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Biomedical subjects

D Vorwerk

Publications and source records attributed to D Vorwerk.

At least 55 records · Page 3Linked to original sources
PubMed1997

[Cerebral sinus thrombosis: rapid test diagnosis by demonstration of increased plasma D-dimer levels (SimpliRED)].

PURPOSE: To perform an initial evaluation of the accuracy in detection of dural sinus and cerebral venous thrombosis using a bed-side test (SimpliRED). MATERIAL AND METHODS: Early diagnosis and treatment of cerebral sinus thrombosis are important. A screening test to decide which patients should undergo further diagnostics would be valuable due to the low incidence. Six patients with MR proven cerebral sinus thrombosis underwent bed-side testing. The SimpliRED kit provides a clearly visible agglutination of the patient's red blood cells in the presence of elevated levels of the crosslinked fibrin derivative (D-dimer) in the sample. RESULTS: The assay yielded a positive result in all six patients, even 56 days following the onset of clinical symptoms. CONCLUSION: The sensitivity of SimpliRED in the detection of sinus venous thrombosis is not known. This assay, therefore, should be evaluated in a large prospective study. In addition, the capability of the test to assess the effect of and predict the duration of anticoagulation therapy should be considered.

Adolescent↗
PubMed1997

Interventional magnetic resonance. Initial clinical experience with a 1.5-tesla magnetic resonance system combined with c-arm fluoroscopy.

RATIONALE AND OBJECTIVES: The authors evaluate the feasibility of performing magnetic resonance (MR) procedures on a 1.5-tesla (T) system combined with conventional c-arm fluoroscopy. METHODS: A 1.5-T MR imaging system was combined with a conventional c-arm fluoroscopy unit in one room. The two systems were connected via a floating table top. Twenty-six interventional procedures (biopsies, MR-portography, percutaneous alcohol injection, laser ablation, fluid aspiration, and breast marking) were performed in 22 patients under MR, fluoroscopic control, or both. For MR guidance, fast gradient echo sequences were used, initiated from a panel at the front of the magnet. Images were displayed on an liquid crystal display screen positioned on the magnet. RESULTS: All MR-guided procedures were performed successfully without complications. The addition of c-arm fluoroscopy was useful for bone interventions and MR-portography. All diagnostic biopsies yielded sufficient amounts of tissue for histologic diagnosis. In breast lesions, the target identified on dynamic MR imaging was marked correctly in each case. In interstitial laser thermotherapy the laser effect could be visualized, and in percutaneous ethanol injection the distribution of the alcohol could be seen. Both imaging systems worked without image distortions and high-quality MR images were obtained. CONCLUSIONS: The combination of a 1.5-T MR imager with a c-arm fluoroscopy system seems to be a promising technical solution for performing interventional MR procedures.

Adult↗
PubMed1997

Color-coded duplex sonography of experimentally induced multilevel stenosis. Evaluation of poststenotic Doppler spectrum.

RATIONALE AND OBJECTIVES: The authors evaluated the influence of a proximal arterial stenosis on the poststenotic doppler spectrum of a second, distal stenosis and determined duplex parameters, which permitted description of the severity of the distal stenosis. METHODS: Moderate (ie, 50%) and severe (ie, 90%) stenoses of the distal aorta and the distal iliac arteries of 10 pigs were created surgically and characterized by angiography. All possible combinations of moderate and severe stenoses were examined. The Doppler spectrum was depicted in the distal iliac and distal femoral arteries of both limbs and analyzed by use of maximum and minimum flow velocity (Vmax, Vmin), acceleration index (modified Handa index), acceleration time, and pulsatility index. RESULTS: In cases of moderate as well as severe proximal stenosis, acceleration index, acceleration time, and pulsatility index of the poststenotic curve of the distal stenosis were significantly reduced (P < 0.05). Independent of the severity of the proximal stenosis, differentiation of moderate as well as severe distal stenosis was possible (P < 0.05) with these parameters. CONCLUSIONS: Despite interference of spectral curves in proximal and distal stenosis, duplex sonography enabled the differentiation of experimental aortic iliac multilevel stenosis.

Animals↗
PubMed1997

Iliac arteries: plain and heparin-coated Dacron-covered stent-grafts compared with noncovered metal stents--an experimental study.

PURPOSE: To compare lumen patency, neointimal thickening, and local inflammatory reaction with noncovered metal stents and plain and heparin-coated Dacron-covered stent-grafts. MATERIALS AND METHODS: In each of 16 sheep, four prostheses were placed in the iliac arteries: a plain and a heparin-coated Dacron-covered Cragg stent-graft, a noncovered Cragg stent, and a noncovered Memotherm nitinol stent. Two prostheses were inserted in the iliac artery on each side. Patency was monitored with angiography and intravascular ultrasound (US). Eight animals were killed at 1-month follow-up, and the other eight at 6 month follow-up. Neointimal thickening and inflammatory foreign-body reaction to the prostheses were determined macroscopically and with light microscopy. RESULTS: More than 50% stenosis developed in 10 heparin-coated and three plain Dacron-covered stent-grafts but not in the noncovered stents. Two heparin-coated and one plain Dacron-covered stent-graft occluded completely. Neointimal thickening and inflammatory reaction were severe with the heparin-coated Dacron-covered stent-grafts, were less with the plain Dacron-covered stent-grafts, and were least with the noncovered stents. CONCLUSION: Neointimal thickening and inflammatory reaction significantly increased with covered compared with noncovered prostheses in the iliac arteries in sheep and were worst with heparin-coated Dacron-covered stent-grafts. If possible, use of noncovered stents should thus be preferred to use of Dacron-covered stent-grafts.

