Rolf W. Gunther, MD • Dierk Vorwerk, MD • Klaus Bohndorf, MD • Klaus C. Klose, MD •
`Dieter Kistler, MD • Helmut Mann, MD • Heinz G. Sieberth, MD • Adam El-Din
`
`Venous Stenoses in Dialysis Shunts: Treatment
`with Self-expanding Metallic Stents1
`
`A flexible, self-expanding metallic
`endoprosthesis was employed for
`the treatment of venous outflow
`stenoses in four patients with a poly-
`tetrafluoroethylene shunt and two
`patients with a Brescia-Cimino
`shunt. The stenoses had led to shunt
`occlusion in five patients and to
`flow impairment in one. In the oc-
`cluded shunts, thrombectomy and
`subsequent balloon angioplasty
`were performed in four patients,
`and percutaneous recanalization
`with angioplasty was performed in
`one. One shunt with decreasing
`flow was percutaneously dilated.
`Since the underlying stenoses re-
`curred in four patients after 24
`hours and did not respond suffi-
`ciently to angioplasty in two pa-
`tients, up to four stents were placed
`in the venous segments. Thrombosis
`of the stents occurred in two pa-
`tients after 24 hours and in one after
`6 weeks and was successfully reca-
`nalized with thrombectomy in two.
`At 2-6 months follow-up, the stents
`and the shunts were patent in five
`patients. In three of these patients,
`intima hyperplasia, associated with
`narrowing of the stent lumen in
`two, was noted within 4 months af-
`ter stent placement.
`
`Index terms: Dialysis, shunts • Interventional
`procedures, 91.456 • Veins, grafts and prosthe-
`ses
`
`Radiology 1989; 170:401-405
`
`1 From the Departments of Diagnostic Radi-
`ology (R.W.G., D.V., K.B., K.C.K.), Plastic and
`Reconstructive Surgery (O.K.), and Internal
`Medicine (H.M., H.G.S.), Klinikum, University
`of Technology, Pauwelsstrasse 1, D-5100 Aa-
`chen, Federal Republic of Germany; and Me-
`din vent SA, Lausanne, Switzerland (A.E.). Re-
`ceived May 17, 1988; revision requested June
`29; revision received August 29; accepted Sep-
`tember 20. Address reprint requests to R.W.G.
`c RSNA, 1989
`
`V ASCULAR stents or endopros-
`
`theses are new clinical adjuncts
`to balloon angioplasty. As early as
`1969, Dotter (1) reported his first ex-
`perimental results with the stenting
`of vessels. Experimental studies were
`also performed with other devices
`(2-6), but the clinical application of
`venous stents is still rather limited
`and mostly restricted to arteries (7-
`9). To our knowledge, there are few
`reports on venous applications (10-
`12).
`Vascular endoprostheses seem to
`provide a framework that prevents
`vascular restenoses and maintains
`the patency of the vessel following
`balloon dilation. Stents have also
`been shown to be useful in reopen-
`ing vessels compressed by extrinsic
`tumors (12). Zollikofer et al (10) re-
`cently reported one case of a failing
`hemodialysis shunt treated with an
`intraluminal stent. We report our
`preliminary experience in six pa-
`tients with the same type of stent for
`the treatment of venous stenoses in
`hemodialysis shunts.
`
`PATIENTS AND METHODS
`The endoprosthesis used (Wallstent;
`Medin vent SA, Lausanne, Switzerland) is
`a tube woven from stainless steel alloy fil-
`aments (0.08-0.10 mm) and is described
`in detail elsewhere (2,10). The stent is
`flexible, self-expanding, and available in
`lengths of 10-100 mm and diameters of
`2.5-14 mm. The standard stents we used
`measured 6-10 mm in diameter when
`fully expanded and were 35 and 65 mm
`long. If larger segments had to be stented,
`several stents were placed in an overlap-
`ping manner with an overlap of at least
`10 mm. With too short an overlap, the ex-
`panding stents may retract and discon-
`nect from each other.
`The delivery system consists of a 7-F in-
`vaginated balloon catheter on which the
`constrained stent is mounted. When the
`delivery balloon is inflated with contrast
`medium (iopamidol) up to 3.5 atm, the
`friction between the membranes of the
`inverted balloon is reduced so the stent
`
`can be deployed easily by withdrawing
`the outer membrane of the balloon. Thus,
`the woven metallic stent progressively
`expands and affixes to the vessel wall
`(Fig 1).
