Reverse endoventricular artificial obturator in tricuspid valve position. Experimental feasibility research study.

The concept of vena contracta space reduction in tricuspid valve position was tested in an animal model. Feasibility of specific artificial obturator body (REMOT) fixed to the right ventricular apex and interacting with tricuspid valve leaflets was evaluated in three different animal studies. Catheter-based technique was used in three series of experiment in 7 sheep. First acute study was designed for evaluation if the screwing mode of guide wire anchoring to the right ventricular apex is feasible for the whole REMOT body fixing. Longer study was aimed to evaluate stability of the REMOT body in desired position when fixing the screwing wire on its both ends (to the right ventricular apex and to the skin in the neck area). X-ray methods and various morphological methods were used. The third acute study was intended to the REMOT body deployment without any fixing wire. In all of 7 sheep the REMOT was successfully inserted into the right heart cavities and then fixed to the right ventricular apex area. When the REMOT was left in situ more than 6 months it was stable, induced adhesion to the tricuspid valve leaflet and was associated with a specific cell invasion. Releasing of the REMOT from the guiding tools was also successfully verified. Deployment of the obturator body in the aim to reduce the tricuspid valve orifice is feasible and well tolerated in the short and longer term animal model. Specific cell colonization including neovascularization of the obturator body was observed.

Small intestinal submucosa sandwich Zilver stent-grafts for TIPS: experimental pilot study in swine.

The aim of this study was the evaluation of preliminary suitability of the piglet small intestinal submucosa (SIS) sandwich Zilver endograft for experimental transjugular intrahepatic portosystemic shunt (TIPS) creation. TIPS was created in six swine. The five surviving animals underwent the follow-up portogram and were sacrificed at four weeks after TIPS creation. Gross and histologic examination was performed in all animals. TIPS creation was successful in all animals. One animal died four days after TIPS creation. In the five surviving animals, one shunt was occluded and four shunts were stenosed on the follow-up portogram. The mean percentage narrowing of the most advanced stenoses was 72% (range, 60%-100%). The most advanced stenosis was located in the parenchymal tract in three shunts and in the hepatic vein portion in one shunt. Gross and histologic examination showed abundant neointimal formation composed mainly of fibroblasts leading to the significant shunt stenoses. The piglet SIS sandwich Zilver stent-graft was found to offer only limited TIPS patency and should not be used for the definitive long-term TIPS study.

Endoluminal treatment of ruptured abdominal aortic aneurysm with small intestinal submucosa sandwich endografts: a pilot study in sheep.

PURPOSE: To evaluate efficacy of small intestinal submucosa (SIS) Sandwich endografts for the treatment of acute rupture of abdominal aortic aneurysms (AAA) and to explore the short-term reaction of the aorta to this material. METHODS: In eight adult sheep, an infrarenal AAA was created transluminally by dilation of a short Palmaz stent. In six sheep, the aneurysm was then ruptured by overdilation of the stent with a large angioplasty balloon. Two sheep with AAAs that were not ruptured served as controls. A SIS Sandwich endograft, consisting of a Z stent frame with 5 bodies and covered inside and out with SIS, was used to exclude the ruptured and non-ruptured AAAs. Follow-up aortography was done immediately after the procedure and before sacrifice at 4, 8, or 12 weeks. Autopsy and histologic studies followed. RESULTS: Endograft placement was successful in all eight sheep. Both ruptured and non-ruptured AAAs were successfully excluded. Three animals with AAA rupture developed hind leg paralysis due to compromise of the arterial supply to the lower spinal cord and were sacrificed 1 day after the procedure. In five animals, three with rupture and two controls, follow-up aortograms revealed no aortic stenoses and no perigraft leaks. Gross and histologic studies revealed incorporation of the endografts into the aortic wall with replacement of SIS by dense neointima that was completely endothelialized in areas where the endograft was in direct contact with the aortic wall. In central portions of the endograft, in contact with the thrombosed aneurysm, endothelialization was incomplete even at 12 weeks. CONCLUSION: The SIS Sandwich endografts effectively excluded simple AAAs and ruptured AAAs. They were rapidly incorporated into the aortic wall. A detailed long-term study is warranted.

