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

Comparison of the Covered Self-Expandable Viatorr CX Stent with the Covered Balloon-Expandable BeGraft Peripheral Stent for Transjugular Intrahepatic Portosystemic Shunt (TIPS) Creation: a Single-Centre Retrospective Study in Patients with Variceal Bleeding

PURPOSE

This study compares the safety and efficacy of the ePTFE-covered self-expansible nitinol stent (VIATORR® Controlled Expansion, Gore, Flagstaff, USA) with the ePTFE-covered, balloon-expandable, metallic stent (BeGraft peripheral, Bentley, Hechingen, Germany) for the creation of the transjugular intrahepatic portosystemic shunt (TIPS).

MATERIAL AND METHODS

From September 2016 to December 2020, 72 consecutive patients receiving TIPS for acute variceal bleeding (rescue and early TIPS, n = 15) or for prophylaxis of variceal rebleeding (n = 57) were enrolled. The main contraindications were patients with vascular liver disease (portal vein thrombosis and Budd-Chiari syndrome). Forty patients (55.6%) received a Viatorr CX stent and 32 patients (44.4%) a BeGraft peripheral stent. Safety endpoints were technical and clinical adverse events and early deaths within 30 days after TIPS implantation. Efficacy endpoints were rebleeding rates, recurrence of large varices requiring endoscopic band ligation, or TIPS revision.

RESULTS

Groups receiving the Viatorr CX or BeGraft peripheral stent were comparable in all respects except the TIPS indication for acute variceal bleeding (5% vs. 25%, p = 0.015). All patients had a successful intervention, and the physical variables of stent implantation (intervention and fluoroscopy time, reduction of the portosystemic pressure gradient) as well as adjunctive embolization of varices were similar in both groups. Severe clinical complications (Viatorr CX: 5% vs. BeGraft peripheral: 3.1%, p = 0.692), post-TIPS hepatic encephalopathy (12.5% vs. 18.8%, p = 0.743) and death (5% vs. 0%, p = 0.793) were not different between Viatorr CX and BeGraft peripheral groups. With respect to efficacy, freedom from rebleeding and from variceal band ligation during follow-up (100% vs. 100%, p = 1.0), as well as the need for shunt revision (10.5% vs. 18.8%, p = 0.327), was comparable.

CONCLUSION

Compared to the present gold standard, the Viatorr CX stent, the balloon-expandable BeGraft peripheral stent, showed similar results with respect to safety and efficacy.

Recent Advances in Manufacturing Innovative Stents

Cardiovascular diseases are the most distributed cause of death worldwide. Stenting of arteries as a percutaneous transluminal angioplasty procedure became a promising minimally invasive therapy based on re-opening narrowed arteries by stent insertion. In order to improve and optimize this method, many research groups are focusing on designing new or improving existent stents. Since the beginning of the stent development in 1986, starting with bare-metal stents (BMS), these devices have been continuously enhanced by applying new materials, developing stent coatings based on inorganic and organic compounds including drugs, nanoparticles or biological components such as genes and cells, as well as adapting stent designs with different fabrication technologies. Drug eluting stents (DES) have been developed to overcome the main shortcomings of BMS or coated stents. Coatings are mainly applied to control biocompatibility, degradation rate, protein adsorption, and allow adequate endothelialization in order to ensure better clinical outcome of BMS, reducing restenosis and thrombosis. As coating materials (i) organic polymers: polyurethanes, poly(ε-caprolactone), styrene-b-isobutylene-b-styrene, polyhydroxybutyrates, poly(lactide-co-glycolide), and phosphoryl choline; (ii) biological components: vascular endothelial growth factor (VEGF) and anti-CD34 antibody and (iii) inorganic coatings: noble metals, wide class of oxides, nitrides, silicide and carbide, hydroxyapatite, diamond-like carbon, and others are used. DES were developed to reduce the tissue hyperplasia and in-stent restenosis utilizing antiproliferative substances like paclitaxel, limus (siro-, zotaro-, evero-, bio-, amphi-, tacro-limus), ABT-578, tyrphostin AGL-2043, genes, etc. The innovative solutions aim at overcoming the main limitations of the stent technology, such as in-stent restenosis and stent thrombosis, while maintaining the prime requirements on biocompatibility, biodegradability, and mechanical behavior. This paper provides an overview of the existing stent types, their functionality, materials, and manufacturing conditions demonstrating the still huge potential for the development of promising stent solutions.

