Effects of Intraluminal Irradiation with Holmium-166 for TIPS Stenosis: Experimental Study in a Swine Model

Objective

We wanted to evaluate the effectiveness of intraluminal irradiation with Holmium-166 (¹⁶⁶Ho) for reducing the pseudointimal hyperplasia (PIH) in the transjugular intrahepatic portosystemic shunt (TIPS) tract in a swine model.

Materials and Methods

TIPS was performed in 12 domestic pigs, after the creation of portal hypertension by intraportal injection of a mixture of N-butyl-2-cyanoacrylate (NBCA) and lipiodol. Five pigs first underwent intraluminal irradiation (30 Gy) in the parenchymal tract with using a ¹⁶⁶Ho solution-filled balloon catheter, and this was followed by the placement of a nitinol stent in the TIPS tract. For the seven control pigs, the balloon was filled with saline and contrast media mixture. Two weeks later, follow-up portography and histological analysis were performed.

Results

TIPS was successfully performed in all twelve pigs with achieving artificially induced portal hypertension. Portography performed two weeks after TIPS showed the patent tracts in the TIPS tracts that were irradiated with ¹⁶⁶Ho (5/5, 100%), whereas either completely (5/6, 83.3%) or partially (1/6, 16.7%) occluded TIPS were seen in the seven pigs of the nonirradiated control group, except in one pig that experienced periprocedural death due to bleeding. Histological analysis showed a statistically significant difference for the maximal PIH (irradiated: 32.8%, nonirradiated: 76.0%, p < 0.001) between the two groups.

Conclusion

Intraluminal irradiation with 30 Gy of ¹⁶⁶Ho for TIPS significantly improved the TIPS patency in a swine model of portal hypertension during a 2-week period of follow-up.     

Comparison of diamond-like carbon-coated nitinol stents with or without polyethylene glycol grafting and uncoated nitinol stents in a canine iliac artery model

Objective

Neointimal hyperplasia is a major complication of endovascular stent placement with consequent in-stent restenosis or occlusion. Improvements in the biocompatibility of stent designs could reduce stent-associated thrombosis and in-stent restenosis. We hypothesised that the use of a diamond-like carbon (DLC)-coated nitinol stent or a polyethylene glycol (PEG)-DLC-coated nitinol stent could reduce the formation of neointimal hyperplasia, thereby improving stent patency with improved biocompatibility.

Methods

A total of 24 stents were implanted, under general anaesthesia, into the iliac arteries of six dogs (four stents in each dog) using the carotid artery approach. The experimental study dogs were divided into three groups: the uncoated nitinol stent group (n = 8), the DLC-nitinol stent group (n = 8) and the PEG-DLC-nitinol stent group (n = 8).

Results

The mean percentage of neointimal hyperplasia was significantly less in the DLC-nitinol stent group (26.7±7.6%) than in the nitinol stent group (40.0±20.3%) (p = 0.021). However, the mean percentage of neointimal hyperplasia was significantly greater in the PEG-DLC-nitinol stent group (58.7±24.7%) than in the nitinol stent group (40.0±20.3%) (p = 0.01).

Conclusion

Our findings indicate that DLC-coated nitinol stents might induce less neointimal hyperplasia than conventional nitinol stents following implantation in a canine iliac artery model; however, the DLC-coated nitinol stent surface when reformed with PEG induces more neointimal hyperplasia than either a conventional or DLC-coated nitinol stent.     

Transcaval TIPS in Patients with Failed Revision of Occluded Previous TIPS

Objective

To determine the feasibility of transcaval transjugular intrahepatic portosystemic shunt (TIPS) in patients with occluded previous TIPS.

Materials and Methods

Between February 1996 and December 2000 we performed five transcaval TIPS procedures in four patients with recurrent gastric cardiac variceal bleeding. All four had occluded TIPS, which was between the hepatic and portal vein. The interval between initial TIPS placement and revisional procedures with transcaval TIPS varied between three and 31 months; one patient underwent transcaval TIPS twice, with a 31-month interval. After revision of the occluded shunt failed, direct cavoportal puncture at the retrohepatic segment of the IVC was attempted.

Results

Transcaval TIPS placement was technically successful in all cases. In three, tractography revealed slight leakage of contrast materials into hepatic subcapsular or subdiaphragmatic pericaval space. There was no evidence of propagation of extravasated contrast materials through the retroperitoneal space or spillage into the peritoneal space. After the tract was dilated by a bare stent, no patient experienced trans-stent bleeding and no serious procedure-related complications occurred. After successful shunt creation, variceal bleeding ceased in all patients.

