Vascular andEndovascular Surgery

Volume 40 Number 6Dec/Jan 2007 460-466

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Endovascular Exclusion of PoplitealArtery Aneurysms With ExpandedPolytetrafluoroethylene Stent-Grafts:Early Results

Hiranya A. Rajasinghe, MD, Argyrios Tzilinis, MD, Theresa Keller, RN,Jeff Schafer RVT, and Sandra Urrea, RVT

460

of PAAs are acute thrombosis andwith limb loss rates that rangeAlthough the size threshold foasymptomatic PAAs is a source ofremain of concern because of term risk of complications, especbus is present.1 However, electiasymptomatic PAAs is generallysurgical candidates with suitableacceptable tibial vessel runoff,report notes some preference by prosthetic grafting via a posterior

Popliteal artery aneurysms (PAA) account formost peripheral artery aneurysms and areclosely associated with aortic, iliac, and femoral

artery aneurysms.1 The most common complications

© 2007 Sage Publications10.1177/1538574406294366

There is increasing interest in using endovascular meth-ods instead of surgical reconstruction to treat poplitealartery aneurysms. Exclusive use of the Viabahn stent-graft, a nitinol stent covered with expanded polytetraflu-oroethylene, was assessed in the treatment of patientswho presented with popliteal artery aneurysms in theabsence of acute limb ischemia. Technical success,endoleaks, graft patency, freedom from amputation, andaneurysm sac flow and size changes were assessed byduplex ultrasound. From June 2004 to March 2006, 16men (mean age, 76 years; range, 65-83) underwentendovascular exclusion of 23 popliteal artery aneurysms(mean diameter, 2.5 cm; range, 1.3-6.7 cm). Ninelesions had partial thrombus on preprocedural dupleximaging. Nineteen of the 23 limbs treated had at least 2-vessel tibial artery runoff. Procedures were performedunder local anesthesia using ipsilateral percutaneousantegrade arterial access. All patients received75 mg/day of clopidogrel afterward. Follow-up assess-ments included direct clinical examinations and duplexultrasonography performed 1, 3, 6, and 12 months afterthe procedure. Primary patency and amputation-free

survival were calculated using Kaplan-Meier analysis.Complete aneurysm exclusion (technical success) wasachieved in all cases. During the mean follow-up of7 months (range, 1-21 months), 22 of 23 treated limbsremained asymptomatic. One stent-graft thrombosisoccurred 6 months after the procedure and was success-fully treated with percutaneous mechanical thrombec-tomy, balloon angioplasty of a stent-graft stenosis, andinsertion of an uncovered nitinol stent. No poplitealartery aneurysm sac size enlargements or endoleaks weredetected. At 12 months, the treated limb mean ankle-brachial index was 1.0 (range, 0.82-1.31) and the pri-mary and secondary patency rates were 93% and 100%,respectively. Early results with Viabahn endovascularstent-graft exclusion of asymptomatic popliteal arteryaneurysms are promising. Patient selection for endovas-cular repair depends on suitable popliteal artery anatomy,extent of aneurysmal degeneration, and quality of tibialarterial runoff.

Keywords: popliteal artery aneurysm; endovascularstent-graft; thrombectomy

distal embolization,1

from 25% to 50%.r treatment of small debate, these lesionsthe cumulative long-ially if mural throm-ve surgical repair of limited to good-risk autogenous vein and although a recentvascular surgeons for approach.2

From Vascular Surgery and Endovascular Intervention, AnchorHealth Centers, Naples, Florida.

Presented at the Society for Clinical Vascular Surgery AnnualMeeting, March 8-11 2006, Las Vegas, Nevada.

Address correspondence to: Hiranya A. Rajasinghe, MD, VascularSurgery and Endovascular Intervention, Anchor Health Centers,800 Goodlette Road, Suite 380, Naples, FL 34102; e-mail: raj@anchorhealthcenters.com.

Endovascular Exclusion of Popliteal Artery Aneurysms With ePTFE / Rajasinghe et al 461

Endovascular treatment of a PAA was first reportedin 1994 by Marin and colleagues.3 An expanded poly-tetrafluoroethylene (ePTFE) graft was attached to astainless steel Palmaz stent to repair a large PAA ina patient with advanced heart disease. Subsequently,numerous small series have been reported using trans-femoral endografting to exclude PAAs. A variety ofstent-grafts have been used for PAA repair, includ-ing other “homemade” stent-grafts,4-7 as well as theWallgraft (Boston Scientific, Natick, Mass),8-11 Corvita(Miami, Fla),10 Passager (Boston Scientific),9,10,12

Cragg Endopro (MinTec, Freeport, Bahamas),9,12,13 andViabahn endoprostheses (formerly Hemobahn; WLGore & Associates, Flagstaff, Ariz).14-17