`If necessary, the procedure can be dis-
`continued by removing the hydraulic
`pressure from the balloon. The stent, still
`within the balloon, can then be recovered
`through a 7-F introducer sheath, which is
`premounted on the introducer catheter.
`Stent deployment is controlled continu-
`ously under fluoroscopic guidance. The
`stent itself is radiopaque; additional metal
`markers on the delivery catheter permit
`the exact placement of the endoprosthe-
`sis. Once the stent is completely open, it
`can no longer be removed percutaneous-
`ly.
`Four patients with synthetic hemodial-
`ysis grafts made of polytetrafluoroethyl-
`ene (PTFE) (Fig 2) and two patients with a
`Brescia-Cimino (BC) (Fig 3) forearm shunt
`were treated.
`Four of the six patients had already un-
`dergone several shunt operations on both
`arms and had finally received a secondary
`synthetic (PTFE) shunt. Two patients pre-
`sented with shunt problems for the first
`time. Two patients had developed recur-
`rent stenoses following previous angio-
`plasty. The shunt was completely occlud-
`ed in five patients (three with the PTFE
`shunt and two with the BC shunt), and in
`one patient shunt function had deterio-
`rated.
`In all PTFE shunts, the graft was surgi-
`cally cleaned of thrombi and hyperplastic
`intima with a Fogarty balloon catheter.
`Thrombectomy was also performed in
`one of the BC shunts. The second occlud-
`ed BC shunt was only percutaneously di-
`lated and stented (Fig 3). Since images of
`the shunt revealed additional stenoses in
`the draining vein following operative re-
`vision, angioplasty was performed with a
`6- or 7-mm balloon with pressures of 10-
`12 atm. If the stenoses did not respond
`sufficiently to dilation or had recurred,
`they were stented with the Wallstent.
`The procedure was performed with lo-
`cal anesthesia. In the PTFE shunts, the
`draining vein was approached percutane-
`
`Abbreviations: BC = Brescia-Cimino, PTFE ..
`polytetrafluoroethylene.
`
`401
`
`W.L. Gore & Associates, Inc.
`Exhibit 1020-1
`
`

`

`ously via the synthetic graft (Fig 2). With
`the BC shunt, the nonoccluded proximal
`part of the draining vein was punctured
`in one patient (Fig 3); in the second pa-
`tient, the stenosis was catheterized via
`the surgically exposed vein near the
`shunt anastomosis.
`Using the Seldinger technique in five
`of six patients, we advanced a 5-F poly-
`ethylene catheter with a slight bend at
`the tip into the draining vein. Once the
`stenosis was overcome, a 0.9-mm guide
`wire was inserted, and the catheter was
`exchanged for an angioplasty balloon
`catheter (6-7-mm balloon). The stenosis
`was dilated several times with pressures
`of 10-12 atm. Since two patients experi-
`enced severe pain during dilation, the
`area around the stenosis was anesthetized
`by means of local infiltration with 1% li-
`docaine. The angioplasty catheter was
`then exchanged for the 7-F delivery cath-
`eter over a guide wire (0.9 mm in diame-
`ter, 2 mm long).
`The diameter of the stent was at least 1
`mm larger than that of the balloon cathe-
`ter used for dilation and varied from 7 to
`10 mm when fully expanded. The origi-
`nal diameter of the vessel was roughly es-
`timated on the basis of the pre- and post-
`stenotic size of the vessel. In only one pa-
`tient who had a small 4-mm outflow vein
`joining a larger vein, an oversize stent of
`6 mm in diameter was used to effect an
`adequate lumen. In this patient, the stent
`was dilated later with a 6-mm balloon,
`since it did not open satisfactorily after
`insertion.
`Prior to stent placement, patients re-
`ceived intravenous injection of 5,000 IU
`heparin, which was continued at 500 IU
`in one patient and at 1,000 IU in three for
`
`24-36 hours. Three patients were treated
`with peroral platelet inhibitors (500 mg/d
`aspirin) following the procedure.
`The patients were followed up between
`2 and 6 months with intravenous or intra-
`arterial fine-needle digital subtraction an-
`giography at intervals of 6-8 weeks or
`earlier if shunt flow decreased.
`
`RESULTS
`All patients but one underwent
`thrombectomy prior to angioplasty
`and stent insertion. In one patient
`with a BC shunt, the occluded ve-
`nous segment was recanalized exclu-
`sively by percutaneous means (Fig 3).