The Evolution of Transjugular Intrahepatic Portosystemic Shunt: Tips

Since Richter's description in the literature in 1989 of the first procedure on human patients, transjugular intrahepatic portosystemic shunt (TIPS) has been worldwide considered as a noninvasive technique to manage portal hypertension complications. TIPS succeeds in lowering the hepatic sinusoidal pressure and in increasing the circulatory flow, thus reducing sodium retention, ascites recurrence, and variceal bleeding. Required several revisions of the shunt TIPS can be performed in case of different conditions such as hepatorenal syndrome, hepatichydrothorax, portal vein thrombosis, and Budd-Chiari syndrome. Most of the previous studies on TIPS procedure were based on the use of bare stents and most patients chose TIPS 2-3 years after traditional treatment, thus making TIPS appear to be not superior to endoscopy in survival rates. Bare stents were associated with higher incidence of shunt failure and consequently patients required several revisions during the follow-up. With the introduction of a dedicated e-PTFE covered stent-graft, these problems were completely solved, No more reinterventions are required with a tremendous improvement of patient's quality of life. One of the main drawbacks of the use of e-PTFE covered stent-graft is higher incidence of hepatic encephalopathy. In those cases refractory to the conventional medical therapy, a shunt reduction must be performed.

Should stent-grafts replace bare stents for primary transjugular intrahepatic portosystemic shunts?

Transjugular intrahepatic portosystemic shunt (TIPS) creation using bare stents is a second-line treatment for complications of portal hypertension due in part to the relatively high number of reinterventions and the occurrence of new or worsened encephalopathy. Initially, custom-made stent-grafts were used for TIPS revision in cases of biliary fistulae. Subsequently, custom stent-grafts were used for de novo TIPS creation. With the introduction of the VIATORR(®) TIPS endoprosthesis a dedicated stent-graft became available for TIPS creation and revision. The VIATORR(®) demonstrated its efficacy and superiority to uncovered stents in retrospective analyses, case-matched analyses, and randomized studies. The improved patency of stent-grafts has led many to requestion the role of TIPS as a second-line therapy. Currently, randomized trials are warranted to redefine the role of TIPS in the treatment of complications of portal hypertension.

The transjugular intrahepatic portosystemic shunt (TIPS)

The creation of an intrahepatic portosystemic shunt via a transjugular approach (TIPS) is an interventional radiological procedure used to treat the complications of portal hypertension. TIPS insertion is principally indicated to prevent or arrest variceal bleeding when medical or endoscopic treatments fail, and in the management refractory ascites. This review discusses the development and execution of the technique, with focus on its clinical efficacy. Patient selection, imaging surveillance, revision techniques, and complications are also discussed.

A novel small-diameter vascular graft: in vivo behavior of biodegradable three-layered tubular scaffolds

Small-diameter vascular grafts are potential substitutes for damaged vessels in patients, but most biodegradable grafts available now are not strong enough. The present study examined the burst strength, radial compliance, suture retention strength for a novel biodegradable tubular scaffold and investigated its behavior in vivo. The tubular scaffold (6-mm i.d., 4 cm long) has three layers including porous polylacticglycolic- acid in both inner and outer layers, a compact polyurethanes layer in midst. Bone marrow stromal cells (bMSCs) were seeded on the scaffolds and cultured for 7 days in vitro to construct tissue engineered vascular grafts which were then implanted in canine abdominal aorta. After 1, 3, 6, 12 and 24 weeks, the grafts were retrieved and evaluated histologically, angiographically and immunohistochemically. The biodegradable tubular scaffolds showed wall thickness of 0.295 mm to 0.432 mm; radial compliance of 3.80%/100 mmHg approximately 0.57%/100 mmHg, burst strength of 160 kPa approximately 183 kPa, and suture retention strength of 1959 N/cm(2) approximately 3228N/cm(2). The implanted grafts were fully patent without any signs of dilation or obstruction after 3 months' implantation. Scanning electron microscopy revealed a confluence endothelial cell layer spreading on the inner surface of the grafts. Immunohistochemistry of the retrieved grafts showed that vWF-stainin, alphaSMA-staining were positive in the inner and medium layer respectively. Masson's trichrome staining showed that amount of collagen fibers existed in the grafts wall. Overall, these novel three-layered scaffolds exhibited favourable mechanical strength, long term patency and good remodeling in vivo.

