Endovascular shunt reduction in the management of transjugular portosystemic shunt-induced hepatic encephalopathy: preliminary experience with reduction stents and stent-grafts

OBJECTIVE: The purpose of this study was to retrospectively evaluate the safety, feasibility, and midterm clinical outcome of the use of three types of reduction stents inserted to manage transjugular intrahepatic portosystemic shunt (TIPS)-induced hepatic encephalopathy refractory to medical treatment. CONCLUSION: The use of a covered reduction stent-graft results in a greater increase in portosystemic gradient immediately after reduction than does use of a bare reduction stent. Relief of TIPS-induced hepatic encephalopathy tends to be greater in patients with reduction stent-grafts than in those with bare reduction stents.     

Recurrent TIPS thrombosis after polyethylene stent-graft use and salvage with polytetrafluoroethylene stent-grafts

Increasing data support the use of polytetrafluoroethylene (PTFE) stent-grafts for de novo and revision transjugular intrahepatic portosystemic shunt (TIPS) applications. Animal experiments have indicated that polyethylene terephthalate (PET) stent-grafts provide no improvement or actually worsen TIPS patency compared with controls, but human TIPS experience with PET grafts is more limited. Herein we describe three patients who underwent de novo creation of TIPS with PET-covered stent-grafts at outside institutions, which resulted in immediate and recurring TIPS thromboses despite repeated thrombectomies. After the failed TIPS were revised with PTFE stent-grafts, the presenting symptoms resolved and uninterrupted patency was achieved.     

Improved patency of transjugular intrahepatic portosystemic shunts in humans: creation and revision with PTFE stent-grafts

PURPOSE: To determine whether polytetrafluoroethylene (PTFE) stent-grafts yield longer patency for creation or revision of transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS: Fourteen PTFE-covered Wallstents were placed in 13 patients with TIPS: seven at shunt creation and seven during revision of TIPS with one to five prior thromboses at 1 day to 1 year after initial TIPS formation. In six cases, prior to stent-graft placement persistent biliary-TIPS fistulas were demonstrated despite repeated shunt revisions with additional metallic stents. RESULTS: All but one graft-lined TIPS were widely patent at a mean duration of venographic follow-up of 19 months (median, 17 months; range, 5-32 months). The limiting percentage of stenosis within the grafted shunts was 0%-10%. One patient developed stent-graft thrombosis; the prior biliary-TIPS fistula was seen despite the graft. A second, parallel PTFE-lined transcaval shunt was created in this patient; it was widely patent at 11-month follow-up. In two asymptomatic patients, stenoses developed in the short, nongrafted portions of the outflow hepatic veins. CONCLUSION: PTFE stent-grafts can markedly prolong TIPS patency, potentially reducing the need for shunt follow-up and revision and the risk of recurrent symptoms associated with shunt stenosis or occlusion.     

Transjugular intrahepatic portosystemic shunt patency and clinical outcome in patients with Budd-Chiari syndrome: covered versus uncovered stents

