British Journal of Radiology 74 (2001),908-912 © 2001 The British Institute of Radiology
A new stent-graft for transjugular intrahepatic portosystemic shunts
J D G Rose, FRCP, FRCR
S Pimpalwar, DMRD
and
R W Jackson, MRCP, FRCR
Department of Radiology, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK
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Abstract
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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.
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Introduction
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The percutaneous transjugular intrahepatic portosystemic shunt (TIPSS) has evolved as an important, minimally invasive treatment in the management of the complications of portal hypertension. However, although extremely efficient in the short-term, shunt dysfunction due to stenosis or occlusion is a common problem within the first year (Figure 1a
). Frequent shunt surveillance and revision is therefore recommended to prevent recurrent symptoms. Although generally successful in maintaining shunt patency, this strategy has significant implications both for the patient and financially. In an effort to prevent TIPSS malfunction, there have been trials of antiplatelet drugs, brachytherapy and various coated stents [1–5]. This paper presents the preliminary results of TIPSS using a stent-graft that only became commercially available in the UK in 2000.
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Figure 1. Early shunt dysfunction associated with severe hepatic vein stenosis. (a) Transfemoral selective venogram. 5 F Simmons catheter. Tight stricture of the hepatic vein proximal to the TIPSS Wallstent and near occlusion of the stent shunt lumen. (b)Transjugular recanalization of the blocked shunt. The distal introducer sheath marker is at the lower end of the Wallstent. Just above this is a small tip marker at the end of the device catheter. The ring marking the caudal margin of the graft is just above the midpoint of the Wallstent. The uncovered distal segment lies between the ring and the tip markers. The introducer sheath and device catheter were inserted a further 2 cm prior to sheath withdrawal and stent-graft deployment 1 cm distal to the end of the Wallstent. (c) Post-deployment image showing restoration of the lumen of the shunt. The proximal marker on the Viatorr stent-graft is visible at the junction of the hepatic vein with the inferior vena cava.
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Materials and methods
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Eight patients (seven male), with a mean age of 53.1 years (range 22–75 years), underwent implantation of the new TIPSS stent-graft between July 2000 and February 2001. The indications for TIPSS were recurrent variceal bleeding (n=7) and intractable ascites (n=1). There were six primary or de novo procedures and two shunt revisions. Details of patients and procedures are summarized in Table 1.
Stent-graft design
The Viatorr stent-graft (WL Gore, Flagstaff, AZ) consists of a self-expanding nitinol stent supporting an expanded polytetrafluoroethylene (ePTFE) graft with a bile resistant membrane. It can be expanded to four times its unexpanded diameter without loss of structural integrity. The stent-graft has two functional segments: a graft-lined segment (4 cm, 5 cm, 6 cm, 7 cm or 8 cm long) that spans the intrahepatic tract and the hepatic vein up to the inferior vena cava (IVC) junction; and a distal 2 cm long "bare" segment, which is positioned in the portal vein (Figure 2). A circumferential radio-opaque gold marker band indicates the junction between the two regions. An additional radio-opaque gold marker is located at the trailing edge of the device to improve its visibility. A choice of diameters (8 mm, 10 mm and 12 mm) is available. The distal "bare" stent framework is constrained beneath a protective plastic access sleeve, which facilitates insertion of the leading end of the device through the haemostatic valve of the introducer sheath. The covered stent-graft immediately proximal to the uncovered segment is confined beneath a removable ePTFE sleeve secured to a dual lumen delivery catheter.
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Figure 2. Viatorr endoprosthesis for TIPSS (images provided by WL Gore Inc). The three diameters available (12 mm, 10 mm and 8 mm) are demonstrated. Note the ring marker visible through the graft material immediately above the uncovered segment.
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Technique
Portal venous access was obtained with the Cook TIPSS set (TIPSI-200; William Cook, Letchworth, UK) using a standard technique [6]. The length of the appropriate stent-graft was determined using a calibrating catheter by measuring the distance between the IVC and the portal vein access site (Figure 3a). The long introducer sheath was positioned in the portal vein, 2–3 cm distal to the portal venous puncture site. The Viatorr delivery catheter was then introduced and pushed into the lower end of the sheath so that the entire distal bare segment was at the level of the portal vein lumen (Figure 1b
). While holding the delivery catheter fixed in this position, withdrawal of the introducer sheath deployed the distal 2 cm of bare stent inside the portal vein. The delivery catheter and the sheath were pulled back carefully until the junctional radio-opaque marker was accurately positioned at the portal venous end of the intrahepatic tract. The introducer sheath was then retracted over the delivery system to expose the entire covered segment to the intrahepatic track. Finally, the constraining sleeve was stripped away by pulling the rip cord, thus deploying the graft-lined segment in the tract and hepatic vein up to the IVC junction (Figures 1c and 3b) The graft was subsequently dilated to its nominal diameter.