Intravascular US-guided direct intrahepatic portocaval shunt with an expanded polytetrafluoroethylene-covered stent-graft

PURPOSE

To retrospectively evaluate the midterm patency rate of the nitinol (Viatorr, W.L. Gore and Associates, Flagstaff, Ariz) stent-graft for direct intrahepatic portacaval shunt (DIPS) creation.

MATERIALS AND METHODS

Institutional Review Board approval for this retrospective HIPAA-compliant study was obtained with waiver of informed consent. DIPS was created in 18 men and one woman (median age, 54 years; range, 45-65 years) by using nitinol polytetrafluoroethylene (PTFE)-covered stent-grafts. The primary indications were intractable ascites (n = 14), acute variceal bleeding (n = 3), and hydrothorax (n = 2). Follow-up included Doppler ultrasonography at 1, 6, and 12 months and venography with manometry at 6-month intervals after the procedure. Shunt patency and cumulative survival were evaluated by using the Kaplan-Meier method and survival curves were plotted. Differences in mean portosystemic gradients (PSGs) were evaluated by using the Student t test. Multiple regression analysis for survival and DIPS patency were performed for the following parameters: Child-Pugh class, model of end-stage liver disease score, pre- and post-DIPS PSGs, pre-DIPS liver function tests, and pre-DIPS creatinine levels.

RESULTS

DIPS creation was successful in all patients. Effective portal decompression and free antegrade shunt flow was achieved in all patients. Intraperitoneal bleeding occurred in one patient during the procedure and was controlled during the same procedure by placing a second nitinol stent-graft. The primary patency rate was 100% at all times during the follow-up period (range, 2 days to 30 months; mean, 256 days; median, 160 days). Flow restrictors were deployed in two (11%) of 19 patients. The 1-year mortality rate was 37% (seven of 19).

CONCLUSION

Patency after DIPS creation with the nitinol PTFE-covered stent-graft was superior to that after TIPS with the nitinol stent-graft.

Urokinase-immobilization suppresses inflammatory responses to polyurethane tubes implanted in rabbit muscles

Urokinase and plasmin appear to have antiinflammatory activity in some injury models, and urokinase immobilization has been clinically used to prevent thrombus formation in various implants, including intravenous indwelling catheters and subcutaneous drainage tubes. In the present study, polyurethane tubes were embedded in rabbit muscle for 3 months and the effect of urokinase immobilization on inflammatory responses to the implanted tubes was studied at 1 week, 1 month, and 3 months. Mononuclear leukocyte accumulation occurred around implanted polyurethane tubes and peaked after 1 month, but was reduced significantly by urokinase immobilization. The treatment also lessened as well as delayed eosinophil accumulation, but did not affect fibrosis caused by implanted tubes. These results indicate suppressive effects of urokinase immobilization on polyurethane-elicited inflammatory responses and suggest that an approach to develop persistently active urokinase immobilization is rational for successful long-term device implantation.

Optimal Covering Material for Stent-Grafts Placed in the Portal Vein in a Canine Model

PURPOSE

We evaluated the suitability of Dacron, polytetrafluoroethylene (PTFE), and small intestinal submucosa (SIS) as a covering material for stent-grafts placed in the portal vein as compared with a bare stent.

