A Quick Fix: Graft Rescue for Iatrogenic Pseudoaneurysm

Introduction

Pseudo-aneurysm formation after vascular reconstruction is a rarely encountered problem in the treatment of peripheral arterial disease (PAD). It has most commonly been described in the vascular surgical literature as a delayed complication of lower extremity bypass surgery, and the usual mode of repair has been surgical. Recent advances in minimally invasive therapy for this clinical entity have centered on ultrasound-guided compression and thrombin injection to obliterate the cavity and restore vascular integrity. With the advent of stent-supported angioplasty, endovascular methods of treatment for iatrogenic pseudoaneurysms have generated renewed interest. The following case outlines the rare occurrence of, and therapy for, a delayed non-anastomotic pseudo-aneurysm caused by balloon angioplasty and self-expanding stent deployment in a previously occluded venous femoral-popliteal bypass graft.

Case Report

A 73-year-old female with diabetes, hypertension and hypercholesterolemia presented to our center with rest pain of the right foot. She had a history of chronic PAD, and had previously undergone left above-knee femoral-popliteal bypass grafting, followed by above-knee right femoral-popliteal bypass grafting using saphenous vein for progressive bilateral lower extremity claudication. The right femoral-popliteal bypass graft was nine months old. Resting ankle-brachial indices were 0.40 on the right and 1.1 on the left. Angiography revealed a totally occluded vein graft in its proximal segment. She then underwent successful recanalization of the graft with balloon angioplasty with a 5 x 60 mm balloon catheter, after an overnight course of catheter-directed lytic therapy with tissue plasminogen activator failed to recanalize the occluded graft. Self-expanding 6 mm diameter nitinol stents were placed at the proximal and distal graft anastomosis to treat severe diffuse residual disease after balloon angioplasty with a satisfactory final angiographic result.

She presented 3 days after this procedure with the acute onset of severe, tearing right thigh pain radiating to the calf. On exam her right thigh was enlarged, tense, warm and diffusely tender to gentle palpation. She had palpable femoral pulses and her popliteal, dorsalis pedis and posterior tibial pulses were brisk and easily visible by Doppler. Arterial Doppler of lower extremities revealed ankle-brachial indices of .54 on the right and 1.01 on the left, essentially unchanged from her post-angioplasty baseline. Emergent CT angiography revealed a 3 cm x 6 cm pseudoaneurysm from rupture of the right femoral popliteal saphenous bypass graft just cephalad to the self-expanding nitinol stent placed in the distal graft.

Retrograde contralateral access was obtained in the left common femoral artery and a 5 Fr catheter was positioned in the graft. Arteriography confirmed rupture of the mid segment of the saphenous vein graft and a large pseudoaneurysm in the mid right thigh. The stents in the proximal and distal graft were patent and there was 1 vessel run-off to the foot (Figure 5). An 0.035” Amplatz Super Stiff™ guidewire (Boston Scientific, Fremont, California) was positioned in the distal graft and a 10 Fr Arrow sheath was positioned in the proximal left common iliac artery. The sheath would not cross over the rather steep aortic bifurcation. Utilizing a “buddy wire” technique with the Amplatz wire and a STORQ soft wire (Cordis Corp, Miami, Florida) positioned in the right common femoral artery, a 7 mm x 5 cm GORE Viabahn stent graft was positioned in the mid segment of the right femoral popliteal bypass graft at the site of the rupture. The stent graft was deployed without incident, with complete coverage of the rupture site. A 5 mm x 40 mm balloon was positioned within the stented segment and two inflations performed to appose the stent graft at nominal pressures. Final angiography revealed complete apposition of the stent with sealing of the leak. Distal popliteal arteriography and infra-popliteal run-off angiography revealed preserved single vessel runoff to the foot. The patient was discharged on a regimen of aspirin and clopidogrel, with resolution of her symptoms. Follow up ankle brachial indices two weeks post procedure were .58 on the right and .95 on the left, demonstrating improvement. Repeat CT angiography performed two weeks post procedure revealed continued integrity and patency of the bypass graft.