Bifurcated drum occluder endograft for treatment of abdominal aortic aneurysm: an experimental study in dogs.

PURPOSE: To evaluate a new, low profile, home-made, bifurcated drum occluder endograft (BDOEG), designed for percutaneous, transcatheter treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAA was created in 10 dogs with over-dilated Palmaz stents. To prevent back filling, the lumbar arteries, inferior mesenteric artery, and common internal iliac arteries were embolized. The BDOEG was constructed of a drum occluder device and two PTFE endografts. The drum device consisted of a modified Z stent with Dacron stretched across and held within the ends of the stent, each with two 8 x 6-mm slits through which PTFE endografts were delivered. The PTFE endografts were 8 mm in diameter and 9.5 cm in length. Preloaded, the BDOEG was delivered through a 10-F sheath from both femoral arteries in a three-step procedure. All 10 animals were treated with BDOEG. Aortography was performed immediately, 6 weeks, and 12 weeks after stent-graft placement. Five animals were killed at 6 weeks and five were killed at 3 months. Gross and histologic evaluation was performed. RESULTS: The infrarenal aortic diameters and both external iliac arteries ranged from 8.0 mm to 10.3 mm (mean, 9.4 mm +/- 0.6) and from 5.2 mm to 6.8 mm (mean, 5.8 mm +/- 0.5), respectively. Creation of the AAA was successful in all 10 dogs. AAA diameters ranged from 13.7 mm to 15.9 mm (mean, 14.9 mm +/- 0.7). Complete exclusion of the AAA was achieved immediately after BDOEG placement and aneurysms remained excluded without perigraft leak to the time of killing in all 10 animals. There was a high incidence of aortoiliac limb occlusion. Occlusion of 12 aortoiliac limbs (60%) caused by intimal hyperplasia at the distal end of the endografts in iliac arteries developed in nine animals (90%). In six animals (60%), one limb occluded and, in three animals (30%), there was occlusion of both limbs. CONCLUSION: This study suggests a new approach for treatment of AAA. BDOEG use reduces sheath size for endograft delivery and may eliminate the need for a surgical cut down on femoral arteries. Tapering of the iliac ends of endografts to the size of the artery will be needed to prevent distal intimal hyperplasia.

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.

Effects of intraarterial thrombin in the swine model.

PURPOSE: To evaluate the effects of catheter-directed thrombin in the peripheral arterial circulation of swine. MATERIALS AND METHODS: Thrombin was injected into a single femoral artery in 20 domestic swine. Each of five animals from four dose groups received 50, 150, 250, or 1,000 U as a single dose. Bilateral femoral arterial flow was monitored for as long as 4 hours and evaluated relative to baseline and contralateral limb flow. Interval arteriographic results were evaluated by segmental patency and a numeric angiographic score. RESULTS: Mean baseline flow was 136 mL/min +/- 44, with an internal arterial diameter of 3.4 mm +/- 0.5. A transient increase in blood flow after thrombin administration was followed by diminished flow and thrombosis. These findings varied directly with dose and inversely with baseline flow. Angiographic and flow abnormalities generally improved with time and recovery was generally better in swine that received 50 or 1,000 U than in other groups. However, one animal that received 1,000 U (13.2 U/mL/min) developed stable, complete limb thrombosis. The degree of recovery varied with thrombin dose and thrombus location. At doses greater than 50 U (0.33 U/mL/min +/- 0.05), abnormalities were commonly persistent. Animals receiving the 150-U dose (1.33 U/mL/min +/- 0.41) had a higher incidence of persistent distal occlusion. Distal occlusions were less likely to resolve than proximal occlusions. CONCLUSIONS: The effect of intraarterial thrombin is directly related to dose and inversely related to baseline blood flow. In swine, a threshold for significant flow disruption and thrombosis exists above a dose of 50 U (0.33 U/mL/min +/- 0.05). A threshold dose for irreversible occlusion may also exist. Although small amounts of thrombin in a high-flow vessel may not cause significant complication, administration into the arterial circulation should be avoided.