METHODS

Using 24 beagle dogs, either bare stents or stent-grafts covered with Dacron, PTFE, or SIS were placed in the main trunk of the portal vein in 6 animals each. Portography was performed immediately after stent placement, and at 2, 4, and 12 weeks thereafter. Next, the extracted stents or stent-grafts were examined histopathologically. Neointimal thickness adjacent to the stent wire and at the midportion between the stent wires was compared among the groups. Then, the neointimal thickness at the sub- and supragraft sites was compared between each stent-graft group. Serial changes in the histologic features of the thickened neointima were also investigated.

RESULTS

No significant difference was noted in the mean stenotic ratio of the portal vein diameter between the bare stent and PTFE groups, whereas it was significantly higher in the Dacron and SIS groups compared with the bare stent group. In neither of the studies on neointimal thickness adjacent to the stent wire and at the midportion between the stent wires were any significant differences noted between the neointimal thickness of the bare stent group and the sum of the neointimal thickness of the PTFE group, whereas the sum of the neointimal thickness of the Dacron and SIS groups was significantly greater than that of the bare stent group at both sites. In the comparison of the supragraft neointimal thickness, the SIS group showed significantly greater thickness than the PTFE group, while the difference between the Dacron and PTFE groups was not significant. In the comparison of the subgraft neointimal thickness, the Dacron and SIS groups showed significantly greater thickness than the PTFE group.

CONCLUSION

The present results indicate that of the three covering materials examined here, PTFE is the most suitable material for grafts placed in the portal vein.

Intravascular ultrasound-guided direct intrahepatic portacaval shunt: midterm follow-up

PURPOSE

To describe the midterm patency and clinical results of the intravascular ultrasound (US)-guided direct intrahepatic portacaval shunt (DIPS) procedure for the treatment of intractable ascites and variceal bleeding.

MATERIALS AND METHODS

From February 23, 1999, to December 18, 2002, inferior vena cava (IVC)-to-portal vein (PV) shunts were created in 40 patients for ascites (n = 35) and bleeding (n = 5). Intravascular US was used to guide direct puncture from the IVC to the PV. The shunts were completed with the use of single (n = 15) or overlapping (n = 25) polytetrafluoroethylene (PTFE)-covered Palmaz stents. These stent-grafts were deployed primarily at diameters of 8 mm. The diameter of the shunt was increased in three cases to achieve a target portosystemic gradient (PSG) of 15 mm Hg or lower. All patients were followed clinically and with portography with manometry.

RESULTS

All DIPSs were created successfully. Mean PSGs were reduced from 23 mm Hg before DIPS creation to 9 mm afterward. During the follow-up period of a maximum of 38 months, 22 of 40 patients died or underwent liver transplantation (mean follow-up, 9 months; median, 6 months). At the time of this report, 18 of 40 patients remain living after follow-up ranging in duration from 8 to 38 months (mean, 22 months; median, 16.5 months). During the follow-up period, there was one stent-graft occlusion and three stenoses. These four patients were successfully treated by additional stent-graft placement. In addition, two patients developed IVC stenosis cephalad to the DIPS, which required IVC stent placement. The primary patency rates by Kaplan-Meier analysis were 100% at 6 months and 75% (95% CI, 53%-97%) at 12 months.

CONCLUSION

Intravascular US-guided direct IVC-to-PV shunts may be created successfully with minimal complications. Primary patency of the shunt is greater than that with conventional TIPS with a bare wire stent and appears equal to that with TIPS with a PTFE-covered stent-graft.

Polytetrafluoroethylene-covered stent grafts for TIPS procedure: 1-year patency and clinical results

OBJECTIVES

Polytetrafluoroethylene (PTFE)-covered stent grafts appear to have the potential to improve TIPS patency, but data available are few and controversial. The aim of this prospective nonrandomized trial was to assess TIPS safety and 1-yr patency with a new commercially available PTFE-covered stent graft in comparison with a group of historical controls treated with conventional stents.

METHODS

Between July 1992 and December 1999, 87 consecutive cirrhotics underwent TIPS with conventional stents, while from January 2000 to November 2001, 32 consecutive cirrhotics were treated with PTFE-covered stent grafts. All patients were followed by the same medical team according to a prospective protocol for a diagnostic work-up and a surveillance strategy.

