Treatment of Mycotic Superior Mesenteric Artery Pseudoaneurysms With Flow-Diverting Stents in One Patient

ABSTRACT: Superior mesenteric artery aneurysms are the third most common visceral artery aneurysms. They have traditionally been reported as mycotic in origin. Superior mesenteric artery aneurysms have a rupture risk and high resultant mortality rate. Surgery remains the mainstay for treating mycotic pseudoaneurysm and involves resection and vascular reconstruction. Endovascular options include coiling, glue embolization, and stent placement. We report the case of an intravenous drug abuser who presented with 2 saccular pseudoaneurysms measuring 1.2 cm and 1.1 cm. The pseudoaneurysms were treated with two Pipeline Embolization Devices (PED; Covidien). Occlusion of the pseudoaneurysms and stent patency were demonstrated at the latest follow-up 13 months later.

VASCULAR DISEASE MANAGEMENT 2014;11(6):E156-E159

Key words: pseudoaneurysm, endovascular therapy, stenting, aneurysm repair, mesenteric artery intervention

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Superior mesenteric artery aneurysms (SMAA) are the third most common (5.5%) visceral artery aneurysms (VAA). They have traditionally been reported as mycotic in origin in 50% to 65% of cases, although this percentage has been lower in more modern series.¹ Superior mesenteric artery aneurysms have a rupture risk of 38% to 50% and high resultant mortality rate (40% to 60%).² Surgery remains the mainstay for treating mycotic pseudoaneurysm, and it involves resection and vascular reconstruction. Endovascular options include coiling, glue embolization, and stent placement. 

Transcatheter therapies have a high technical success rate and low associated periprocedural morbidity rate in treating VAA.² Kunzle et al have reported the use of covered stent-grafts to treat both visceral true aneurysms and PA, with excellent long-term clinical outcome and patency in a series of 19 patients, including 3 with mycotic aneurysms.³ 

Recently, flow-diverting stents (FDS) have been increasingly used in treating VAAs. Sfyroeras et al performed a recent literature review and found FDSs used to treat 28 visceral aneurysms, including the renal artery (n=6), the SMA (n=2), and the common hepatic artery (n=1). Technical success was achieved in all cases. In all but two patients, aneurysm thrombosis was achieved, and volume reduction was observed in 24 of 28 aneurysms.⁴ The Cardiatis Multilayer Flow Modulator (Cardiatis) was used in 26 of 28 cases, the SILK Arterial Reconstruction Device (Balt Extrusion) was used in 1 of 28 cases, and the Pipeline Embolization Device (Covidien) was used in 1 of 28 cases. 

Case Presentation 

IRB approval was waived for this retrospective case report. The patient was a 44-year-old male IV drug abuser who presented with spinal discitis/osteomyelitis, paraspinal abscesses and bacteremia. Paraspinal abscesses and blood cultures grew Methicillin-sensitive Staphylococcus aureus. Computed tomography angiogram of the abdomen revealed two pseudoaneurysms arising from the SMA proximal to the ileocolic branch, without active extravasation (Figure 1A).

Technique

Selective SMA angiogram demonstrated 2 saccular aneurysms arising approximately 4.5 cm distal to the origin of the SMA, measuring 11.2 mm x 12.3 mm (8 mm neck) and 11.5 mm x 11.6 mm (7 mm neck). The SMA diameter proximal to the aneurysms was 4.5 mm, and distally it was 4.4 mm. Through a Marksman microcatheter (Covidien), 2 Pipeline Embolization Devices measuring 5 mm x 30 mm and 5 mm x 35 mm were deployed across the segment of the superior mesenteric artery giving rise to the 2 pseudoaneurysms. Stent size was chosen to oversize 10% greater than the native vessel diameter. The second stent was deployed because the proximal landing zone of the first stent was felt to be too close to the margin of the most cephalad aneurysm. In retrospect, a single 5 mm x 35 mm stent would have given adequate coverage given the proximal and distal landing zone anatomy. Post stent deployment angiogram showed flow in the SMA. There was attenuated filling of the pseudoaneurysm sacs (Figure 1B) and stasis of contrast on the delayed images.

Follow-up

Clinically, the patient improved during the hospital stay and was discharged with low-level back pain related to osteomyelitis. The patient remained afebrile and without elevated white count. Computed tomography angiography of the abdomen 1 month later demonstrated minimal intravenous contrast outside the stents’ lumens, which was expected, given the nature of the flow-diverting stents and decreased sac volume. The patient was maintained on 8 weeks of intravenous Oxacillin for the Methicillin-sensitive S aureus and aspirin and clopidogrel (Plavix) for 6 months. Computed tomography angiography of the abdomen 3 months later demonstrated complete thrombosis of the pseudoaneurysms (Figure 1C). Initial follow-up was performed with a mesenteric duplex arterial study in an attempt to reduce radiation dose; however, the stents were not visualized. The patient remains without symptoms and with patent stents at follow-up of 13 months, with no further intervention.

Discussion

Flow-diverting stents are designed with braided and woven metallic layers, which have an overall coverage of the inner vessel wall of  30% to 50% and porosity of 50% to 70%. This construction allows for hemodynamic alteration of both the excluded aneurysm, which will exhibit decreased flow velocity and vortex, and the normal side branches, which maintain patency due to laminar flow. The Pipeline Embolization Device was chosen in this case to avoid completely isolating the infected pseudoaneurysms. By gradually thrombosing the pseudoaneurysms and altering the flow dynamics within the sac, it is possible that FDSs allow antibiotic penetration while thrombosis is occurring, although this point is speculative. Infection remains a concern when any foreign device is placed within an infected vascular bed, and close clinical follow-up is required. Alternatively, the option of placing a covered stent has proven to have therapeutic value in some mycotic aneurysms.³ 

Editor’s Note: Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Bordegaray reports honoraria from Endovascular Forum, and Dr. Narayanan reports consultancy to Biocompatibles International, Angiodynamics, Inc., and Boston Scientific. 

Manuscript received September 29, 2013; provisional acceptance given November 11, 2013; final version accepted March 11, 2014.

Address for correspondence: Matthew R. Bordegaray, MD, Jackson Memorial Hospital, University of Miami Miller School of Medicine, Radiology, 1611 NW 12th Ave, Miami, FL 33136 United States. Email: mbordegaray@med.miami.edu

References  

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2. Tulsyan N, Kashyap VS, Greenberg RK, et al. The endovascular management of visceral artery aneurysms and pseudoaneurysms. J Vasc Surg. 2007;45(2):276-283
3. Kunzle S, Glenck M, Puippe G, Schadde E, Mayer D, Pfammatter T. Stent-graft repairs of visceral and renal artery aneurysms are effective and result in long-term patency. J Vasc Interv Radiol. 2013;24(7):989-996. 
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