Conclusion

Transcaval TIPS placement is an effective and safe alternative treatment in patients with occluded previous TIPS and no hepatic veins suitable for new TIPS.     

Interventional Management of Malignant Colorectal Obstruction: Use of Covered and Uncovered Stents

Objective

We wanted to evaluate usefulness of uncovered stent in comparison with covered stent for the palliative treatment of malignant colorectal obstruction.

Materials and Methods

Covered (n = 52, type 1 and type 2) and uncovered (n = 22, type 3) stents were placed in 74 patients with malignant colorectal obstruction. Stent insertion was performed for palliative treatment in 37 patients (covered stent: n = 23 and uncovered stent: n = 14). In the palliative group, the data on the success of the procedure, the stent patency and the complications between the two groups (covered versus uncovered stents) were compared.

Results

The technical success rate was 89% (33/37). Symptomatic improvement was achieved in 86% (18/21) of the covered stent group and in 92% (11/12) of the uncovered stent group patients. The period of follow-up ranged from three to 319 days (mean period: 116±85 days). The mean period of stent patency was 157±33 days in the covered stent group and 165±25 days in the uncovered stent group. In the covered stent group, stent migration (n = 11), stent fracture (n = 2) and poor expansion of the stent (n = 2) were noted. In the uncovered stent group, tumor ingrowth into the stents (n = 3) was noted.

Conclusion

Self-expanding metallic stents are effective for relieving malignant colorectal obstruction. The rate of complications is lower in the uncovered stent group than in the covered stent group.     

The Efficacy of Metallic Stent Placement in the Treatment of Colorectal Obstruction

Objective

To evaluate the efficacy of newly designed covered and non-covered coated colorectal stents for colonic decompression.

Materials and Methods

Twenty-six patients, (15 palliative cases and 11 preoperative) underwent treatment for the relief of colorectal obstruction using metallic stents positioned under fluoroscopic guidance. In 24 of the 26, primary colorectal carcinoma was diagnosed, and in the remaining two, recurrent colorectal carcinoma. Twenty-one patients were randomly selected to receive either a type A or type B stent; for the remaining five, type C was used. Type A, an uncovered nitinol wire stent, was lightly coated to ensure structural integrity. Type B (flare type) and C (shoulder type) stents were polyurethane covered and their diameter was 24 and 26mm, respectively. The rates of technical success, clinical success, and complications were analyzed using the chi-square test, and to analyse the mean period of patency, the Kaplan-Meier method was used.

Results

Thirty of 31 attempted placements in 26 patients were successful, with a technical success rate of 96.8% (30/31) and a clinical success rate of 80.0% (24/30). After clinically successful stent placement, bowel decompression occurred within 1-4 (mean, 1.58 ± 0.9) days. Five of six clinical failures involved stent migration and one stent did not expand after successful placement. In the preoperative group, 11 stents, one of which migrated, were placed in ten patients, in all of whom bowel preparation was successful. In the palliative group, 19 stents were placed in 15 patients. The mean period of patency was 96.25 ± 105.12 days: 146.25 ± 112.93 for type-A, 78.82 ± 112.26 for type-B, and 94.25 ± 84.21 for type-C. Complications associated with this procedure were migration (n=6, 20%), pain (n=4, 13.3%), minor bleeding (n=5, 16.7%), incomplete expansion (n=1, 3.3%), and tumor ingrowth (n=1, 3.3%). The migration rate was significantly higher in the type-B group than in other groups (p=0.038).

Conclusion

Newly designed covered and non-covered metallic stents of a larger diameter are effective for the treatment of colorectal obstruction. The migration rate of covered stents with flaring is higher than that of other types. For evaluation of the ideal stent configuration for the relief of colorectal obstruction, a clinical study involving a larger patient group is warranted.     

Percutaneous Biliary Drainage Using Open Cell Stents for Malignant Biliary Hilar Obstruction

Objective

To evaluate the feasibility, safety and the effectiveness of the complex assembly of open cell nitinol stents for biliary hilar malignancy.

Materials and Methods

During the 10 month period between January and October 2007, 26 consecutive patients with malignant biliary hilar obstruction underwent percutaneous insertion of open cell design nitinol stents. Four types of stent placement methods were used according to the patients'' ductal anatomy of the hilum. We evaluated the technical feasibility of stent placement, complications, patient survival, and the duration of stent patency.