RESULTS

The two groups were comparable for age, sex, etiology, and severity of cirrhosis. The 1-yr probability of remaining free of shunt dysfunction tended to be higher in the covered stent group: 76.3% (95% CI = 58.7-93.9%) versus 57.5% (95% CI = 46.6-68.4%); log rank test: p = 0.055. However, stenoses inside the stent were significantly higher in patients with bare stents (88% vs 17%), while stenoses at the hepatic or portal vein were more frequent in PTFE-covered stent-graft group (50% vs 9% and 33% vs 3%, respectively), (chi2 = 15.42; df = 2.0; p = 0.0004). Stenoses inside the covered portion of the stent did not occur. One-year cumulative rebleeding, encephalopathy, and survival were similar.

CONCLUSIONS

PTFE-covered stents are able to solve pseudointimal hyperplasia within the stent tract, but have a high incidence of hepatic or portal vein stenosis. Improvements in stent design and insertion techniques are necessary to fully achieve the potential benefit of this new device.

Improved clinical outcome using polytetrafluoroethylene-coated stents for TIPS: results of a randomized study

BACKGROUND & AIMS

A 50% dysfunction rate at 1 year is one of the main drawbacks of the transjugular intrahepatic portosystemic shunt procedure. Preliminary experimental and clinical studies suggest that the use of stents covered with polytetrafluoroethylene could tremendously decrease this risk.

METHODS

Eighty patients with cirrhosis and uncontrolled bleeding (n = 23), recurrent bleeding (n = 25), or refractory ascites (n = 32) were randomized to be treated by transjugular intrahepatic portosystemic shunts with either a polytetrafluoroethylene-covered stent (group 1; 39 patients) or a usual uncovered prosthesis (group 2; 41 patients). Follow-up Doppler ultrasound was scheduled at day 7, at 1 month, and then every 3 months for 2 years. Angiography and portosystemic pressure gradient measurements were performed 6, 12, and 24 months after the transjugular intrahepatic portosystemic shunt procedure and whenever dysfunction was suspected. Dysfunction was defined as a >50% reduction of the lumen of the shunt at angiography or a portosystemic pressure gradient >12 mm Hg.

RESULTS

After a median follow-up of 300 days, 5 patients (13%) in group 1 and 18 (44%) in group 2 experienced shunt dysfunction (P < 0.001). Clinical relapse occurred in 3 patients (8%) in group 1 and 12 (29%) in group 2 (P < 0.05). Actuarial rates of encephalopathy were 21% in group 1 and 41% in group 2 at 1 year (not significant). Estimated probabilities of survival were 71% and 60% at 1 year and 65% and 41% at 2 years in groups 1 and 2, respectively (not significant).

CONCLUSIONS

The use of polytetrafluoroethylene-covered prostheses improves transjugular intrahepatic portosystemic shunt patency and decreases the number of clinical relapses and reinterventions without increasing the risk of encephalopathy.

Percutaneous inferior vena cava-to-portal vein shunt (PIPS) using a stent-graft: preliminary results

PURPOSE

To present preliminary results of an inferior vena cava (IVC)-to-portal vein shunt (PIPS) that is created through the caudate lobe of the liver.

METHODS

Sixteen patients (13 men; mean age 50 years, range 32-63) were referred for PIPS procedures because of bleeding varices (n = 11), intractable ascites (n = 4), and hepatorenal syndrome (n = 1). The severity of liver disease was Child's B in 2 and Child's C in 14. The PIPS was created by a transhepatic puncture through the IVC and the portal vein; an endograft made of polytetrafluoroethylene sutured to a Palmaz stent was placed through a jugular approach.

