Vascular graft infection

Background

• May be extracavitary (in the groin or lower extremities) or intracavitary (in the abdomen or thorax)

Microbiology

• Staphylococcus aureus (30-60%)
• Coagulase-negative staphylococci (10-30%)
• Gram-negative bacilli (10-30%), including Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae
• Viridans group streptococci and enterococci (5%)
• Others: Candida, polymicrobial infections
• Culture-negative (5-30%)

Etiologies

• Intraoperative contamination (most common)
• Contiguous spread from superficial infection or intraabdominal infection
• Direct inoculation during subsequent procedure
• Hematogenous spread, less common after the early postoperative period (first 2 months) due to endothelialization

Clinical Manfestations

• Varies by site of graft and infection
• Can be early-onset (first 2 months) or late-onset (after 2 months)
• Late-onset infections tend to be indolent without sepsis

Samson Classification

• Classification of peripheral arterial prosthetic graft infections 1
• Minor infections
  • Group I: infection no deeper than the dermis
  • Group II: infection of subcutaneous tissue without visible involvement of graft
• Group III: infections involving graft but not anastomosis
• Group IV: infections involving exposed anastomosis without bacteremia or anastomotic bleeding
• Group V: infections involving graft-to-artery anastomosis with bacteremia or anastomotic bleeding

Diagnosis

• Diagnosis is made clinically
• Ultrasound is usually the initial imaging procedure, followed by CTA or MRI if US is equivocal
• CT- or US-guided aspiration can be helpful for a microbiologic diagnosis

Imaging

• Imaging is a mainstay of diagnosis, and is reviewed in 2
• Ultrasound is typically the first-line choice, and can evaluate perigraft collections as well as guide aspiration
• CT-CTA is the first-line choice for intracavitary infections
  • CTA has sensitivity 67% and specificity 63%, but is more sensitive and specific for more complex infections
  • Can be hard to distinguish from post-operative changes
• MRI is less well studied, but may be better able to distinguish perigraft fluid from inflammation and fibrosis than CT
• Radiolabelled WBC scan can be very helpful in distinguishing sterile inflammation from infection and likely has very high sensitivity and specificity

Aortic Graft Infection

• There is a MAGIC Case Definition for AGI, based on consensus3

Management

• Local infection without graft involvement: antibiotics with or without incision and drainage (groups I & II)
  • Duration 2 to 4 weeks
• Infection involving graft but without bacteremia or anastomotic bleeding (groups III & IV)
  • Incision and drainage
  • Preservation of graft, or reconstruction with allograft, autograft, or prosthetic material
  • 4 to 6 weeks of IV followed by 3 to 6 months of oral
• Infection with bacteremia or anastomotic bleeding (group V)
  • Extra-anatomic revascularization followed by graft excision
  • 4 to 6 weeks IV followed by 6 months oral

Further Reading

• Vascular Graft Infections, Mycotic Aneurysms, and Endovascular Infections: A Scientific Statement From the American Heart Association. Circulation. 2016;134:e412-e460. doi: 10.1161/CIR.0000000000000457