Results

Bilobar biliary stent placement was conducted in 26 patients with malignant biliary obstruction-T (n = 9), Y (n = 7), crisscross (n = 6) and multiple intersecting types (n = 4). Primary technical success was obtained in 24 of 26 (93%) patients. The crushing of the 1st stent during insertion of the 2nd stent occurred in two cases. Major complications occurred in 2 of 26 patients (7.7%). One case of active bleeding from hepatic segmental artery and one case of sepsis after procedure occurred. Clinical success was achieved in 21 of 24 (87.5%) patients, who were followed for a mean of 141.5 days (range 25-354 days). The mean primary stent patency period was 191.8 days and the mean patient survival period was 299 days.

Conclusion

Applying an open cell stent in the biliary system is feasible, and can be effective, especially in multiple intersecting stent insertions in the hepatic hilum.     

Inhibition of pseudointimal hyperplasia in swine TIPS models: the efficacy of local delivery of paclitaxel using a perforated balloon catheter

The aim of this study was to investigate the efficacy and feasibility of local delivery of paclitaxel to inhibit pseudointimal hyperplasia/intimal hyperplasia in swine transjugular intrahepatic portosystemic shunt (TIPS) models TIPS were created in seven healthy domestic swine (15-20 kg). Before TIPS stent insertion, we performed a short-term infusion of paclitaxel (treatment group: n = 4) and saline (control group: n = 3) into the TIPS tract using a balloon catheter in which two 0.010 inch holes were created on opposite sides of the balloon. Paclitaxel or saline was given to all animals via the hepatic parenchymal and venous outflow tract. The animals were followed for up to two weeks and then killed. Gross and histological evaluations of the shunts were performed, and the maximum pseudointimal/intimal hyperplasia thicknesses were calculated for each animal The average infusion time of paclitaxel or saline was 7.6 min (6-9 min). At gross and histological evaluation, considerable pseudointimal hyperplasia had formed in the control group and statistically significant differences were found upon microscopic evaluation in the maximum pseudointimal hyperplasia thickness between the control (2.41 mm, range 1.7-3.16 mm) and animals receiving paclitaxel (0.63 mm, range 0.42-0.98 mm, p<0.05) Local delivery of paclitaxel at the time of TIPS creation may have been effective in reducing pseudointimal/intimal hyperplasia in swine TIPS models.     

Intraluminal irradiation for TIPS stenosis: preliminary results in a swine model.

PURPOSE: To evaluate the ability of 32phosphorus intraluminal irradiation to reduce pseudointimal hyperplasia in a transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: TIPS were successfully placed in 11 swine with normal portal pressures. Six animals received 15.2 Gy intraluminal irradiation to the hepatic parenchyma and venous outflow tract at the time of TIPS placement with use of a NA32P-filled balloon angioplasty catheter. Five control animals underwent TIPS and balloon angioplasty with saline. All animals were followed up for 28 days, at which time percutaneous portography was performed, the animals were killed, and the tissue around the TIPS stent was processed for histologic analysis. Maximum pseudointimal hyperplasia as a percentage of estimated TIPS diameter was calculated for each animal. RESULTS: At the time of euthanasia, all five control TIPS and all but one irradiated TIPS were occluded. Histologic analysis demonstrated considerable variability in the degree of pseudointimal hyperplasia within each TIPS and between animals. No statistically significant difference was found in the maximum pseudointimal hyperplasia, measured as a percentage of stent radius, between control (80.2%+/-17.4%) and irradiated animals (69.2%+/-25.2%). CONCLUSIONS: Irradiation of TIPS with 15.2 Gy 32P delivered at the time of TIPS placement did not significantly improve TIPS patency or reduce the degree of pseudointimal hyperplasia in swine with normal portal pressures.     

Stent Placement for Chronic Iliac Arterial Occlusive Disease: the Results of 10 Years Experience in a Single Institution

Objective

We wanted to retrospectively evaluate the long-term therapeutic results of iliac arterial stent placement that was done in a single institution for 10 years.

Materials and Methods

From May 1994 to April 2004, 206 patients who underwent iliac arterial stent placement (mean age; 64±8.8) were followed up for evaluating the long term stent patency. Combined or subsequent bypass surgery was performed in 72 patients. The follow up period ranged from one month to 120 months (mean; 31±25.2 months). The factors that were analyzed for their effect on the patency of stents were age, the stent type and diameter, the lesion site, lesion shape, lesion length, the Society of Cardiovascular and Interventinal Radiology criteria, the total run off scores, the Fontaine stage and the cardiovascular risk factors (diabetes mellitus, hypertension and smoking). Follow-up included angiography and/or CT angiography, color Doppler sonography and clinical evaluation with the ankle-brachial index.

