Fresh arterial allograft as a replacement for an infected common femoral prosthetic graft and recurrent false aneurysm

Summary

Replacing an infected vascular prosthetic conduit with an allograft is a possible solution of this complication given the low recurrence of infection. It is most commonly utilized for cases where the use of autologous tissue is not an option. We present the case of a 70-year-old patient who had undergone repeated vascular reconstructions in the right lower limb. He was admitted to our department due to a progressively growing mass in the right groin and subsequently placed on the waiting list for a fresh allograft. The patient had the infected false aneurysm and prosthetic material of the femoral bifurcation replaced with an arterial allograft. The previous femoral popliteal autovenous bypass graft was reimplanted into the allograft. There were signs of sepsis during the operation; however, the blood culture was negative. Cultures from neither the wound nor the drain revealed the presence of any bacteria. The patient was discharged on the seventh post-operative day with prophylactic antibiotics. An early followup confirmed that there were no signs of recurrent infection and that the reconstruction remained patent. Seven and half months after the surgery, the femoral popliteal bypass graft became occluded and a conservative approach was chosen. A small thrombosed false aneurysm of the graft was revealed two years after the surgery due to transient non-compliance of the patient to immunosuppression therapy. It was treated conservatively. Two and a half years after the surgery, the allograft still remains open and the limb is preserved.

Keywords:

infection – blood vessel prosthesis – allograft

INTRODUCTION

Although rare, vascular graft infection (VGI) is one of the most dangerous complications in vascular surgery. VGI has been reported in up to 2.8% of femoropopliteal bypasses [1]. Surgical site infection (SSI) is the strongest risk factor for VGI [2]. With respect to artificial conduits, the potential of these prostheses becoming infected varies according to their structure. The virulence of different bacterial species determines the clinical presentation of prosthetic infection. Staphylococcus aureus, Pseudomonas spp., and Gram-negative organisms are associated with a higher incidence of anastomotic disruption, whereas Staphylococcus epidermidis induces a smoldering infection that may not become clinically apparent for some years [3]. Para-anastomotic aneurysm can develop as a late complication of arterial reconstruction [4]. It is often associated with infection but it can be caused by a sterile degenerative process, as well [5]. Aneurysms can bring about life-threatening consequences, such as an erosion of adjacent tissue, distal embolization from a mural thrombus, and a rupture of the aneurysmal sac [6]. Vascular graft infection is diagnosed through a combination of clinical signs, blood sample tests, and imaging methods such as ultrasound examination or computed tomography (CT). CT angiography (CTA) has been considered as the reference imaging standard in VGI diagnosis thanks to its ability to visualize the characteristic features of VGI [7]. Currently the most preferable methods to treat VGI include in situ reconstruction using infection-resistant materials, combined with removal of the infected graft material, aggressive debridement of the arterial bed, and targeted antimicrobial therapy. Historically, extra- anatomic reconstruction was the method of choice to avoid placement of a new graft in infected tissue [8]. In selected patients, the most suitable technique is transplantation of a cold-stored or a cryopreserved vascular allograft [9].

CASE REPORT

A 70-year-old male patient with a history of multiple vascular reconstructions of the right lower limb was referred to our center due to recurrence of a false aneurysm in the right groin. He had been receiving treatment for hypertension and chronic obstructive bronchopulmonary disease. He smoked twenty cigarettes a day for most of his adult life but quit the habit a year ago. The patient had no history of diabetes mellitus or cardiac ischemia. Clinical examination determined palpable pulses to the peripheral arteries, and we did not observe any tissue loss or sensorimotor deficit in the right lower limb. He had undergone multiple previous vascular reconstructions in the right lower limb, the first of which took place 16 years ago and involved a femoropopliteal below-knee bypass with an autologous reverse graft of the great saphenous vein. Occlusion of the bypass developed two weeks after primary reconstruction. The patient then underwent a thrombectomy of the bypass, and a new reconstruction between the common femoral artery and the deep femoral artery was performed due to an aneurysm at the proximal anastomosis of the original bypass. After fourteen years with no complications, recurrence of the false aneurysm developed again in the right groin. This was resolved by resecting the aneurysmatic sac and substituting the common femoral artery with a knitted silver-coated polyester graft. The distal segment of the graft was implanted into the autologous bypass and a jump bypass was also created to the deep femoral artery. During the last year, he had two more vascular reconstructions in the right groin. An aneurysm developed at the proximal anastomosis of the femoral popliteal bypass graft, which was treated by replacement with an expanded polytetrafluoroethylene (ePTFE) prosthesis. Thrombolysis of the bypass followed using angioplasty and a stent was implanted into the proximal anastomosis due to occlusion one year after the final replacement of the false aneurysm. An eight-month complication-free period followed the completion of all of these reconstructions.

