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Vascular and Interventional Radiology |
1 From the Department of Radiology, Division of Angiography and Interventional Radiology (M.C., S.A.T., K.H., M.S., J.L.) and Department of Gastroenterology and Hepatology (M.P.R.), University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. Received December 20, 2000; revision requested February 14, 2001; revision received March 16; accepted April 30. Address correspondence to M.C. (e-mail: manfred.cejna@univie.ac.at).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: The ePTFE-covered nitinol stent-graft was used to create TIPS in 16 patients with recurrent variceal bleeding (n = 13) or refractory ascites (n = 3). Follow-up was performed with duplex ultrasonography, clinical assessment, and venography at 6 months. Technical success and portosystemic pressure gradients (PPGs) before and after stent-graft implantation and at follow-up were assessed. Two patients died during follow-up. Histopathologic follow-up data were available for one patient at autopsy and for the other after liver transplantation.
RESULTS: The implantation technical success rate was 100%. Mean (± SD) PPG was reduced from 24 mm Hg ± 5 to 9 mm Hg ± 2. Histopathologic analysis of the explanted endoprostheses revealed no inflammatory response or neointima formation. The venographic follow-up data available for 10 patients demonstrated 100% in-graft patency (mean follow-up, 289 days ± 26). Revisions with implantation of a new ePTFE-covered nitinol stent-graft or another commercially available stent in 10 patients were necessary because of hepatic vein stenosis above the grafted portion and/or relative diameter mismatch causing TIPS dysfunction.
CONCLUSION: The ePTFE-covered nitinol stent-graft was used successfully to create TIPS and has the potential to prolong TIPS patency upon complete coverage to the hepatocaval junction.
Index terms: Hypertension, portal, 95.711 • Liver, interventional procedures, 761.1269, 95.1268 • Shunts, portosystemic, 95.453 • Stents and prostheses, 95.1268 • Venography, 95.124
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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Previously published reports (6–9) of noninvasive techniques for follow-up after TIPS creation and revision have indicated good sensitivity and specificity for the detection of stenoses, but these techniques might not be ideal for predicting optimal shunt function or recurrence of a portosystemic gradient, because they help determine only shunt patency. Although routine invasive shunt surveillance and revisions are a necessary part of the care of patients with TIPS, they are resource demanding and invasive and do not completely protect patients against the dangers associated with shunt malfunctions that may occur between imaging intervals. These drawbacks may limit the perceived long-term value of TIPS, which are still considered by many to be largely a bridge to orthotopic liver transplantation (10) or a rescue procedure to be performed only when other treatments fail.
Stent-grafts have demonstrated high potential in creating durable TIPS in animals (11,12) and in pilot clinical studies (13,14), but the devices used in these studies were custom-made, and this prevented their widespread routine use. Herein, we report our study results with what is, to our knowledge, the first dedicated TIPS stent-graft, the VIATORR endoprosthesis (W. L. Gore and Associates, Flagstaff, Ariz). Our primary objective was to evaluate the safety and performance of this endoprosthesis, as used to create TIPS in patients with portal hypertension and related complications.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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The institutional review board at our institution approved the protocol for TIPS creation with stent-grafts. Signed informed consent was obtained from each patient prior to enrollment. The patient numbers in Tables 1–3 are the enrollment numbers assigned to the patients. During the multicenter study, 10 patients in whom TIPS were created were not included because of an unclear infection status (n = 6) or the unavailability of the TIPS stent-graft at the time of the procedure (n = 3) or because a severely kinked 12-F sheath prevented the use of the TIPS stent-graft. Thus, standard bare-stent implantation was performed in these patients. After completion of the study and during enrolment of the next four patients, no patients were excluded.
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Inclusion Criteria
Included in the study were patients with complications associated with portal hypertension, such as variceal bleeding, gastropathy, inaccessible varices, diuretic resistant ascites, and/or hepatic hydrothorax, all of which were refractory to or intolerant of conventional endoscopic or medical therapies. Patients had to be at least 21 years of age and able to comply with the protocol requirements, including follow-up procedures. In addition, the patient had to be willing to accept blood or blood products.
