Aneurysmal Degeneration of Autologous Vein Bypass Grafts

Abstract

<h3>Introduction and Objective</h3> Symptomatic aneurysmal degeneration of autologous vein grafts is a rare complication of open infrainguinal revascularization. The exact etiology is not well understood. Proposed mechanisms include conduit arterialization with progression of systemic atherosclerosis, vasculitis, or infections. There may also be a component of repeated mechanical strain as most are adjacent to the knee joint. We describe four cases of aneurysmal degeneration in the distal portions of femoral-to-popliteal bypasses using reversed saphenous vein grafts (rSVG). <h3>Case Report</h3> A retrospective chart review of a single surgeon from 2000-2020 was conducted at a tertiary care institution with a total of 165 infrainguinal bypasses performed. 4 patients were identified with aneurysmal degeneration of their grafts. Discrete aneurysms at the proximal or distal anastomoses were excluded. All patients were male, and ages ranged from 45 to 76. They had undergone previous femoral-to-popliteal bypasses using reversed saphenous vein grafts. Three of the patients had the procedure performed for popliteal artery aneurysms. One had a bypass performed for traumatic injury to the lower extremity at age 25. Two patients also had generalized aneurysmal disease including abdominal aortic aneurysms treated with endovascular aortic repair prior to the popliteal artery bypass. All patients had hypertension. Two patients were current smokers, one was a previous smoker, and one was a never smoker. Clinical presentations included pain and swelling with revision occurring at an average of 12.5 years post-bypass creation. One patient presented with foot discoloration concerning for distal embolization. Computed tomography confirmed graft aneurysms ranging from 2-4 cm occurring near the knee joint. Two patients had diffuse aneurysmal disease of almost the entire vein graft while the other two had aneurysmal segments around the knee joint. All the grafts had been tunneled subcutaneously and were patent on presentation, but with irregular mural thrombus in the aneurysm. All patients underwent revision with interpositions grafts of the aneurysmal segment; two used rSVGs and two used polytetrafluoroethylene. On one-month follow-up, all patients reported symptomatic improvement with duplex scan and clinical exam demonstrating graft patency. All patients postoperatively were continued on aspirin and statin. At six-month follow-up, one patient had graft occlusion requiring a new femoral-to-tibioperoneal trunk bypass. <h3>Discussion and Conclusion</h3> Aneurysmal degeneration of autologous vein conduits is uncommon. Etiologies point to the same systemic influences and risk factors as native aneurysms. We believe advanced atherosclerotic progression led to significant inflammatory changes, plaque development, and vessel weakening in our patients. However, we propose a component of repeated mechanical stretch must also be recognized, especially in the setting of subcutaneously tunneled vein bypass, located at the knee near the acute angulation prior to the popliteal anastomosis. This location is subject to constant physical stretch and microtrauma with knee movement. Patients with multiple aneurysms are also more prone to aneurysmal degeneration, and frequent graft surveillance is warranted in this population.