Percutaneous Balloon-assisted Aspiration Thrombectomy of Clotted Hemodialysis Access Grafts

Dialysis Access Intervention

Percutaneous Balloon-assisted Aspiration Thrombectomy of Clotted Hemodialysis Access Grafts1 Melhem J.A. Sharafuddin, MD Saadoon Kadir, MD Subash J. Joshi, MD David Parr, R N Index terms: Dialysis, shunts, 91.452 Grafts, interventional procedure Grafts, stenosis or thrombosis Thrombectomy Abbreviation: BAT= balloon-assisted aspiration thrombectomy

JVIR 1996;7:177-183

'From the Department of Radiology, S t Louis University Health Sciences Center, St Louis, MO(M.J.A.S., s.K.); N O I - ~ ~ County Radiology, 3156 Pershall ~ ds t, Louis, MO 63136 (S.K., D.P.);and Metro

North St. Louis (S.J.J.). From the 1995 SCVIR annual meeting. Received April 13, 1995; revision requested May 24; final revision received September 14; accepted September 18. Address correspondence to M.J.A.S.

o SCVIR, 1996

PURPOSE: To present experience with percutaneous balloon-assisted aspiration thrombectomy (BAT)for the treatment of patients with clotted hemodialysis access grafts. MATERIALS AND METHODS: BAT was performed with use of 7-F intravascular sheaths and a Fogarty balloon catheter. It was tested with an in vitro flow-circuit model. Twenty consecutive BAT procedures were performed in 15 patients with clotted grafts. The balloon catheter was advanced through the sheath to the arterial anastomosis. The balloon was inflated and withdrawn while suction was applied from the sideport to recover thrombus. The procedure was repeated for the venous limb. BAT was used alone in 12 procedures and in combination with urokinase in eight procedures. RESULTS: Almost complete thrombectomy was achieved in all tubes (in vitro), with very low venous and arterial embolic fractions. Technical success (restored graft thrill and almost complete thrombectomy) was achieved in 18 cases (90%).Clinical success (patency after l week of dialysis) was achieved in 17 cases (85%). CONCLUSION: Percutaneous BAT is feasible in recently clotted dialysis grafts. THE advantages of mechanical techniques for revascularization of clotted hernodialysis access grafts include shortened procedure time, decreased bleeding risk, and lower cost (1-11). Despite their growing popularity, percutaneous balloon catheter thrombectomy techniques that involve the deliberate embolization of thrombus into the central venous circulation remain controversial (6,121. In this report, we describe balloon-assisted aspiration thrombectomy (BAT), a new percutaneous mechanical thrombectomy technique for the treatment of clotted dialysis grafts in the outpatient interventional radiology practice setting. BAT was designed to improve the eaciency of aspiration of soft thrombus, compared with unassisted aspiration. It was also designed to reduce the risk of venous embolization, with the risks of current balloon catheter-mediated

mechanical thrombectomy techniques. BAT involves the combination of thrombus pullback (via a compliant balloon catheter) with an aspiration thrombectomy mechanism. The findings presented here from in vitro experiments and early clinical experience demonstrate the feasibility of this technique.

MATERIALS AND METHODS Basic BAT Technique While suction is applied from the side arm of an introducing sheath, clot is pulled back with a coaxially inserted Fogarty balloon catheter (Baxter, Deerfield, 111). In addition to providing a thrombus-sweeping effect, the compliant Fogarty balloon catheter maintains a seal against the graft wall during pullback that results in a pressure buildup within the lumen. This favors rapid aspiration and fragmentation of soft

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thrombus. The pressure surge within the lumen during the pullback maneuver may be greatly accentuated in the presence of outflow stenosis, and can result in a steeper aspiration gradient. As a result, BAT produces its thrombectomy effect by means of the dual mechanisms of brisk aspiration of soft thrombus and direct thrombus disruption and mechanical thrombolysis due to forced transit of clot through narrow passages. In addition, the rapid transit of aspirate into the sheath results in a Venturi effect that favors aspiration of additional clot material not mobilized by the balloon.

