0-75). The thresholds ranged between 15 mA and currents not tolerated by the animal. For 200-microseconds 1.67-kHz 30-mA stimulation, the mean pressure change was 28 mm Hg (0-75 mm Hg, n = 16). On 10 occasions, the pressure increased further after termination of the stimulus (off response), with a mean of 48 mm Hg (10-85). Electrical currents elicit a mechanical response in the small intestine of the intact animal, which resembles the in vitro observations. Currents necessary to evoke contractions in the physiologic range are tolerated by the trained animal.

Anesthesia, General↗
PubMed1989

Electrical pulse train and single pulse stimulation of the small intestine: acute and chronic studies in the dog.

In vitro tests have shown that electric currents may lead either to relaxation or contraction of the bowel wall. Because voluntary changes of the intestinal motility could be useful in the treatment of intestinal disorders, we investigated the reactions elicited by electrostimulation of the small intestine in the intact animal. Stimulating electrodes, electroenteromyogram electrodes, and pressure monitoring tubes were used to instrument a 5-cm segment of the proximal jejunum in five dogs in acute studies and in two dogs in chronic studies. Single pulses of 200 ms elicited a pulsatile pressure increase of 10-35 mm Hg. Pulse train stimulation was followed by a more complex reaction. Trains of 500-microseconds, 910-Hz pulses at 30 mA evoked a 50-80 mm Hg pressure increase, 1-ms, 10-Hz trains caused an initial relaxation, followed by a pressure increase during stimulation and a further pressure increase after termination of the burst. These reactions were similar to those observed by Campbell working with colon in vitro. The chronic fasted animals reacted to 500 microseconds, 910-Hz, 25-mA stimulation with a mean pressure increase of 26 mm Hg (n = 10) and to 200-microseconds, 1.67-kHz, 30 mA stimulation with 28 mm Hg (n = 16). In the fasted animals a pressure increase during stimulation predominated (Campbell type I), whereas in the fed animal an additional off response after termination of the stimulation was the most common type of reaction (Campbell type II). Initial relaxation (Campbell type III) could be elicited by 1-ms, 10-Hz trains.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Hemodynamic effects of mexiletine and disopyramide after cardioplegic arrest.

To study the hemodynamic side effects of mexiletine and disopyramide when administered before cardioplegic arrest 15 dogs underwent sham cardiac surgery with a 90-min period of aortic cross-clamping. 5 dogs served as control, 5 were given 8 mg/kg/day mexiletine and another five 11 mg/kg/day disopyramide for 1 week before surgery. On the day of surgery a continuous infusion was started. After reperfusion treated animals exceeded their preischemic blood pressure and regained their preoperative cardiac output. Compared to control animals left ventricular work was higher in the treated animals after reperfusion. The two tested type I antiarrhythmics tend to add to myocardial protection when given before cardioplegic arrest and do not exhibit negative inotropic side effects.

Animals↗
PubMed1989

[Subjective noise perception and objective measurement of loudness following heart valve replacement with the St. Jude Medical and Duromedics Edwards bileaflet prostheses].

The performance of heart valve prostheses is generally judged by the rate of valve-related complications and the hemodynamic performance. Patients may be severely bothered by the metallic click generated by the closure of the valve. In 74 patients after valve replacement with Duromedics Edwards (DE) (n = 38) and St. Jude Medical (SJM) (n = 36) prostheses the sound energy was recorded and correlated to the complaints of the patients. At a distance of 10 cm the DE valves produced a significantly higher sound pressure with 47 +/- 7 db(A) compared to the SJM valves with 39.8 +/- 5 db(A) (p = 0.001). The noise level was also different for the valves in aortic or mitral position. After splitting into frequency bands the highest sound pressure was observed in the high frequency ranges (8 to 16 kHz) which represents the metallic click. 65% of patients were aware of the noise generated by the valve, 16% had sleep disturbances and 22% would prefer a more silent valve type. 12 of 38 patients with DE valves and 4 of 36 patients with SJM valves wished to have a less noisy valve type (Chi square p = 0.003). In annoyed patients the valves produced a higher sound amplitude of 49 +/- 8 db(A) as compared to undisturbed patients with 42 +/- 6 db(A) (p = 0.002). The noise level of mechanical heart valves should be considered before selection of a prosthesis, because the metallic click bothers patients and the complaints correlate with measured sound energy.

Adult↗