Multi-site interventional real-time procedure demonstrations with the use of integrated services digital network connections.

PURPOSE: To evaluate the effectiveness and cost of commercially available video conferencing units and standard Integrated Services Digital Network (ISDN) connections for real-time multi-site transmissions of interventional procedures. METHODS: A network of five separate interventional radiology departments-three in the Czech Republic and one each in Austria and the USA-was established using Polyspan (Polycom in the USA) View Stations and ISDN connections. This network was used for transmissions of 16 live interventional procedures to the Sixth International Workshop on Interventional Radiology in Prague, Czech Republic in June 2000. RESULTS: The transmissions were successful and of sufficient quality to contribute to the educational success of the workshop. The cost of the ISDN transmissions was a fraction of satellite transmission costs. CONCLUSION: Multi-site real-time interventional procedure transmissions using video conferencing Polyspan (Polycom) View Stations and ISDN connections are a promising means of improving interventional tele-education and decreasing its cost.

Small intestinal submucosa covered expandable Z stents for treatment of tracheal injury: an experimental pilot study in swine.

PURPOSE: To evaluate efficacy of small intestinal submucosa (SIS) as a stent covering in healing experimentally created tracheal defects and to explore the trachea's reaction to placement of SIS-covered stents. MATERIAL AND METHODS: A tracheal defect with a diameter of approximately 10 mm was created in six swine with use of a blade or electrocauterization. A double-body, self-expandable SIS-covered Gianturco Rösch Z stent was placed into the trachea to cover the defect. The animals were observed, and were killed when they developed respiratory problems. Autopsy and histologic studies were performed. RESULTS: The SIS-covered stents were accurately placed without immediate complications related to placement. All animals developed respiratory problems on follow-up. One animal died 9 days after procedure because of pneumonia, the others five were killed at 12, 17, 18, 28, and 56 days because of stridor, wheezing, and cough. At autopsy and histology, the tracheal defects were found to be completely healed, with epithelial lining and regeneration of submucosal glands. Animals whose defects were created with a blade demonstrated cartilage remodeling between 9 and 18 days, and apparent deposition of new cartilage at 28 days after SIS placement. The defects made by electrocauterization showed only fibrous tissue with no cartilage regeneration. The tracheal lumen was narrowed by overgrowth of granulation tissue, particularly at the end wires of the stents. In three animals, polypoid masses caused 60%, 70%, and 80% tracheal obstruction, respectively. CONCLUSION: Placement of SIS-covered stents contributed to rapid and effective healing of large tracheal defects. Rigidity and oversizing of Gianturco Rösch Z stents led to secondary changes of the tracheal wall, causing significant airway obstructions. Smaller size and flexible stents should be selected for future work.

The square stent-based large vessel occluder: an experimental pilot study.