In Vitro Experiments Six polyvinyl tubes (transparent, smooth walled, 30 cm long, 7 mm inner diameter) were filled with fresh human blood collected from one healthy volunteer. The blood was allowed to clot a t 4°C for 24-48 hours. Thrombus volume in each clotted tube was calculated by subtracting the serum volume from the volume of blood initially placed in the tube. Mean thrombus volume per tube was 6.8 mm3 (range, 6.5-7.2 mm3). Each tube was placed in a flow circuit perfused with normal saline solution a t 50 mm Hg, in parallel with a low-resistance bypass conduit. Filters (80-pm pores; adapted from the Fenwal transfusion set, Baxter, Deerfield, Ill) were interposed in the inflow and outflow limbs to trap "arterial" and "venous" emboli, respectively. BAT was performed with a 4F Fogarty balloon catheter that was inflated with 1mL of saline. The balloon catheter was advanced coaxially through a 7-F sheath (Cook, Bloomington, Ind), introduced from the "venous" end of the clotted tube (Fig 1). Manual suction was maintained from the side port of the sheath by a second operator as the inflated balloon was pulled back. Thrombectomy fraction was defined as the thrombus aspirated or lysed during BAT, in addition to the embolized thrombus. This fraction was calculated by subtracting residual volume of clot in the tube from the initial volume of clot and dividing the difference by the initial

Figure 1. (a) Flow-circuit model used for in vitro evaluation of BAT is shown. (b) In vitro BAT maneuver, performed in a clotted tubular graft model via a single access "venous-end" sheath, is shown.

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volume of clot. Residual and embolic thrombus fractions were also determined by calculating their respective volume ratios relative to initial clot volume.

Clinical Application Patient selection.-From May to November 1994,20 consecutive BAT procedures were performed in 15 patients with acutely thrombosed polytetrafluoroethylene hemodialysis access grafts. There were 12 tube grafts and three loop grafts. Fourteen grafts were in the forearm, and one was in the upper arm. There were six men and nine women aged 40-88 years (average, 60 years). The average approximate time that had passed since graft thrombosis was 36 hours (range, 12-72 hours). Most procedures were performed in a private outpatient interventional radiology practice setting. Appropriate informed consent was obtained before all procedures. Premedication and monitoring.All procedures were performed with patients in a state of conscious sedation. Analgesia was achieved with intravenously titrated midazolam (Versed; Roche Laboratories, Nutley, NJ) and fentanyl citrate (Janssen Pharmaceuticals, Titusville, Fla). We did not routinely administer prophylactic antibiotics before

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the procedures. Pulse oximetry, respiratory rate, and hemodynamic parameters were continuously monitored during and immediately after the procedure. Graft access.-After local anesthetic infiltration, a single-wall, 18gauge, angiographic needle was used to puncture the graft. Graft thrombosis was confirmed by gently injecting contrast material. Access of both arterial and venous ends was achieved by using the oppositesheaths technique (Fig 2). In two grafts (straight, tubular configuration) in which BAT was used subsequent to initial pharmacothrombolytic therapy, there was only one access site via a sheath placed a t the venous end of the graft. The sheaths served as ports for coaxial functions (such as central venous mapping, BAT, directed pharmacothrombolysis, balloon angioplasty, stent placement). BAT maneuver.-A Fogarty balloon catheter, introduced from the venous-end sheath, was advanced toward the arterial anastomosis. I t was inflated near the arterial anastomosis without crossing the presumed location of the arterial anastomotic plug. The arterial anastomosis can be located by using landmarks from prior angiograms, surgical clips, and physical examina-

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Figure 2. (a,b)Clinical technique of percutaneous BAT in a clotted forearm loop graft is shown.

tion with marker placement. Pullback thrombectomy of the soft thrombus residing behind the arterial plug was performed from the arterial end of the graft toward the sheath by withdrawing the Fogarty balloon catheter while constant suction was maintained manually from the side port of the sheath (Fig 2). Next, BAT of the venous end of the graft was performed from the opposite sheath. I t is important that the venous outflow not be pretreated before the initial BAT passes, as this may reduce efficacy and pose a higher risk of central embolization. Additionally, if flow is restored during ongoing BAT, then manual compression can be applied to the arterial end of the graft to ensure graft collapse during aspiration and to reduce blood loss. Multiple BAT maneuvers were repeated until no further thrombus was recovered. If flow was not restored to the graft, then the arterial anastomosis was declotted to restore pulsatile flow into the graft; a collapsed, nonflowing graft after multiple BAT passes indicates persistent occlusive thrombus a t the arterial inflow. Once functional flow was restored, 5,000 IU of heparin was administered directly into the graft, and digital subtraction angiography was performed (with Hexabrix or Conray 60; Mallinckrodt Medical, S t Louis, Mo) to check for residual thrombus and to assess the venous outflow (Fig 3). If a sheath became impacted by aspirated fragments,