`The underlying cause of shunt occlu-
`sion in five patients and shunt dys-
`function in one patient was venous
`outflow stenosis. In addition, all pa-
`tients with PTFE shunts had pseu-
`dointimal proliferation within the
`graft as demonstrated during throm-
`bectomy.
`Venous outflow stenoses ranged
`from 3 to 13 em long. They recurred
`24 hours after balloon angioplasty in
`four patients and did not respond
`sufficiently to dilation in two, de-
`spite the high pressure applied (10-
`12 atm). Since the individual lengths
`of the stents were 3.5 and 6.5 em
`each, several had to be used in four
`patients to stent the stenosis ade-
`quately. One patient received four
`stents and three patients received
`two stents in an overlapping manner,
`and two patien~s received one stent.
`
`Thus, the stents covered venous seg-
`ments of 3.5 em (two patients), 4.5
`em, 5.5 em, 7 em, and 16 em in
`length. Improved shunt flow and
`improved patency of the stenoses
`were evident immediately after stent
`insertion . The stenoses were still visi-
`ble but less pronounced (Figs 2, 3).
`The constant pressure on the vessel
`wall caused the stents to fully open
`within 1-2 weeks after insertion.
`In one patient with a BC shunt, the
`vein was 4 mm in diameter after dila-
`tion with a 5-mm balloon. After the
`
`Images show self-expanding
`Figure 1.
`stent being deployed by gradual withdrawal
`of the invaginated balloon.
`
`c.
`e.
`a.
`b.
`f.
`d.
`Images of a 79-year-old patient show angioplasty and insertion of a self-expanding stent in an occluded hemodialysis shunt
`Figure 2.
`(PTFE) that resulted from stenosis of the draining vein. (a) After thrombectomy of the graft, severe stenosis was found in the draining vein.
`Arrows indicate cephalad direction of the shunt flow. Arrowheads indicate retrograde filling of a side branch. (b) Improved patency is ap-
`parent after balloon dilation ( 12 atm) of the stenosis. (c) After insertion of one stent (3.5 em long, 10 mm in diameter), the draining vein is
`fully patent. No extravasation occurred. (d) Two months later, the stenosis recurred distal to the stent. (e) Insertion of a second stent overlap-
`ping the first. Note patency of the covered side branch immediately after stent placement. (f) Good patency of the stents and the bridged
`side branches after 3 months. Shunt functioned well until patient died of heart failure 6 months after stent placement.
`
`402 • Radiology
`
`February 1989
`
`W.L. Gore & Associates, Inc.
`Exhibit 1020-2
`
`

`

`insertion of a 6-mm stent, however,
`the flow did not improve, since the
`stent did not open satisfactorily. For
`this reason, the stent was dilated
`with a 6-mm balloon, which resulted
`in an immediate improvement of
`flow . However, thrombosis devel-
`
`oped in the vein within 24 hours, de-
`spite the administration of 1,000 IU I
`h heparin. Thrombectomy was per-
`formed twice and resulted in tempo-
`rary patency for 24 hours. Although
`an image of the shunt did not show
`an obstacle either on the arterial or
`
`a.
`
`b.
`
`c.
`
`d.
`
`e.
`
`Volume 170 • Number 2
`
`the venous side, the shunt occluded
`again and could not be salvaged.
`Of the three patients receiving two
`stents, two were treated in two ses-
`sions (ie, after intervals of 1 week
`and 2 months). In the first patient,
`the shunt occluded 24 hours after
`thrombectomy and percutaneous
`stent insertion. It was assumed that
`the shunt had to be abandoned, but
`after a second thrombectomy of the
`graft was performed 1 week later, an
`image of the shunt revealed a recol-
`lapsing venous stenosis distal to the
`stent as the cause of the early shunt
`occlusion. The second overlapping
`stent placed in the stenotic vein
`yielded the desired patency. In the
`second patient, only the tightest part
`of the stenosis was stented initially,
`since the rest of the stenosis respond-
`ed well to angioplasty. Two months
`later, however, the stenosis distal to
`the stent recurred and was then suc-
`cessfully stented with a second endo-
`prosthesis (Fig 2).
`Thrombosis of the stent developed
`in three patients. Early thrombosis of
`the stent occurred in two patients af-
`ter 24 hours, despite anticoagulation
`treatment with 1,000 IU /h heparin,
`and was successfully recanalized
`with thrombectomy in one patient.