PURPOSE: The purpose of this study is in vitro and in vivo experimental evaluation of a square stent-based vascular occlusion device for large vessels. MATERIALS AND METHODS: Square stent-based large vessel occluders (LVO) 5 mm-50 mm in size were constructed from stainless-steel square stents covered by porcine small intestine submucosa (SIS). The LVOs with two back-side barbs were delivered through a guiding catheter. The LVOs with two back-side barbs and two frontal barbs were front-loaded and delivered coaxially. A pusher with a retention mechanism at its end was used for deployment. In vitro testing for competency was performed with use of a flow model with pressure increases. In an experimental pilot study in seven pigs and five dogs, 16 LVOs were placed into the aorta (n = 4), common iliac artery (n = 2), pulmonary artery (n = 4), and medial sacral artery (n = 6). Four animals received two LVOs in different locations. Angiography was performed before and after placement of each LVO. Animals were followed for as long as 3 months with use of angiography and were then killed for gross and histologic evaluation. RESULTS: In vitro LVOs with two and four barbs were easily collapsed and pushed through or front-loaded into guiding catheters (6-F for a 5-mm occluder, 10-F for a 50-mm occluder). A 20-mm LVO adapted to tubular structures 10-15 mm in diameter, forming polygons 17-18.5 mm in length. In the flow model, LVOs endured pressure increases to 300 mm Hg. In vivo, the LVOs self-expanded and adapted to the vessel without migration in all cases. The locking pusher allowed precise LVO placement and engagement of its barbs into the vessel wall before complete deployment, preventing dislodgment by blood flow. Complete arterial occlusion occurred within 10-20 minutes and arteries remained occluded until the animal was killed in all cases. After 2 months, histologic evaluation revealed replacement of SIS by host tissue and its remodeling with variable fibrocytes, fibroblasts, and some inflammatory cells. Complete endothelialization was seen on both sides of the LVO. CONCLUSION: The SIS LVO is effective and reliable for acute and chronic occlusion in a high flow model in an experimental animal.

Treatment of refractory benign biliary stenoses in liver transplant patients by placement and retrieval of a temporary stent-graft: work in progress.

PURPOSE: To evaluate patency of refractory benign biliary strictures in liver transplant patients treated with retrievable stent-grafts. MATERIALS AND METHODS: Eight male liver transplant patients who ranged in age from 42 to 52 years developed nine symptomatic biliary strictures (intrahepatic left duct, 1; hilar, 2; anastomotic, 6). These strictures had recurred despite multiple previous attempts of treatment (n = 33), including angioplasty (n = 27), surgery (n = 1), atherectomy (n = 1), metallic stent (n = 1), and prolonged catheter drainage (n = 3). As an alternative method of treatment for these refractory biliary strictures, transhepatic placement of expanded polytetrafluoroethylene stent-grafts across the strictures was performed through 10-F sheaths. In total, 14 stent-grafts were placed to treat the nine lesions, and nine of these stent-grafts were subsequently retrieved through 12-16-F sheaths. RESULTS: Stent-grafts were deployed successfully. Delayed migrations in two patients required additional stent-graft placement. One patient died of pneumonia 1 month after stent-graft placement; the remaining seven patients had stent-grafts successfully removed at 3-10 months (mean, 5.6 months). Nine intended stent-graft retrievals were performed successfully, with two requiring use of elongated forceps. Immediately after treatment, all strictures were widely patent. Five to 6 months after stent-graft removal in these seven patients, significant strictures recurred in four of eight lesions (50%). One patient underwent surgical revision. At 6-29 months (mean, 12 months) after stent-graft removal, the remaining six patients were without clinical or laboratory evidence of biliary obstruction, despite three patients with significant recurrent strictures. CONCLUSION: Temporary stent-graft placement for treatment of benign biliary strictures in liver transplant patients is technically feasible. Longer follow-up with larger patient series is necessary to assess effectiveness and possible broader applications.

Aortic and venous valve for percutaneous insertion.

The purpose of this paper is to present in vitro and in vivo experimental evaluation of a new, artificial, bicuspid, aortic and venous valve. Valves were constructed from square stents with barbs covered by porcine small intestine submucosa (SIS). A valve 15 mm in diameter was tested in a flow model (2.5 l/min) with pressure measurement. A 100-ml rubber bag attached to a side arm of the flow model simulated heart ejection fraction. In acute (n=6) and short-term (n=3) experiments conducted in four swine and four dogs, valves ranging from 16-28 mm in diameter were placed into the ascending aorta through 10 F sheaths; three were placed subcoronary and six in a supracoronary position. Function and stability of the valves were studied with pressure measurements and aortograms. Three short-term animals were sacrificed for gross and histologic evaluation at one, two and four weeks respectively. In an acute experiment, venous valves with four barbs were placed into the IVC through an 8 F guiding catheter in three dogs. For longer-term testing, valves were placed into the IVCs and iliac veins of three young swine. The animals were followed up after two weeks with venograms, then were sacrificed for gross and histologic evaluation.

