CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 1, January–April 2023 50 AFRICA used in vascular surgery today, the search for the ideal graft closest to human vascular tissue still continues. While synthetic components provide strength and durability to the grafts, biological components facilitate textural adaptation. All biological materials may undergo biological degeneration over time, with the formation of aneurysms or stenotic lesions. Aneurysmal degeneration of biological grafts may impair graft patency by causing thrombosis as well as local symptoms.1 Three years later, aneurysmatic degeneration was observed in the biosynthetic graft used in this case, and a thrombus had also formed within the aneurysm. However, graft patency performance was not affected by this degeneration, causing only the local symptom of pulsatile swelling. An aneurysm is a vascular condition that can be defined as localised abnormal dilation of a vessel due to weakness. Weak points in grafts that lead to aneurysms may be caused by infection, trauma, anastomosis lines, intra-operative damage, intrinsic graft failure due to manufacturing flaws, improper sterilisation or storage, and expansion of the polyester mesh providing strength to the graft wall.1,5 However, the position of the graft in the extremity and the patient’s systemic diseases, such as hypertension, dyslipidaemia and autoimmune diseases, may also contribute to aneurysm formation. Articles reporting that aneurysms develop in all different types of grafts implanted in the same patients support this thesis.5 Aneurysms can be classified as true or false aneurysms. The definition of true aneurysms includes an increase in vessel diameter of 50% or more and involves all three layers of the vessel wall.6 True aneurysms are more regular in shape and different in appearance. They are more likely to have a wide neck compared to a pseudo-aneurysm.7 In this case, the aneurysm was compatible with a true aneurysm, 48 mm wide in the middle of the graft, and there was no history of trauma and no sign of local infection causing leakage at the incision line. Aneurysm formation is multifactorial and it is not always possible to determine the exact cause, as in this case. Nevertheless, we considered the patient’s existing systemic diseases and graft degeneration, which may occur over time due to mechanical flexion forces loaded on the inguinal region, as predisposing factors for this patient’s non-anastomotic aneurysm formation. The potential degeneration of biosynthetic grafts and the formation of a true aneurysm, as observed in autologous vein grafts, is a well-known problem. In a recent study, a synthetic PTFE graft and OBVG were compared for infra-inguinal bypass surgery, and graft performance was found to be similar. However, while no aneurysm was observed after two years with PTFE, 8% aneurysm was observed in the OBVG.4 Koch et al.2 reported only a small aneurysm rate of 1.1% in a series of 267 operations with an eight-year observation period. Another study reported a total of 12.6% aneurysmatic degeneration, 10.7% of which were non-anastomotic, in the OBVGs used for femoropopliteal bypass surgery.1 The fact that such different rates were reported for aneurysm formation in OBVGs makes us think that the underlying predisposing factors are predominantly patient related. However, more comprehensive studies are needed to confirm this situation. OBVG is presently the closest to the ideal arterial prosthetic graft currently available on the market as a bypass graft for cases where autologous vein use is not possible. The three-year patency rate of the above-knee OBVG was reported to be 83.7 to 98%.3 However, it has a tendency to develop late biodegeneration with possible graft aneurysm formation due to the negative features of the biological material. Aneurysm formation can result in thrombus formation over time. This, in turn, disrupts the patency of the graft, causing ischaemia, rupture, haematoma and infections, and is lifethreatening. Therefore, peripheral graft patients shouldbe followed regularly with physical examination and duplex ultrasound to reduce graft failure rates and detect rare complications such as degenerative aneurysm. In addition, patients should be instructed to seek immediate hospitalisation in cases of unexplained peripheral swelling along the leg graft tracing. Open surgery (repair of aneurysmal degeneration or replacement of the entire graft) is the most commonly preferred treatment for aneurysmatic peripheral bypasses. However, percutaneous implantation of the stent graft may be an alternative treatment in patients at high risk. If there is no suitable area for distal anastomosis in open surgery, aneurysmal degeneration repair should be chosen. In our case, as there was no suitable area for distal anastomosis, we excised the aneurysmatic biological graft segment and performed synthetic PTFE graft interposition. Conclusion Despite technological advances in tissue engineering of vascular grafts, degenerations can be seen at different rates in biosynthetic vascular grafts. Therefore, as in our case, the fact that physical examinations of patients are normal (palpable pedal pulses) or the absence of claudication complaints in the control examinations performed after the femoropopliteal bypass do not mean that the synthetic graft is healthy. In particular, we believe that performing radiological imaging of the graft at more frequent periods (six months) will be beneficial for the early detection of graft-related complications. References 1. Neufang A, Duenschede F, Espinola-Klein C, et al. Contemporary results with the biosynthetic glutaraldehyde denatured ovine collagen graft (Omniflow II) in femoropopliteal position. J Vasc Surg 2020; 71(5): 1630–1643. 2. Koch G, Gutschi S, Pascher O, et al. Analysis of 274 omniflow vascular prostheses implanted over an eight-year period. ANZ J Surg 1997; 67(9): 637–639. 3. Toktaş F, Çayır MÇ, Özsin KK, et al. Long-term outcomes of Omniflow II biosynthetic vascular graft in lower extremity arterial revascularization. Turk Gogus Kalp Damar Cerrahisi Dergisi 2018; 26(3): 407–413. 4. Van de Laar BC, van Heusden HC, Pasker-de Jong PC, van Weel V. Omniflow II biosynthetic grafts versus expanded polytetrafluoroethylene grafts for infrainguinal bypass surgery. A single-center retrospective analysis. Vascular 2021 Jul 1: 17085381211029815. 5. Yamamoto S, Hoshina K, Kimura H, Okamoto H, Shigematsu K, Miyata T, et al. Clinical analysis of non-anastomotic aneurysms of implanted prosthetic grafts. Surg Today 2014; 44(10): 1855–1862. 6. Viljoen C, Szymanski P, Osman N, et al. Intimomedial mucoid degeneration causing aortic and renal artery aneurysms in a young adult. Cardiovasc J Afr 2016; 27(1): 49–52. 7. Corriere MA, Guzman RJ. True and false aneurysms of the femoral artery. Semin Vasc Surg 2005; 18(4): 216–223.
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