After this period, the patient started to observe a growing bulge in the right groin again. He was readmitted to our department from another hospital. CTA revealed a false aneurysm that measured approximately 5 cm in diameter (Fig. 1). Given that vascular infection was highly suspicious, we did not carry out additional examinations such as CT/PET. Due to the repeated occurrence of these problems and to the fact that utilizing autologous tissue was not an option (the patient had undergone a femorotibial bypass with a graft of the autologous great saphenous vein in the left lower limb, as well), the patient was put on the waiting list for a fresh arterial allograft. During the hospitalization period, the false aneurysm grew and posed a risk of bleeding. Seven days after the patient was admitted to our department, a suitable arterial allograft was made available for transplantation. The graft was compatible with the AB0 system of the recipient. It comprised the bifurcation of the common iliac artery to the internal and external iliac artery. The external iliac artery continued to the common femoral artery (Fig. 2–B).

The operation involved the removal of the false aneurysm and the common femoral prosthetic graft, as well as consistent debridement of the infected tissues (Fig. 2–A). The proximal anastomosis was constructed between the patient’s external iliac artery and the proximal part of the arterial allograft. The distal anastomosis was created between the previous autologous bypass and the distal part of the graft (Fig. 2–D). The internal iliac artery of the allograft was used to perform a bypass to the deep femoral artery in order to preserve collateral blood supply to the patient‘s leg (Fig. 2–C). During the operation the patient developed an episode of hypotension, tachycardia, and a rash, and as a result, he required vasopressor support. This septic episode was most likely caused by the release of certain bacteria into the blood. A blood culture was taken during the operation but revealed no signs of bacteria. Other cultures were taken for microbiological examination but those results were also negative. After being stabilized at our anesthesiology department, the patient was readmitted to our intensive care unit (ICU) on the second post-operative day. The subsequent period was uneventful. The patient recovered well, with no signs of inflammation, and the reconstruction remained patent. He was discharged with oral antibiotics and a set dose of tacrolimus on the seventh post-operative day. During the entire period, C-reactive protein levels were normal or slightly elevated (maximum 66 mg/L on the third post-operative day), and his white blood cell count was also normal. An early follow-up visit on the fourteenth day post-surgery confirmed patency of the reconstruction on Doppler ultrasound imaging. The wound healed by primary intention and the stitches were removed. In accordance with our immunosuppressive protocol, patients remain on tacrolimus until the reconstruction is patent. The trough level of tacrolimus is controlled periodically and we aim for levels of 5–7 μg/L.

According to regular follow-ups, there was an occlusion of the femoral popliteal vascular reconstruction in the right leg four months after the final surgery. Two attempts at thrombolysis were made, the second of which proved successful (Fig. 3). Three and half months later, the bypass reoccluded, and a conservative approach was indicated. The patient suffers from non-limiting claudications of both legs; however, no tissue loss was observed. The aneurysmatic degeneration of the allograft developed after two years because our patient was not taking tacrolimus correctly. He left out follow-ups for one year and was not using the necessary medication for three to four months. The ultrasound revealed a thrombosed pseudoaneurysm near the distal allograft anastomosis, stable in size in the last three months. The patient started taking his medication correctly, including an antiplatelet agent and a statin. The tacrolimus level was in the therapeutic range again. At present, two and a half years later, the arterial allograft remains open, and therefore vascular supply to the limb is preserved, partially due to deep femoral artery and perforating arteries.

DISCUSSION

Vascular graft infection is one of the most threatening complications in vascular surgery. There is more than one option to resolve this situation. Conservative treatment of lower limb VGI without removing the infected vascular graft is rarely an option because it is associated with high mortality (up to 45% at five years) [10]. Generally, vascular graft replacement involving removal of the infected graft and all infected tissue is recommended. Reconstruction using an autologous graft is a preferable option when feasible. Utilizing an arterial or venous allograft is another possibility in cases where the autologous graft is missing. Obviously, we can also use a prosthetic graft, but the reinfection rate is high versus the non-prosthetic solution [2].