Stent-grafts for de novo TIPS: technique and early results.

PURPOSE: To evaluate the potential benefits of placing a polytetrafluoroethylene (PTFE)-covered stent-graft during initial creation of a transjugular intrahepatic portosystemic shunt (TIPS) in clinical practice. MATERIALS AND METHODS: De novo TIPS were created with a PTFE stent-graft in four male and four female patients with symptomatic portal hypertension awaiting liver transplant. Their ages ranged from 35 to 62 (mean, 47) years. Patients were followed with TIPS ultrasound (US) and/or venography until liver transplantation or death; one remains under active study. Six recovered specimens underwent gross and microscopic evaluation. RESULTS: All TIPS placements were successful. Six shunts were primarily patent, with a mean patency of 289 days, through completion of the study. Five were found to be patent at transplant and one was found to be patent at autopsy. Explant evaluation revealed a smooth, thin layer of neointima and exclusion of biliary secretions. Three patients developed a total of four stenoses (one tandem lesion) during follow-up, leading to revision in two patients. Mean primary and total patency in these patients was achieved after 279 and 463 days, respectively. A previously occult moderate stenosis was detected after explant in another patient. Only one (nonsignificant) stenosis clearly developed in an area covered by PTFE. CONCLUSION: Placement of a de novo PTFE stent-graft during TIPS creation is feasible and may extend primary shunt patency. Appropriate positioning of the stent-graft is critical.

Percutaneous transjugular kidney biopsy in swine with use of a side-cutting needle with a blunt-tipped stylet.

PURPOSE: To evaluate a new 19-gauge blunt-tipped, side-cutting, single throw transjugular biopsy needle for transvenous kidney biopsies. MATERIALS AND METHODS: Transjugular transvenous kidney biopsies were performed with a modified 70-cm biopsy needle utilizing fluoroscopic guidance in nine swine. Three tissue specimens were obtained with four biopsy device passes in five animals and three biopsy device passes in four animals. Renal arteriography and venography were performed immediately before and after renal biopsy. Five animals were killed immediately after biopsy. Four animals were allowed to recover and underwent arteriography and venography prior to being killed, which varied from 1 to 6 weeks. Gross and histologic examinations of the biopsied kidney were performed after euthanasia. A pathologist reviewed all biopsy specimens for quality based on the number of glomeruli present. RESULTS: Results of immediate and delayed arteriography and venography were normal in all cases. Histologic evaluation of all biopsy specimens demonstrated a range of two to 13 glomeruli per sample (mean, 6.5), with successful acquisition of the cortex. In one animal killed immediately after biopsy, a small subcapsular hematoma was present. CONCLUSION: The 19-gauge, side-cut biopsy needle with a blunt-tip stylet proved to be efficacious for obtaining renal cortical samples in right swine kidneys via a transjugular approach.

Twin-tube endografts for aortic aneurysms: an experimental feasibility study.

PURPOSE: To explore feasibility of twin-tube endografts (TTEGs) for treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAAs were created in six dogs by overdilation of Palmaz stents. TTEGs made of seven 9.5-mm-diameter Gianturco Rösch Z (GRZ) stents and covered with PTFE were deployed simultaneously from both femoral arteries through 10-F sheaths to exclude the AAA. Follow-up aortography was performed immediately and at 2, 4, and 8 weeks. Two dogs were killed at 4 weeks and four were killed at 8 weeks. Gross and histologic examinations were performed. RESULTS: AAA creation and TTEG placement were successful in all six dogs. TTEGs completely excluded AAAs in five dogs. Minor temporary perigraft leak was seen in one dog immediately after stent placement. Four dogs had TTEGs patent to termination at 8 weeks. In two dogs with oversized TTEGs, one of the twin endografts occluded at 2 weeks. At autopsy, TTEGs were formed in semicircular shape and histology did not show any significant inflammatory reaction. CONCLUSION: TTEGs show promise for treatment of AAA, with the potential of reducing the introductory sheath size. Further experimental studies, particularly with TTEGs extended into iliac arteries, are warranted.

