Mark R. Etherton, MD, PhD
The advent of efficacious endovascular thrombectomy (EVT) for ischemic stroke secondary to acute occlusion of proximal anterior circulation vessels has allowed for the characterization of occlusive lesions. Understanding the underlying pathology of these occlusive lesions could be informative for predicting the success of the endovascular intervention as well as prognostication of clinical outcomes.

In the present study, Hwang et al. characterized residual stenosis post EVT at the site of the arterial occlusive lesion in an Asian population with acute ischemic stroke secondary to middle cerebral artery M1 occlusion. In this population with a high prevalence of intracranial atherosclerotic disease (ICAD), the authors’ hypothesis was that residual stenosis, as defined by the Arterial Occlusive Lesion (AOL) scale, would be sequelae of in situ thrombo-occlusion (IST) with underlying ICAD. Angiographic imaging during EVT and follow up imaging (MR or CT angiography) 5 to 7 days post-procedure was performed to assess stenosis.
Out of 163 patients enrolled in the study, 74 patients (45.5%) had partial recanalization (AOL 2) on post-procedural angiography. Rates of favorable clinical outcomes at 3 months (defined as mRS of 2 or less) did not differ between the group with partial (AOL 2) versus complete recanalization (AOL 3). Forty patients (24.5%) in the study were determined to have IST as their stroke etiology, and all of these patients had residual stenosis present on the post-procedural angiogram (AOL 2). 27% of patients with partial recanalization compared to only 1.1% of patients with complete recanalization developed instant reocclusion during EVT. In addition, those patients with partial recanalization during EVT were more likely to have worse stenosis or occlusion (10.8% vs 1.1%) on follow-up imaging. On multivariable regression analysis, delayed reocclusion in patients with partial recanalization was predicted by excellent baseline collateral-flow (OR 8.477; 95%CI 1.169-61.464) and neurological worsening post-procedure (OR 10.388; 95%CI 1.287-83.876).

It is important to note that the authors used a radiologic-based approach to identify IST that was based on the presence and severity (>50%) of residual stenosis and the presence of ICAD. The majority of patients with IST determined using these criteria were classified as partial recanalization with residual stenosis exceeding 50% on follow-up angiography. This study suggests that IST is a common cause of large vessel occlusion in an Asian population and that residual stenosis is associated with increased risk of reocclusion and early neurologic deterioration. Going forward, work should include controlling for endovascular approach utilized and characterizing the pathologic correlates for radiographic-determined IST.