PURPOSE: To retrospectively compare primary patency and reintervention rates, clinical outcome, and improvement in hepatic dysfunction (Child-Pugh score) in patients with Budd-Chiari syndrome treated with transjugular intrahepatic portosystemic shunt (TIPS) using bare stents or expanded polytetrafluoroethylene (PTFE)-covered stents. MATERIALS AND METHODS: Approval of study and treatment protocol and waiver of informed consent for the retrospective study were obtained from institutional review board. Informed consent was obtained from each patient before procedure. Four male and nine female consecutive patients (mean age, 35.7 years) with Budd-Chiari syndrome treated with TIPS from January 1994 to November 2003 were included. In six patients, TIPS creation was performed with bare stents (group A). After April 2001, TIPS creation was performed in seven patients with expanded PTFE-covered stent-grafts (group B). Follow-up (group A mean, 22.7 months +/- 10.53 [standard deviation]; group B mean, 23.1 months +/- 7.81) was performed at 7 days, 30 days, and 3 months and subsequently every 3 months. Liver function was evaluated every 3 months. Primary end points were 6- and 12-month TIPS patency rates. Secondary end points were reintervention rate and clinical outcome. Patency rates were estimated (Kaplan-Meier method) and compared (log-rank test). Continuous (Mann-Whitney U test) and categoric (chi(2) test) data were compared. Significant differences before and after treatment were determined (Wilcoxon test). RESULTS: Mean primary patency duration was 4.46 months +/- 3.40 in group A and 22.29 months +/- 8.15 in group B. In group B, a significant increase in primary patency rate (100% and 85.7% vs 16.7% and 0% at 6 and 12 months; P < .001, log-rank test) and a decrease in reintervention rate (0.29 +/- 0.49 vs 6.17 +/- 1.72, P < .001) were observed. Both groups had a significantly decreased Child-Pugh score; group B had a more persistent and significantly higher reduction. CONCLUSION: Expanded PTFE-covered stent-grafts significantly increased primary patency rate of TIPS in patients with Budd-Chiari syndrome, with reduced reintervention rate and prolonged clinical improvement.     

Type 1 collagen as an endovascular stent-graft material for small-diameter vessels: a biocompatibility study

PURPOSE: To compare patency rates and degrees of neointimal hyperplasia between bovine type 1 collagen stent-grafts and uncovered control stents in small-diameter vessels (< or =4 mm). MATERIALS AND METHODS: Uncovered stainless-steel, balloon-expandable stents (n = 5) and type 1 collagen stent-grafts (n = 6) were implanted via the femoral arteries with use of 4-mm balloon catheters into the abdominal aorta of New Zealand White rabbits. Ten animals were available for follow-up. Subjects were followed for 1 month (three uncovered stents; three collagen stent-grafts) or 4 months (two uncovered stents; two collagen stent-grafts). Angiography was performed before animal sacrifice and luminal compromise was compared between groups. Histologic and immunohistochemical analysis was performed to determine presence of neointima and neointimal thickness and area; these parameters were also compared between groups. RESULTS: All stents and stent-grafts remained patent at both time points. Luminal compromise was not detectable angiographically in any subject. Maximum neointimal thickness was less than 5 mum for all subjects. Neointimal thickness and area were not statistically significantly different between groups. CONCLUSIONS: Type 1 collagen stent-grafts demonstrate excellent hemocompatibility and biocompatibility in small-diameter vessels in rabbits.     

Autologous vein stent-graft: feasibility study

PURPOSE: To evaluate expandable stents healed into vein wall as autologous vein stent-grafts for endoluminal grafting. MATERIALS AND METHODS: Balloon expandable stents were placed into external jugular veins of eight dogs. Stent and vein patency was followed by ultrasonography. Five weeks after stent placement, jugular veins with endothelialized stent were harvested. The autologous vein stent-grafts were divided into two groups. In group A, autologous vein stent-grafts (n = 3) were placed immediately into Baker solution for microscopic examination. In group B, autologous vein stent-grafts (n = 3) underwent mechanical manipulation; they were compressed, mounted on angioplasty balloon, pushed through a 9-F sheath and dilated. The autologous vein stent-graft endothelialization and changes after mechanical manipulation were evaluated by light and electron microscopy. RESULTS: Stent placement was successful in seven dogs. One stent migrated into the pulmonary artery. One well placed stent was damaged by compression dressing and thrombosed. At 5 weeks, gross and microscopic examinations revealed the autologous vein stent-grafts were fully covered by a 0.115- +/- 0.036-mm-thick neointimal layer. Small wall thrombus was observed in one autologous vein stent-graft. Repeated manipulations did not result in any intimal damage or stent loosening in the autologous vein stent-grafts. CONCLUSION: Expandable stents healed into a vein have potential to be used as autologous vein stent-grafts for endoluminal grafting without risk of disruption during percutaneous transcatheter introduction.     

