Predictors of early unfavorable outcomes in low NIHSS stroke patients undergoing thrombectomy: A case-control analysis of the Canadian OPTIMISE registry.

Abstract

Background: The benefit of endovascular thrombectomy (EVT) for patients with large vessel occlusion (LVO) stroke and National Institutes of Health Stroke Scale (NIHSS) ≤5 remains uncertain. Despite their initially mild presentations, many experience early deterioration and poor long-term outcomes. However, EVT carries procedural risks. We aimed to determine the prevalence of early unfavorable outcomes in EVT-treated low NIHSS patients and identify modifiable predictors.

Material and methods: We conducted a retrospective case-control study using the Canadian OPTIMISE registry which captured EVT data nationwide (2018-2021). Adult patients with LVO stroke and admission NIHSS ≤5 treated with EVT were included. The primary endpoint, "early unfavorable outcome," was a composite of early neurological deterioration (NIHSS increase ≥4 within 24 h), symptomatic intracranial hemorrhage, in-hospital death, or discharge to long-term care. Cases were all patients meeting this endpoint; controls were matched 4:1 by age, sex, and baseline NIHSS. Modifiable predictors were analyzed using multivariable conditional logistic regression.

Results: Among 439 EVT-treated low NIHSS stroke patients, 50 (11%) experienced early unfavorable outcomes and were matched to 200 controls without unfavorable outcome. Unsuccessful reperfusion (TICI <2b) was the only modifiable factor significantly associated with early unfavorable outcomes (aOR 41.52, 95% CI 5.31-324.62, p<0.001). Prior IV thrombolysis, thrombectomy technique, and procedural complications were not associated.

Conclusions: About one in ten EVT-treated low NIHSS patients experienced early unfavorable outcomes. Unsuccessful reperfusion was the strongest determinant. While reperfusion success is multifactorial and not entirely modifiable, this finding suggests that additional efforts to achieve complete recanalization in selected patients can be considered in appropriately selected patients. These findings provide real-world multicenter evidence pending the completion of ongoing randomized trials evaluating EVT in low NIHSS stroke.