Exclusion Criteria
The exclusion criteria were (a) congestive heart failure, (b) polycystic liver disease, (c) severe hepatic failure (with bilirubin level > 5.0 mg/dL [>85.5 µmol/L]), (d) severe hepatic encephalopathy, (e) known cavernous portal vein occlusion, (f) concomitant disease or coexistent morbidity such that the patient would be unlikely to survive the procedure or the required follow-up period or be ineligible for liver transplantation, (g) creation of TIPS in patient with Budd-Chiari syndrome, and (h) presence or suspicion of active systemic, hepatobiliary, or ascitic fluid infection. The exclusion criteria discovered during the procedure were gastric varices secondary to splenic vein thrombosis and inability to advance the appropriately sized hemostatic introducer sheath into the portal vein.
End Points
The primary end points of this study included delivery success, which was characterized by technical success and hemodynamic success, and performance, which was characterized by 6-month patency at venography. Secondary end points included monitoring of the patient with respect to event-free survival by means of assessments of complications and the degree of venographic stenosis observed 6 months after treatment.
Color Duplex Ultrasonography
Shunt patency and flow velocity (ie, magnitude and direction) were examined by performing noninvasive color duplex ultrasonography (US) at discharge and 1, 3, 6, and 12 months after TIPS treatment. All suspected shunt abnormalities were confirmed by performing venography and portosystemic pressure gradient (PPG) measurements. All patients were examined sonographically with a US imaging unit (ATI Ultramark 9 HDI; Advanced Technology Laboratories, Bothell, Wash). For color duplex US evaluation, a 3–2-MHz C76 curved broadband transducer was used. The US criteria for shunt dysfunction were (a) in-shunt flow greater than 200 cm/sec, (b) 50% or greater decrease in in-shunt flow, as compared with the in-shunt flow measured at the discharge examination, and (c) recurrence of ascites. (6). We also evaluated the signs of TIPS complication (eg, liver hematoma), the signs of occlusion in the intrahepatic central portal vein, and the patency of hepatic veins at discharge and at follow-up examinations (especially in patients 9 and 10 when the stent-graft was positioned up to the hepatocaval junction). We also checked for signs of potential graft infection (ie, formation of echo-poor areas surrounding the graft) at follow-up US examination. US was performed by all the authors except M.P.S. or by experienced interns in the Department of Interventional Radiology.
TIPS Stent-Graft Endoprosthesis
The evaluated endovascular TIPS prosthesis (Figs 1–3) consists of an ultrathin inner ePTFE tube, externally radially reinforced by a wrapping of ePTFE film that is resistant to bile permeation. The blood-contacting inner layer is made of ePTFE and has a microstructure and mechanical properties that are similar to those of the conventional vascular graft from the same manufacturer (GORE-TEX Vascular Graft; W. L. Gore and Associates). Structural support is provided by an external self-expanding nitinol stent with high radial strength, with an outer layer of macroporous ePTFE to facilitate ingrowth of liver parenchyma and hence better incorporation into the liver parenchyma.
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The TIPS endoprosthesis is available in a range of sizes, with diameters of 8, 10, and 12 mm and lengths ranging from 4 to 8 cm. All sizes can be inserted through a 10-F sheath. (The first 10 implantations were performed with devices that required a 12-F sheath.) The stent-graft delivery system accepts an 0.035-inch guide wire.
TIPS Procedure, Stent-Graft Implantation, and Follow-up Venography
The right jugular vein was punctured with US guidance. A standard 10-F TIPS set (TIPSI-200; William Cook Europe, Bjaeverskov, Denmark) was used for TIPS creation in all patients. Once successful puncture of the portal vein was achieved, a soft-tip guide wire was advanced into the portal vein. After advancement of a 5-F calibration catheter, a venogram was obtained, with 45 mL of nonionic contrast medium (iopamidol [Jopamiro], 300 mg of iodine per milliliter; Bracco Diagnostics, Milano, Italy) administered at 12 mL/sec, to determine the portal vein anatomy and identify varices. The soft-tip guide wire was then replaced with a 180-cm-long, 0.035-inch guide wire (J-Tip Amplatz-Wire; William Cook Europe). After dilating the parenchymal tract with an 8 x 40-mm Olbert balloon (Boston Scientific International, Natick, Mass), we advanced the 40-cm-long, 10-F sheath (CheckFlo; William Cook Europe) (or 12-F sheath [CheckFlo II; William Cook Europe] for the first 10 implantations) into the portal vein. The stent-graft delivery catheter was then introduced into the sheath.