Utility of CT angiography and MR angiography for the follow-up of experimental aneurysms treated with stents or Guglielmi detachable coils

BACKGROUND AND PURPOSE: Previous studies have depicted arterial and aneurysmal anatomy with three-dimensional time-of-flight (3D-TOF) MR angiography before and after treatment with Guglielmi detachable coils (GDCs) and with CT angiography before and after treatment with stents and stent-grafts. We investigated the ability of time-resolved contrast-enhanced 3D MR angiography (3D MR digital subtraction angiography [DSA]) to accurately depict the anatomy of experimental lateral aneurysms before and after treatment with GDCs and a variety of stents or stent-grafts, and compared these findings with 3D-TOF MR angiography without and with contrast enhancement and CT angiography. METHODS: Two nitinol stents, two nitinol-polytetrafluoroethylene (PTFE) stent-grafts, and two stainless steel stents were deployed in three dogs with experimental carotid aneurysms. In a fourth animal, one of three aneurysms was completely occluded with GDCs. The other two aneurysms were loosely packed to ensure persistence of some residual aneurysmal lumen. Cut-film angiography, CT angiography, 3D-TOF MR angiography without and with contrast enhancement, and 3D MR DSA were performed in all dogs before and 3 weeks after treatment. RESULTS: 3D MR DSA was superior to conventional 3D-TOF MR angiography without and with contrast enhancement in accurately depicting experimental lateral aneurysms and superior to CT angiography in depicting aneurysms treated by GDCs. 3D MR DSA and CT angiography were comparable in depicting vessels treated with nitinol stents and stent-grafts, whereas CT angiography was superior for showing vessels treated by stainless steel stents. CONCLUSION: We recommend further development and clinical evaluation of 3D MR DSA for imaging cerebral aneurysms before and after treatment with GDCs. 3D MR DSA or CT angiography may be useful for evaluating vessels containing nitinol stents or nitinol-PTFE stent-grafts, whereas CT angiography should be used for follow-up of vessels treated by stainless steel stents.     

经颈静脉门腔分流术中Fluency覆膜支架应用的临床观察

目的 评价Fluency覆膜支架在经颈静脉门腔分流术(TIPS)中的临床效果.方法 搜集21例采用Fluency覆膜支架行TIPS治疗患者的临床病例资料进行回顾性分析.本组患者随访时间2.0～24.0个月,平均(10.1±4.6)个月;均为门静脉高压上消化道大出血,其中原发性肝癌门静脉主干癌栓伴大出血1例,布加综合征1例.分析患者术后支架开通情况,门静脉压力及肝功能变化情况.对手术前后门静脉压力及肝功能变化情况的比较采用配对t检验.结果21例患者共放支架25枚,均成功放置,支架直径10 mm 2枚、8 mm为23枚;覆膜支架长度6～8 cm.所有患者术后上消化道出血停止;门静脉压力由术前平均(25.4±3.5)mm Hg(1mm Hg=0.133 kPa)降为(15.4±2.8)mm Hg,手术前后差异有统计学意义(t=12.495,P<0.01).随访期间,1例原发性肝癌伴门静脉主干癌栓患者于术后4个月死亡,1例随访期间发现原发性肝癌的患者术后24个月死亡,1例门静脉高压上消化道大出血患者于术后2个月死于多器官功能衰竭,1例于术后15个月出现肝静脉端狭窄,行第2枚支架治疗效果良好,余17例随访7～17个月支架无狭窄.患者死亡前1周复查超声示支架均通畅.3例术后出现一过性肝性脑病前驱症状,经对症处理后好转.存活6个月以上的19例患者,术前Child肝功能评分(6.3±1.4)分,术后6个月评分(6.4±1.9)分,两者差异无统计学意义(t=0.645,P>0.05).结论采用Fluency覆膜支架行TIPS术,能明显提高TIPS术后开通率,但长期效果及肝性脑病的评价尚需验'证.     