the sheath was removed over the wire, declotted manually, and reintroduced. Sheath disimpaction was required a n average of twice per access site per procedure. When the sheath appeared to be damaged, it was exchanged for a new sheath. Adjunctive procedures.-Adjunctive pharmacothrombolytic therapy with 250,000 IU of urokinase (Abbott Laboratories, North Chicago, Ill) was occasionally administered by using the pulse spray method when native venous clot was found or when a substantial residual thrombus persisted after multiple BAT passes. Additional mechanical thrombectomy techniques, other than BAT, occasionally were used to treat refractory thrombus. These techniques included percutaneous transluminal balloon angioplasty for thrombus maceration and compression. Stenotic lesions a t the arterial anastomosis, within the graft, and in the venous outflow were dilated by using transluminal angioplasty balloons (Medi-techBoston Scientific, Watertown, Mass). Directional atherectomy (Simpson catheter; Advanced Cardiovascular Systems, Temecula, Calif) and stent placement (Wallstent; Schneider, Minneapolis, Minn) were reserved for elastic or poorly responsive outflow/venous stenoses. Parameters studied and followup.-Approximate time elapsed since thrombosis (as estimated bv the patient or referring physician or nurse), graft type and configuration,

primary and adjunctive procedures, number of BAT passes, and volume of aspirate were recorded. Procedure duration (time from the beginning of the procedure to its termination including access, thrombectomy, thrombolysis or other adjunctive procedures, and hemostasis) and thrombectomy time (time required to establish unrestricted flow through the graft) were noted. Technical success was defined as restored graft pulse and complete or near-complete thrombectomy seen a t digital subtraction angiography. Clinical success was defined as graft patency after 1 week of dialysis. Follow-up after BAT was obtained by reviewing the records from the dialysis unit and the outpatient interventional radiology center to determine graft function, patency, angiographic follow-up, and the need for subsequent surgical procedures (be it graft revision or replacement). Graft failure was defined as referral to surgery. "Primary patency" was used to describe graft patency after a successful initial BAT treatment, whereas "secondary patency" was used to refer to the cumulative duration of graft patency after subsequent consecutive BAT or adjunctive procedures that succeeded in restoring or maintaining graft patency. Patency rates were presented in the form of a life table by using the Kaplan-Meier analysis. Mean patency intervals were also determined.

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RESULTS In Vitro Experiments Almost complete thrombectomy was achieved in all six tubes (mean, 99%; range, 97%-100%). A single pass was sufficient in five tubes, and two passes were needed in one tube. Substantial mechanical thrombolysis resulted from clot compression and forced aspiration, with the release of free red blood cells into the eMuent as evidenced a t microscopic examination. Of the recovered particulate thrombus, 98% was aspirated (range, 97%-98%), and 2% was embolized into the venous outflow and trapped in the venous filter (range, 0-2%). No arterial embolization occurred in any of the tubes. The mean total aspirate volume was 50 mL (range, 40-60 mL) and consisted of perfusate, free red blood cells, and particulate clot fragments. The mean total volume of particulate thrombus filtered from the aspirate was 1.75 mL (range, 1.25-2.5 mL).

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Clinical Procedures BAT was used alone (12 procedures) or after an unsuccessful trial of urokinase (two procedures). In a n additional six procedures, BAT was performed initially and was followed by adjunctive urokinase (250,000 IU, pulse-spray infusion) (Table 1). ~h~ average number of BAT passes was five per access (range, 3-10 passes)' The mean of aspirate from passes a flush used in each aspiration syringe) was 105 mL (range, 75-250 mL). Large thrombus fragments were frequently recovered from the aspirate, and the majority of recovered particulate thrombus was aspirated during the first two passes. Total procedure time ranged from 90 to 270 minutes (mean, 175 minutes 55 [standard deviation]). Thrombectomy time ranged from 15 to 125 minutes (mean, 59 minutes & 40). When the use of BAT alone (12 procedures) was compared with the use of BAT combined with urokinase (eight procedures), both the thrombectomy time and the total procedure duration were significantly reduced when BAT was the sole pro-

