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Biomedical subjects

A Moritz

Publications and source records attributed to A Moritz.

194 records · Page 11Linked to original sources
PubMedDate not supplied

Radiologic search for embolized leaflets of prosthetic heart valves: a report of two cases.

In a radiologic search for embolized leaflets of Edwards-Duromedics bileaflet valves in 2 patients, the embolized fragments were localized in the iliac vessels using computed tomography. Sonography was successful in one case and standard X-ray films of the abdomen were negative in both cases. In vitro investigations with Björk-Shiley and Edwards-Duromedics leaflets suggested that standard X-ray films of the abdomen and pelvis should be considered as the first investigational technique. If negative, computed tomography of the lower abdomen should be done.

Adult↗
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Biventricular pacing for successful weaning from extracorporal circulation in an infant with complex tetralogy of fallot.

Biventricular pacing therapy is an innovative therapy for improving cardiac output in adult patients with severe heart failure. However, this technique is not yet used in infants with congenital heart disease. We present a six month old infant with tetralogy of fallot and atresia of the left pulmonary artery in which biventricular stimulation led to improved left ventricular function and successful weaning from extracorporeal circulation.

Cardiac Output, Low↗
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Measurement of aortic flow velocity during transesophageal echocardiography in the transgastric five-chamber view.

Continuous-wave Doppler echocardiography of aortic flow velocity has a variety of clinical and research applications. Recently, continuous-wave Doppler echocardiography has been added to transesophageal echocardiographic systems. However, alignment of the Doppler beam with aortic flow is not possible with standard single and biplane views. A modified transesophageal echocardiographic view; the transgastric five-chamber (TG5C) view, allows for measurement of aortic flow velocity but its feasibility and accuracy in an unselected consecutive population have not yet been described. The feasibility of obtaining the TG5C view and measuring aortic flow velocity was assessed in 58 consecutive transesophageal echocardiographic investigations. The TG5C view was obtained in 97% and adequate Doppler flow velocity signals were obtained in 91% of patients. The accuracy of measurements was assessed in 24 patients in whom flow signals from both the TG5C and standard transthoracic views could be obtained. The correlation between TG5C and transthoracic views was excellent, with r values of 0.968 and 0.952 for peak aortic flow velocity and mean aortic flow velocity, respectively. Accurate aortic flow velocity measurements can be obtained in most patients during transesophageal echocardiography with the TG5C view. This view has great utility in a variety of situations in which adequate transthoracic imaging is not possible, especially the operating room and intensive care unit.

Adolescent↗
PubMedDate not supplied

Sustained heart failure induced by repeated microsphere injections for left ventricular assist device testing.

A subacute to chronic heart failure model was established to test left ventricular assist device (LVAD) systems. Five calves were anesthetized and instrumented. Heart failure was induced by daily injection of polystyrene microspheres (37-70 microns) into a left coronary catheter. The last three animals had an atrio-aortic pulsatile LVAD implanted. Cardiac output (CO) decreased from 12 to 5.5 L/min, and SV from 120 to 60 ml, whereas left atrial pressure (LAP) increased from 12 to 25 mmHg within 10 to 20 days in the two animals without LVAD support. Both animals stopped eating and drinking. The LVAD experiments were terminated after 5, 10, and 11 days. Cardiac function was determined during daily pump-off tests. After repeated microsphere injections, LAP increased to 30 and 50 mmHg, and CO decreased to 4 and 6 L/min without pump support. Daily stepwise microsphere injections induce a sclerotic cardiomyopathy in a safe and reliable manner.

Animals↗
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Compliance and formation of distal anastomotic intimal hyperplasia in Dacron mesh tube constricted veins used as arterial bypass grafts.

