Residency · Residency · Vascular Surgery

Inflammation, Infection, and the Vascular System

Systemic Inflammation and Vascular Disease

Inflammatory Biomarkers

C-reactive protein (CRP) is an acute-phase reactant whose high-sensitivity form (hs-CRP) independently predicts cardiovascular events. The JUPITER trial demonstrated that rosuvastatin reduced cardiovascular events in patients with elevated hs-CRP despite having normal low-density lipoprotein (LDL) cholesterol levels, highlighting the role of inflammation beyond lipid levels. Interleukin-6 (IL-6) acts as an upstream driver of CRP production and serves as a central mediator of vascular inflammation. The CANTOS trial provided strong evidence for the inflammatory hypothesis of atherosclerosis by showing that canakinumab, an anti-IL-1-beta monoclonal antibody, reduced cardiovascular events independently of lipid lowering. Fibrinogen, another acute-phase reactant, also functions as a thrombotic factor and serves as an independent cardiovascular risk marker.

Chronic Inflammatory States Affecting Vascular Disease

Several chronic inflammatory conditions increase the risk of vascular disease. Rheumatoid arthritis is associated with a two- to threefold increased cardiovascular risk due to accelerated atherosclerosis. Systemic lupus erythematosus leads to premature atherosclerosis and is often complicated by antiphospholipid antibodies. Chronic kidney disease contributes to vascular pathology through uremic inflammation and calcific arteriopathy. Human immunodeficiency virus (HIV) infection causes chronic immune activation and metabolic derangements related to antiretroviral therapy, both of which promote vascular disease. Periodontal disease has also been epidemiologically linked to cardiovascular disease, suggesting a role for chronic oral inflammation.

Vasculitides

Large Vessel Vasculitis

Takayasu Arteritis

Takayasu arteritis is characterized by granulomatous inflammation involving the aorta and its major branches. It predominantly affects young women aged 15 to 40 years, with a higher prevalence in Asian populations. Pathologically, it manifests as panarteritis with granulomatous inflammation, intimal hyperplasia, medial fibrosis, and adventitial scarring, which can lead to stenosis, occlusion, or aneurysm formation. Clinically, the disease progresses through two phases: an early systemic phase marked by fever, malaise, and elevated erythrocyte sedimentation rate (ESR), and a late occlusive phase often referred to as "pulseless disease" due to arterial stenoses. Classification is based on the arterial segments involved, ranging from Type I (aortic arch branches) to Type V (combined involvement). Diagnosis relies on imaging modalities such as computed tomography (CT) angiography or magnetic resonance (MR) angiography, which reveal wall thickening, stenosis, or aneurysms. Positron emission tomography (PET)-CT can detect active inflammation. Treatment begins with corticosteroids as first-line therapy, supplemented by immunosuppressants like methotrexate, azathioprine, or tocilizumab (an anti-IL-6 agent). Surgical or endovascular interventions are reserved for periods of disease quiescence due to a high restenosis rate if performed during active inflammation. Surgical principles emphasize bypass from uninvolved to uninvolved arteries, avoiding anastomosis to inflamed segments, and generally avoiding endarterectomy.

Giant Cell Arteritis (Temporal Arteritis)

Giant cell arteritis is the most common primary systemic vasculitis in adults over 50 years old. It involves granulomatous inflammation of medium and large arteries, with a predilection for the extracranial branches of the carotid artery, including the temporal and ophthalmic arteries. The subclavian and axillary arteries, as well as the thoracic aorta, are also frequently affected. Clinically, patients present with new-onset headache, jaw claudication, scalp tenderness, and visual disturbances such as anterior ischemic optic neuropathy, which constitutes an ophthalmologic emergency. There is a notable overlap with polymyalgia rheumatica in 40-60% of cases. Diagnosis is supported by markedly elevated ESR (often above 100) and CRP levels. Temporal artery biopsy remains the gold standard, requiring a 2-3 cm specimen due to skip lesions; bilateral biopsies are recommended if suspicion is high. Ultrasound may reveal a "halo sign" around the artery. Treatment involves high-dose corticosteroids (prednisone 40-60 mg/day or intravenous methylprednisolone if visual symptoms are present), and therapy should not be delayed pending biopsy results. Tocilizumab has been shown in the GiACTA trial to be effective as a steroid-sparing agent. Vascular complications include a 17-fold increased risk of thoracic aortic aneurysm necessitating long-term surveillance, upper extremity arterial stenosis, and aortic dissection.

