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Biomedical subjects

D Vorwerk

Publications and source records attributed to D Vorwerk.

At least 127 records · Page 7Linked to original sources
PubMed1988

[Color-coded duplex sonography (angiodynography) in the evaluation of arteriovenous shunts].

In 21 hemodialysis patients colour coded duplex sonography (angiodynography) was performed on 23 av-fistulae. In all patients topographic shunt pathways could be evaluated sufficiently, which corresponded well to digital subtraction angiography, that was available in a number of cases. Pathology could be easily identified by morphologic tissue changes in combination with altered flow patterns. The advantage of angiodynography in av-fistulae is a combined information about both morphology and flow dynamics, which can be won in an absolutely noninvasive manner.

Adult↗
PubMed1988

[Localization of an ACTH-producing pituitary microadenoma using bilateral and simultaneous catheterization of the inferior petrosal sinus].

The experience with bilateral simultaneous inferior petrosal sinus catheterization and determination of the ACTH-concentration in 21 patients is reported. Venous blood sampling in the right and left inferior petrosal sinus was obtained before and after stimulation with Corticotropin-Releasing-Hormone (CRH). In 13 patients with Cushing's Syndrome a ACTH gradient (central versus peripheral) was measured. In all patients who were operated (11/13) a microadenoma was confirmed. In all patients with a central/peripheral gradient of the ACTH-levels at the same time an ipsi versus contralateral gradient between the two sides could be established after administration of CRH, which allowed a correct localization of the microadenoma. In 11 of 13 patients the site of the microadenoma was confirmed intraoperatively.

Adenoma↗
PubMed1988

Superselective embolization of inoperable renal carcinoma in patients with solitary kidney.

Arterial embolization is a palliative procedure in the management of advanced renal carcinoma. In solitary kidneys tumors may also be embolized under certain circumstances, i.e. patients with resectable tumors but inoperable because of poor general condition or patients with nonresectable tumors presenting with hemorrhage or paraneoplastic activity. Experience with 2 cases of selective embolization of inoperable renal cancer in solitary kidneys is presented and the indications for embolization, considering deterioration of renal function, are outlined.

Aged↗
PubMed1988

[Venous thrombolysis and venous angioplasty].

Venous thrombosis of the upper extremities was successfully lysed in 7 patients using selective infusion of urokinase. Selective lysis requires a lower dosage of urokinase and has a lower rate of side effects. Venous angioplasty was applied in 2 patients with stenoses of the subclavian vein, 3 with stenosis in dialysis shunts, and 1 patient with a long stenosis of the iliac vein. Venous angioplasty was successful and particularly useful in dialysis shunt stenoses.

Angioplasty, Balloon↗
PubMed1988

[The percutaneous vena cava umbrella filter in the prevention of pulmonary embolism].

The Kimray-Greenfield filter is the most commonly used of all filters. Percutaneous insertion technique has made this filter more attractive also for interventional radiology. Its drawbacks are, in particular, the large calibre of the insertion instruments and its low effectivity in case of eccentric placing. Good results have been obtained to date with the specially developed cava filters that can be introduced percutaneously. Clinical and experimental studies have shown that some filters are particularly effective, such as the "basket filter"; at the same time, these have also a higher thrombogenicity. However, independent of the choice of the cava filter, it seems that the operatively inserted filters are increasingly a thing of the past.

Filtration↗
PubMed1987

First clinical results with a new caval filter.

A new percutaneous inferior venacaval filter was used in 15 patients. The filter is constructed of stainless steel wires formed into a helical basket and anchoring legs. It can be inserted through a 10F catheter in an antegrade or retrograde fashion and can also be retrieved percutaneously. In a follow-up period of up to 13 months, the filter was well tolerated. One patient died of recurrent embolism despite filter protection. Local thrombogenicity was noted in 2 patients, but no other side effects were observed. Short-term heparinization following filter insertion is advisable. Heparin coating of the filter is under evaluation.

Adult↗
PubMed1987

[Determination of normal values in the assessment of measurements and side differences in the ultrasonic study of the shoulder joint].

