Graft infections after surgical aortic reconstructions

Abstract

Prosthetic vascular grafts are frequently used to reconstruct (part) of the aorta. Every surgical procedure caries a certain risk for infection and when a prosthetic aortic graft is implanted, this may lead to an aortic graft infection (AGI). Endovascular techniques have gradually replaced open surgical reconstructions as first line of treatment for aorto-iliac diseases. Nowadays, open reconstructions are primarily reserved for patients unsuitable for endovascular reconstructions or for redo surgical procedures, both of which have been identified as risk factors for graft infection. Most knowledge on AGI is derived from relatively older studies and may no longer be applicable in the current endovascular era. AGI is a rare and heterogenous disease and this results in a lack of knowledge on the incidence and on the best diagnostic and treatment options.

Data on the incidence of aortic graft infections is scarce and mainly comes from outdated case-series. These series are criticized because they lack a uniform definition of AGI and include a combination of patients with very different infectious risk profiles. In this thesis, strict inclusion and follow-up criteria were used to determine up to date 2 year incidence for AGI (4.5% (95% CI: 2.4 - 6.6)).

Establishing the diagnosis AGI is difficult and relies heavily on imaging modalities such as 18F-Fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) scanning. 18F-FDG is a radioactive labeled glucose analog. Both inflammatory and infectious processes show an increased uptake of 18F-FDG and PET is therefore unable to differentiate between inflammation and infection. This thesis shows that the uptake patterns of uninfected vascular grafts display a large overlap with the pathological uptake patterns of infected grafts. This leads to the conclusion that the PET scan is inadequate in differentiating between uninfected and infected grafts in most cases. Assessing PET-scans is a complex process in which visual pattern interpretation and supplemental parameters are used to interpret the images. However, in this thesis, none of the commonly used parameters to interpret PET images were able to firmly diagnose AGI.

The surgical treatment of AGI relies on the removal of all infectious material (debridement) and constructing an alternative vascular route to the lower limbs. The treatment of a patient with an aortic graft infection should be tailor-made in which the choice of reconstruction depends on anatomic details, patient characteristics, and graft availability.

The debridement is often the most extensive part of the operation and by removing the graft itself, long ischemic times arise. The associated surgical trauma is severe and a significant part of the patients with AGI is not able to endure extensive surgery. Vacuum Assisted Closure directly on exposed infected vascular grafts in the groin, is a limited surgical approach with which an 87% successful wound healing can be attained. While this shows that VAC is able to safely preserve exposed (and infected) grafts in the groin, it is by no way a treatment of the infection itself. This therapy relies on antibiotics to suppress the infection to a level in which a patient is not systemically ill.