Results

Two hundred and eighty-four stents were placed in 249 limbs of 203 patients. The technical success rate was 98% (203/206). The primary patency rates of the stents at 3, 5, 7 and 10 year were 87%, 83%, 61% and 49%, respectively. One hundred seventy-seven patients maintained the primary stent patency until the final follow up and 26 patients showed stenosis or obstruction during the follow up. Secondary intervention was performed in thirteen patients. Lesions in the external iliac artery (EIA) or lesions in both the common iliac artery (CIA) and EIA were a poor prognostic factor for stent patency. The run off score and stent diameter also showed statistically significant influence on stent patency. The overall complication rate was 6%.

Conclusion

Iliac arterial stent placement is a safe treatment with favorable long term patency. Lesions in the EIA or lesions in both the EIA and CIA, poor run off vessels and a stent having the same or a larger diameter than 10 mm were the poor prognostic factors for long term stent patency.     

The Primary Patency and Fracture Rates of Self-Expandable Nitinol Stents Placed in the Popliteal Arteries, Especially in the P2 and P3 Segments, in Korean Patients

Objective

We wanted to evaluate the status of self-expandable nitinol stents implanted in the P2 and P3 segments of the popliteal artery in Korean patients.

Materials and Methods

We retrospectively analyzed 189 consecutive patients who underwent endovascular treatment for stenoocclusive lesions in the femoropopliteal artery from July 2003 to March 2009, and 18 patients who underwent stent placement in popliteal arterial P2 and P3 segments were finally enrolled. Lesion patency was evaluated by ultrasound or CT angiography, and stent fracture was assessed by plain X-rays at 1, 3, 6 and 12 months and annually thereafter.

Results

At the 1-month follow-up, stent fracture (Type 2) was seen in one limb (up to P3, 1 of 18, 6%) and it was identified in seven limbs at the 3-month follow-up (Type 2, Type 3, Type 4) (n = 1: up to P2; n = 6: P3). At the 6-month follow-up, one more fracture (Type 1) (up to P3) was noted. At the 1-year follow-up, there were no additional stent fractures. Just four limbs (up to P2) at the 2-year follow-up did not have stent fracture. The primary patency was 94%, 61% and 44% at 1, 3 and 6 months, respectively, and the group with stent implantation up to P3 had a higher fracture rate than that of the group that underwent stenting up to P2 (p < 0.05).

Conclusion

We suggest that stent placement up to the popliteal arterial P3 segment and over P2 in an Asian population can worsen the stent patency owing to stent fracture. It may be necessary to develop a stent design and structure for the Asian population that can resist the bending force in the knee joint.     

Evaluation of the Biodurability of Polyurethane-Covered Stent Using a Flow Phantom

Objective

To evaluate the biodurability of the covering material in retrievable metallic stents covered with polycarbonate polyurethane.

Materials and Methods

Using a peristaltic pump at a constant rate of 1ml/min, bile was recirculated from a reservoir through a long tube containing four stents. Each of these was removed from the system every two weeks and a radial tensile strength test and scanning electron microscopy (SEM) were performed. Each stent, removed at 2, 4, 6 and 8 weeks, was compared with a control stent not exposed to bile juice.

Results

Gross examination showed that stents were intact at 2 weeks, but at 4, 6 and 8 weeks cracks were observed. The size of these increased gradually in accordance with the duration of exposure, and at 8 weeks several large holes in the polyurethane membrane were evident. With regard to radial tensile strength, extension and peak load at break were 84.47% and 10.030 N/mm, 54.90% and 6.769 N/mm, 16.55% and 2.452 N/mm, 11.21% and 1.373 N/mm at 0, 2, 4 and 6 weeks, respectively. Scanning electron microscopy at 2 weeks revealed intermittent pitting and cracking, and examination at 4, 6 and 8 weeks showed that the size of these defects was gradually increasing.

Conclusion

When the polyurethane membrane was exposed to bile, biodegradation was first observed at week two and increased gradually according to the duration of exposure.     