Alloys↗
PubMed1997

Perigraft inflammation due to Dacron-covered stent-grafts in sheep iliac arteries: correlation of MR imaging and histopathologic findings.

PURPOSE: To evaluate with magnetic resonance (MR) imaging the inflammatory perigraft response after implantation of Dacron-covered and noncovered arterial endovascular prostheses in sheep. MATERIALS AND METHODS: Four prosthesis types--two Dacron-covered nitinol stent-grafts (plain and heparin-coated) and two noncovered nitinol stents (Memotherm and Cragg)--were each inserted into the external iliac arteries of eight sheep. MR imaging before and after gadolinium enhancement was performed 5-8 days and 1 month after implantation (before the animals were killed). Macroscopic and microscopic examinations of the vessels were performed, and findings were correlated with those on MR images. RESULTS: Severe inflammatory perigraft responses to the heparin-coated Dacron-covered stent-grafts were found; MR images demonstrated contrast enhancement and edema. Macroscopic examination showed marked vascular wall thickening and adhesions around the Dacron fabric; microscopic examination showed a pronounced inflammatory foreign-body response. There was a moderate inflammatory response to the plain Dacron-covered stent-grafts and almost no response to noncovered stents. CONCLUSION: In sheep, MR imaging findings of perigraft soft-tissue edema and contrast enhancement correlated well with histopathologic findings of severe perigraft inflammation due to heparin-coated Dacron-covered stent-grafts.

Alloys↗
PubMed1997

Percutaneous interventions to support failing hemodialysis fistulas and grafts.

Different methods of percutaneous management offer an approach to nearly every type of failing hemodialysis fistula. Technically, shunt intervention is highly successful and associated with a low complication rate. It is quick, inexpensive and can be performed on an outpatient basis with immediate dialysis via the fistula thereafter. Nearly all techniques of interventional radiology have their place in this strategy and skilled training is mandatory to achieve excellent results. Reobstruction has to be accepted as part of the process. Frequent but timely reintervention is therefore part of shunt maintenance and protection.

Angioplasty, Balloon↗
PubMed1996

[Secondary stabilization of aortic bifurcation Chuter endoprostheses by implantation of self-expanding metal stents].

The use of conventional graft fabric for the bifurcated Chuter endovascular graft may result in a kink instability since crimping has been removed. Especially in elongated arteries that are frequently found with aortic aneurysms this may cause stenosis of the kinked graft and subsequent thrombosis. Bilateral stabilisation of the graft limbs along its total length proved sufficient to stabilise the graft thus preventing secondary thrombosis.

Angiography, Digital Subtraction↗
PubMed1996

Aortic and iliac stenoses: follow-up results of stent placement after insufficient balloon angioplasty in 118 cases.

PURPOSE: To demonstrate follow-up results of stent placement in aortic and iliac stenoses. MATERIALS AND METHODS: A total of 109 patients with 118 aortoiliac stenoses underwent placement of self-expanding stents. Mean length of the stenotic segments was 3 cm +/- 2 (standard deviation). Mean ankle-arm index at rest was 0.58 +/- 0.2. A total of 101 patients were followed up angiographically or clinically. RESULTS: A mean of 1.2 stents +/- 0.5 were inserted per case. Clinical stage improved in 112 cases; it improved two or more stages in 89 cases. Mean ankle-arm index improved to 0.92 +/- 0.17. Total and major complication rates were 6.8% and 3.4%, respectively. Subacute occlusion occurred in four patients. Late stent obstruction occurred after a mean of 27 months (range, 16-48 months) in 10 cases. Primary patency was 95% after 1 year and 88% after 2 years; 4-year patency was 82%. Secondary patency was 96% after 1 year and 93% after 2 years. Three- and 4-year secondary patency were both 91%. CONCLUSION: Placement of self-expanding stents in iliac stenoses is technically safe and offers sufficient follow-up patency.

Angiography, Digital Subtraction↗
PubMed1996

Hemodialysis fistulas and grafts: use of cutting balloons to dilate venous stenoses.

To evaluate percutaneous transluminal angioplasty (PTA) with a cutting balloon performed in stenosed hemodialysis fistulas and grafts, 19 venous lesions in 15 patients were treated with a cutting balloon with an inflated diameter of 3-6 mm. The grade of stenosis ranged from 40% to 90% (mean, 65% +/- 15 [standard deviation]). Cutting PTA was performed before conventional PTA in seven patients and was followed with conventional PTA with larger balloons in seven patients. The balloon expanded completely in all patients, and no balloon waist remained. The mean grade of stenosis decreased to 14% +/- 9. Cutting PTA increased the technical success of balloon dilation of hemodialysis fistulas and grafts.