Sonography of the rotator cuff with measurement of relevant soft tissue structures was performed in 120 persons without evidence of shoulder pathology. Although the extension of all structures varied markedly, no significant differences were found on comparing both sides. However, with regard to the variability of side differences, a limited side difference must be accepted as a normal finding. Sex, age and other body-related variables did not correlate well and were not useful in the assessment of the dimension of rotator cuff structures.

Adult↗
PubMed1987

[Initial experiences with angiodynography (color-coded duplex sonography) in the follow-up of vena cava filters].

In vena cava filter thrombosis, plain films and real-time B-mode ultrasound are not reliably diagnostic. Angiodynography (colour-coded duplex ultrasound) was performed in 15 patients as an alternative to invasive methods. Despite of the relatively low depth of the used 5 MHz transducer, in 14 patients blood flow in the vena cava could be identified successfully. A nearly total occlusion of filter could be demonstrated in one case; in another patient partial thrombosis was not detected. Flow alterations around the filter were seen in the majority of cases. First experiences with the method were satisfying with regard to the particular problem.

Color↗
PubMed1987

[Long-term follow-up of vena cava filters: real-time sonography and the native x-ray image].

In 16 patients with vena cava filters (12 Günther filters, 4 Kimray-Greenfield filters) a follow-up study was performed by ultrasound and abdominal plain film. Ultrasound allows to identify type and location of the filter as well as the entrapment of emboli. Abdominal radiography is useful for exact evaluation of changes in filter position. Combination of sonography and plain films is considered to be most suitable for follow-up studies of caval filters.

Adult↗
PubMed1987

[Diagnosis of obstruction and stone passage following ESWL therapy (extracorporeal shock-wave lithotripsy)].

78 patients with ureteral formations of stone fragments after ESWL therapy have been controlled by both ultrasound and plain abdominal films. Detection of renal stone fragments was possible similarly by sonography or radiographs. The plain films demonstrated well location and length of the "Steinstrasse", which did not necessarily cause obstruction. Combination of sonography and plain abdominal film allows an easy follow-up after ESWL therapy, so i.v. urogramm is not aquired routinely.

Adult↗
PubMedDate not supplied

Neointima formation following arterial placement of self-expanding stents of different radial force: experimental results.

PURPOSE: Radial force delivered by self-expanding stents has been discussed as a factor affecting thickness of neointima formation. METHODS: Two types of Wallstents were studied experimentally in vitro and in vivo. Due to an altered braiding angle of the stent filaments, one stent type (LS type) delivers half the radial force to the vascular wall than the conventional type. The radial force was evaluated in a compression-expansion test which related changes in stent length to the compressing force. Fourteen LS and 16 conventional stents were implanted into 15 femoropopliteal arteries of 10 dogs. Autopsy was performed after 4 weeks (14 stents) or 6 months (16 stents). RESULTS: All stents remained patent over the follow-up period with no evidence of stenosis. Neointimal overgrowth was complete and smooth in all. Medial atrophy was a constant finding after placement of both types. Neointimal thickness did not exceed 100 microns after 4 weeks and 6 months and did not significantly differ between LS stents and conventional stents. CONCLUSION: It is concluded that in normal dogs self-expanding stents of the Wallstent type do not induce neointimal buildup that exceeds 100 microns in the femoropopliteal artery. A reduced radial force was not found to result in reduced neointima formation.

Animals↗
PubMedDate not supplied

New device for wire and catheter capturing: in vivo experiments and first clinical experience.

PURPOSE: A new self-expanding tulip sheath was tested for percutaneous wife capturing in a femoro-femoral pull-through maneuver. METHODS: In six sheep, a self-expanding tulip sheath was introduced into the right iliac artery. A 5 Fr catheter and an 0.035-inch guidewire were guided into the iliac artery from a left femoral approach. Thirty-six tests were performed to guide the guidewire out of the right groin using the tulip sheath, by catching the catheter first in 18 tests and just by catching the guidewire in the other 18. As a control, six tests were performed using a conventional sheath. We performed one clinical arterial application. RESULTS: There was prompt capture of the wire in 35 of 36 tests using a self-expanding sheath. Five of six tests using a conventional sheath failed. The clinical application of the tulip principle was successful. CONCLUSION: Using the self-expanding tulip sheath to facilitate wire capture during pull-through maneuvers, even in difficult situations, is promising.

