Neutrophil-to-Lymphocyte Ratio Associated With Adverse Events After Endovascular Aneurysm Repair (EVAR)

Abstract

Background: The blood neutrophil-to-lymphocyte ratio (NLR) is a surrogate biomarker of systemic inflammation with important prognostic significance in multiple disease processes, including cardiovascular diseases. It is inexpensive, widely available, and may be related to the outcomes of patients after surgery. We aimed to investigate the possible association of NLR with the outcomes of patients following endovascular aneurysm repair (EVAR).

Methods: This single-center, retrospective study of a prospectively maintained database evaluated 777 patients with a diagnosed abdominal aortic aneurysm (AAA) who underwent EVAR and were longitudinally followed between 2001 and 2017. NLR was defined as the ratio of absolute neutrophil count to absolute lymphocyte count. The mortality and reinterventions were used to evaluate outcomes using the appropriate univariate models, and the effect of clinical variables on NLR was further investigated using multivariate modelling.

Results: The median NLR for all patients was 3 IQR [2.2 - 4.6]. A cut-off point of 3.6 was uncovered in a training set of 388 patients using the maximally ranked statistic method. Patients with NLR < 3.6 had significantly improved mortality rates (P< 0.0001) in the training set, and results were internally validated in a testing set of 389 patients (P = 0.042). Multivariate analysis revealed that high NLR (HR 1.4 95% CI [1.0 - 2.0]; P< 0.05) remained an independent predictor of mortality in a multivariate analysis controlling for characteristics such as comorbidities, age, and maximal aortic diameter. 5-year mortality and 30-day, 1-year and 5-year reinterventions were all higher in the high NLR group.

Conclusion: High NLR was significantly associated with higher rates of death at 5 years as well as higher rates of reinterventions at 30 days, 1 year and 5 years. We also suggest that an internally validated cut-off point of NLR >3.6 may be clinically important to help segregate patients into high and low NLR categories. It remains unclear whether NLR is directly linked to adverse events post-EVAR or whether it is a surrogate for an inflammatory state that predisposes patients to higher risk of death or reinterventions.

Keywords: Aneurysm; EVAR; Inflammation; Neutrophil-to-Lymphocyte.