The aim of this observational study is to investigate the relationship between postimplantation syndrome (PIS) and laboratory inflammatory parameters following endovascular aortic repair (EVAR/TEVAR). PIS is a systemic inflammatory response that may occur after EVAR or TEVAR and lacks a standardized clinical definition. This study seeks to determine whether specific laboratory biomarkers-particularly white blood cell count, C-reactive protein (CRP), interleukin levels, and neutrophil-to-lymphocyte ratio (NLR)-can serve as reliable indicators for the diagnosis and assessment of PIS.

Endovascular repair of thoracic and abdominal aortic aneurysms (EVAR/TEVAR) has become a preferred alternative to open surgical repair due to its association with reduced perioperative morbidity and mortality. However, a notable proportion of patients undergoing these procedures may develop postimplantation syndrome (PIS), a systemic inflammatory response first described in 1999. Despite its clinical relevance, PIS remains poorly defined, with varying diagnostic criteria across the literature.

PIS is typically characterized by postoperative fever, fatigue, and an increase in inflammatory markers such as white blood cell (WBC) count, C-reactive protein (CRP), and interleukin-6 (IL-6). The neutrophil-to-lymphocyte ratio (NLR), a readily obtainable marker from complete blood count tests, has also gained attention as a reliable indicator of systemic inflammation. In contrast, procalcitonin levels in PIS patients often remain within normal limits, helping differentiate PIS from bacterial infections.

In this prospective observational study, 200 patients undergoing elective EVAR or TEVAR procedures under general anesthesia were included. All procedures were performed via bilateral femoral artery access using open femoral incisions. Patients were followed postoperatively and assessed for the development of PIS based on clinical and laboratory parameters.

Body temperature was measured at regular intervals, and inflammatory markers-including CRP, WBC count, IL-6, NLR, and procalcitonin-were recorded preoperatively and at 24, 48, and 72 hours postoperatively. PIS was defined as the presence of fever (>38°C) in association with elevated CRP and/or leukocytosis, in the absence of any clinical or microbiological evidence of infection.

Preliminary results showed that patients who developed PIS had significantly higher postoperative levels of WBC, CRP, IL-6, and NLR, while procalcitonin levels remained normal, supporting a non-infectious inflammatory etiology. Imaging and laboratory evaluations ruled out alternative sources of infection. No significant differences were observed in operative time or graft type between patients with and without PIS.

All data were collected prospectively and analyzed using the SPSS statistical software. The study aims to clarify the diagnostic criteria of PIS by identifying specific laboratory biomarkers that can reliably differentiate PIS from other postoperative complications, particularly infection. Furthermore, by better understanding the inflammatory response following EVAR/TEVAR, the study may contribute to improved postoperative management strategies.

Inclusion Criteria

• Patients aged ≥18 years
• Undergoing elective EVAR or TEVAR for abdominal or thoracic aortic aneurysm
• Ability to provide informed consent
• Availability of baseline and follow-up laboratory data (including IL-6, NLR, CRP, leukocyte count, procalcitonin, etc.)

Exclusion Criteria

• Evidence of active infection at the time of procedure
• Known autoimmune or inflammatory disease (e.g., rheumatoid arthritis, lupus)
• Current use of immunosuppressive or anti-inflammatory therapy
• Malignancy under active treatment
• End-stage renal or hepatic failure
• Emergency or ruptured aneurysm repair
• Incomplete postoperative laboratory data

The study population consists of adult patients (≥18 years) who underwent elective endovascular aneurysm repair (EVAR) or thoracic endovascular aortic repair (TEVAR) for abdominal or thoracic aortic aneurysms at a single tertiary care center. All participants had available pre- and postoperative laboratory data necessary for the evaluation of post-implantation syndrome and inflammatory biomarkers.

Individual participant data (IPD) will not be made publicly available due to institutional policies and the potential for overlapping use of the same dataset by other researchers within the institution. However, data may be shared upon reasonable request, provided that appropriate ethical approvals and data-sharing agreements are in place