We advanced the device in position over the standard guide wire (J-Tip Amplatz-Wire) and deployed the uncovered portion by sequentially withdrawing the sheath from the portal vein. The sheath and delivery system were then gently retracted until a definite resistance (the portoparenchymatous junction) was felt, the device was held in place, the sheath was completely withdrawn into the inferior vena cava (IVC), and the covered portion of the stent-graft was released by means of retraction of the deployment line. The stent-graft was dilated with high-pressure balloons of sizes equivalent to the nominal diameters of the grafts.
Shunt venography, with 45 mL of iopamidol administered at 12 mL/sec, was performed to monitor shunt patency and lumen diameter after implantation for assessment of delivery success. Our aim was to implant the stent-graft up to the proximal-middle hepatic vein portion and thus not block the hepatic veins completely. The unavailability of exact-fitting stent-grafts necessitated complete coverage to the IVC in only two patients (patients 9 and 10). On calibrated venograms we measured the complete tract length up to the IVC and recorded the diameters, lengths, and numbers of devices used per patient, as well as the total combined graft length when two devices were implanted with overlap.
Depending on the clinical status of the patient, either a central venous catheter was inserted or manual compression at the jugular puncture site was performed. Follow-up venography and revisions were performed as described earlier, but the intervention was started with a 7-F sheath (Terumo; Radiofocus, Leuven, Belgium). We used 6-F guiding catheters (Multipurpose or Cobra; Johnson and Johnson, Cordis Division, Miami, Fla) for TIPS recanalization. The sheath was replaced with a 10- or 12-F catheter (CheckFlo II) when revision with a second ePTFE-covered nitinol TIPS stent-graft had to be performed. Device implantation and follow-up venography were performed by all the authors except M.P.S.
PPG Measurement
The mean atrial pressure was measured prior to portal vein puncture, and the mean portal pressure was measured after puncture and before dilation of the tract. The PPG was calculated as the mean portal pressure minus the mean atrial pressure. After completion of the TIPS procedure, the mean atrial pressure and mean portal pressure were measured again. Follow-up PPG measurements were performed whenever contrast material–enhanced venography was performed. The cutoff value for hemodynamic success was a PPG of 12 mm Hg or lower.
Medication Protocols
We injected 5,000 IU of heparin after successful passage of the catheter into the portal vein. After the TIPS procedure, the patients received 40 mg of enoxaparin (Lovenox; Gerot Pharmaceuticals, Vienna, Austria) twice a day for at least 2 days (maximum of up to 1 week, depending on the mobility of the patient). After the procedure, the patients began taking 75 mg of clopidogrel (Plavix; Sanofi Winthrop, Vienna, Austria) per day for up to 1 month. Before insertion of the graft, all patients, except those who had been taking a broad-spectrum antibiotic medication, received 2 mg of ceftriaxone (Rocephin; Hoffman-La Roche, Vienna, Austria) intravenously as a perioperative prophylaxis. If central venous catheters were placed, antibiotic medication was continued for 1 week.
Definition of Patency and Complications
Primary patency was defined as the time to first intervention due to stenosis or occlusion (ie, absence of flow through the shunt). Stenosis requiring intervention was defined as a greater than 50% venographic narrowing of the shunt lumen and/or an elevation of the PPG to greater than 12 mm Hg. Additional in-graft patency rates were obtained to discriminate between in-graft stenosis and above-the-graft hepatic venous stenosis. Secondary patency was defined as the time to complete loss of function after revision. We checked for TIPS-related complications (eg, encephalopathy, recurrence of bleeding and/or ascites, and peritonitis) at discharge and at the follow-up clinical examinations. In inpatients, complications were assessed at the time of occurrence; in outpatients, complications were assessed retrospectively after notification and/or after chart review.
Histopathologic Specimen Preparation and Scanning Electron Microscopy
In two patients, the stent-grafts were retrieved after orthotopic liver transplantation (patient 3) or at autopsy (patient 13) 41 and 28 days, respectively, after TIPS creation and fixated in 4.5% paraformaldehyde. The specimens and surrounding hepatic parenchyma were opened longitudinally and photographed. Multiple cross-sections and longitudinal sections were obtained and stained with hematoxylin-eosin or paragon. For scanning electron microscopy, the specimens were rinsed in 0.1 mmol of cacodylate buffer, fixed in 1% osmium-tetroxide, dehydrated in ethanol, air dried with hexamethydisilazane sputter coated with gold, and examined with scanning electron microscopes (model 1000; Amray, Bedford, Mass and PSEM II; Aspex, Delmont, Pa) at x100 and x500 magnifications. We looked for the amount of endothelialization, neointima formation, and inflammatory response (ie, number and relative proportion of neutrophils, lymphocytes, and macrophages) and the healing characteristics of the stent-grafts. Histopathologic work-up was performed by a pathologist from the histologic department of the manufacturer of the ePTFE-covered nitinol TIPS stent-graft (W. L. Gore and Associates).