Pseudoaneurysm (PA) formation after vascular surgical reconstruction is most commonly associated with disruption of an arterial anastomosis after either aortofemoral bypass or infrainguinal bypass, or as a complication of dialysis graft fistulas.⁷ The cumulative risk of clinically significant PA’s after surgery remains small between 2–6%.⁷ The incidence of false aneurysm formation after balloon angioplasty is also rare; only a few case reports describing the clinical phenomenon exist.^4–6,9,19 Palmaz et al reported two cases of PA formation in a review of the initial multicenter experience with iliac stenting, suggesting that stents may contribute significantly to the risk of PA formation.²⁰ Pseudoaneurysms can, if left untreated, be complicated by thrombosis, rupture or distal embolization. Active hemorrhage with continuing expansion, severe unremitting pain and impending compartment syndrome are among the indications for urgent surgical intervention. Early surgical repair is usually mandated in these cases, with interposition graft placement being the procedure of choice.⁷ Non-anastomotic pseudoaneurysm (PA) formation in femoropopliteal bypass grafts has been noted to occur primarily in PTFE conduits, in some cases due to continued graft dilatation with time.¹ In other cases, PA formation was related to graft failure from iatrogenic infection.¹⁷

Isolated cases of spontaneous late non-anastomotic PA formation have been associated with the Dardik umbilical vein prosthesis in the femoropopliteal segment.³ Iatrogenic non anastomotic PA formation has also been described as a rare late complication of balloon PTA of stenotic femoropopliteal vein grafts and after balloon thrombo-embolectomy for graft occlusion. In a retrospective review of 101 angioplasty procedures performed for salvage of stenotic and failing infrainguinal vein grafts, Alexander et al noted late PA formation at the site of PTA in only two cases.¹⁴ One PA was successfully treated with thrombin injection and the other was managed with surgical revision of the graft. Biederer et al reported a case of late false aneurysm formation in the body of a PTFE femoropopliteal bypass graft seven years after Fogarty balloon thromboembolectomy performed for graft occlusion.¹⁷ Intraoperative findings on graft revision included a hardened, brittle prosthesis covered with atherosclerotic material. Microscopic examination revealed disruption of the conduit wall at the site of the false aneurysm.¹⁷ Maleux et al reported the occurrence of a PA of the native iliac artery at the distal end of a covered common iliac artery stent at the site of prior balloon angioplasty, and postulated that among the possible causes were localized vessel wall dissection by the angioplasty balloon and the additive effect of the interaction between vessel wall and the expanding stent graft itself.¹⁰

PA formation in our case occurred rapidly, within 3 days after stent supported balloon angioplasty of the occluded femoropopliteal saphenous vein bypass graft conduit. Also, the location of the PA in the graft was in its distal body, at the site of a series of multiple aneurysmal dilatations of the graft that occurred soon after balloon angioplasty. The leak occurred in the native graft well cephalad to the proximal edge of the slightly oversized self-expanding nitinol stent deployed in the distal graft, suggesting that the graft segments exposed to the highest radial wall tension were those that were aneurysmal from balloon dilatation. It is also likely that the forces exerted on this segment of graft were exacerbated by the continuous expansile force of the nitinol stent itself.

Aneurysm formation at the site of prior angioplasty has been rarely described in the literature and its true prevalence is unknown; Vive et al reported two cases of late aneurysm formation out of 726 attempted PTA segments, occurring five to ten months after the angioplasty procedure.¹¹ Local predisposing factors were postulated to include the balloon-to-artery ratio, inflation duration and pressure. Factors such as direct external stress and over-stretching of graft material have long been implicated in non-anastomotic PA formation within femoropopliteal Dacron and PET grafts (2, 1). It is likely that these same factors conspire to cause PA formation in vein grafts.