Dacron-covered stent-grafts in transjugular intrahepatic portosystemic shunts: initial experience

PURPOSE: To retrospectively review the authors' experience with use of a Dacron-covered stent-graft in transjugular intrahepatic postosystemic shunts (TIPS). MATERIALS AND METHODS: The need for internal review board approval was waived. Informed consent was obtained from all patients. The study was compliant with the Health Insurance Portability and Accountability Act. A retrospective analysis was performed of 16 patients who received a Dacron-covered stent-graft during revision or de novo creation of TIPS. There were 13 men and three women aged 44-80 years (mean age, 61 years). Primary unassisted and assisted patency rates and secondary patency rates were estimated. The primary unassisted patency of patients who underwent de novo placement of stent-grafts (n = 10) was compared with that of patients with stent-grafts placed during shunt revision (n = 6); in all patients, stent-grafts were placed within stents. Primary unassisted patency was also compared between patients in whom the covered stent was confined to the parenchymal tract (n = 7) and those in whom the stent extended 1 cm or more into the portal vein (n = 9). Patency was estimated with the Kaplan-Meier method, and group comparisons were performed with the log-rank test. RESULTS: Primary unassisted patency rates following stent-graft placement at 4, 12, and 24 months (+/- standard error) were 64% +/- 14, 54% +/- 15, and 40% +/- 16, respectively. The rates for primary assisted patency were 78% +/- 12, 67% +/- 14, and 67% +/- 14 and those for secondary patency were 91% +/- 9, 81% +/- 12, and 54% +/- 23. At 12 months, primary unassisted patency with de novo stent-graft placement was 90% +/- 9, whereas that with stent-grafts placed during TIPS revision was 17% +/- 15 (P = .005). At 12 months, the primary unassisted patency in patients with stent-grafts confined to the parenchymal tract was 75% +/- 22, and that of patients with stent-grafts extending at least 1 cm into the portal vein was 40% +/- 17 (P = .21). CONCLUSION: In this small series, satisfactory long-term patency was observed among patients in whom Dacron-covered stent-grafts were placed during revision or de novo creation of TIPS. More favorable outcomes were observed when the stent-graft was placed during de novo TIPS creation and when the device was confined to the parenchymal tract.     

Multislice CT angiography of the iliac arteries in the presence of various stents: in vitro evaluation of artifacts and lumen visibility.

RATIONALE AND OBJECTIVES: To evaluate the imaging characteristics of various iliac artery stents and stent-grafts in a multislice, computed tomography angiography (MSCTA) phantom study. METHODS: Twelve types of stents and three stent-grafts made of different materials (steel, nitinol, tantalum, cobalt-based alloy) were implanted in plastic tubes with an 8-mm inner diameter filled with iodinated contrast medium diluted to 200 HU. To evaluate the influence of scan parameters on artifacts, the Palmaz stent (as one example) was scanned with a four-slice scanner (Siemens VolumeZoom) with different detector collimations and pitches. All other stents were examined with a collimation of 4 x 1 mm and a table feed of 4 mm/rotation. Axial images and multiplanar reformations were evaluated regarding artifact size, lumen visibility, and intraluminal attenuation values. RESULTS: Higher pitch values caused more pronounced artifacts. Image quality and delineation of the stent struts improved with thinner detector collimation. The size of the stent-related artifacts and the visibility of the stent lumen depended on the underlying stent material and design. Pronounced artifacts, resulting in an insufficient delineation of the stent lumen, were caused by the Strecker tantalum stent and the Zenith stent. Moderate artifacts were caused by the Wallgraft, Passager, Palmaz P 395 and P 424, Bridge, Perflex, and ZA stents. Some artificial lumen narrowing but good lumen delineation was seen with the Strecker nitinol, Symphony, Memotherm, SMART, Corinthian, and Wallstent stents. CONCLUSIONS: Scanning parameters, stent material, and stent design influence lumen assessability and image quality in MSCTA. Detailed lumen assessment is impossible in the Strecker tantalum and Zenith stents and limited in the Wallgraft, Passager, Palmaz P 395 and PS 424, Bridge, Perflex, and ZA-stent stent-grafts but feasible in all other examined products.     