`Thrombosis in a BC shunt following
`insertion of an oversize stent has
`been previously mentioned. In one
`patient who slept overnight on the
`arm containing the shunt, thrombo-
`sis developed 6 weeks after stent in-
`sertion and was successfully man-
`aged with thrombectomy.
`In three patients with restored
`shunt function (two with PTFE
`shunts and one with aBC shunt), he-
`modialysis was resumed within 24
`hours via the treated shunt. The re-
`maining three patients, two of them
`with early shunt thrombosis, under-
`went hemodialysis via a Sheldon
`catheter.
`The stents and shunts were patent
`in five patients at 2-6 months follow-
`
`Images of a 53-yt.>ar-old man
`Figure 3.
`show percutaneous rt.'canalization of an oc-
`cluded BC shunt and insertion of two over-
`lapping stents. (a) Brachial arteriogram
`shows occlusion of the BC shunt (arrow) at
`the venous anastomosis of the radial artt.>rv.
`(b) Puncture of the palpable draining vei~
`and catheterization of occludt.>d venous seg-
`ment with a 5-F catheter with a slight bend
`at tip. (c) lnsufficienl shunt function after
`balloon dilation (6-mm balloon) of the oc-
`cluded segment. (d) Insertion of two over-
`lapping stents (3.5 em long. 7 mm in diame-
`ter). (e) Good patency of the shunt (arrow) is
`apparent after stent placement. Follow-up is
`currently at 2 months.
`
`Radiology • 403
`
`W.L. Gore & Associates, Inc.
`Exhibit 1020-3
`
`

`

`up. There was no stent migration. In
`two patients, intima hyperplasia with
`narrowing of the stent lumen was
`noted within 4 months after stent
`placement (Fig 4). Discrete intima
`hyperplasia without stenosis was ob-
`served in one patient. One 79-year-
`old patient without shunt problems
`after stent placement died 6 months
`later of heart failure (cause of death
`unrelated to the procedure). A speci-
`men of the stented vein was not ob-
`tained.
`
`DISCUSSION
`Nonoperative techniques for the
`management of complications in he-
`modialysis shunts are of increasing
`importance. Shunt occlusion and
`graft thrombosis are the complica-
`tions most frequently encountered
`and usually result from venous out-
`flow stenoses or, less often, from in-
`adequate inflow due to arterial le-
`sions (13-16). In the patients in our
`study, venous outflow obstruction
`was the basic problem.
`To salvage shunts, surgical correc-
`tion of such venous stenoses has
`been preferred for a long time
`(14,15). Stenoses can also be treated
`percutaneously with balloon angio-
`plasty, and thrombosis can either be
`lysed with selective infusion of uro-
`kinase or mechanically fragmented
`(I 7 -19). Balloon angioplasty may also
`be combined with thrombectomy
`and removal of the neointima within
`the graft to restore shunt patency
`(I 8). Long-term results in the repair
`of stenosed hemodialysis shunts with
`angioplasty are not perfect, as the
`shunts have a 1-year patency rate of
`45% ( 19). The self-expanding, flexible
`metallic stent used in this small se-
`ries may help improve long-term
`shunt function.
`Venous stenoses in hemodialysis
`shunts are due to fibrosis and intima
`hyperplasia and are often found in
`secondary shunts such as PTFE
`shunts (13-16). These stenoses may
`be extremely tight and resist com-
`plete dilation even at high pressures.
`The purpose of the treatment de-
`scribed is to achieve and maintain
`the patency of the stenosis with the
`insertion of a self-expanding metallic
`stent.
`Several types of stents have been
`described in the literature (1-10). The
`stent used in this series is flexible,
`self-expanding, and woven from fine
`stainless steel wires and covers only
`20% of the vessel surface (2). Most
`important for the treatment of tight
`stenoses is the fact that the stent ex-
`
`404 • Radiology
`
`c.
`a.
`b.
`Images of a 29-year-old man show angioplasty and stent placement in a failing
`Figure 4.
`hemodialysis shunt (PTFE). Intima hyperplasia developed within the stent after 4 months.
`(a) Image of shunt after dilation of a recurrent venous stenosis (after successful balloon an-
`gioplasty 5 months previously). (b) Good patency after angioplasty with a 7-mm balloon and
`after insertion of two overlapping stents (3.5 em long, 8 mm in diameter). (c) Four months
`after insertion, the stents are expanded, but hyperplastic intima narrows the lumen. Shunt is
`still functioning.