Late vein graft disease is typically due to myointimal hyperplasia or intrinsic structural abnormalities of the vein as progressive arterialization of the venous conduit occurs over time. Long-term follow-up studies of arterialized vein grafts have revealed severe degeneration from progressive atherosclerosis. Histopathological analysis of vein graft aneurysms demonstrates endothelial disruption, medial necrosis, loss of elastic elements, and fibrous proliferation.⁸ Extensive balloon angioplasty of a diffusely diseased and previously occluded vein graft, as in this case, likely exacerbates the preexisting structural abnormalities of the conduit, leading to focal weakening of the venous wall and subsequent rupture when the conduit is re-exposed to high pressure pulsatile arterial flow. Also, the arterialized graft is likely to be susceptible to barotrauma-induced micro-tears from balloon angioplasty. Such tears, depending on the path of initial guidewire traversal in a totally occluded graft, may also be subintimal in location and lead to delayed rupture. In one of the earliest case reports of graft-associated pseudoaneurysms, Miller et al reported finding longitudinal graft tears, collagenous scar tissue and laminated organized thrombus after excision of a PA from the body of an 18-month-old Teflon femoro-popliteal bypass graft.¹⁸

Stenting of pseudoaneurysms has been reported in the literature for over a decade, but reports of endoluminal stent graft placement to treat false aneurysms of infra-inguinal bypass grafts are few, perhaps because bypass graft PA formation itself is a rare phenomenon. Brountzos et al recounted the use of a Hemobahn stent graft to successfully treat anastomotic pseudoaneurysm of the common femoral artery in a critically ill patient who had previous aorto-femoral bypass.¹² Others have reported lukewarm success with this technique in the femoropopliteal segment, when the technique was still in its infancy and the learning curve quite steep.¹³

The endoluminal method remains an attractive option for treating graft-related false aneurysms. It avoids the need for reoperation in a previously scarred area, and in the case of abdominal and thoracic false aneurysms, obviates the necessity to enter a major body compartment. The advent of newer lower profile stent graft devices has renewed interest in this particular approach to the treatment of pseudoaneurysms. Zanchetta et al described the successful deployment of a Wallgraft endoprosthesis to treat a large non-anastomotic PA of a Dardik human umbilical vein femoropopliteal endoprosthesis occurring seven years after surgery.³ Successful endovascular stent graft repair of pseudoaneurysm of the native popliteal artery following total knee arthroplasty has also been performed with a Wallgraft device.¹⁶ Gretener et al reported the successful stent graft exclusion of a true aneurysm in the body of a femoro-distal venous bypass graft in a patient with active Behcet’s disease and two prior surgical repairs of recurrent false aneurysms of the graft anastomoses.¹⁵

Although long-term patency of the venous bypass was not achieved, the procedure was successful in preventing rupture of the aneurysm in a patient deemed unsuitable for reoperative repair. To our knowledge, this is the first reported case of successful stent graft repair of an iatrogenic nonanastomotic PA caused by balloon angioplasty of a femoropopliteal saphenous vein graft. In our view, when faced with an especially large PA located deep to the artery likely caused by a tear in the conduit, or in the setting of pseudoaneurysms with multiple feeding points, stent graft repair becomes the superior choice to other minimally invasive methods such as thrombin injection and ultrasound guided compression. Indeed, this approach may offer less risk to the patient than open surgical repair, especially in the cases where extensive surgical exploration of deep tissue may be required and in the case of a “hostile” surgical field created by active inflammation or tissue fibrosis and scarring. The long-term patency rate of such an approach, however, deserves close scrutiny. Duplex ultrasound and CT angiography surveillance after repair will likely become useful diagnostic tools to detect late sequelae such as endoleak, stent strut fracture, kinking, and stent graft migration.

Summary

We report a case of successful stent graft repair of an iatrogenic PA created by percutaneous recanalization of an occluded saphenous vein femoro-popliteal bypass graft. Deployment of covered stents should be considered in the treatment of large pseudoaneurysms with extensive surrounding hematoma that might otherwise be considered only suitable for surgery. Stent graft repair may be preferable to reoperative surgery in the management of bypass graft pseudoaneurysms, in patients with significant medical comorbidity and those in whom surgical access for repair remains a challenge. As the frequency of endovascular interventions increases, stent graft repair will likely play an important role in the treatment of both iatrogenic and noniatrogenic vascular injury.