Medium Vessel Vasculitis

Buerger Disease (Thromboangiitis Obliterans)

Buerger disease is a non-atherosclerotic, segmental inflammatory disorder affecting small and medium arteries and veins. It almost exclusively occurs in young male smokers under 45 years of age. Pathologically, it is characterized by a highly cellular inflammatory thrombus with intact vessel wall architecture, distinguishing it from atherosclerosis, and contains microabscesses within the thrombus. Clinically, it presents with distal extremity ischemia manifesting as digital gangrene, superficial thrombophlebitis, and Raynaud phenomenon. The disease progresses proximally with continued tobacco use. Diagnosis is clinical, based on age under 45, smoking history, distal extremity ischemia, and exclusion of autoimmune or hypercoagulable states and proximal atherosclerotic sources. Angiography typically shows corkscrew collaterals and segmental occlusions. The only treatment that alters the disease course is absolute tobacco cessation, including avoidance of smokeless tobacco and marijuana. Bypass surgery is generally ineffective due to poor distal targets. Iloprost may be used for critical ischemia, and sympathectomy remains controversial. Prognosis is favorable with amputation-free survival exceeding 90% if complete cessation is achieved, but the amputation rate is high with continued tobacco use.

Small Vessel Vasculitis (Vascular Surgery Relevance)

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA), may involve mesenteric ischemia and renal artery involvement, which are relevant to vascular surgery. Polyarteritis nodosa, a medium-vessel vasculitis often associated with hepatitis B infection, can cause mesenteric and renal microaneurysms at branch points, posing a risk of rupture.

Mycotic Aneurysms

Definition and Pathogenesis

Mycotic aneurysms are infected aneurysms of arteries. Despite the name "mycotic," which implies fungal infection, most are caused by bacteria. Pathogenesis includes septic emboli from endocarditis, bacteremic seeding of pre-existing aneurysms or atherosclerotic plaques, contiguous spread from adjacent infections, and direct trauma or injection. These processes weaken the arterial wall by destroying the media, leading to pseudoaneurysm or true aneurysm formation.

Microbiology

The most common causative organisms are Staphylococcus aureus and Salmonella species, especially in the atherosclerotic aorta. Other pathogens include Streptococcus, Enterococcus, Escherichia coli, and various gram-negative bacteria. Fungal infections such as Candida and Aspergillus occur primarily in immunocompromised patients. Mycobacterium tuberculosis is a rare cause in developed countries. Syphilitic aortitis caused by Treponema pallidum is now historical but was associated with ascending aortic aneurysm, aortic insufficiency, and coronary ostial stenosis.

Clinical Features

Patients typically present with fever, leukocytosis, and positive blood cultures. A painful, pulsatile, and rapidly expanding mass is common. Imaging may reveal periaortic soft tissue stranding and gas on CT. Atypical locations such as the suprarenal aorta or superior mesenteric artery, or saccular morphology in unusual sites, raise suspicion. Presentation may include contained rupture.

Diagnosis

CT angiography is the primary imaging modality, showing saccular aneurysms, periaortic inflammation or gas, and adjacent vertebral body erosion. Blood cultures are positive in approximately 50-70% of cases. PET-CT can identify occult infection. Intraoperative cultures of the arterial wall are essential for guiding therapy.

Management

Medical management requires prolonged intravenous antibiotics for at least six weeks, with lifelong suppression in some cases. Surgical principles include wide debridement of infected tissue. Revascularization options include extra-anatomic bypass through clean tissue planes, such as axillobifemoral bypass for aortic infection followed by excision of the infected segment, which is the traditional approach. Alternatively, in-situ reconstruction using autogenous conduits like the femoral vein (neoaortoiliac system or NAIS procedure), cryopreserved allografts, or rifampin-soaked prosthetic grafts is increasingly favored for infrarenal aortic infections due to better patency and lower risk of aortic stump blowout. Endovascular repair serves as a temporizing measure in ruptured mycotic aneurysms but is generally not definitive because of persistent infection around the graft.

Vascular Graft Infection

Incidence and Risk Factors

Vascular graft infections occur in 1-3% of aortic grafts and 3-6% of infrainguinal grafts. Risk factors include groin incisions, redo surgeries, wound complications, immunosuppression, and emergency procedures. Bacterial biofilms form on graft surfaces, protecting pathogens from antibiotics and immune clearance.