Dilated and varicose veins constricted with a Dacron mesh tube were successfully used as arterial bypass grafts to avoid nonautogenous vascular prostheses. Mesh constriction has also been used to adapt the venous graft lumen to the diameters of grafted arteries. The influence of the external mesh on the wall elasticity of such venous grafts and the reactions of the host artery were not investigated. Elastic properties of mesh constricted autologous veins used as arterial grafts in femoropopliteal reconstructions, as well as consecutive formation of distal anastomotic intimal hyperplasia (DAIH), were investigated in this experiment. Twenty-four autologous venous grafts were implanted in 12 sheep. Grafts were left natural (Groups 1 and 3) or were constricted with an external Dacron mesh (Groups 2 and 4); their diameters were left unchanged (Groups 1 and 2) or were matched to the diameter of the host artery (Groups 3 and 4). Wall elasticity of the graft, distal anastomosis, and distal artery were measured by locally applied crystal transducers during surgery and follow-up. Formation and localization of DAIH was evaluated histomorphologically after a median of 8.3 months. Graft wall elasticity was found to be lower (54.6 vs. 147.9, P = 0.006) and overall DAIH was found to be higher in mesh tube grafts (49.42 vs. 20.8 microns, P = 0.001, Mann-Whitney U-test). No differences in elasticity and DAIH formation were observed between grafts with adapted and large diameters. Constriction of venous grafts by a Dacron mesh tube reduces graft wall elasticity and promotes formation of DAIH. To avoid such an increased mismatch in compliance while making use of the advantages of this method, the external mesh tube must not be brought close to the distal anastomotic area itself.

Anastomosis, Surgical↗
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Complications of port-access cardiac surgery.

Port-Access cardiac surgery is a recent technology that is undergoing rapid development. The learning curve associated with this technique is a challenge even for the skilled and experienced cardiac surgeon. Mainly because of femoral cannulation, the use of guidewires, and working through small incisions, Port-Access cardiac surgery contains certain pitfalls that are clearly associated with the technology involved. These pitfalls currently require troubleshooting, but as the technology progresses, this may become less of an issue. Communicating these pitfalls to others is important to help others to avoid or better manage complications and to contribute to improving the technology of Port-Access techniques.

Cardiac Surgical Procedures↗
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Polarization-sensitive optical coherence tomography of dental structures.

Optical coherence tomography (OCT) has been developed during the last 10 years as a new noninvasive imaging tool and has been applied to diagnose different ocular and skin diseases. This technique has been modified for cross-sectional imaging of dental structures. In this first preliminary study the technique was applied to obtain tomographic images of extracted sound and decayed human teeth in order to evaluate its possible diagnostic potential for dental applications. Classical OCT images based on reflectivity measurements and phase retardation images using polarization-sensitive OCT were recorded. It was demonstrated that polarization-sensitive OCT can provide additional information which is probably related to the mineralization status and/or the scattering properties of the dental material. One of the attractive features of OCT is that it uses near-infrared light instead of ionizing radiation. Furthermore, high transversal and depth resolution on the order of 10 microm can be obtained. Present limitations, e.g. the limited penetration depth, and possible solutions are discussed.

Dental Caries↗
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Improved biocompatibility by postfixation treatment of aldehyde fixed bovine pericardium.

Long-standing release of locally cytotoxic aldehyde concentrations is responsible for lack of spontaneous endothelialization and increased calcification of glutaraldehyde fixed bovine pericardium. Postfixation treatment with amino acids made in vitro endothelialization of bioprosthetic heart valves possible. Such treated pericardium calcified significantly less (13 +/- 4 micrograms/mg dry weight) than did conventionally processed pericardium (114 +/- 25 micrograms/mg) after 63 days of subcutaneous implantation in rats. To test the ability for spontaneous in vivo endothelialization, 5 sheep had 6 mm grafts made from postfixation treated pericardium (PTP) implanted into the carotid artery, compared to PTFE grafts on the contralateral side, which spontaneously endothelialize in animal models. In a pregnant animal, both grafts occluded. All remaining pericardial grafts remained patent, but one additional PTFE graft occluded and another one was stenosed. The area covered with red thrombus was significantly smaller in the PTP grafts (3.05 +/- 3.9%) than in the PTFE grafts 42 +/- 14% (p = 0.0036); TEM and SEM showed endothelial cells growing directly on the PTP, but only on myofibroblasts in PTFE grafts. Postfixation treatment of glutaraldehyde fixed pericardium aids spontaneous endothelialization and decreases tissue calcification.

Animals↗
PubMedDate not supplied

Four year follow-up of the Duromedics Edwards bileaflet valve prostheses.