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Figure 3. Clinical application of percutaneous BAT in a clotted arm loop graft is shown. (a) Digital subtraction angiogram during contrast material injection shows thrombosis of the loop graft. (b) Digital subtraction angiogram of the graft after successful BAT and percutaneous transluminal balloon angioplasty of the venous outflow is shown. ( c ) Digital subtraction angiogram of the graft inflow shows a residual, irregular filling defect a t the arterial anastomosis that corresponds to a partly fragmented arterial plug. (d) The plug is shown to be cleared from the arterial anastomosis after compression and maceration with transluminal balloon angioplasty.

cedure (P < .001 and P < .005, respectively) (Table 2). The hemostasis time varied from 20 to 120 minutes (mean, 35 minutes). We did not measure activated clotting times before access removal. No local or systemic hemorrhagic complications were noted, and no signs or symptoms of pulmonary or peripheral arterial embolism occurred during any of the procedures. Technical success was achieved in 18 procedures (90%)performed in 13 patients, including one procedure in which early thrombosis occurred

within 24 hours. Clinical success was achieved in 17 procedures (85%) performed in 12 patients (Table 2). Mean duration of patency after a technically successful procedure was 102 days f 92 (range, 1-285 days; n = 18). Primary and secondary patency rates were determined, a t follow-up of 6-9.5 months, for all 15 treated patients (including those with technically unsuccessful procedures). Primary patency rate after BAT was 87% initially, and it gradually dropped to 80% a t 1week, 53% a t 4 weeks, 47% a t 12 weeks, and

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central veins have become increasingly popular (6-9,191. However, these techniques pose a risk for Technical Clinical Procedure Thrombectomy symptomatic pulmonary embolism, Success Success Duration* Time* especially in patients with cardiopRate (%) (min) Rate (%) n (min) Procedure ulmonary compromise (12,191. We therefore favor the technique of perAll types 20 175 k 55 59 f 40 90 85 cutaneous BAT in which aspiration BAT alone 12 140k 45 28 f 14 ... ... Combination 8 225f 75 105 f 45 71 71 thrombectomv and thrombus ~ u l l BAT followed 6 220 108 50 50 back are com6ined. by UK Simple percutaneous aspiration UK followed 2 240 95 100 100 thrombectomy, originally described by BAT for peripheral thromboembolectomy (201, has been successfully used as Note.-PTA = percutaneous transluminal angioplasty, UK = urokinase. *Given as mean k standard deviation. an adjunctive form of therapy in cases of clotted hemodialysis access (15). Percutaneous pullback embolectomy into a standard hemostatic sheath with a Fogarty balloon cathTable 1 eter (without concomitant aspira1 Datencv Summary of Procedures Pertion) has been performed in the peformed in Clotted Dialysis Grafts ripheral arteries (21,22). However, Procedures n when the target vessel is larger than the diameter of the sheath, use of BAT pullback embolectomy can result in BAT alone 12 thrombus material remaining in the BAT followed by UK 6 UK followed by BAT 2 lumen or embolizing distally (23). Adjunctive We hypothesized that a technique 0.61 I I I , I 1 ....: . ? .:... PTA 16 which combined balloon thrombecArterial anastomosis 8" tomy and aspiration might provide 0.5 Venous anastomosis 15" 0 5 10 15 efficient thrombectomy in clotted diVenous outflow 5 Weeks alysis grafts while lowering the risk Directional atherectomy 3 of embolization. Figure 4. Life-table analysis of priStent placement 2 mary and secondary graft patency after We demonstrated the feasibility Note.-PTA = percutaneous translua 6-month follow-up period is shown. of BAT with an in vitro model of minal angioplasty, UK = urokinase. clotted dialysis grafts; near-complete "The number of PTA procedures inthrombectomy was achieved in all clude those performed for residual experiments. The predominant fracthrombus or thrombus refractory to underlying central venous stenosis tion of the cleared thrombus was asBAT. in another. Another late graft failpirated (mean, 98%),with a low veure occurred as a result of graft innous and no arterial embolic fracfection, which necessitated graft retion (2% and 0%, respectively), placement. 33% a t 24 weeks; the secondary pawhich demonstrates the low risk of tency rates were 87%, 80%, 73%, embolic com~lications. 60%, and 40%, respectively (Fig 4). Our early experience with 20 proDISCUSSION Mean primary patency interval was cedures performed in patients with Mechanical thrombectomy is be92.5 days f 92.4 (range, 0-215 days; clotted dialysis access grafts also ing used increasingly for percutanen = 151, and mean secondary pademonstrated the clinical feasibility ous declotting of thrombosed dialytency interval was 107.5 days f 105 of BAT. The technical success and sis grafts. It may be used alone or in patency rates achieved with BAT (range, 0-370 days; n = 15). combination with directed pharmaBoth cases of technical failure were comparable to those achieved and the one case of early thrombosis cothrombolytic therapy (1-8,11,13with current standard modalities 18). Mechanical thrombectomy may within 24 hours occurred as a result (6,13,15,24,25).In addition, no emtake the form of external massage, of persistent venous outflow probbolic or hemorrhagic complications aspiration or maceration with rotalems due to the presence of small were encountered. We currentlv use tional devices and baskets, or delibnative veins or a lack of response to BAT as the primary thrombectimy erate central venous displacement. balloon angioplasty. Rethrombosis modality in patients with acutely Mechanical thrombectomy techafter technically successful BAT thrombosed dialysis grafts. BAT niques in which balloon catheters were related to severe hypotension may also be used as an adjunctive during hemodialysis in one graft and are used to sweep thrombus into the modality to reduce the thrombus Table 2 Early Results of BAT