Statistical Analyses
If not otherwise indicated, all data were reported as means plus or minus standard errors of the means. The reported patency rates, based on functional and/or morphologic data obtained at venography, were calculated with the Kaplan Meier method. Calculations were performed by using a statistical software program (SPSS/PC; SPSS, Chicago, Ill).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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Initially, placement of one ePTFE-covered nitinol TIPS stent-graft was performed in 13 patients, and placement of two TIPS endoprostheses was required in three patients (Tables 2 and 3). The diameters used were 8 mm (n = 2), 10 mm (n = 12), and 12 mm (n = 2). In patient 13, a cobalt-based alloy stent (Wallstent; Boston Scientific, Natick, Mass) also had to be placed into the portal vein because of extrinsic compression of approximately 50%, which was later confirmed to be caused by hepatocellular carcinoma. Because of the extrinsic compression, the PPG between the right intrahepatic portal vein and the vena cava was less than 12 mm Hg and the PPG between the main trunk of the vena porta and the vena cava was 14 mm Hg. The mean PPG (± SD) was reduced from 24 mm Hg ± 5 (range, 16–37 mm Hg) to 9 mm Hg ± 2 (range, 5–14 mm Hg).
Follow-up Data and Additional Procedures
In two patients (patients 4 and 16), coil embolization of gastric varices was performed. In patient 3, venographic follow-up and two revisions were performed within 1 month after TIPS creation. The mean duration of venographic follow-up was 289 days ± 26. Patient 21 was lost to follow-up after undergoing US 3 weeks after TIPS creation. Patients 25 and 26 underwent only US follow-up at 3 months.
Residual stenosis within the segments with grafts was less than 15% at follow-up venography in all cases. All TIPS lined with ePTFE-covered nitinol endoprostheses were widely patent at follow-up venography (Figs 4, 5). No early thromboses were detected. Ten patients were available for 6-month follow-up venography 134–262 days after TIPS creation, and six of them underwent two venographic examinations. Overall, venograms were available at 5–451-day follow-up in 11 patients. The in-graft primary patency at 6 months, as determined by performing venography, was 100% (10 of 10 patients). However, the overall primary shunt patencies based on morphologic criteria determined by using the Kaplan-Meier method (<50% stenosis) were 90% at 6 months (one cumulative event, nine of 16 patients at risk) and 50% at 9 months (five cumulative events, five of 16 patients at risk). Shunt patency rates based on morphologic and functional criteria (>50% stenosis and/or PPG >12 mm Hg) were 82% at 6 months (two cumulative events, nine of 16 patients at risk) and 45% at 9 months (five cumulative events, four of 16 patients at risk). These dysfunctions occurred mostly because of hepatic vein stenosis above the graft portion of the endoprosthesis (n = 8). The secondary morphologic patency was 100% throughout the study, and the secondary combined morphologic and functional patency was 81% at 6 and 9 months (two cumulative events, 10 of 16 patients at risk), because of two relative shunt dysfunctions (in patients 2 and 8) despite stent-graft patency.
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In patient 8, venography performed 134 days after implantation of an 8-mm ePTFE-covered TIPS endoprosthesis because of recurrent ascites demonstrated a significant pressure gradient (PPG, 28 mm Hg) predominantly in the uncovered hepatic vein. The patient was treated with implantation of a second ePTFE-covered TIPS endoprosthesis, as well as with a nitinol stent (Smart stent; Johnson and Johnson, Cordis Division, Miami, Fla) over the portoparenchymatous junction; the PPG after revision was 16–18 mm Hg. Repeated paracentesis was required during the follow-up period until the diuretic medication was increased to result in a drastic relief of symptoms with only minimal ascites. At the time this article was written, the TIPS was stable at 330-day follow-up and the PPG was 18 mm Hg. Hepatocellular carcinoma had been detected and was treated with magnetic resonance–guided percutaneous ethanol instillation.