Dr. Gary J. Becker young investigator award: comparison of small-diameter type 1 collagen stent-grafts and PTFE stent-grafts in a canine model--work in progress

PURPOSE: To report an in-progress experiment in a canine model in which two types of small-diameter stent-grafts-one constructed of polytetrafluoroethylene (PTFE) and the other of a new, type 1 collagen material-were compared regarding vessel patency, intimal hyperplasia formation, and tissue reaction. MATERIALS AND METHODS: Six mongrel dogs weighing 30-35 kg were used. Stent-grafts of 4-mm diameter and 20-mm length were constructed with use of balloon-expandable stainless-steel stents wrapped with either PTFE or a new type 1 collagen graft. Stent-grafts were placed in deep femoral arteries bilaterally (PTFE on one side, collagen on the other). Animals were followed for 2 weeks (n = 2), 6 weeks (n = 2), or 12 weeks (n = 2). Percent stenosis based on angiographic findings as well as thickness and area of neointimal hyperplasia were compared at each time point and compared with use of the Student t test. RESULTS: All devices were patent in the immediate postimplantation period. Five of six collagen stent-grafts and five of six PTFE implants were patent at follow-up. In-stent stenosis was undetectable angiographically in all five patent collagen stent-grafts. All five patent PTFE stent-grafts showed demonstrable in-stent stenosis (10%-60%), indicating a trend toward improved patency in collagen stent-grafts versus PTFE stent-grafts (P = .07). Neointimal hyperplasia was absent at 2 weeks in the collagen stent-grafts. Neointimal thickness increased to a maximum of 360 microm at 12 weeks in the collagen stent-grafts. For PTFE stent-grafts, neointimal hyperplasia was present in all samples and reached a maximum of 770 microm at 12 weeks (P = .03). CONCLUSIONS: Even in small-diameter vessels, type 1 collagen stent-grafts demonstrate excellent patency rates and favorable histologic findings. The type 1 collagen stent-graft technology merits further developmental efforts in preclinical models.     

Polyurethane-coated dacron-covered stent-grafts for TIPS: results in swine

Purpose: To evaluate shunt patency after placing a new polyurethane-coated Dacron-covered spiral Z stent-graft to create a transjugular intrahepatic portosystemic shunt (TIPS). Methods: TIPS stent-grafts were placed in six young swine, using polyurethane-coated, Dacron-covered spiral Z stent-grafts. Animals were followed weekly by transhepatic portal venography until shunt occlusion or up to 6 weeks, then were sacrificed for gross and histologic evaluation. Results: Five of six TIPS stent-grafts were found to be occluded by 3 weeks and none were patent at 6 weeks. Histologic evaluation demonstrated a marked foreign body reaction with superimposed thrombosis occluding the graft lumen. Conclusion: Polyurethane-coated Dacron-covered stent-grafts do not improve TIPS patency.     

In vitro evaluation of intravascular stent artifacts in three-dimensional MR angiography