`
`erts constant pressure on the wall un-
`til the stenosis is opened to the pre-
`determined diameter of the stent.
`Vascular stents appear promising,
`but their biocompatibility must be
`thoroughly investigated. From ani-
`mal experiments (2,3,10), it is known
`that the stents, although thrombo-
`genic, are well tolerated and are cov-
`ered with endothelium within a few
`weeks. Although Rousseau et al (2)
`and Zollikofer et al (10) did not ob-
`serve intima hyperplasia or observed
`only minimal proliferation in normal
`veins in their experimental series, in-
`tima hyperplasia may develop within
`stented veins in humans (Fig 4). Zol-
`likofer et al (10) recently described
`two cases in which intima hyperpla-
`sia had developed in a stented vein
`within 6 weeks after stent placement.
`This may also occasionally occur in
`femoral arteries in humans, accord-
`ing to our limited experience in 50
`patients with arterial stents.
`The mechanism of intima hyper-
`plasia may be partly explained by the
`studies of Duprat et al (3). In canine
`arteries, they showed that a stent/ar-
`
`tery ratio of more than I :2 is associat-
`ed with increased intima prolifera-
`tion and thrombosis. Thus, it seems
`to be important to avoid oversize
`stents and overstretching of the ves-
`sel.
`The early complications of stents
`that result in thrombosis may be
`managed with thrombectomy or local
`thrombolysis (10). In our small series,
`despite thrombectomy and subse-
`quent administration of 1,000 IU /h
`heparin, one occluded shunt could
`not be kept patent, although there
`was no evidence of a vascular obsta-
`cle on angiograms. Whether the
`oversize stent resulted in over-
`stretching of the vein is a matter for
`consideration. In this patient, the
`shunt could not be salvaged. Late
`thrombosis in one patient may be at-
`tributed to the fact that the patient
`slept on the arm containing the
`shunt.
`Long-term results will certainly
`depend on the degree of intima pro-
`liferation narrowing the venous lu-
`men and on the characteristics of the
`venous wall adjacent to the stent.
`
`February 1989
`
`W.L. Gore & Associates, Inc.
`Exhibit 1020-4
`
`

`

`Significant intima hyperplasia with-
`in the stent was noted in two of five
`patients (Fig 4) and had not jeopar-
`dized shunt function. Should the hy-
`perplasia progress, angioplasty will
`be scheduled. In one of our patients,
`progression of the stenosis distal to
`the stent was observed and then
`treated with a second stent (Fig 2).
`Interestingly, side branches of the
`stented veins may remain open (Fig
`2e, 2f), a phenomenon also observed
`in arteries (2).
`Intravascular stenting of venous
`outflow stenoses is suited for PTFE
`grafts, as the stent does not affect the
`puncture site for hemodialysis. In BC
`shunts, however, a venous segment
`long enough for puncture should be
`retained (Fig 3) because the stent can-
`not be punctured. The stent can be
`palpated and avoided during punc-
`ture. If the venous segment to be
`punctured is too short, stenting of
`the stenosis is useless.
`Regarding the early use of the he-
`modialysis shunt following stent
`placement, we would not consider it
`necessary to spare the shunt with
`fully restored function for a certain
`period of time.
`Although long-term results are
`currently lacking and the rate of
`long-term patency has yet to be es-
`tablished, we consider this technique
`to be a useful adjunct to balloon an-
`gioplasty in the nonoperative man-
`agement of a failing hemodialysis
`shunt. In postangioplasty dialysis
`shunt stenoses, Glanz et al (19) re-
`ported a 1-year patency rate of 45%
`and a 2-year patency rate of 24%. The
`results with long stenoses of more
`than 4 em were even poorer. Thus,
`
`angioplasty alone does not solve the
`problem of recurrent venous outflow
`obstruction, but we E:Xpect to im-
`prove the long-term results with the
`intravascular stent-particularly in
`the stenoses of long segments-and
`to prolong shunt patency. Since pa-
`tients undergoing hemodialysis have
`to also undergo multiple surgical cor-
`rections of their vascular accesses,
`prolongation of shunt patency of
`even 6-9 months may be regarded as
`a benefit.