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Figure 3. Primary TIPSS procedure. (a) A 10 F transjugular sheath lies in the right hepatic vein. A 5 F marker or calibration catheter has been inserted, which enabled measurement of the length of the intrahepatic track and the vein between the track and the inferior vena cava. (b) Post-deployment image after insertion of a 10 mm x 60 (+20) mm Viatorr device.
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Results
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The stent-graft was successfully deployed in all patients (see Table 1). The diameters of the stent-grafts used were 8 mm (n=1), 10 mm (n=5) and 12 mm (n=2). The mean portosystemic pressure gradient decreased from 18.7 mmHg to 6.4 mmHg. At a median follow-up of 60 days (range 21–215 days) all implanted shunts remained patent, with no recurrence of variceal bleeding or ascites.
There was one intraprocedural complication: a contained retroperitoneal leak at the site of hepatic venous puncture, which was sealed off effectively with the stent-graft. This patient remained haemodynamically stable and made an uneventful recovery. There was no other significant periprocedural morbidity and no 30-day mortality.
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Discussion
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The undoubted Achilles heel of TIPSS formation is the high rate of shunt dysfunction over time. A primary patency rate of around 50% at 2years [7, 8] is not unusual and gives an indication of the severity of this problem. When occurring soon after the primary procedure, shunt obstruction is usually due to acute thrombosis [9]. Exposure of flowing blood within the shunt to thrombogenic factors released from the hepatic parenchyma appears to be the cause. Bile from transected ducts and mucin produced by biliary epithelium [9, 10] have been implicated. Later shunt dysfunction is generally due to shunt stenosis, either owing to neointimal hyperplasia, typically within the draining hepatic vein (Figure 1), or to pseudointimal hyperplasia within the parenchymal track [7, 8, 11, 12].
The primary use of covered stents in TIPSS, that is to exclude hepatic parenchymal factors and to promote an improvement in shunt patency, is an attractive idea. However, the only clinical reports so far describe the use of a Gianturco–Wallstent combination covered with PTFE [13] and the Cragg Endopro (nitinol stent covered with Dacron polyester) [14, 15]. These studies seem to justify cautious optimism, in particular for the use of a shunt lined with PTFE. The Dacron-covered stent-grafts did not appear to improve primary patency, although it should be emphasized that these were only pilot studies. The additional benefit offered by all types of covered stent for the primary TIPSS procedure is that it enables endovascular treatment of an extrahepatic portal venous laceration [16, 17].
The secondary management of early or recurrent TIPSS dysfunction with a covered stent is also a persuasive concept in that a significant number of such cases will be related to biliary fistulae [10, 18]. Assuming that transluminal access down the blocked primary stent can be achieved, use of a covered stent may be justified where a fistula can be demonstrated or there has been an early occlusion.
The ideal stent-graft for TIPSS should be composed of very thin material to allow the use of a low profile introducer system. It should be biocompatible, non-thrombogenic and impermeable to bile, but porous enough to allow satisfactory incorporation into the surrounding tissue. A number of materials and stent designs have been used experimentally. Stents covered by woven Dacron [4, 5, 14, 19] have, in general, given disappointing results. However, PTFE-covered stents have improved rates of primary patency in animals and show higher rates of incorporation andendothelialization and better biocompatibility than the woven polyester grafts [2, 3, 13, 18].
The new commercially available stent-graft described in this paper appears to offer many of the advantages listed above for the "ideal" TIPSS device. Whilst the Viatorr is not covered by graft material at the distal or portal venous end, the ePTFE covering on the proximal device could partially obstruct hepatic venous outflow. This is a legitimate concern, but it does seem that isolated segmental hepatic venous occlusions are unlikely to be of clinical significance and that hepatic venous collateral circulation will develop [13, 20]. Hepatic venous outflow obstruction generally manifests itself with obvious clinical signs, and biochemical evidence is usually non-specific and late. The limited follow-up of the patients treated with the Viatorr so far indicates no evidence of any untoward complications. Given the high rate of shunt dysfunction due to hepatic venous stenosis, it seems prudent to also cover this portion of the shunt [2, 8, 11].
Finally, the cost of the commercial stent-graft is an important issue when considering the financial burden of the primary TIPSS procedure. The stent cost will be increased by approximately 100% when using a Viatorr stent compared with any of the currently popular uncovered stents. Only long-term surveillance will indicate whether any of this additional cost will be offset by reduced re-intervention rates in the future.
Received for publication March 7, 2001.
Revision received June 15, 2001.
Accepted for publication June 25, 2001.
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Abstract
Introduction