Repetitive stress forces of elongation, torsion, com-pression, and flexion-extension of the femoropopliteal(FP) arterial segment at the knee can lead to stent-graftfracture, kinking, migration, and occlusion. These fac-tors represent a challenge to endovascular repair andlimit its application for PAA repair. The Viabahn devicewhich became available in 2003 has design character-istics favorable for popliteal artery implantation. Thisendoprosthesis is constructed of an ultrathin sheet ofePTFE supported by a self-expanding nitinol stent per-mitting flexibility and strength. Device deployment isover a 0.035-inch wire and proceeds from the cathetertip to the hub allowing accurate distal-to-proximalartery implantation and less “buckling” of the stent-graft. Since its introduction, our group has exclusivelyused the Viabahn stent-graft when performing endovas-cular exclusion of PAAs in asymptomatic patients. Thisreport details our initial experience in treating 23 PAAsin 16 men.

Methods

Patients

Between June 2004 and March 2006, all patientswith asymptomatic PAAs referred to our practice wereconsidered for endovascular repair. The inclusion cri-teria for a stent-graft exclusion procedure included aPAA diameter 1.5 times the diameter of the proximaladjacent vessel segment and/or the presence of muralthrombus in aneurysmal segment, and the presenceof at least one nondiseased tibial artery runoff vesselon duplex scanning. Patients with contraindicationsto antiplatelet or anticoagulant therapy, no in-line tib-ial artery runoff, or acute limb ischemia (Rutherfordclass I, IIa, IIb, or III) were excluded from considera-tion for endovascular treatment. Two patients wereincluded in this report with mild ipsilateral limb

edema without any evidence of acute limb ischemia.All patients in whom a Viabahn endoprosthesis wasused provided informed consent before the insertionprocedure.

Endovascular Technique

All procedures were performed using local anesthesiaand conscious sedation with the patient in the supineposition using a dedicated angiosuite. Antegradeaccess to the ipsilateral superficial femoral artery(SFA) is obtained by means of a 5 F short-lengthsheath. A diagnostic arteriogram (Figure 1) is obtainedto localize the PAA, measure the diameter of the distalSFA (proximal landing zone), and assess the distalpopliteal artery for suitability as a distal landing zone.A ruler placed along the knee joint helps to estimatethe length and number of stent-grafts necessary forsatisfactory PAA exclusion.

The PAA is crossed with a 260-cm long, 0.035-inch floppy Glidewire (Terumo Medical, Somerset,NJ) and parked in a tibial artery. Heparin (5000 U)is administered intravenously. The sheath is upsizedto accommodate the selected Viabahn endoprosthe-sis. With use of an exchange catheter, the floppy

Figure 1. Arteriogram shows a popliteal artery aneurysm 4.5cm in diameter, a 9-mm distal superficial femoral artery, and an8-mm distal popliteal artery (landing zones).

462 Vascular and Endovascular Surgery / Vol. 40, No. 6, Dec/Jan 2007

Glidewire is exchanged for a stiff wire. A 0.035-inchstiff Glidewire is employed for a Viabahn device 5 to8 mm in diameter, whereas a 0.018-inch SV5 wire isused for a 9- to 13-mm device. The stiff wire allowsthe prosthesis to track easier (without “jumping”)and eliminates any redundancy, particularly if thefemoral-popliteal segment is tortuous or ectatic. TheViabahn device is deployed so that there is a seal ofat least 1 to 1.5 cm in the proximal and distal land-ing zones. The distal landing zone consisted of theinfrageniculate popliteal segment. There were nocases of compromise or coverage of the anterior tib-ial artery origin with the covered endoprosthesis toachieve adequate distal seal. For PAAs that require 2or more endoprostheses to achieve successful occlu-sion, at least 2 cm of endograft overlap is provided.

A completion angiogram is then performed. If alarge type I endoleak is observed (Figure 2), the prox-imal and distal unfolding of the device is assessed todetermine whether the seal is adequate. A noncompli-ant percutaneous transluminal angioplasty (PTA)balloon is sized for the landing zone diameters andinflated to profile. In most instances, this eliminatesthe endoleak. If the endoleak persists, the repair canbe extended proximally by using a larger device(Figure 3). A completion angiogram for a technicallysuccessful procedure shows complete PAA exclusionwith preservation of tibial vessel runoff. Depending onthe size of the endoprosthesis selected the sheath sizecan vary from 8 F to 12 F. All procedures were per-formed without the use of a closure device. Manualcompression following sheath removal was used forpuncture seal when the activated clotting time fellbelow 150. After the procedure, patients received 75mg/day of clopidogrel for anticoagulation and areadvised to refrain from prolonged knee flexion inexcess of 90 degrees.