Furthermore, revisions were performed in eight asymptomatic patients. In these patients, the outflow hepatic vein above the grafted portion had developed a flow-limiting stenosis with a resultant increase in portal venous pressure (Fig 4). The stenoses were treated by means of implantation of a second ePTFE-covered TIPS endoprosthesis in patients 2, 4, 7, 8, 15, 16, and 20. Follow-up venography in patient 15 depicted less than 10% restenosis along the complete tract, with a PPG of 9 mm Hg at 351-day follow-up. In patient 14, cobalt-based alloy stent implantation was performed at 190-day follow-up and hepatic venous stenosis necessitated angioplasty at 292-day follow-up (Table 2). In all of the patients who underwent revision, a mismatch of the tract length up to the IVC and the stent-graft length could be seen, and all revisions were necessary because the stent-graft initially did not cover the complete tract to the IVC (Table 3).
Two patients with coverage of the complete tract up to the IVC (patients 9 and 10) remained asymptomatic at follow-up venography, with a PPG of less than 12 mm Hg (Fig 5). In these two patients, no tract-to-graft mismatch was measured (Table 3). There were no signs of hepatic infarction or partial Budd Chiari syndrome. We did not detect signs of hepatic infarction or potential graft infection at follow-up examinations.
Complications
There were no puncture-related complications such as hematoma in the neck region. As indicated earlier, an additional intervention-associated thrombus in the splenic vein (in patient 16) was detected and treated. One patient (patient 1) died 28 days after TIPS implantation due to cardiac decompensation following pneumonia. The reason for implantation in this patient was intractable ascites, which was worsened owing to renal insufficiency, failed renal transplantation, and ongoing hemodialysis. Another patient (patient 13) died 31 days after TIPS implantation. In this patient, hepatocellular carcinoma was diagnosed after TIPS implantation and treated with percutaneous ethanol instillation 14 days after TIPS creation. The patient then had clinical signs of fulminant peritonitis and died. Autopsy results demonstrated possible rupture of the hepatocellular carcinoma causing the peritonitis. The TIPS stent-graft itself was patent at autopsy, and there were no histopathologic signs of inflammation (Fig 6). Therefore, neither of these mortalities was considered to be device related, but one of these cases (patient 1) could be considered to be procedure related.
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Histopathologic Findings
Histopathologic evaluation of the stent-graft explanted from patient 3 after orthotopic liver transplantation showed the uncovered stent-graft to be free of thrombus. The interior of the covered portion was multifocally covered by small accumulations of fibrin that contained small to moderate numbers of macrophages. In one area, the luminal surface of the implant was covered by a thin layer of fibrous connective tissue containing moderate numbers of macrophages. The outer thin layer of the ePTFE-covered TIPS endoprosthesis was multifocally separated from the overlying closed structure layer by moderate amounts of fibrous connective tissue containing aggregates of macrophages. The surface of the fibrous connective tissue in some areas contained small fibrin thrombi.
All devices in patient 13 (Fig 6) were patent, and the luminal surfaces were multifocally covered by layers of acute thrombus material that were temporally consistent with the time of device implantation. The wires of the cobalt-based alloy stent and the chain-link structure of both ePTFE-covered TIPS endoprostheses were multifocally covered by small amounts of amorphous proteinaceous material. Multifocally present between the abluminal surface of the ePTFE-covered TIPS endoprostheses and the hepatic parenchyma and host vessels were resolving thrombi, which were temporally consistent with the time of device implantation. The thrombi were composed of large amounts of vascularized fibrous connective tissue that contained fibrin, erythrocytes, amorphous proteinaceous material consistent with normal healing, and small numbers of inflammatory cells. Microscopic changes in the liver were consistent with the clinical diagnosis of hepatitis C. There was no microscopic evidence of infection directly related to either the ePTFE-covered TIPS endoprostheses or the cobalt-based alloy stent. Scanning electron microscopy revealed multiple foci of endothelialization adjacent to and covering acute fibrin thrombi on the luminal surface of the cobalt-based alloy stent and on the covered structure of the distal ePTFE-covered TIPS endoprosthesis (Fig 6c).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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An effective TIPS stent-graft or other shunt-directed therapy ideally addresses all three forms of shunt stenosis: bile-related and non–bile-related tract stenoses and hepatic venous stenosis. Arguably, the graft material used would be biocompatible, microporous, nonthrombogenic, and relatively impermeable to bile and tissue and would provide a substrate for endothelial lining. The microstructure of ePTFE can be altered to suit many of these needs. It can be made so that it is less permeable on its abluminal surface while retaining a higher porosity on its endoluminal surface to facilitate endothelialization and healing. This concept should be addressed with the described ePTFE-covered TIPS stent-graft, which has two layers—an outer porous layer and an inner nonporous ePTFE layer—and both a covered and noncovered nitinol stent portion.
