Abstract WMP64: Late Lesion Growth Following Endovascular Therapy: Is 24 Hours Too Early to Assess Acute Infarct Size Including the Effects of Secondary Injury?

Abstract

Background: Measurement of “final” lesion volume at 24hr following endovascular therapy (post-EVT) has been used in multiple studies as a surrogate for clinical outcome. However, despite successful recanalization, a significant proportion of patients do not experience favorable clinical outcome. Methods: This is a prospective study of acute ischemic stroke patients at two stroke centers who met the following criteria: i) anterior large vessel occlusion (LVO) acute ischemic stroke, ii) attempted EVT, iii) written informed consent obtained, and iv) had MRI post-EVT at 24hr and 5-day. We defined “Early” and “Late” lesion growth as ≥10mL lesion growth between baseline and 24hr DWI, and between 24hr DWI and 5-day FLAIR, respectively. Results: One hundred fourteen patients met study criteria with median age 67 years, 56% female, median admit NIHSS 19, 54% received IV or IA thrombolysis, 67% with M1 occlusion, and median baseline DWI volume 28.2mL. Successful recanalization was achieved in 86% and 67% had complete reperfusion, with an overall favorable clinical outcome rate of 54%. Nearly two thirds (65%) of the patients did not have Late lesion growth with a median volume change of -0.2mL between 24hr and 5-days and an associated high rate of favorable clinical outcome (65%). However, ~1/3 of patients (35%) did have significant Late lesion growth despite successful recanalization (85% TICI 2b/3). Late lesion growth patients had a 26.2mL change in Late lesion volume and 19.9mL change in Early lesion volume. These patients had an increased hemorrhagic transformation rate of 68% with only 1 in 3 patients having favorable clinical outcome. Late lesion growth was independently associated with incomplete reperfusion, hemorrhagic transformation, and unfavorable outcome even after adjusting for admit NIHSS and Early lesion growth. Conclusions: Approximately 1 out of 3 patients had Late lesion growth following EVT, with a favorable clinical outcome occurring in only 1 out of 3 of these patients. Identification of patients with Late lesion growth could be critical to guide clinical management and inform prognosis post-EVT. Additionally it can serve as an imaging biomarker for the development of adjunctive therapies to mitigate reperfusion injury.