Factors Affecting Clinical and Radiological Outcome in Endovascular Management of Acute Ischemic Stroke Due to Large Vessel Occlusion

Overview

Acute ischemic stroke (AIS), particularly if it is caused by a large-vessel occlusion (LVO), is a severe and life-threatening disease. Endovascular therapy (EVT) has rendered safe and effective treatment of AIS due to LVO possible, and new thrombolytic agents and neuroprotectants could soon complement pharmacological AIS therapy. These treatments are highly time dependent. Hence, the overarching goal in the management of patients with AIS is to rapidly and safely transfer, diagnose, and treat patients with AIS (1). The only available 2 treatment options are intravenous alteplase and endovascular therapy (mechanical clot removal), both of which are highly time dependent. Thus, rapid patient transfer, diagnosis, and treatment are crucial, and time-consuming imaging methods and overly selective treatment selection criteria should be avoided (2). Imaging is crucial for AIS management, as it confirms the diagnosis and guides treatment, with intravenous tissue plasminogen activator (alteplase) and/or EVT, the 2 evidence-based treatment strategies for AIS. Every 30-min delay in recanalization decreases the chance of a good functional outcome by 8% to 14% (3). Clinical outcome after large-vessel occlusive strokes depends on admitting clinical condition, successful recanalization, and robust collateral circulation. However, predicting successful recanalization and quantifying collateral status in the acute setting remain elusive (4). Successful recanalization has many predictive factors. Strong evidence supports increasing clot length being associated with poor recanalization. Current imaging techniques completed in the acute setting suggest that clot length can be estimated with a clot burden score (5). Studies consistently show that independent predictors in clinical outcome remain the patient's admission clinical condition as evaluated by baseline NIH Stroke Scale (NIHSS) scores and ischemic lesion volume. Emphasis on lesion volume suggested that stroke mechanism, particularly lacunar strokes with their smaller ischemic volumes, could be an independent predictor for favorable clinical outcome. However, predicting clinical outcome with stroke mechanism, particularly in large vessel occlusions (LVO), remains elusive (6). As thrombus origin site (i.e., vein, artery, or heart) is thought to play a role in clot composition, cardioembolic and paradoxical strokes with their greater fibrin content and red cells were thought to be more susceptible to fibrinolysis than heterogeneous, chronic thrombotic arterial plaques formed in artery-to-artery strokes. However, studies continue to show that stroke mechanism does not influence recanalization or clinical outcome after intravenous rt-PA (IVtPA) (7). Radiological signs that are readily available on a patient's index CT scan have generated interest as predictors for patients undergoing EVT for LVO AIS. For example, poor baseline collateral flow status and Alberta Stroke Program Early CT Score (ASPECTS), assessed via CT angiography, are associated with a larger ischemic core and worse functional outcomes. Other radiological variables which have been investigated include clot characteristics including clot length, density, surface phenotype, truncal versus branch-type occlusions and the presence of a meniscus sign. Further radiological variables that have been studied pertain to vascular anatomy and include parameters that quantify vascular tortuosity such as the aortic arch type (8). Despite advances in the management of acute ischemic stroke due to large-vessel occlusion, significant variability still exists in both clinical and radiological outcomes among patients. Moreover, the relative contribution and interaction of different clinical and imaging predictors in determining treatment success and functional recovery remain not fully established. In addition, there is still no complete consensus regarding the most reliable predictors of recanalization and favorable outcomes in the acute setting, particularly in relation to thrombus characteristics, collateral status, and vascular anatomy (9). Therefore, this study aims to evaluate factors affecting clinical and radiological outcome in management of acute ischemic stroke due to large vessel occlusion.