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load before pharmacothrombolysis present in clotted dialysis grafts and can be resistant to standard and meor other thrombectomy techniques. chanical therapies (3). Because of We have successfully used BAT as a the rubberlike consistencv and wall rescue therapy after failed initial adherence of these thromvbi compharmacologic thrombolysis. The pared with fresh thrombi, both the significantly lower primary patency thrombus plug and chronic, wall-adrates (P < .001) noted after six BAT procedures that required subsequent herent thrombi may not be amenable to complete aspiration with adjunctive urokinase therapy (comBAT. Although we have occasionally pared with the rates of 12 procedures in which BAT was used alone) recovered whitish, rubberlike fragments during BAT, refractory reflect the complexity of underlying problems that lead to graft thrombo- thrombus may persist after multiple passes. Balloon angioplasty, mesis in the former situation. chanical maceration, and mechaniThe secondary patency rates cal displacement into the central veachieved in our study are probably nous system have been advocated by deceptively low because many of the many as management options for repatients with grafts previously fractory thrombus (6,8,11,13,16).Of treated with BAT were referred for these methods, we have found balsurgical declotting instead of percutaneous declotting when subsequent loon angioplasty to be especially helpful for the treatment of the arteepisodes of thrombosis occurred rial thrombus plug and wall-adher(nine of 15 patients). One should ent, chronic thrombi. note that at subsequent thrombosis Because of the frequent occurafter initial BAT, there was no sigrence of sheath impaction, newer nificant difference in the mean pasheath designs that incorporate a retency between patients referred movable hemostatic valve may be back for percutaneous intervention preferable. This would allow disimand those referred for surgical paction to be performed without redeclotting (83 days vs 107 days, respectively; P = .47). This finding removal of the sheath. In addition, diflects the unpredictable referral pat- rect administration of heparin into the graft can help prevent de novo tern for patients with hemodialysis thrombosis. With the exception of access thrombosis. In the absence of one small hematoma, no major ada randomization process, the route verse effects or complications were of treatment after graft rethromboencountered in our series. The time sis largely depends on the referral needed to achieve hemostasis after pattern of the nephrologist and the BAT was substantially prolonged in day-to-day availability of intervenour series, a finding that can be attional and surgical resources. tributed to the use of both large In acutely thrombosed dialysis punctures and heparin. Determinagrafts, some thrombus may not be tion of activated clotting time at the amenable to thrombectomy with completion of the procedures could BAT. Types of thrombus that can be performed to better determine persist after BAT include a plateletthe effect of heparin. Large puncrich thrombus plug a t the arterial tures can pose a potential risk of heanastomosis and a chronic, wall-admatoma and pseudoaneurysm. herent thrombus. In our experience, Structural damage to the graft marefractory thrombus after BAT apterial is another theoretical concern, h eared either as a variable-size fillespecially after multiple percutaneing defect at the arterial anastomosis or as multiple, irregular, wall- ous declotting procedures. We did not observe any such complication in adherent filling defects within the our patients. However, substantial graft. The thrombus plug that frequently resides at the arterial anas- structural damage to polytetrafluoroethylene grafts has been reported tomosis of clotted hemodialysis after repeated needle punctures grafts is usually resistant to pharmacothrombolytic therapy (13). (26). In summary, this study demonChronic, organizing, and wall-adherstrates the theoretical and clinical ent thrombi are also frequently