ePTFE was used as a cover material for the described nitinol TIPS stent-grafts because clinical and animal studies (17–20) of TIPS created with polyethylene teraphthalate–covered stents have not demonstrated better results than have those of TIPS created with bare stents. The explanation for the high reobstruction rate is the porosity of polyester-covered stent-grafts. This porosity allows transgraft tissue growth, a phenomenon that may limit the success of such covered stent-grafts in humans. Evidence of the obvious bile permeability of polyester is the fact that bile has been detected in human tissue samples from TIPS neointima in these polyester stent-grafts (19).
Nishimine et al (11) and Haskal et al (12) reported the benefits of lining porcine TIPS with ePTFE graft material. Shunts created in pigs typically become highly stenotic or occluded within 2–4 weeks after TIPS creation. ePTFE covering increased patency from 8% to 50% at 1-month follow-up. Haskal and colleagues (12) did not detect bile staining in 50 subsequent porcine ePTFE TIPS stent-grafts. In the Haskal et al study (12), the abluminal surfaces of the porcine grafts were encompassed by a thick layer of myofibroblasts and extracellular collagen matrix identical to that seen narrowing the lumina of TIPS structures in humans.
In our study, two TIPS revisions were necessary because of relative dysfunction caused by the chosen stent-graft diameter, and therefore they were not related to obstruction of the ePTFE-covered TIPS stent-graft. In addition, a number of reinterventions (in nine of 10 patients) still were necessary to maintain shunt function. The majority of TIPS revisions were necessary because of hepatic vein stenosis above the grafted portion. Thus, long-term uninterrupted patency can be achieved only with optimal and precise placement up to the IVC, which has been reported as critical for success (14).
At the beginning of our study, we did not choose to cover the complete tract, to avoid a partial Budd-Chiari syndrome, by blocking the hepatic veins causing thrombosis. All patients with complete coverage of the hepatic vein (patients 9 and 10) were symptom free at follow-up (up to 460 and 451 days, respectively), with no signs of hepatic infarction or partial Budd-Chiari syndrome. We did not detect signs of hepatic infarction or potential graft infection at follow-up examinations. These results demonstrate the feasibility and safety of complete tract coverage. In addition, these findings, combined with the results obtained by Haskal (14), indicate that complete coverage seems to be advisable for realizing the high potential of ePTFE stent-grafts for revision-free long-term patency.
In previous randomized clinical trials (21–28) to compare TIPS creation with endoscopic therapies, the average rate of variceal rebleeding after TIPS creation was reported to be 0%–47%. In nearly all cases, the rebleeding after TIPS creation was related to shunt stenosis or occlusion. If the problem of TIPS stenosis were solved, or at least markedly reduced, then the absolute rates of TIPS-related rebleeding would decrease further, as would the number of required surveillance examinations and invasive shunt revisions and their associated costs and patient morbidity.
These issues were partly considered in two human trials (13,14) involving the use of ePTFE stent-grafts for the creation and revision of TIPS. However, even with all the reports combined, experience with TIPS stent-grafts in humans is still limited, especially compared with the experience with bare stents, or compared with alternative treatment modalities such as sclerotherapy and/or banding in patients with recurrent variceal bleeding or paracentesis in patients with ascites. In neither of the two human trials was a homogeneous study population documented; thus, all results previously obtained can be categorized as evidence of technical feasibility for use in humans, with potential prospects for longer patency rates if the procedures are used correctly. We conclude from the results of these previous studies and our studies that there were no early shunt failures after TIPS creation with stent-grafts or device-related complications such as graft infection.