Aged↗
PubMed1996

Hydrodynamic thrombectomy of haemodialysis grafts and fistulae: results of 51 procedures.

PURPOSE: To describe efficacy of hydrodynamic thrombectomy for occluded dialysis native and graft fistulae in 51 instances. MATERIALS AND METHODS: Fifty-one hydrodynamic thrombectomies of 34 native and graft a-v fistulae were performed. There were 32 thrombectomies in PTFE grafts and 19 procedures in native Brescia-Cimino fistulae. Multiple thrombectomies were performed in 11 of 34 fistulae. The estimated occlusion time was 36.4+/-22 h. The length of the occluded segment ranged from 2 to 50 cm (mean 28.8 cm). In all cases, a 7 F hydrodynamic thrombectomy catheter was used. Double-cannulation technique was used for graft fistulae, single-cannulation for native fistulae. Additionally, balloon dilatation was performed in all 51 cases, stenting in six, and aspiration thrombectomy in two cases. RESULTS: Arterialized flow was re-established by hydrodynamic thrombectomy and PTA in 43 of 51 cases (84%). By additional use of other techniques, technical success improved to 46 of 51 procedures (90%). Early re-thrombosis occurred in six cases within 24 h of thrombectomy (11%). Clinical success was achieved in 39 of 46 technically successful cases (85%). Cumulative patency was calculated at 63% after 1 week, 57% after 1 month, 48% after 3 months, 37% after 6 months, and 32% after 12 months. Patency of native fistulae after thrombectomy was better than patency of grafts. CONCLUSIONS: Hydrodynamic thrombectomy is an effective percutaneous technique for declotting haemodialysis fistulae and grafts recently thrombosed.

Adult↗
PubMed1995

[Therapy of an abdominal aortic aneurysm using transfemoral endovascular implantation of a bifurcation prosthesis].

Transfemoral intraluminal placement of a woven-dacron bifurcation prosthesis was undertaken to bridge an infrarenal aortic aneurysm (4.6 cm diameter) in a 65-year-old man with chronic coronary heart disease. The Chuter-Gianturco introducing system was used via the right femoral artery to anchor the prosthesis immediately below the origins of the renal arteries. After fixing the right branch of the prosthesis the left one was secured via the left femoral artery. No leakage was demonstrated on the 7th post-operative day and the aneurysm was satisfactorily bridged. Regular follow-up tests showed a normal circulation. Spiral computed tomography after 18 months confirmed complete thrombosis of the aneurysm.--This case shows that the described method is a promising alternative in the treatment of abdominal aneurysm.

Aged↗
PubMed1995

[The percutaneous CT-guided treatment of osteoid osteomas: a combined procedure with a biopsy drill and subsequent ethanol injection].

PURPOSE: The purpose of this study was the clinical evaluation of a percutaneous treatment modality in patients with an osteoidosteoma. PATIENTS AND METHODS: 6 patients with an osteoidosteoma of the upper (n = 1) and lower (n = 5) extremity which were confirmed on plain film radiographs and computed tomography underwent CT controlled drill biopsy of the nidus with subsequent injection of 96% ethanol into the biopsy channel to sclerose probably remaining remnants of the nidus. The procedure was started under local anaesthesia, but drilling of the nidus was carried out under a short general anaesthesia using ketamine. RESULTS: The intervention was successful in all patients. No postinterventional infection occurred and no recurrence was observed in any of the patients in a follow-up time between 0.5 and 2 years. CONCLUSION: Although only 6 patients were treated until now, we conclude that this combined procedure using a bone biopsy system and the subsequent injection of alcohol is a safe and successful procedure for percutaneous treatment of osteoidosteoma.

Adolescent↗
PubMed1995

[Percutaneous treatment possibilities in thrombotic occlusion of Brescia-Cimino dialysis shunts].

PURPOSE: Acute thrombotic occlusion of Brescia-Cimino forearm fistulae is a severe complication. Aspects of percutaneous therapy include balloon dilatation, thrombolysis and mechanical thrombectomy. We report on 21 cases with obstructed shunts. Clinical evaluation and palpation helped to select each shunt for an individual therapeutic approach. PATIENTS AND METHODS: One patient presented with a proximal arterial occlusion, three patients with a small occluding thrombus, 4 patients with a severe stenosis but only a small amount of thrombus and 13 patients with an extended amount of clot material. RESULTS: 7 patients underwent balloon dilatation alone, three patients thrombolysis with rtPA and 11 patients hydrodynamic thrombectomy. Arterialized shunt flow was reestablished in 20 of 21 cases. The shunt was reused for dialysis in 17 cases. Reobstruction within two weeks after intervention occurred in two cases. CONCLUSIONS: With regard to the individual clot size, different percutaneous methods are available for successful shunt recanalisation.

Acute Disease↗