RESULTS

In 13 (81%) patients, the portal vein-to-IVC tracts were successfully created. The postprocedural portal vein-IVC gradients varied from 1 to 9 mm Hg (mean 5). There were 2 deaths in the 30-day periprocedural period from adult respiratory distress syndrome and hepatorenal syndrome. A third patient died at 31 days from liver failure owing to continuing alcohol abuse. In addition, there was 1 case of peritoneal bleeding treated with blood product replacement. The follow-up period ranged from 14 to 671 days (mean 343). None of the patients treated for variceal bleeding had another bleeding episode, but 2 patients who had a PIPS procedure for refractory ascites did not benefit from the procedure. Postprocedure, 46% (6/13) of the patients had hepatic encephalopathy, which was unchanged from baseline. The primary and secondary patency rates at 365 days were 60% and 65%, respectively.

CONCLUSIONS

The preliminary results using a stent-graft to create an IVC-portal vein shunt are encouraging and support further work to better determine the role of this procedure.

Experimental evaluation of a new transcatheter vascular embolization device in the swine model

PURPOSE

To evaluate a new transcatheter device suitable for arterial embolization in an animal model.

MATERIALS AND METHODS

A new prototype self-expanding braided embolic device (Embolizor), consisting of nitinol wire strands fixed at either end with platinum-iridium bands and covered with a film of polyethylene, was deployed through 5-F diagnostic catheters into renal artery branches in five swine. Standard stainless-steel spring coils were deployed in other renal branches and served as controls. The animals underwent follow-up selective renal arteriography to determine presence or absence of vessel recanalization or device migration 15-23 days after device deployment. Histopathologic evaluation of target vessels and peripheral renal parenchyma was also performed.

RESULTS

Ten Embolizors and 10 stainless-steel coils were deployed in arteries ranging in size from 1.8 to 3.0 mm in diameter. The Embolizor was easily and precisely deployed. Angiographic evidence of vascular occlusion in the Embolizor group was noted within 30 seconds in eight device deployments and within 5 minutes in two. No early or delayed device migration was noted on follow-up arteriography. In the control group, seven of 10 previously occluded arteries were recanalized. No recanalization was noted in the Embolizor group. Light microscopy revealed evidence of infarction in all specimens examined. Whereas three specimens in the Embolizor group contained occasional giant cells, there were numerous multinucleated giant cells present within the interstices of all control spring coils.

CONCLUSION

The Embolizor was easily, precisely, and successfully deployed through standard selective diagnostic angiographic catheters. Short-term follow-up demonstrated no recanalization or migration of the device. The Embolizor was shown on histopathologic analysis to have no significant foreign body reaction.

Preliminary results of a new expanded-polytetrafluoroethylene-covered stent-graft for transjugular intrahepatic portosystemic shunt procedures

OBJECTIVE

The purpose of our study was to evaluate the feasibility and the safety of transjugular intrahepatic portosystemic shunts (TIPS) with a new expanded-polytetrafluoroethylene-covered stent and the influence of the covering on occlusion rate.

SUBJECTS AND METHODS

Twenty cirrhotic patients (57 +/- 11 years old) admitted with a history of esophageal variceal bleeding (n = 11), refractory ascites (n = 5), or both (n = 4) were included. Five of the patients were treated for TIPS revision, and 15 as de novo TIPS placements. The endoprostheses used were composed of a 2-cm noncovered nitinol stent and a 4- to 8-cm expanded-polytetrafluoroethylene graft covering, and were placed from the portal vein to the ostium of the hepatic vein. Patients underwent Doppler sonography at discharge and again at 1, 3, 6, 9, 12, and 15 months and underwent venography with portosystemic pressure gradient measurement at 6 months and whenever necessary.

RESULTS

At the time of this writing, complications included three TIPS restenoses and one recurrent ascites successfully treated by balloon dilation, two cases of segmentary liver ischemia, and one patient with encephalopathy that required shunt reduction. After TIPS placement, the portosystemic pressure gradient dropped from 18 +/- 5 to 5 +/- 4 mm Hg. Primary and secondary patency rates were 80% and 100%, respectively, at 387 days.

CONCLUSION

These results clearly show the feasibility of TIPS placement with the Gore TIPS endoprosthesis stent-graft and its improved patency compared with results in the literature for bare stents. These preliminary results must be certified further with randomized comparative trials between covered and noncovered TIPS stents.