Improved Patency of Transjugular Intrahepatic Portosystemic Shunt: The Efficacy of Cilostazol for the Prevention of Pseudointimal Hyperplasia in Swine TIPS Models

Purpose To investigate the efficacy of oral administration of cilostazol to inhibit pseudointimal/intimal hyperplasia in swine TIPS models. Methods Successful TIPS creation was carried out in 11 of 12 healthy young pigs (20–25 kg). In the treatment group (n = 6), both cilostazol and aspirin were administered daily, from the first day of TIPS creation. The control group (n = 5) was administered only aspirin. The animals were followed-up for 2 weeks and then killed. The specimen (including portal vein, hepatic parenchymal tract, hepatic vein, and inferior vena cava) and stents were carefully bisected in a longitudinal fashion. The control group was compared with the treatment group by means of a gross and histologic evaluation of the degree of pseudointimal/intimal hyperplasia in the shunt. Results At the gross evaluation, the control group showed considerably more pseudointimal/intimal hyperplasia than the treatment group. Using microscopic evaluation, there was a statistically significant difference (p < 0.05) in the mean maximum pseudointimal/intimal hyperplasia thickness between the control group (2.97 ± 0.33 mm) and treatment group (0.73 ± 0.27 mm). Conclusion Oral administration of cilostazol may have been effective in reducing pseudointimal/intimal hyperplasia in swine TIPS models.     

Comparative study of the corrosion behavior of peripheral stents in an accelerated corrosion model: experimental in vitro study of 28 metallic vascular endoprostheses

PURPOSE

Clinical cases of stent-fractures show that corrosion behavior might play a role in these fractures. Implanted in vivo, especially in combination with other implanted foreign materials, these metallic products are exposed to special conditions, which can cause a process of corrosion. Here, we aimed to test the corrosion potential of stents made of different materials in an in vitro setting.

METHODS

A total of 28 peripheral stents of different materials (nitinol, cobalt-chromium-nickel, tantalum, V4A) and surface treatments (electropolish, mechanical polish, no polish) were tested in vitro. Corrosion was accelerated by applying a constant voltage of 3.5 V and amperage of 1.16 mA in 0.9% NaCl.

RESULTS

Nitinol stents showed the lowest susceptibility to corrosion and the longest period without damage. The Memotherm II^® (BARD Angiomed^®) was the only stent that showed neither macroscopic nor microscopic damages. The worst performing material was cobalt-chromium-nickel, which showed corrosion damages about ten times earlier compared to nitinol. Considering the reasons for termination of the test, nitinol stents primarily showed length deficits, while V4A and tantalum stents showed fractures. Cobalt-chromium-nickel stents had multiple fractures or a complete lysis in equal proportions. When placed in direct contact, nitinol stents showed best corrosion resistance, regardless of what material they were combined with. In terms of polishing treatments, electropolished stents performed the best, mechanical-polished stents and those without polishing treatment followed.

CONCLUSION

The analysis of corrosion behavior may be useful to select the right stent fulfilling the individual needs of the patient within a large number of different stents.Congenital stenosis or volume decreasing processes due to accumulation of tissues or by outside pressures are the most common indications for vascular interventional therapies. After the initial “cardiac catheterization” by Forssmann et al. (1) in 1929, percutaneous interventional techniques for treatment of vasoconstricting processes was continued constantly, whereby the use of permanent mechanical stents has gained an increasingly important role.Stents used in clinical practice should fulfill certain conditions to achieve an un-problematic application as well as an optimal result. The following properties apply to this ideal: good biocompatibility, low shortening, high-density in X-ray, high patency rates, low thrombogenicity, rapid endothelialization without excessive intimal hyperplasia, high flexibility and longitudinal elasticity, sufficient pressure stability at high centrifugal force, technical ability to secure application and exact positioning, and good expansion ratio for safe percutaneous application also with larger prostheses (2, 3). With the approval of stents for clinical use in 1986, the use of stents in peripheral vessels was also practiced on human patients. Palmaz et al. (4) published the first results of the clinical use in 1988 in one of the first multicenter trials on the use of stents in stenosed atherosclerotic iliac arteries. After the successful development of Palmaz^® stents and Wallstents^® as prototypes of balloon-expandable and self-expanding stents, a variety of new stents have been developed.The stents used today are made of different materials. These include nickel titanium alloys (nitinol), surgical stainless steel (V4A), tantalum, and cobalt compounds. Implanted in the human body, especially in combination with other implanted foreign materials, these metallic products are exposed to special conditions causing a process of corrosion. The higher the ionic conductivity of a liquid is, the faster the reaction. For this reason, liquids that contain a high proportion of electrolytes, such as blood with its high proportion of NaCl, cause much faster corrosion of materials (5).We aimed to perform a comparative study regarding the corrosion behavior of peripheral stents, to reffect the behavior of implanted stents in patients and contribute to find a safer indication in the selection of vascular prostheses. Likewise, we tested the hypothesis that the polishing process influences their corrosion behavior.     