In the case of our patient, there was no suitable autologous tissue, owing to his history of autologous bypasses in both legs. In addition, there was a repeated recurrence of the false aneurysm in the right groin after utilization of a prosthetic graft. In light of these complications, we decided to use a fresh arterial allograft. Fresh allograft transplantation has a long history in the Czech Republic; standard use of cryopreserved vascular allografts was introduced into clinical practice in 2011. In 2015, the numbers of transplanted fresh allografts versus cryopreserved allografts in the Czech Republic were nearly equal. It is solely at the discretion of the surgeon to place the patient on the waiting list for either a fresh or cryopreserved allograft. Czech law allows for the use of fresh allografts in the field of organ transplantation (regulated by Act No. 285/2002 Coll.) [11]. We prefer utilizing fresh allografts at our center. We carry out approximately 10–20 procedures annually using vascular allografts. The autologous superficial femoral vein is rarely utilized in our unit. Fresh allografts are the preferred option because of their relative abundance in a large transplantation center and their lower costs compared to cryopreserved grafts.

According to Furlough et al. who evaluated 57 patients undergoing reconstructions using cryopreserved arterial allografts in infected fields, early post-operative complications occurred in 14% of the patients. These consisted of bleeding, superficial wound infection, and, in one case, graft reinfection that required repeated allograft repair. Late conduit-related complications occurred in 15.8% of the patients. There was only one instance of late graft reinfection involving a left to right femorofemoral allograft bypass, which occurred in a patient who had previously undergone an unsuccessful aorto-bi-iliac bypass in the right limb. The authors also described two instances of late complications involving pseudoaneurysmal degeneration of the allograft. Both of them were treated with endovascular stent repair [12]. Another study reported a 94% rate of resistance to allograft infection within the first 30 postoperative days. The study also mentions that of a total of 18 patients undergoing reconstruction with cryopreserved allografts due to a previous vascular graft infection, 3 patients with AB0 incompatible allograft experienced late allograft related complications [13]. Therefore, allografts represent a suitable alternative that can be used in an infected field due to their low incidence of reinfection.

A biohybrid vascular graft with a viable endothelial layer is another possible option in cases where the application of a prosthetic graft is contraindicated and an allograft is not available. This technique uses endothelial cells from a subcutaneous vein segment, bone marrow cells or human endothelial progenitor cells. These cells can be seeded onto the prosthetic graft lumen. A viable endothelial layer possesses the best antithrombogenic and, possibly, anti-infective qualities. Totally-engineered blood vessels are the last option. Synthetic or natural polymer materials provide a temporary scaffold for vascular tissue regeneration, and are gradually removed and replaced by the newly-forming tissue [14]. These approaches are, however, limited to scarce clinical trials [15].

According to the latest guidelines of the European Society for Vascular Surgery [2], long-term antimicrobial therapy is recommended for vascular graft infection. If the prosthetic material can be removed and a thorough debridement of all infected tissue is achieved, intravenous therapy for a minimum of two weeks followed by an oral regimen for another two to four weeks is indicated. If the infected material is replaced by a new vascular graft, four to six weeks of intensive antimicrobial therapy is normally proposed to prevent recurrent infection. In our case, antimicrobial therapy consisted of one week of post-operative intravenous antibiotics followed by another week of oral antibiotics. Because all cultures tested negative, we decided to cease further antimicrobial therapy.

CONCLUSION

Vascular graft infection poses a serious problem. We presented the case of a patient who had undergone repeated vascular reconstructions in the right lower limb due to recurrence of a false aneurysm in the groin. This complication was solved by replacing the infected graft with an arterial allograft. Our case report shows the suitability of using an allograft and the importance of immunosuppression after this type of vascular reconstruction.

List of abbreviations:

CT          – computed tomography

CTA       – computed tomography angiography

ePTFE – expanded polytetrafluoroethylene

ICU     – intensive care unit

SSI     – surgical site infection

VGI    – vascular graft infection

Supported by Ministry of Health, Czech Republic – conceptual development of research organization (“Institute for Clinical and Experimental Medicine – IKEM, IN 00023001“).

Conflict of interests

The authors declare that they have not conflict of interest in connection with this paper and that the article has not been published in any other journal, except congress abstracts and clinical guidelines.

MUDr. Martina Pluchová

Department of Transplantation Surgery, IKEM

e-mail: plum@ikem.cz

ORCID: 0009-0001-9081-6673