Follow-up

Follow-up evaluations in this series included clinicalexaminations and duplex ultrasonography performed1, 3, 6, and 12 months after the procedure. The duplexscanning studies assessed the patency of the stent-graft, the presence of any endoleaks (longitudinal andtransverse planes), the presence of any enlargement ofthe aneurysm sac, and the ankle-brachial index (ABI).

Data Analysis

Data were obtained retrospectively from the patients’records and compiled. Primary endpoints were technical

Figure 2. Angiogram obtained after deployment of a Viabahnendoprosthesis (10 mm x 10 cm) shows a large type I endoleak.

Figure 3. Completion angiogram obtained after deploymentof an additional Viabahn endoprosthesis in the same limb as inFigure 2 shows elimination of the endoleak and complete exclu-sion of the popliteal artery aneurysm.

Endovascular Exclusion of Popliteal Artery Aneurysms With ePTFE / Rajasinghe et al 463

success (ie, uncomplicated insertion of the endopros-thesis and immediate PAA exclusion), primary patencyof the stent-graft (ie, no intervention required to main-tain patency), and freedom from amputation of thetreated leg. The secondary endpoint was secondarypatency. Patency rates and freedom from amputationwere assessed by using the log-rank test for Kaplan-Meier survival analysis (SPSS, Chicago, Ill).

Results

Sixteen patients (all men) with 23 PAAs were includedin the series. Table 1 shows patient and lesion charac-teristics. The mean (± SD) pre-procedure ABI in 14limbs with values measured was 1.02 ± 0.07 (range,0.85-1.11); the postoperative value (most recent follow-up; n = 15) was 1.10 ± 0.14 (range, 0.78 ± 1.31). Themean ABI increase among limbs assessed both beforeand after treatment (n = 8) was 0.1 (range, 0-0.26).

Complete aneurysm exclusion was achieved in allcases (technical success rate, 100%). During a meanfollow-up time of 7 months (range, 1-21 months), 22of 23 treated limbs remained asymptomatic. A singlepatient was lost to follow-up after 6 months. The1-year primary patency rate was 93% (Figure 4); the

secondary patency rate was 100% (Figure 4). No ampu-tations were required. No enlargements of PAA sac sizeor late endoleaks were observed on duplex scanningduring follow-up.

Stent-graft thrombosis occurred in 1 patient6 months after endovascular exclusion of a 3 cmpopliteal artery aneurysm with 2-vessel tibial arteryrunoff. Review of the patients’ post-procedure duplexfollow-up at 1 and 3 months failed to reveal anyevidence of endograft deformity or velocity profilechanges. At the time of acute stent-graft thrombosis,the patient had presented with acute calf pain andparesthesias of the toes. Duplex testing confirmed thepresence of stent-graft thrombosis, and the patientwas treated in the angiography suite on an emergentbasis. He was found to have acute occlusion of theFP segment at the proximal end of the Viabahn endo-prosthesis. Patency was reestablished by percutaneousmechanical thrombectomy with preservation of tibialartery runoff. The underlying lesion appeared to be astenosis at the SFA proximal landing zone caused byincomplete unfolding of the stent-graft during initialdeployment. The stenosis was subsequently treated byinsertion of an uncovered nitinol SMART stent(Cordis Endovascular, Warren, NJ). The patient wasdischarged 48 hours later on an anticoagulation regi-men consisting of warfarin and aspirin.

Discussion

Open arterial reconstruction for the treatment ofasymptomatic PAA is a well-established procedurewith excellent patency and durability.18-20 Five-yearpatency rates for surgical repair of PAA haveapproached 80%, and limb salvage rates are generallygreater than 90%. A popliteal aneurysm diameter of 2cm or greater, the presence of thrombus, and poorrunoff in asymptomatic patients have been identifiedas risk factors for the development of limb-threateningcomplications and are the rationale for intervention.21

However, there has been debate on the “appropriate”threshold diameter for surgical repair. Ascher andcolleagues22 found the natural history of small PAAs(> 1.2 cm) was not as benign as had previously beenthought, and there is a substantial risk of thrombosisand thromboembolization. Although the mortalityrate for surgical repair is less than 1%, wound com-plications may affect more than 30% of patients,and surgical repair is generally limited to good-riskpatients who have an available satisfactory autoge-nous conduit for arterial reconstruction, although arecent report demonstrates prosthetic reconstruction

Table 1. Patient and Popliteal Artery Aneurysm Characteristics

Characteristic Value*

Mean age (y) (range) 76 (65-83)Location of PAA

Left leg 14 (61)Right leg 9 (39)

Limbs with/without symptoms 2 (9)/21 (91)Concomitant aneurysms

Abdominal aortic 13 (57)Iliac 5 (22)Femoral 9 (39)

Mean ± SD PAA diameter 2.7 ± 1.3 (1.3-6.7)(cm) (range)

PAAs with/without thrombus 9 (39)/14 (61)Mean ± SD SFA diameter 6.6 ± 1.4 (5-9.6)(mm) (range)

Mean ± SD BK PA diameter 5.8 ± 1.7 (4-9)(mm) (range)

Tibial artery runoff vessels3 14 (61)2 5 (22)1 4 (17)

n = 16 men with 23 popliteal artery aneurysms.* Values are number (percentage) unless otherwise indicated.PAA, popliteal artery aneurysm; SFA, superficial femoral artery;BK, below-knee; PA, popliteal artery.