Microbiology

Early infections (within four months) are typically caused by Staphylococcus aureus and gram-negative bacteria. Late infections (after four months) often involve Staphylococcus epidermidis, a biofilm-producing coagulase-negative staphylococcus. Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly prevalent.

Presentation

Early infections present with wound infection, anastomotic bleeding, and sepsis. Late infections may manifest as draining sinuses, pseudoaneurysms, graft-enteric fistulas, or erosions. A "herald bleed," an upper gastrointestinal hemorrhage in a patient with an aortic graft, suggests a graft-enteric fistula.

Diagnosis

Computed tomography with intravenous contrast reveals perigraft fluid collections persisting beyond three months postoperatively, gas, pseudoaneurysms, or contrast extravasation. White blood cell-labeled nuclear scans and PET-CT can detect occult infections. Esophagogastroduodenoscopy (EGD) is used to diagnose graft-enteric fistulas and may visualize the graft within the duodenum.

Management

When feasible, total graft excision is the treatment of choice. Revascularization can be performed via extra-anatomic bypass or in-situ reconstruction, as described in the mycotic aneurysm section. Partial graft preservation with local debridement, muscle flap coverage, and antibiotic therapy may be considered for low-virulence infections involving only one limb of a bifurcated graft.

<image>Medical illustration showing the different types of vasculitis organized by vessel size: large vessel (Takayasu arteritis affecting the aorta and major branches, giant cell arteritis affecting temporal and subclavian arteries), medium vessel (Buerger disease affecting digital and small extremity arteries, polyarteritis nodosa affecting mesenteric arteries), and small vessel (ANCA-associated vasculitis). Use a human body silhouette with highlighted affected arteries for each condition.</image>

<image>Illustration comparing arterial cross-sections in three conditions: (1) atherosclerotic plaque with lipid core and fibrous cap, (2) Buerger disease showing highly cellular inflammatory thrombus with microabscess and intact vessel wall, and (3) mycotic aneurysm showing bacterial colonies, medial destruction, and pseudoaneurysm formation. Label key distinguishing pathological features for each.</image>

<image>Surgical management algorithm for infected aortic graft showing CT scan findings leading to two pathways: extra-anatomic bypass (axillobifemoral graft through clean tissue planes followed by infected graft excision and aortic stump closure) versus in-situ reconstruction (excision of infected graft with replacement using femoral vein, cryopreserved allograft, or rifampin-soaked Dacron). Show the relevant anatomy for each approach.</image>

Key Clinical Pearls

The CANTOS trial definitively proved that inflammation directly drives atherosclerotic events independently of lipid levels. Giant cell arteritis constitutes an ophthalmologic emergency; therefore, high-dose steroids should be initiated immediately if vision is threatened, without waiting for biopsy results. Buerger disease is unique among vasculitides in that tobacco cessation alone alters the disease course, with no other effective treatments available. In Takayasu arteritis, surgical intervention should only be performed during disease quiescence because revascularization during active inflammation carries a high risk of failure. Salmonella species exhibit a particular tropism for the atherosclerotic aorta, and bacteremic seeding can lead to rapidly expanding mycotic aneurysms. Graft-enteric fistula must be suspected in any patient with a prior aortic graft who presents with gastrointestinal bleeding, known as a "herald bleed," and esophagogastroduodenoscopy must include visualization of the fourth portion of the duodenum. In-situ reconstruction using femoral vein (the NAIS procedure) has become the preferred approach for aortic graft infections at many centers due to its resistance to infection and improved patency compared to extra-anatomic bypass.

References

• Ridker PM et al. Antiinflammatory therapy with canakinumab for atherosclerotic disease (CANTOS). N Engl J Med. 2017;377:1119-1131.
• Hunder GG et al. The American College of Rheumatology 1990 criteria for the classification of giant cell arteritis. Arthritis Rheum. 1990;33:1122-1128.
• Olin JW. Thromboangiitis obliterans (Buerger's disease). N Engl J Med. 2000;343:864-869.
• Clagett GP et al. Creation of a neo-aortoiliac system from lower extremity deep and superficial veins. Ann Surg. 1993;218:239-249.
• Wilson WR et al. Management of infected aortic grafts. J Vasc Surg. 2016;63:332-345.

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