RATIONALE AND OBJECTIVES: To evaluate the intraluminal signal characteristics of various stents and stent-grafts in contrast-enhanced three-dimensional MR angiography (3D MRA) in vitro. METHODS: Fourteen stents made of different materials (steel, nitinol, tantalum, cobalt-based alloy, polyethylene) and six stent-grafts were implanted in plastic tubes simulating the common iliac artery. The tubes were filled with gadopentetate dimeglumine in water at a concentration of 25 mmol/L and positioned in a plastic container filled with water. For imaging, the container was placed in the center of the magnet, parallel, orthogonal, and diagonal to the z axis. A 3D gradient-echo sequence (T1-FFE) was acquired with the following parameters: repetition time 5.3 ms, echo time 1.6 ms, flip angle 50 degrees, slice thickness 1.5 mm, and acquisition matrix 256 with zero filling to 512. To evaluate the influence of the frequency-encoding gradient on the appearance of the artifacts, stents were examined with their axes oriented in all three directions both with the frequency-encoding gradient in the feet-head and right-left directions. The size and pattern of stent-related artifacts were evaluated semiquantitatively for each measurement. RESULTS: Five different components of artifacts could be distinguished: homogeneous signal reduction inside the stent, narrowing of the stent lumen, structures of various shapes inside the stents, signal reduction or signal increase at the ends of the stents, and shift of the intraluminal signal orthogonal to the longitudinal axis of the vessel. The size of the artifacts depended heavily on the material of the stent. The polyethylene stent showed no artifacts, the tantalum stent only minor artifacts. Nitinol stents were characterized by artifacts at both ends and signal reduction intraluminally. Stents made of steel demonstrated the strongest artifacts, characterized by almost complete signal loss intraluminally. The characteristics of the artifacts of all stents depended on the direction of the stent relative to the frequency-encoding gradient. CONCLUSIONS: Three-dimensional MRA follow-up after stent placement may be applicable for stent patency evaluation in all instances. However, grading of stenoses seems to be unrealistic in steel stents and in most nitinol stents.     

Covered Stent-Graft Treatment of Traumatic Internal Carotid Artery Pseudoaneurysms: A Review

Objective To review the literature concerning the management with placement of covered stent-grafts of traumatic pseudoaneurysms of the extracranial internal carotid artery (ICA) resulting from penetrating craniocervical injuries or skull base fractures. Method We have reviewed, from the Medline database, all the published cases in the English literature since 1990 and we have added a new case. Results We identified 20 patients with traumatic extracranial ICA pseudoaneurysms due to penetrating craniocervical injuries or skull base fractures who had been treated with covered stent-graft implantation. Many discrepancies have been ascertained regarding the anticoagulation therapy. In 3 patients the ICA was totally occluded in the follow-up period, giving an overall occlusion rate 15%. No serious complication was reported as a result of the endovascular procedure. Conclusion Preliminary results suggest that placement of stent-grafts is a safe and effective method of treating ICA traumatic pseudoaneurysms resulting from penetrating craniocervical injuries or skull base fractures. The immediate results are satisfactory when the procedure takes place with appropriate anticoagulation therapy. The periprocedural morbidity and mortality and the early patency are also acceptable. A surveillance program with appropriate interventions to manage restenosis may improve the long-term patency.     

Stent-graft treatment of extracranial carotid and vertebral arterial lesions

Five patients with pseudoaneurysms of the carotid artery (n = 4) and an arteriovenous fistula of the vertebral artery (n = 1) were treated with stent-grafts. Commercially made devices were used in all but one of the patients. In four of the five patients, the pathology was successfully excluded. One patient had a small type-I endoleak. There were no immediate procedure-related complications or neurologic sequalae. All experienced immediate resolution of symptoms. One patient was lost to follow-up after discharge and another died 2 weeks after intervention. The remaining patients remained asymptomatic with patent stent-grafts after follow-up periods of 14, 16, and 46 months, respectively.     

A new stent-graft for transjugular intrahepatic portosystemic shunts.

The transjugular intrahepatic portosystemic shunt (TIPSS) has become an effective method of treatment for the complications of portal hypertension, however shunt dysfunction is common. Covered stent-grafts have been tested in animal models, and customized or "home-made" devices have been deployed in several institutions. We report the use of a new commercially available TIPSS stent-graft in six patients undergoing primary shunting as well as two cases of revision or secondary TIPSS. The device has proved relatively easy to handle and appears to have the technical features likely to improve primary patency. Further follow-up is required to properly assess shunt patency and re-intervention rates.     