464 Vascular and Endovascular Surgery / Vol. 40, No. 6, Dec/Jan 2007

via a posterior approach is preferred by some vascularsurgeons.2,23,24

Enthusiasm for endovascular repair of PAAs hasgrown because of its potential for decreased bloodloss, reduced hospital stays, and faster recovery. Manystent-graft devices have been used, but in general arenot suited for deployment in the FP segment becauseof their relative stiffness and poor compliance withrepetitive stress forces of elongation, rotation, flex-ion, and extension. The design of the Viabahn deviceappears to overcome many of these problems. Tielliuand colleagues17 reported using both the Hemobahnand Viabahn endoprostheses for endovascular repairof a large group of PAAs and had good early out-comes. However, their study suffers from a patientpopulation that included both asymptomatic patientsand those with acute limb ischemia along with achange in their protocol for anticoagulation fromaspirin to clopidogrel over the study period. Moreover,all their cases involved open surgical exposure toallow a transfemoral endovascular repair using a 12 Fsheath marginalizing the advantage of an endovascu-lar approach. The mixing of both asymptomatic andsymptomatic patients along with changes in devicedesign and anticoagulation across the study periodmakes the predictive value of different variables onstent-graft occlusion difficult to assess.

Endovascular treatment of PAA in our study-group, composed of a consecutive series of patients

who presented in the absence of acute limb ischemia,resulted in promising early results which comparefavorably with open arterial reconstruction. Technicalsuccess, (ie, PAA exclusion with preservation of tibialvessel runoff using a percutaneous approach) wasachieved in all cases. The primary stent-graft patencyrate at 1 year was 93%, and no limb amputations wereperformed. Only 1 re-intervention for graft thrombo-sis occurred and was successfully treated resulting ina 1-year secondary patency rate of 100%. In the sin-gle patient with a stent-graft thrombosis, no nativeSFA or popliteal artery occlusive disease was identi-fied with either pre-procedural duplex testing or dur-ing the follow-up period. Device failure was the resultof incomplete unfolding of the stent-graft at its prox-imal landing zone end, which follow-up duplex testingfailed to reveal. We suspect that this happenedbecause during our initial experience with theViabahn device, the endoprosthesis was allowed toseal at the proximal and distal landing zones withoutroutine PTA of the proximal and distal landing zones.Subsequently, PTA has been routinely performed atthe landing zones, with the PTA balloon sized to theartery to allow for complete seal and elimination ofany potential endograft deformities.

Prior reports have demonstrated improved graftpatency and limb salvage with 2 or more tibial arteryrunoff as compared to single vessel runoff in thesurgical treatment of PAA.18

Figure 4. Kaplan-Meier analysis of 1-year primary patency of stent-grafts used to exclude popliteal artery aneurysms and Kaplan-Meier analysis of 1-year secondary patency of stent-grafts used to exclude popliteal artery aneurysms.

Endovascular Exclusion of Popliteal Artery Aneurysms With ePTFE / Rajasinghe et al 465

In our study, the vast majority (19/23) of limbstreated had at least two vessel runoff. The impact oftibial artery runoff on graft patency and limb salvagewith endovascular therapy is unknown because thelone thrombosis occurred in a patient with two vesselrunoff and was suspected to have occurred from alesion involving the stent graft device. Further long-term follow-up is warranted to determine the impor-tance of tibial artery runoff.

No late endoleaks or aneurysm sac enlargementsoccurred in our series of endovascular PAA exclusions.This experience contrasts with that of open surgicalrepair, after which a small incidence of aneurysm sizeenlargement caused by retrograde filling via collateralvessels has been observed.25

Conclusions

We have demonstrated early success in the endovas-cular treatment of PAA with Viabahn endoprostheses.Long-term success will require judgment of this pro-cedure in the context of open arterial reconstruction,which is well established. At present, close duplex sur-veillance has been performed post-endovascular PAArepair, although the single stent-graft thrombosis wasnot predicted on the basis of the preceding duplexfollow-up studies. Computed tomography angiogra-phy was not used in any of the follow-up evaluations;however, long-term follow-up for sac flow and evalu-ation for endoprosthesis deformities may be moreaccurately assessed with this imaging modality. Thequality of tibial arterial runoff as a predictor of graftpatency may require further follow-up in determiningpatient selection.

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