Abstract Number ‐ 155: CT Perfusion May Optimize Selection Of Elderly Patients For Mechanical Stroke Thrombectomy
Authors: Singh Romil , Hackett Chris , Saini Harneel , Cerejo Russell M , Malhotra Konark , Williamson Richard 
Published: April 2023

Introduction
Prior studies have demonstrated that CT perfusion (CTP) may be used to select patients for mechanical stroke thrombectomy (MST) with acute ischemic stroke owing to major artery obstruction in the anterior circulation for up to 24 hours. There is limited data on CTP selection of elderly patients aged ≥ 90 years old. We aimed to examine whether selecting nonagenarians with CT perfusion (CTP) imaging would allow for better outcomes. Specifically we aimed to examine hypoperfusion intensity ratio (HIR) and early infarct growth rate (EIGR) to optimize MST selection of nonagenarians.

Methods
This is a single center retrospective study from a large academic medical center. Patients included were at least 90 years old, presented with an anterior circulation acute ischemic stroke due to large vessel occlusion (LVO) and were treated with mechanical stroke thrombectomy (MST) between January 2018 and April 2022. Patients without CT perfusion (CTP) imaging prior to MST and without complete data were excluded. HIR was defined as time to maximum (Tmax 10 seconds/ Tmax 6 seconds). EIGR was defined as (relative cerebral blood flow < 30% / last known well to CTP). Primary outcome was modified Rankin Scale (mRS) at 90 days, analyzed using an ordinal regression analysis and adjusted for baseline mRS, NIHSS, and possible confounding variables identified in univariate analyses. Secondary outcomes were: excellent reperfusion (TICI ≥ 2C), procedural complications of MST and symptomatic intracranial hemorrhage (sICH). The secondary outcomes were analyzed using binomial logistic regressions in two blocks where confounding variables were entered first, followed by variables of interest: HIR and EIGR.

Results
During the study epoch 70 nonagenarians were treated with MST. After exclusions, 59 nonagenarians were analyzed in the study. Despite selecting patients with CTP, 35 (59.3%) of patients reached mortality at 90 days. Additionally, only 9 (15.3%) patients achieved mRS of 0 – 2 or baseline mRS (if baseline mRS > 2) at 90 days. HIR was found to be correlated with 90 day mRS (shift to next worse mRS), adjusted odds ratio (aOR) = 14.41 [95%CI 1.16, 179.11] p = 0.04, but not EIGR, aOR = 0.98 [95%CI 0.90, 1.06], p = 0.58. Neither HIR nor EIGR were not associated with excellent reperfusion, p = 0.38 and p = 0.88, respectively. Patients with higher EIGR were more likely to experience proceduralcomplications, aOR = 1.16 [95%CI 1.03, 1.31], p = 0.01, but there was no difference in HIR, p = 0.28. Lastly, there were no differences in HIR or EIGR and sICH, p = 0.07 and p = 0.68, respectively.

Conclusions
Very elderly patients aged 90 years or older experienced high rates of mortality and low proportions of good outcomes at 90 days. Nonagenarians with better collaterals as measured by HIR may have better outcomes at 90 days. Additionally, nonagenarians with faster growing ischemic cores may be more likely to experience complications during MST.