A Case of Late Femoral Pseudoaneurysm Caused by Stent Disconnection

We present the case of a late superficial femoral artery stent disconnection causing an asymptomatic pseudoaneurysm successfully treated with a stent-graft. A 67-year-old female was referred to our department for evaluation of claudication of the left lower limb and was diagnosed to have a total occlusion of the superficial femoral artery. Three nitinol stents were used to revascularize this artery. At 48 months, duplex-ultrasonography control revealed the presence of a 45-mm saccular femoral dilatation; X-rays and CT angiography showed fractures of the proximal stents and the presence of a pseudoaneurysm at the site of the distal stents disconnection. The pseudoaneurysm was excluded using two stent-grafts. We conclude that patients and surgeons should be aware of structural complications with all stents. Rigorous follow-up controls should be mandatory. Endovascular repair proved to be feasible and durable to manage a previous endovascular procedure.     

Endovascular Exclusion of Visceral Artery Aneurysms with Stent-Grafts: Technique and Long-Term Follow-up

This paper describes four cases of visceral artery aneurysms (VAAs) successfully treated with endovascular stent-grafts and discusses the endovascular approach to VAAs and the long-term results. Four balloon expandable stent-grafts were used to treat three splenic artery aneurysms and one bleeding common hepatic artery pseudoaneurysm. The percutaneous access site and the materials were chosen on the basis of CT angiography findings. In all cases the aneurysms were successfully excluded. In one case a splenic infarction occurred, with nonrelevant clinical findings. At 16- to 24-month follow-up three patients had patent stents and complete exclusion and shrinkage of the aneurysms. One patient died due to pancreatitis and sepsis, 16 days after successful stenting and exclusion of a bleeding pseudoaneurysm. We conclude that endovascular treatment using covered stent-grafts is a valid therapeutic option for VAAs. Multislice CT preoperative study helps in planning stent-graft positioning.     

Shortening and Migration of Wallstents after Stenting of Central Venous Stenoses in Hemodialysis Patients

PURPOSE: To report our results for the placement of central venous stents in patients undergoing hemodialysis. METHODS: Ten Wallstents (Schneider, Bülach, Switzerland) were placed in 10 patients with shunt thrombosis, shunt dysfunction or arm swelling associated with central vein stenosis or occlusion. Technical success, patency and complications were evaluated. RESULTS: Stent deployment was successful in all cases. In seven cases (70%) there was significant delayed stent shortening. In two of these cases there was also stent migration. All these cases required additional stents. Primary patency rates at 6, 12 and 24 months were 66%, 25% and 0. Twenty-three additional procedures (percutaneous transluminal angioplasty or stenting) were required to achieve secondary patency rates at 6, 12 and 24 months of 100%, 75% and 57%. CONCLUSION: Stent placement in the central veins of dialysis patients has a high technical success rate resulting in symptomatic relief and preservation of access. Repeat interventions are required to maintain patency. Significant delayed shortening of the Wallstent occurred in 70% of patients which may have affected the patency rates. Strategies are suggested to avoid this problem.     

Venous stenoses in dialysis shunts: treatment with self-expanding metallic stents

A flexible, self-expanding metallic endoprosthesis was employed for the treatment of venous outflow stenoses in four patients with a polytetrafluoroethylene shunt and two patients with a Brescia-Cimino shunt. The stenoses had led to shunt occlusion in five patients and to flow impairment in one. In the occluded shunts, thrombectomy and subsequent balloon angioplasty were performed in four patients, and percutaneous recanalization with angioplasty was performed in one. One shunt with decreasing flow was percutaneously dilated. Since the underlying stenoses recurred in four patients after 24 hours and did not respond sufficiently to angioplasty in two patients, up to four stents were placed in the venous segments. Thrombosis of the stents occurred in two patients after 24 hours and in one after 6 weeks and was successfully recanalized with thrombectomy in two. At 2-6 months follow-up, the stents and the shunts were patent in five patients. In three of these patients, intima hyperplasia, associated with narrowing of the stent lumen in two, was noted within 4 months after stent placement.