`•
`
`References
`1. Dotter C. Transluminally-placed coil-
`spring endoarterial tube grafts: long-term
`patency in canine popliteal artery. Invest
`Radioll969; 57:5-10.
`2. Rousseau H, Puel J, Jaffrey F, et al. Self-
`expanding endovascular prosthesis: an ex-
`perimental study. Radiology 1987;
`164:709-714.
`3. Duprat G Jr, Wright KC, Charnsangavej C,
`Wallace S, Gianturco C. Self-expanding
`metallic stents for small vessels: an experi-
`mental evaluation. Radiology 1987;
`162:469-472.
`4. Lawrence DO Jr, Charnsangavej C, Wright
`KC, Gianturco C, Wallace S. Percutane-
`ous endovascular graft: experimental eval-
`uation. Radiology 1987; 163:357-360.
`5. Maass D, Zollikofer CL, Largiader F, Sen-
`ning A. Radiological follow-up of trans-
`luminally inserted vascular endoprosthe-
`ses: an experimental study using expand-
`ing spirals. Radiology 1984; 152:659-663.
`6. Palmaz JC, Sibbitt RR, Reuter SR, Tio FO,
`Rice WJ. Expandable intraluminal graft:
`a preliminary study. Radiology 1985;
`156:73-77.
`7. Palmaz JC. Balloon-expandable intravas-
`cular stent. AJR 1988; 150:1263-1269.
`8. Sigwart U, Puel J, Mirkovirtch V, Joffre F,
`Kappenberger L. Intravascular stents to
`prevent occlusion and restenosis after
`transluminal angioplasty. N Eng! J Med
`1987; 316:701-706.
`9. Strecker EP, Romaniuk R, Schneider B, et
`al. Perkutan implantierbare, durch bal-
`lon aufdehnbare gefassprothese. Dtsch
`Med Wochenschr 1988; 113:538-542.
`
`10. Zollikofer CL, Largiader l, Briihlman WF,
`Uhlschmid GK, Marty AH. Endovascular
`stenting of veins and grafts: preliminary
`clinical experience. Radiology 1988;
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`11. Charsangavej C, Carrasco CH, Wallace S,
`et al. Stenosis of the vena cava: prelimi-
`nary assessment of treatment with ex-
`pandable metallic stents. Radiology 1986;
`161:295-298.
`12. Putnam JS, Uchida BT, Antonovic R,
`ROsch J. Superior vena cava syndrome as-
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`ment with expandable wire stents. Radiol-
`ogy 1988; 167:727-728.
`13. Connolly JE, Brownell DA, Levine EF,
`McCart M. Complications of renal dialy-
`sis access procedures. Arch Surg 1984;
`119:1325-1328.
`14. Raju S. PTFE grafts for hemodialysis ac-
`cess: techniques for insertion and man-
`agement of complications. Ann Surg 1987;
`206:666-673.
`15. Palder SB, Kirkman RL, Whittemore AD,
`Hakim RH, Lazarus M, Tilney NL. Vas-
`cular access for hemodialysis: patency
`rates and results of revision. Ann Surg
`1985; 202:235-239.
`16. Kherlakein GM, Roedersheimer LR, Ar-
`baugh JJ, Newmark KJ, King LR. Com-
`parison of autologous fistula versus ex-
`panded polytetrafluoroethylene graft fis-
`tula for angioaccess in hemodialysis. Am J
`Surg 1986; 152:238-243.
`17. Davis GB, Dowd CF, Bookstein JJ, Ma-
`roney TP, Lang EV, Halasz N. Throm-
`bosed dialysis grafts: efficacy of intra-
`thrombotic deposition of concentrated
`urokinase, clot maceration, and angio-
`plasty. AJR 1987; 149:177-181.
`18. Smith TP, Hunter OW, Darcy MD, Casta-
`neda-Zuniga WR, Amplatz K. Throm-
`bosed synthetic hemodialysis access fistu-
`las: the success of combined thrombec-
`tomy and angioplasty (technical note).
`AJR 1986; 147:161-163.
`19. Glanz S, Gordon DH, Butt KMH, Hong J,
`Lipkowitz GS. The role of percutaneous
`angioplasty in the management of chronic
`hemodialysis fistulas. Ann Surg 1987;
`206:777-781.
`
`Volume 170 • Number 2
`
`Radiology • 405
`
`W.L. Gore & Associates, Inc.
`Exhibit 1020-5
`
`