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.

Intravascular US-guided direct intrahepatic portacaval shunt with a PTFE-covered stent-graft: feasibility study in swine and initial clinical results

PURPOSE

To determine the feasibility of the creation of a direct intrahepatic inferior vena cava (IVC)-to-portal-vein shunt with puncture guided by a transfemorally placed intravascular ultrasound (IVUS) probe and use of a polytetrafluoroethylene (PTFE)-covered stent-graft.

MATERIALS AND METHODS

In five swine, transjugular access was used to perform a direct puncture from the IVC to the portal vein with use of a modified Rosch-Uchida Portal Access set directed with real-time IVUS (9 MHz) introduced from a transfemoral venous approach. The direct intrahepatic portocaval shunt (DIPS) was then created with single or overlapping PTFE-covered Palmaz stents placed through a 10-F sheath and dilated to a diameter of 8 mm. Follow-up was performed with transhepatic portography at 2, 4, and 8 weeks. Animals were killed when shunts occluded or at the termination of the study at 8 weeks. Gross and microscopic histologic study was performed on sacrificed animals. A similar technique was used to create DIPS in five patients with intractable ascites, with follow-up by US and venography.

RESULTS

All experimental DIPS created in swine were created without complications. Portal vein punctures were achieved in four of five swine on the first or second pass of the needle. Follow-up transhepatic portography at 2 weeks demonstrated occlusion of two shunts, both explained by technical reasons at sacrifice. At 4 and 8 weeks, the remaining three shunts were patent on portography. Histology showed a thin neointimal lining with no significant tissue ingrowth or hyperplasia. Clinically, in five patients, successful puncture of the portal vein from the IVC was achieved in one to three passes. Creation of DIPS led to a reduction of mean portosystemic gradient from 18-29 mm Hg (mean, 24 mm Hg) to 9-10 mm Hg (mean, 9 mm Hg). One patient died of liver failure 2 days after creation of DIPS. The other four patients were doing well 2-15 months (mean, 8 months) after the procedure, with patency confirmed by US and venography.

CONCLUSION

Creation of DIPS is technically feasible, and the direct IVC-to-portal-vein puncture can be done accurately with real-time IVUS guidance. Further studies and longer follow-up are necessary to determine if the short length of the PTFE-covered stent-graft and avoidance of the hepatic vein will increase the long-term patency compared to standard transjugular intrahepatic portosystemic shunt creation.

Porous and nonporous polycarbonate urethane stent-grafts for TIPS formation: biologic responses

PURPOSE

To evaluate the biologic response to transjugular intrahepatic portosystemic shunts (TIPS) lined with polycarbonate urethane endografts and the effects of different porosity formulations.

MATERIALS AND METHODS

Seventeen TIPS were created in non-modified portal hypertensive miniswine with use of porous (n = 6), nonporous (n = 7) polycarbonate urethane stent-grafts, and control Wallstents TIPS (n = 4). Eight-week venography, histology, scanning electron microscopy, and immunohistochemical analyses were performed.

RESULTS

The mean 8-week percent parenchymal tract shunt stenosis was 75%, 46%, and 26% in the control, porous, and nonporous groups, respectively. Occlusions developed in one control, one porous, and two nonporous shunts. The biologic response to porous grafts included marked inflammation and encapsulation and permeation of the grafts by a thick fibrous pseudointima. Nonporous grafts evoked little inflammation or pseudointima. Mature thrombus lined the occluded shunts (under which little luminal pseudointima or endothelium was present). The control group showed typical pseudointimal hyperplasia enveloping the intraparenchymal portions of the stents.

CONCLUSIONS

The healing response of the porous and nonporous grafts markedly differed. Unlike the porous grafts and control stents, the nonporous endografts elicited little inflammation or luminal pseudointimal hyperplasia, although sporadic thrombosis was problematic in this normotensive model. Graft use in high-flow situations (ie, human TIPS, possibly in concert with antiplatelet agents) may allow desired shunt patency prolongation.