Cath Lab Digest

ABSTRACT: Infection of prosthetic vascular grafts is a rare but severe complication in reconstructive vascular surgery. It carries a potential vital risk of bacteremia and sepsis. In spite of improved surgical techniques and use of systemic antibiotics, the prevalence of infection of prosthetic vascular grafts is 1%-6% and is associated with high morbidity and mortality. The early diagnosis of this complication can significantly reduce morbidity and mortality.

VASCULAR DISEASE MANAGEMENT 2012:9(7):E113-E120

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Infection of prosthetic vascular grafts is a rare but severe complication in reconstructive vascular surgery.¹ It carries a potential vital risk of bacteremia and sepsis. Despite improved surgical techniques and use of systemic antibiotics, the prevalence of infection with prosthetic vascular grafts is 1%-6%² and is associated with high morbidity and mortality.³ The early diagnosis of this complication can significantly reduce morbidity and mortality.

When diagnosing graft infections, imaging methods such as ultrasonography, computed tomography, and magnetic resonance imaging are widely available.^4,5 However, morphological imaging techniques lack the capacity to differentiate between active infection and reparative tissue reactions.⁶

Positron emission tomography (PET) using radioactive fluorine-positron emission tomography-fluoro-D-deoxyglucose (18F-FDG-PET) is a widely used and well-established clinical tool for oncology. It provides added diagnostic accuracy in orthopedics for diagnosing suspected chronic osteomyelitis as well as the detection and localization of infectious diseases.^14,15 The added value of hybrid imaging combining PET with CT modalities has been recognized and evaluated for tumor staging of the lung,¹⁶ stomach,¹⁷ intestine,¹⁸ thymus,²⁹ head, and neck.¹⁹ 18F-FDG is a radiotracer of increased intracellular glucose metabolism. It therefore shows higher activity (uptake) in malignant tissue, as well as in infectious and inflammatory processes.

Material and Methods

The protocol of this retrospective study has been submitted to the Ethical Commission of the University Hospital of Geneva (Geneva, Switzerland).

Patients

The study population consisted of 17 consecutive patients with suspected vascular graft infection between June 2006 and July 2010 (15 males; 44-90 years). The time elapsed from the primary surgery was between 4 weeks and 7 years. During the first intervention, patients received different vascular grafts. Of the total number of patients included in the study, 5 underwent surgical repair of the abdominal aorta, 3 underwent procedures for chronic or acute dissected abdominal aorta, and 2 subjects were surgically treated for ruptured aneurysm of the abdominal aorta. One patient required replacement of the ascending thoracic aorta whereas the remaining 11 patients were surgically treated for chronic peripheral artery diseases of the lower extremities (Table 1). Nine out of the 17 patients received Dacron prostheses: 4 in the abdominal aorta, 1 in the ascending aorta, and 4 in the lower extremities. Two patients had xenografts in the abdominal aorta; 2 were treated with homografts in the lower extremities; and 4 with polytetrafluoroethylene (PTFE) prosthetic grafts. The decision for the prosthesis was made according to the surgical indication.

All 17 patients underwent complete staging examinations (physical, blood and wound cultures, diagnostic CT of the abdomen and lower extremities). In cases manifesting fluid collection (liquid vs hematoma vs abscess) around the prosthesis as revealed by CT, whole-body 18F-FDG PET-CT was performed.

In all patients, graft infections were suspected on the basis of symptoms (local pain, macroscopically detected local inflammatory signs), pathological changes around the wound, and fever. The laboratory parameters included white blood cells (WBCs), C-reactive protein (CRP), and blood cultures (Table 2).

Blood analyses showed increased infection parameters such as WBCs >10 g/L in 10 patients and CRP >50 mg/L in 15 patients. Four patients showed positive blood cultures. Blood cultures were done only in patients with temperatures >38°C at the time of hospital admission without the benefit of antibiotic treatment. Accordingly, this was manifested in 5 cases.

The time interval after implantation of the first graft was between 4 weeks and 7 years until the first sign warranted suspicion of infection and re-hospitalization. There is usually ≥4 weeks postoperative delay for PET imaging to avoid false-positive imaging results due to postoperative inflammation.