Percutaneous Placement of Self-Expandable Metallic Stents in Patients with Obstructive Jaundice Secondary to Metastatic Gastric Cancer after Gastrectomy

Objective

To evaluate the outcomes of patients undergoing percutaneous placements of a biliary stent for obstructive jaundice secondary to metastatic gastric cancer after gastrectomy.

Materials and Methods

Fifty patients (mean age, 62.4 years; range, 27-86 years) who underwent percutaneous placements of a biliary stent for obstructive jaundice secondary to metastatic gastric cancer after gastrectomy were included. The technical success rate, clinical success rate, complication rate, stent patency, patient survival and factors associated with stent patency were being evaluated.

Results

The median interval between the gastrectomy and stent placement was 23.1 months (range, 3.9-94.6 months). The 50 patients received a total of 65 stents without any major procedure-related complications. Technical success was achieved in all patients. The mean total serum bilirubin level, which had been 7.19 mg/dL ± 6.8 before stent insertion, decreased to 4.58 mg/dL ± 5.4 during the first week of follow-up (p < 0.001). Clinical success was achieved in 42 patients (84%). Percutaneous transhepatic biliary drainage catheters were removed from 45 patients (90%). Infectious complications were noted in two patients (4%), and stent malfunction occurred in seven patients (14%). The median stent patency was 233 ± 99 days, and the median patient survival was 179 ± 83 days. Total serum bilirubin level after stenting was an independent factor for stent patency (p = 0.009).

Conclusion

Percutaneous transhepatic placement of a biliary stent for obstructive jaundice secondary to metastatic gastric cancer after gastrectomy is a technically feasible and clinically effective palliative procedure.     

Percutaneous Unilateral Biliary Metallic Stent Placement in Patients with Malignant Obstruction of the Biliary Hila and Contralateral Portal Vein Steno-Occlusion

Objective

To investigate the outcomes of percutaneous unilateral metallic stent placement in patients with a malignant obstruction of the biliary hila and a contralateral portal vein steno-occlusion.

Materials and Methods

Sixty patients with a malignant hilar obstruction and unilobar portal vein steno-occlusion caused by tumor invasion or preoperative portal vein embolization were enrolled in this retrospective study from October 2010 to October 2013. All patients were treated with percutaneous placement of a biliary metallic stent, including expanded polytetrafluoroethylene (ePTFE)-covered stents in 27 patients and uncovered stents in 33 patients.

Results

A total of 70 stents were successfully placed in 60 patients. Procedural-related minor complications, including self-limiting hemobilia (n = 2) and cholangitis (n = 4) occurred in six (10%) patients. Acute cholecystitis occurred in two patients. Successful internal drainage was achieved in 54 (90%) of the 60 patients. According to a Kaplan-Meier analysis, median survival time was 210 days (95% confidence interval [CI], 135-284 days), and median stent patency time was 133 days (95% CI, 94-171 days). No significant difference in stent patency was observed between covered and uncovered stents (p = 0.646). Stent dysfunction occurred in 16 (29.6%) of 54 patients after a mean of 159 days (range, 65-321 days).

Conclusion

Unilateral placement of ePTFE-covered and uncovered stents in the hepatic lobe with a patent portal vein is a safe and effective method for palliative treatment of patients with a contralateral portal vein steno-occlusion caused by an advanced hilar malignancy or portal vein embolization. No significant difference in stent patency was detected between covered and uncovered metallic stents.     

Use of Self-Expanding Stents for the Treatment of Vertebral Artery Ostial Stenosis: a Single Center Experience

Objective

To evaluate our early experience using self-expanding stents to treat atherosclerotic vertebral artery ostial stenosis (VAOS), with respect to technical feasibility and clinical and imaging follow-up results.

Materials and Methods

A total of 20 lesions in 20 patients underwent stenting of the VAOS using a self-expanding stent (Precise RX; Cordis Neurovascular, Miami Lakes, FL). Two patients were asymptomatic. We analyzed the technical success rate, causes of technical failure, occurrence of any vascular or neurological event, and the occurrence of any neurological abnormality or in-stent restenosis (ISR) seen on follow-up. The imaging follow-up was performed with Doppler ultrasound (DUS) as a primary screening modality.