The long-term patency rates from our study are lacking. Another limitation was the relatively small number of patients included. However, the mid-term follow-up results showing an absence of in-graft stenosis are promising. To our knowledge, there currently is no valid study with a description of any beneficial effect of oral anticoagulation or antiplatelet medication alone on TIPS patency rates (29,30). It is our opinion that the platelet aggregation inhibitors used in our study did not influence the good in-graft patency rates, although it was our intent to prevent early stent-graft thrombosis. Bridging the complete tract to the IVC could result in higher patency rates and reduced reintervention costs in the long-term and thus make TIPS a more economic solution for the treatment of portal venous hypertension and its associated complications, despite the higher costs for the graft (14). However, the potentially higher unobstructed patency rates associated with a higher incidence of encephalopathic complications might restrict the broad use of TIPS. In addition, the potential graft infections in cases of bacteriemia, which often occur after TIPS creation, must be taken into account (31,32).
The main findings of the present study are that (a) when the described commercially developed ePTFE-covered nitinol stent-graft was used for the first time to effectively create TIPS, we observed no device-related complications, and (b) there was no in-graft neointimal formation for up to 1 year, as demonstrated on follow-up venograms. These findings demonstrate a high potential for uninterrupted patency after TIPS creation. The results reported herein confirm the promising results of previous studies (13,14). In summary, our study results demonstrate the feasibility and potential efficacy of creating TIPS with an off-the-shelf commercially available TIPS stent-graft. Prolonged shunt patency upon complete TIPS tract coverage from the time of shunt creation might be achieved. Before the practical value of these stent-grafts can be completely assessed, however, the reported results must be confirmed in larger prospective randomized trials in which TIPS stent-grafts are compared with bare stents. Such trials are currently underway.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Author contributions: Guarantors of integrity of entire study, M.C., J.L.; study concepts, M.C., M.P.R., S.A.T., K.H., J.L.; study design, M.C., M.P.R., J.L.; literature research, M.C.; clinical studies, M.C., S.A.T., K.H., M.S., J.L.; data acquisition, M.C., S.A.T., K.H., M.S., J.L.; data analysis/interpretation, M.C., M.P.R., S.A.T., K.H., J.L.; statistical analysis, M.C.; manuscript preparation, M.C., J.L.; manuscript definition of intellectual content, M.C., M.P.R., S.A.T., K.H., J.L.; manuscript editing, revision/review, and final version approval, all authors.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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  H. Hoppe, S. L. Wang, and B. D. Petersen Intravascular US-guided Direct Intrahepatic Portocaval Shunt with an Expanded Polytetrafluoroethylene-covered Stent-Graft Radiology, January 1, 2008; 246(1): 306 - 314. [Abstract] [Full Text] [PDF]
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R. Gandini, D. Konda, and G. Simonetti Transjugular Intrahepatic Portosystemic Shunt Patency and Clinical Outcome in Patients with Budd-Chiari Syndrome: Covered versus Uncovered Stents Radiology, October 1, 2006; 241(1): 298 - 305. [Abstract] [Full Text] [PDF]
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C. T. Lau, M. Scott, S. W. Stavropoulos, M. C. Soulen, J. A. Solomon, and T. W. I. Clark Dacron-covered Stent-Grafts in Transjugular Intrahepatic Portosystemic Shunts: Initial Experience Radiology, August 1, 2005; 236(2): 725 - 729. [Abstract] [Full Text] [PDF]
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P. Rossi, F. M. Salvatori, F. Fanelli, M. Bezzi, M. Rossi, G. Marcelli, D. Pepino, O. Riggio, and R. Passariello Polytetrafluoroethylene-covered Nitinol Stent-Graft for Transjugular Intrahepatic Portosystemic Shunt Creation: 3-year Experience Radiology, June 1, 2004; 231(3): 820 - 830. [Abstract] [Full Text] [PDF]
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 D. C. Madoff, M. J. Wallace, K. Ahrar, and R. R. Saxon TIPS-related Hepatic Encephalopathy: Management Options with Novel Endovascular Techniques RadioGraphics, January 1, 2004; 24(1): 21 - 36. [Abstract] [Full Text] [PDF]
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M. J. Wallace, K. Ahrar, L. C. Stephens, and K. C. Wright Transvenous Extrahepatic Portacaval Shunt: Feasibility Study in a Swine Model Radiology, July 1, 2003; 228(1): 119 - 125. [Abstract] [Full Text] [PDF]
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