Aortic Dissection↗
PubMedDate not supplied

Suitability of incorporated vascular stents for surgical patch-plasty: an experimental study.

PURPOSE: Evaluate the feasibility of expanding arterial and venous stents incorporated into the vessel wall by surgical patch-plasty in an experimental study. METHODS: An 8-mm Wallstent was percutaneously implanted into the carotid artery of 11 sheep and into the ipsilateral jugular vein in three of them. Three months after implantation, a patch-plasty was performed on the incorporated stents using a 0.4-mm-thick synthetic patch made of polytetrafluoroethylene (PTFE). Stent patency was monitored by color-coded duplex ultrasound and angiography for 6 months after operation. RESULTS: No suture dehiscence or aneurysm formation were observed. Nine of 11 arterial and 2 of 3 venous stents remained fully patent during follow-up. In arteries, complications encountered were a complete stent thrombosis early after surgery, as well as a floating thrombus in the stent, found at final angiography after 6 months. In veins, one partial stent thrombosis was observed. Microradiographic and histological examinations revealed marked intimal hyperplasia in both arterial and venous stents. Intimal hyperplasia was significantly more pronounced in patched than in stented arterial segments (p < 0.005). CONCLUSION: Patch-plasty surgery of previously incorporated vascular stents is technically feasible. Mid-term patency rates were acceptable.

Aneurysm↗
PubMedDate not supplied

Puncture of stents implanted into veins and arteriovenous fistulas: an experimental study.

PURPOSE: Puncture of venous Wallstents and nitinol stents with dialysis needles was tested in an animal study. METHODS: In 15 sheep, divided into a group with prior surgical unilateral carotid-jugular shunt creation (9 sheep) and a second group without shunt creation (6 sheep), a self-expanding nitinol stent and/or a Wallstent were bilaterally placed into the jugular veins. After 1 month, 10 nitinol stents and 9 Wallstents were punctured weekly with a 15-gauge cannula over a period of 15 weeks. Stent patency was followed up by color-coded duplex ultrasound and angiography. After sacrifice, high resolution X-rays of the removed vessels were taken to assess stent deformation. From histological slices, neointimal thickness inside the stents was measured and analyzed statistically. RESULTS: Puncturing of both the nitinol stent and the Wallstent was technically feasible. Stent deformations were not found. One stent stenosis, probably related to puncture, was observed. The pattern of intimal hyperplasia differed between the nitinol stent and the Wall-stent. Outward bulge of the vascular layers over the stent struts was greater in nitinol stents. In the relevant area in between the stent struts there was no significant difference in intimal thickness between the two types of stents. Intimal thickness was more pronounced in shunted than in nonshunted animals only in the Wall-stent subgroup (p = 0.025) and more pronounced in punctured than in nonpunctured stents only in the nitinol stent subgroup (p = 0.018). CONCLUSION: Puncturing of stents was feasible without major short-term complications. Therefore, stent implantation into the punctured segment of a hemodialysis fistula may be indicated if there is no alternative treatment.

Alloys↗
PubMedDate not supplied

Iliocaval stenosis and iliac venous thrombosis in retroperitoneal fibrosis: percutaneous treatment by use of hydrodynamic thrombectomy and stenting.

A case of bilateral iliac stenosis and caval stenosis due to retroperitoneal fibrosis was treated by caval stenting and iliac balloon angioplasty, but was complicated by subsequent iliac thrombosis. Venous thrombectomy was successfully achieved by hydrodynamic thrombectomy, and iliac patency was stabilized by bilateral stent insertion.

Angioplasty, Balloon↗