Long-term results of treatment of benign central venous obstructions unrelated to dialysis with expandable Z stents.

PURPOSE: To evaluate long-term patency of self-expanding Z stents for treatment of benign central venous obstructions unrelated to dialysis. MATERIALS AND METHODS: Z stents were placed in 19 patients, (ages 26-72 years) with severe symptomatic obstructions of the superior or inferior venae cavae and their large branches and portal vein caused by surgical or catheter injury (n = 8), fibrosis (n = 5), cirrhosis (n = 3), Budd-Chiari syndrome (n = 2), and extrinsic compression (n = 1). Fourteen patients underwent stent placement primarily, five after local urokinase infusion for superimposed thrombosis. Follow-up was performed with ultrasound and venography. RESULTS: Venous congestive symptoms quickly resolved in all patients after stent placement. The follow-up period was from 1 to 94 months. Twelve patients have died during follow-up from 1 to 37 months although all remained asymptomatic until death. Six patients remain alive, asymptomatic, with patent stents, and with follow-up from 24 to 94 months. Primary patency was 83%, and secondary patency was 100%. One patient with a patent stent at 12 months was lost to follow-up. No stent migrations, perforations, infections, or significant complications occurred. CONCLUSION: Benign central venous obstructions are effectively treated by the placement of self-expandable Z stents. Placed percutaneously into obstructive lesions with a minimum risk, these stents offer long-term durability and patency.

Retrievable IVC square stent filter: experimental study.

PURPOSE: In vitro and in vivo evaluation of a new retrievable, home-made, inferior vena cava (IVC) Square stent filter (SSF) with two trapping levels. METHODS: In vitro, the SSF was compared in a flow model with the stainless steel Greenfield filter (SGF) for emboli-trapping efficiency by serially passing 300 emboli of 3 and 6 mm in diameter and 15-30 mm in length in each type of filter. Nine swine were used for the in vivo testing of the SSF for deployment and retrievability, emboli-trapping efficiency, stability, and self-centering ability and two were used (total of 11 swine) for testing repositioning and retrievability of the SSF at 2 weeks and for gross and histologic IVC changes at 2 months. RESULTS: In vitro, the SSF and SGF had similar efficiency in trapping large emboli but the SSF had significantly better efficiency than the SGF for trapping all sizes of emboli (91.7% vs 81%), medium size emboli (93% vs 80%), and small emboli (86% vs 69%). Efficiency decreased in both filters from the first to the fifth embolus in each series but was still significantly better for the SSF. With the SSF, 89% of emboli were caught at the primary and 11% at the secondary filtration level. In the nine animals used for acute studies, the SSF was easily placed in all 27 attempts, assumed a central position 26 times, and was easily retrieved in 21 of 22 attempts. One tilted filter needed additional manipulation for retrieval. During emboli injection in five swine, the SSF had 97.2% emboli-trapping efficiency and demonstrated good stability. In the two animals used for longer-term evaluation, the filters were easily retrieved 2 weeks after implantation. Histologic evaluation at 2 months showed neointimal proliferation around the SSF wires in contact with the IVC wall, which was otherwise normal. CONCLUSION: The SSF is a promising filter. It is easy to place and retrieve, is stable after placement, and has high efficiency for trapping emboli. Promising results justify further experimental and eventual clinical studies with a commercially manufactured SSF.

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.

Percutaneous retroperitoneal splenorenal shunt: an experimental study in swine.

