Post-operative neutrophil-to-lymphocyte ratio and outcome after thrombectomy in acute ischemic stroke

 We don't need more useless prediction of bad outcomes. Do the damn research that prevents those outcomes!

Post-operative neutrophil-to-lymphocyte ratio and outcome after thrombectomy in acute ischemic stroke

Shen-Jie Li¹, Shan-Shan Cao¹, Pei-Sheng Huang¹, Xin Nie², Yang Fu¹ and Jian-Ren Liu^1*

• ¹Department of Neurology, Stroke Center, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
• ²Biostatistics Office of Clinical Research Unit, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Background: Neutrophil to lymphocyte ratio (NLR) is a novel inflammatory marker to predict adverse cardiovascular events. However, there is a lack of data on hemorrhagic transformation (HT) and neurological outcome after mechanical thrombectomy in acute ischemic stroke (AIS). We investigated whether NLR before and after thrombectomy for patients with AIS was associated with HT and neurological outcomes.

Methods: We performed a retrospective analysis of consecutive patients with anterior circulation AIS who underwent thrombectomy. HT was evaluated by CT within 24 h after thrombectomy. Clinical data had been collected retrospectively; laboratory data were extracted from our electronic hospital information system. NLR was obtained at admission (NLR1) and immediately after thrombectomy (NLR2). The main outcomes were post-interventional intracranial hemorrhage and unfavorable functional status (modified Rankin scale scores of 3–6) 3 months post-stroke.

Results: A total of 258 patients with AIS, according to the NIHSS (median 14), were included. NLR2 was higher in patients who developed HT after thrombectomy and unfavorable neurological outcomes 3 months post-stroke (p < 0.001) than in those without HT or favorable outcomes, even after correction for co-factors [Odds Ratio (OR) 1.35 for HT, 95% confidence interval (CI)1.16–1.57, p < 0.001, and 1.85 for unfavorable outcome, 95%CI 1.57–2.17, p < 0.001]. The optimal cutoff value for the NLR2 as an indicator for auxiliary diagnosis of HT and the unfavorable outcome was 8.4 and 8.8, respectively.

Conclusion: NLR immediately after thrombectomy is a readily available biomarker of HT and neurological outcomes in patients with AIS.

Introduction

Acute ischemic stroke (AIS) is a common disease that affects elderly people (1). A randomized controlled trial confirms the improved reperfusion, early neurologic recovery, and functional outcome of thrombectomy compared to intravenous thrombolysis (IVT) (2). However, hemorrhagic transformation (HT) is a secondary intracranial hemorrhage after thrombectomy, with an incidence of about 10%. It is a major complication of thrombectomy and AIS in the acute phase (3), which often indicates a poor prognosis (4). Therefore, to improve the effectiveness of thrombectomy in clinical practice, it is of great significance to identify the risk factors of HT after thrombectomy.

Inflammation and immune responses run through all stages of cerebral ischemia and stroke progression, and when an ischemic stroke occurs, brain tissue releases pro-inflammatory chemokines, triggering strong inflammatory responses (5). Ischemic stroke reperfusion occurs after an endovascular procedure, and the damaged tissue is reoxygenated (6), resulting in the accelerated production of reactive oxygen species (ROS) and reactive nitrogen species. Inflammation caused by increased free radicals triggers the accumulation of inflammatory cells in the ischemic area. Interactions between endothelial cells and inflammatory cells lead to the release of many cytokines and amplify ischemic injury through reperfusion. Circulating neutrophils enter injured brain regions shortly after ischemia and then participate in disrupting the blood–brain barrier (BBB) and increasing tissue damage (7, 8). The greater the number of neutrophils, the greater the enhancement of tissue damage, as they lead to the release of inflammatory mediators, ROS, and various proteolytic enzymes. Lymphopenia may reflect cortisol-related stress responses and sympathetic tone (9), which may increase pro-inflammatory cytokine production (10). NLR as a reflection of innate (neutrophil) and adaptive (lymphocyte) immune responses has been extensively studied to assess the severity of inflammation associated with systemic or local diseases. Compared with a single index, a comprehensive index has higher validity and specificity. An increased NLR level with neutrophil exaltation and lymphocyte depletion suggests an imbalance in the interplay between central and peripheral inflammation induced by stroke.

However, previous studies focused on higher preoperative NLR levels as an independent predictor of symptomatic intracerebral hemorrhage (sICH) after thrombectomy (11). Stroke-related inflammation may be more closely related to HT after thrombectomy and functional status 3 months post-stroke, and NLR can be more accurately assessed in early follow-up after thrombectomy.

In the present study, we sought to investigate the association of NLR levels immediately after thrombectomy with thrombectomy-related HT and neurological outcomes in patients with AIS.

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