Results

One instance of technical failure was caused by failure of the guidewire passage. The stent diameter was 5 mm, and post-stenting balloon dilatations were necessary in all cases. Stent misplacement requiring placement of an additional stent occurred in four cases. Following a 14.8 month average clinical follow-up time, two patients showed anterior circulation ischemia, which was not attributed to the VAOS we treated. Following a 13.7 month average DUS follow-up, five patients showed a mild degree of diffuse or focal intimal thickening in the stent lumen; however, none of the stenosis showed luminal loss of more than 50% and no stent fracture was noted.

Conclusion

The use of self-expanding stents for treating VAOS was technically feasible and helped to improve artery patency during our limited follow-up interval.     

Temporary placement of covered retrievable expandable nitinol stents with barbs in high-risk surgical patients with benign prostatic hyperplasia: work in progress

Purpose

To report the use of a newly constructed, covered, retrievable, expandable nitinol stent with barbs to overcome the problem of stent migration associated with conventional covered prostatic expandable stents and to evaluate prospectively the technical feasibility and clinical effectiveness of the stents in patients with benign prostatic hyperplasia (BPH).

Materials and Methods

A covered retrievable expandable nitinol stent with four barbs was placed with use of an 18-F stent delivery system in seven consecutive patients with symptomatic BPH who had high operative risks. Age range of patients was 62–83 years (mean 74 years). In cases in which the stent migrated, it was replaced with a stent with eight barbs. The stents were routinely removed 4 months after placement using a 21-F stent removal set.

Results

Stent placement was technically successful and well tolerated in six of the seven patients. The remaining patient needed a second stent placement after removal of the first stent. The stent with four barbs migrated into the urinary bladder in four patients (57%); three of these patients received a second stent with eight barbs with good results, and the fourth patient did not need further treatment because his symptoms improved. Routine removal of the stent 4 months after placement was performed in three of the seven patients with good results.

Conclusions

Retrievable stents with eight barbs seem to overcome the problem of stent migration associated with conventional prostatic expandable stents. Preliminary results suggest that stents with barbs are both feasible and effective in patients with BPH.     

Accuracy of multislice CT angiography for the assessment of in-stent restenoses in the iliac arteries at reduced dose: a phantom study

Objective

We investigated the potential of low-dose CT angiography for accurate assessment of in-stent restenoses (ISRs) of the iliac artery.

Method

A Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), custom-made wax simulating hyperplastic tissue and a nitinol stent were used to simulate a patient with clinically relevant iliac artery ISRs. The cylindrical lumen was filled with a solution of iodine contrast medium diluted in saline, representing a patient''s blood during CT angiography. The phantom was subjected to standard- and low-dose angiographic exposures using a modern multidetector (MD) CT scanner. The percentage of ISR was determined using the profile along a line normal to the lumen axis on reconstructed images of 2 and 5 mm slice thickness. Percentage ISRs derived using the standard- and low-dose protocols were compared. In a preliminary study, seven patients with stents were subjected to standard- and low-dose MDCT angiography during follow-up. The resulting images were assessed and compared by two experienced radiologists.

Results

The accuracy in measuring the percentage ISR was found to be better than 12% for all simulated stenoses. The differences between percentage ISRs measured on images obtained at 120 kVp/160 mAs and 80 kVp/80 mAs were below 6%. Patient image sets acquired using low-exposure factors were judged to be of satisfactory diagnostic quality. The assessment of ISR did not differ significantly between image sets acquired using the standard factors and those acquired using the low-exposure factors, although the mean reduction in patient effective dose was 48%.

