Abstract TMP61: Lesion Growth Continues Beyond 24 Hours Following Endovascular Therapy In Some Patients With Successful Recanalization

Introduction: Lesion volume on MRI or CT provides evidence of tissue response to successful recanalization by endovascular therapy. The most appropriate time to estimate “infarct” volume remains unclear. Largely for convenience, 24-48 hours has been used in clinical trials and registry datasets which may be too early to determine the final infarct volume. The objective of this study was to quantify the comparability of lesion volume using MRI measured at 24 hours versus 5 days in acute stroke patients following successful recanalization. Methods: Patients were included if they consented to the prospective GUARDS study between April 2018 through February 2022, had LVO of the anterior circulation, were treated with EVT, achieved complete revascularization defined as TICI 2b/3, and imaged with MRI at 2 hours, 24 hours, and 5 days post EVT. Two independent readers measured lesion volumes using a semi-automated validated approach on DWI at 2 and 24 hours, and FLAIR at 5 days. Statistical comparisons of lesion volumes across time points were performed. Lesion growth was defined as change in lesion volume and percent change compared to lesion volume at 2 hours. Results: Sixty-nine patients met all study criteria and were included. Median age was 66 years, 55% female, median admit NIHSS of 18, 62% with M1 LVO, and 46% treated with IV thrombolysis. Post-EVT median lesion volumes were 24mL, 35mL, and 45mL respectively for 2-hour DWI, 24-hour DWI, and 5-day FLAIR. Lesion growth based on median percent change from the 2-hour DWI was 39% [21-96] and 52% [12-145] at 24 hours and 5 days. The difference in lesion growth based on percent change from 24 hours to 5 days was not significant (p=0.17). However, there was a significant difference based on change in lesion volume, 12mL [2-25] at 24 hours and 16mL at 5 days (p=0.029). Fifty-one (74%) patients had DWI volumes at 24 hours that were ≥80% of their FLAIR volumes at 5 days. However, 18 (26%) patients continued to have lesion growth beyond 24 hours, median lesion growth of 18mL,with 11 (61%) of those having lesion growth >20mL. Conclusions: Lesion growth >20mL continues in some patients beyond 24 hours, suggesting that infarct volume at 5 days should be used as the imaging outcome when assessing tissue response to recanalization.