PURPOSE: To evaluate the technical possibility of creating a percutaneous retroperitoneal splenorenal shunt (PRESS) in swine as a minimally invasive treatment of portal hypertension. MATERIALS AND METHODS: Five normal domestic swine underwent creation of a PRESS. A modified transjugular intrahepatic portosystemic shunt puncture set was introduced from the right femoral vein into the left renal vein. The proximal splenic vein was punctured transvenously through the retroperitoneal cavity. Noncovered metallic stents were then placed to connect both veins. The animals were sacrificed 1 hour after the procedure, after follow-up splenic venography and necropsy were performed. RESULTS: Puncture of the splenic vein and stent placement were successfully completed in all cases. In four of five cases, the splenic venogram revealed good flow from the splenic vein to the left renal vein through the shunt track 1 hour after creation of the PRESS, and there was no evidence of leakage. No changes in vital signs were noticed. At necropsy, a small retroperitoneal hematoma along the stent and minimal intraperitoneal bleeding were observed. The stents were found in the retroperitoneal cavity connecting both veins in all animals. CONCLUSION: Creation of a PRESS is technically possible, and further experimental studies of its efficacy are warranted.

Transjugular intrahepatic portosystemic shunt with silicone-covered Wallstents: results in a swine model.

PURPOSE: To evaluate the use of impermeable silicone-covered Wallstents for transjugular intrahepatic portosystemic shunt creation. MATERIALS AND METHODS: A transjugular intrahepatic portosystemic shunt was created in 14 young swine (weight, 20-32 kg) by using impermeable silicone-covered Wallstents. In eight animals, the silicone covering extended from the portal vein to the inferior vena cava. In two swine, the silicone covering ended short of the inferior vena cava, in two it ended short of the portal vein wall, and in two it ended short at each end. Follow-up transhepatic portal venography was performed weekly for 6 weeks or until the shunt was occluded. Animals were then sacrificed for gross and histologic evaluation. RESULTS: Only two of 14 shunts were patent after 3 weeks; both were stenosed with luminal narrowing of more than 50% in the middle of the shunt. By 6 weeks, all shunts were occluded. At histologic evaluation, a marked foreign-body reaction with superimposed thrombosis was demonstrated. CONCLUSION: In comparison with uncovered Wallstents, impermeable silicone-covered Wallstents are associated with decreased patency at transjugular intrahepatic portosystemic shunt creation. This is likely due to increased thrombogenicity and a foreign-body reaction.

Stent-grafts for revision of TIPS stenoses and occlusions: a clinical pilot study.

PURPOSE: To assess the clinical and technical results of stent-graft placement for revision of transjugular intrahepatic portosystemic shunt (TIPS) stenoses and occlusions. MATERIALS AND METHODS: Six patients who developed recurrent TIPS stenosis or occlusion of the parenchymal tract underwent shunt revision with use of polytetrafluoroethylene (PTFE) stent-grafts anchored at both ends by Z stents and centrally supported by Wallstents. RESULTS: Before graft placement, mean primary patency was 50 days (range, 9-100 days). Patients underwent one to eight revisions with angioplasty or stent placement (mean, 3.2). Three patients had biliary-TIPS fistulas documented with use of a prototype double occlusion balloon catheter. Stent-grafts were successfully placed within the obstructed shunt, creating an excellent lumen in all cases. The portosystemic gradient was decreased from a mean of 24.3 mm Hg (range, 12-35 mm Hg) to a mean of 10.3 mm Hg (range, 7-16 mm Hg). Five of six patients were asymptomatic and no complications occurred (median clinical follow-up, 331 days). One patient died of pre-existing multi-organ system failure. The duration of primary patency after stent-grafting was improved (mean, 229 days; range, 27-324 days) and the difference approached statistical significance despite the small sample size (P = .056, paired t test). Three patients remained primarily patent at a mean venographic follow-up of 315 days. One shunt occluded at 1 month from residual thrombus in the portal vein, and one stenosis occurred that was secondary to misplacement of the original stent-graft. Patency was re-established in each of these patients. CONCLUSION: PTFE covered stent-grafts are effective for shunt revision in patients with tract stenosis or occlusion and appear to improve TIPS patency.