The Duromedics Edwards (DE) bileaflet valve prosthesis was withdrawn from the market after 12 leaflet escapes had been reported in 20,000 implants. Effort is necessary to identify the failure mode to improve valve design or production, but the rate of other valve related complications will tell if it is worthwhile reintroducing this prosthesis. Five-hundred and sixty-four DE valves have been implanted in 508 patients between September 1983 and May 1988. Two-hundred and sixty-eight had aortic valve replacement (AVR), 183 mitral valve replacement (MVR) and 56 double valve replacement (DVR); the perioperative mortality was 6.9%. Follow-up has been 98.7% complete for a total of 1064 patient years and a mean follow-up of 26 months (range 3 to 54 months). Late mortality was 3.7%/yr and actuarial survival was 85 +/- 3% without and 78 +/- 3% including operative mortality after 54 months. Event free actuarial rates (linearized rates in parenthesis) were 93 +/- 2% (1.5%/yr) for thromboembolism, 91.7 +/- 1.9% (2.3%/yr) for anticoagulant related hemorrhage, 89 +/- 4.8% (2.3%/yr) for valve failure, 93 +/- 2% (1.8%/yr) for valve related mortality, 72 +/- 4.8% (6.3%/yr) for all valve related morbidity and mortality and 83 +/- 4.4% (3%/yr) for treatment failure. Two leaflet escapes occurred in the study group (0.18%/yr), both patients survived reoperation. The concept of reducing thrombus formation by a specially designed irrigating hinge mechanism was proven by a low rate of thromboembolism in our clinical follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
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Electrical control of intestinal reservoirs in a chronic dog model.

Pouches constructed from small intestine are used to replace reservoir function after extirpative surgery of the colon. Such pouches empty in an involuntary and uncontrolled fashion. To see whether emptying could be voluntarily controlled, ileal and jejunal reservoirs were constructed in eight dogs under general anesthesia. Four pairs of stainless steel electrodes were attached to the serosa at 5 cm intervals, and the pouches were intubated for pressure measurements with 1.67 mm polyethylene catheters. All lines were brought subcutaneously to the neck where they were maintained under a protective jacket. One to four weeks later, the pouches were stimulated with trains of square wave pulses at frequencies between 3 Hz and 1.67 KHz. The pouches were injected with contrast, and the results were monitored by fluoroscopy. Intrapouch pressure increases as high as 80 mmHg were seen after stimulation at 3 Hz, 100 msec and 6 Hz, 50 msec (10 to 25 mA) and emptying was induced. Pressure increases were also seen after stimulation with 330 Hz, 1 msec and 10 Hz, 1 msec pulse trains, but emptying was not documented. Abdominal wall contraction during stimulation was a problem but could be inhibited by interposing an insulating silastic sheet. The conclusion was made that it is possible to electrically induce emptying of intestinal reservoirs in a chronic dog model.

Animals↗
PubMedDate not supplied

Increase of intra-abdominal fat in patients treated with continuous ambulatory peritoneal dialysis.

OBJECTIVE: To evaluate changes in amount and distribution of body fat in patients treated with continuous ambulatory peritoneal dialysis (CAPD). DESIGN: Prospective study. Computed tomography (CT) and dual energy x-ray absorptiometry (DEXA) were used for determination of body composition at commencement of CAPD, and after a mean of 7.2 months of dialysis treatment. SETTING: CAPD unit at an academic teaching hospital. PATIENTS: The study included 19 consecutive patients who started CAPD during a 15-month time frame. Of these 19 patients, 12 (8 males) with a mean initial age of 60 years completed the study. MAIN OUTCOME MEASURES: Siemens Somatom HiQ (Erlangen, Germany) was used for CT of the abdomen and of the right thigh. Fat and muscle areas were expressed as square centimeters. The proportion of total fat mass was determined by body composition analysis using DEXA (DPX-L densitometer) (Lunar, Madison, WI, U.S.A.) and expressed as percentage of total body weight (FA%). RESULTS: Body weight changed from 67.1 to 68.4 kg (p = 0.20), and the intra-abdominal fat area increased 22.8% (p = 0.02). This increase was predominantly seen in male patients (p = 0.007). The FAT% changed from 27.8% to 30.9% (p = 0.25), without difference between sexes. CONCLUSION: The increase of intra-abdominal fat found in this study may suggest a mechanism by which the established risk for CAPD patients to develop cardiovascular morbidity and mortality may be at least partially explained.

Abdomen↗