Conclusion

A reduction in exposure factors during MDCT angiography of the iliac artery is possible without affecting the accuracy in the determination of ISRs.Follow-up in patients treated with peripheral arterial stent implantation is usually performed with clinical examination, ankle–brachial index measurement, exercise testing and proof of patency using duplex ultrasonography. However, digital subtraction angiography (DSA) is still considered to be the best imaging technique for the assessment of in-stent restenosis (ISR) and stent patency in the iliac and proximal superficial femoral arteries following stent implantation as it offers the unique advantage of incorporating diagnostic confirmation and endovascular treatment in a single session. Apart from the relatively high patient radiation burden, the main disadvantage of DSA relates to its invasive nature. DSA is associated with a certain risk for potentially serious complications. Over the last few years, there has been a continuous effort to improve the safety and effectiveness of percutaneous revascularisation in peripheral arterial occlusive disease. A host of technological advances associated with endovascular treatment have been recently developed including novel angioplasty balloons and “shape memory” nitinol stents [1]. Currently, nitinol stents are considered to be the most modern solution for revascularisation of aortoiliac and lower extremity arteries [1]. In addition, the advent of multislice CT angiography during the last few years has provided a non-invasive alternative for the assessment of stented vessels. The use of modern 16- and 64-slice CT systems was recently proven to significantly improve spatial resolution and lumen visualisation, rendering multidetector CT (MDCT) angiography a powerful tool for ISR assessment [2-8].MDCT imaging is considered to be a high-dose diagnostic procedure resulting in absorbed doses to patient tissues of 10–100 mGy. The cumulative dose to patient tissues from multiple CT examinations may often approach or even exceed radiation dose levels known to significantly elevate the probability for cancer induction [9, 10]. MDCT systems are rather complicated systems, and appropriate adaptation of exposure factors to achieve optimisation of the examination is a complex task influenced strongly by the specific diagnostic demands [11]. Given that image quality in modern CT is often higher than that required to achieve diagnostic confidence [12], we felt that it would be interesting to study whether there is any potential for dose reduction in MDCT angiography imaging for ISR assessment. The purpose of the current study was to investigate the effect of reducing the exposure parameters during MDCT angiography on the assessment of clinically relevant ISR in patients with nitinol stents in the external iliac or proximal superficial femoral artery.     

Transcaval Transjugular Intrahepatic Portosystemic Shunt: Preliminary Clinical Results

Objective

To determine the feasibility of transcaval transjugular intrahepatic portosystemic shunt (TIPS) creation in patients with unusual anatomy between the hepatic veins and portal bifurcation, and inaccessible or inadequate hepatic veins.

Materials and Methods

Transcaval TIPS, performed in six patients, was indicated by active variceal bleeding (n=2), recurrent variceal bleeding (n=2), intractable ascites (n=1), and as a bridge to liver transplantation (n=1). The main reasons for transcaval rather than classic TIPS were the presence of an unusually acute angle between the hepatic veins and the level of the portal bifurcation (n=3), hepatic venous occlusion (n=2), and inadequate small hepatic veins (n=1).

Results

Technical and functional success was achieved in all patients. The entry site into liver parenchyma from the inferior vena cava was within 2 cm of the atriocaval junction. Procedure-related complications included the death of one patient due to hemoperitoneum despite the absence of contrast media spillage at tractography, and another suffered reversible hepatic encephalopathy.

Conclusion

In patients with unusual anatomy between the hepatic veins and portal bifurcation, and inaccessible or inadequate hepatic veins, transcaval TIPS creation is feasible.     

Transjugular Intrahepatic Portosystemic Shunt Flow Reduction with Adjustable Polytetrafluoroethylene-Covered Balloon-Expandable Stents Using the “Sheath Control” Technique

Purpose

A complication of transjugular intrahepatic portosystemic shunts (TIPS) placement is refractory portosystemic encephalopathy (PSE) often requiring TIPS reduction. We report the results of a “sheath control technique” utilizing constraining sheaths during deployment of polytetrafluoroethylene (PTFE)-covered balloon-expandable stents, minimizing stent migration, and providing additional procedural control.

Methods

TIPS reduction was performed in 10 consecutive patients for PSE using Atrium iCast covered stents (Atrium Maquet Getinge Group, Germany). Within the indwelling TIPS stent, a 9 mm × 59 mm iCast stent was deployed with 2 cm exposed from the sheath’s distal end and the majority of the stent within the sheath to create the distal hourglass shape. During balloon retraction, the stent was buttressed by the sheath. The proximal portion of the stent was angioplastied to complete the hourglass configuration, and the central portion of the stent was dilated to 5 mm. Demographics, pre- and post-procedure laboratory values, and outcomes were recorded.

Results

Ten patients underwent TIPS reduction with 100 % technical success. There was no stent migration during stent deployment. All patients experienced initial improvement of encephalopathy. One patient ultimately required complete TIPS occlusion for refractory PSE, and another developed TIPS occlusion 36 days post-procedure. There was no significant trend toward change in patients’ MELD scores immediately post-procedure or at 30 days (p = 0.46, p = 0.47, respectively).

Conclusion

TIPS reduction using Atrium iCast PTFE balloon-expandable stents using the “sheath control technique” is safe and effective, and minimizes the risk of stent migration.