HISTOPATHOLOGICAL CHARACTERISTICS OF EXPLANTED HUMAN PROSTHETIC ARTERIAL GRAFTS - IMPLICATIONS FOR THE PREVENTION AND MANAGEMENT OF GRAFT INFECTION

Objective: to study the histopathological characteristics of prostheti c vascular graft infection. Design: prospective clinical study over 2 years. Setting: University Hospital. Materials: 36 infected and 29 uni nfected (control) chronically implanted vascular prostheses (half aort ic) were removed and 352 sections prepared. Chief outcome measures: li ght microscopy (multiple stains), scanning electron microscopy (SEM), and multiple culture techniques to identify characteristics of healing , infection, and microorganisms. Main results: Acute inflammation (AI) (neurophils, granulocytes and necrosis) were seen in 75% of infected grafts, were most prominent in the perigraft tissue and rarely seen on the luminal surface. These were usually well localised, leaving the r emainder of a graft well incorporated with no signs of infection. In 2 5% of clinically infected, culture-positive grafts there was no signif icant acute inflammation. Chronic inflammation (CI) (macrophages, lymp hocytes, monocytes, giant cells) was seen in 70% of both control and i nfected grafts. In 50% of both groups a significant lymphocytic popula tion was composed exclusively of T-lymphocytes suggesting a true host vs. graft response. Unincorporated chronically implanted grafts (>1 yr ) were seen with equal frequency in the two groups although more diffu sely unincorporated grafts were infected. Microorganisms were cultured from 23 infected grafts (64%) and were, at microscopy, mostly found o utside the graft and nerves on the luminal side. Conclusions: This dat a cast doubt on criteria commonly used to distinguish graft infections and host vs. graft reactions from normal graft healing. Acute and chr onic inflammation are not predictive of infection.