Association of Preoperative Neutrophil-to-Lymphocyte Ratio With Rates of Adverse Events After Thoracic Endovascular Aneurysm Repair

Abstract

While the short-term mortality benefit of thoracic endovascular aneurysm repair is well-described, factors affecting reintervention rates remain less understood. The neutrophil to lymphocyte ratio (NLR) is an inexpensive and extensively available biomarker that acts as a surrogate for systemic inflammation with demonstrated prognostic significance in cardiovascular diseases following surgical intervention. We aimed to investigate the association of NLR with post-thoracic endovascular aneurysm repair reinterventions in patients with a descending thoracic aortic aneurysm or type B aortic dissection. This single-institution, retrospective study included 107 patients who underwent thoracic endovascular aneurysm repair and were longitudinally followed between 2001 and 2018. Baseline clinical characteristics, follow-up information, and preoperative blood work were collected. NLR was defined as the ratio of absolute neutrophil count to absolute lymphocyte count. Adverse events were defined as type I and III endoleaks, type II endoleaks, graft infections, or any other complications requiring reintervention. High and low NLR groups were determined based on the median NLR score. Clinical characteristics and the adverse event-free interval between the two groups were compared using the appropriate statistical methods. The median NLR for all patients was 3.5 and was used to separate patients into high and low NLR groups (median, 2.56 [interquartile range, 1.91-2.98] and 9.22 [interquartile range, 6.12-10.9]). Baseline clinical characteristics were not significantly different between the two groups. The number of adverse events was higher in the high NLR group. (30% vs 58%; χ2 P = .013). Patients in the low NLR group also showed longer reintervention-free intervals in a univariate Kaplan-Meier analysis (log-rank P = .02). High NLR remained significantly associated with worse event-free intervals after controlling for age and important comorbidities (Table; hazard ratio, 2.11 [interquartile range, 1.08-5.4.12]; P = .030). Inspection of complete blood cell count values suggest that the difference in NLR may be mediated by an increase in neutrophil count. Patients with a NLR of greater than 3.5 exhibited higher rates of postoperative outcomes compared to patients with lower NLR. While corrective reinterventions may not necessarily affect mortality, they have significant impact on cost and patient health. Further investigation is required to reliably determine the optimal categorical cut point and whether NLR directly affects outcome or if it acts as an aggregate marker of a patient’s preoperative physiologic state.TableMultivariate analysisClinical variableHazard ratio [95% confidence interval]P valueMLR groupLowReferenceHigh2.105 [1.075-4.123].030Age0.997 [0.974-1.021].830DiagnosisAneurysmReferenceTBAD0.981 [0.459-2.095].960DiabetesNoReferenceYes0.344 [0.096-1.233].101SmokingActiveReferenceFormer0.844 [0.270-2.643].771Never1.186 [0.354-3.979].782Chronic kidney diseaseNoReferenceStage III1.445 [0.653-3.149].354Stage IV0.781 [0.097-6.306].817Stage V0.514 [0.063-4.213].535HypercholesterolemiaNoReferenceYes1.279 [0.661-2.475].465No. of devices implanted1Reference21.314 [0.636-2.715].46131.473 [0.654-3.317].35045.696 [0.622-52.135].124MLR, TBAD, type B aortic dissection. The effect of neutrophil to lymphocyte ratio on reintervention rate was controlled for conditions known to affect systemic inflammation or outcome after thoracic endovascular aneurysm repair.Boldface entries indicate statistical significance. Open table in a new tab