feasibility of using BAT to treat recently thrombosed hemodialysis access grafts. This technique can be tailored to the individual situation; it involves the use of readily available components and is easily adaptable for use with adjunctive treatments. BAT appears to be just as effective as standard treatment modalities. In addition, no signs or symptoms of pulmonary or peripheral arterial embolism were noted during any of the clinical procedures. Use of BAT alone (without pharmacothrombolytic therapy) helps avoid the high cost and hemorrhagic risks associated with pharmacothrombolytic therapy. References 1. Vonverk D, Sohn M, Schurmann K, Hoogeveen Y, Gladziwa U, Giinther RW. Hydrodynamic thrombectomy of hemodialysis fistulas: first clinical results. JVIR 1994; 5313-821. 2. Schmitz-Rode T, Gunther RW. Oscillating probe aspiration thrombectomy: comparative in vitro evaluation of two concepts. Cardiovasc Intervent Radiol 1992; 15:151153. 3. Schmitz-Rode T, Pfeffer JG, Bohndorf K, Giinther RW. Percutaneous thrombectomy in the acutely thrombosed dialysis graft: in-vitro evaluation of four devices. Cardiovasc Intervent Radiol 1993; 16:72-75. 4. Schmitz-Rode T, Bohndorf K, Gunther RW. The recanalization of thrombosed hemodialysis shunts by oscillating-probe aspiration and with a mesh basket. ROFO 1993; 158:49-52. [German] 5. Uflacker R, Rajogopalan PR, Vujic I, Chita MA, Stutley JE, Kilpatrick PS. Percutaneous mechanical thrombectomy of dialysis fistulae: a randomized study (abstr). JVIR 1995; 6:9. 6. Trerotola SO, Lund GB, Scheel PJ, Savader SJ, Venbrux AC, Osterman FA. Thrombosed dialysis access grafts: percutaneous mechanical declotting without urokinase. Radiology 1994; 191:217-226. 7. Walser EM, Finn NJ, Morgan RA, Wittich GR, Crow WN. Hybrid therapy for thrombosed dialysis grafts (abstr). JVIR 1995; 6:lO. 8. Middlebrook MR, Amygdalos MA, Soulen MC, et al. Thrombosed dialysis grafts: percutaneous mechanical balloon declotting versus

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21. McDermott JC, Crummy AB, Starck EE. Balloon embolectomy catheter used percutaneously. Radiology 1986; 160:279-283. 22. Zimmerman JJ, Cipriano PR, Hayden WG, Fogarty TJ. Balloon embolectomy catheter used percutaneously. Radiology 1986; 158:260-262. 23. Vonverk D, Giinther RW, Clerc C, Schmitz-Rode T, Imbert C. Percutaneous embolectomy: in vitro investigation of the self-expanding tulip sheath. Radiology 1992; 182:415418. 24. Kumpe DA, Cohen MAH, Durham JD. Treatment of failing hemodialysis access sites: comparison of surgical treatment with thrombolysislangioplasty. Semin Vasc Surg 1992; 5:118-127. 25. Schuman E, Quinn S, Standage B, Grass G. Thrombolysis versus thrombectomy for occluded hemodialysis grafts. Am J Surg 1994; 167:473-476. 26. Delorme JM, Guidoin R, Canizales S, e t al. Vascular access for hemodialysis: pathologic features of surgically excised ePTFE grafts. Ann Vasc Surg 1992; 6:517-524.