Abstract TP461: Screening CT Angiography to Identify Patients at Low Risk for Delayed Cerebral Ischemia Following Subarachnoid Hemorrhage

Abstract

Introduction: Delayed Cerebral Ischemia (DCI) occurs during a risk period of 3-21 days following aneurysmal subarachnoid hemorrhage (aSAH) and is associated with worse outcomes. The identification of patients at low risk for DCI might permit triage to less intense monitoring and management. While large-vessel vasospasm (LVV) is a distinct clinical entity from DCI, the presence of moderate-severe LVV is associated with a higher risk of DCI. Hypothesis: The absence of moderate-severe LVV on screening CT angiography (CTA) performed within the first few days of the DCI risk period will accurately identify patients at low risk for subsequent DCI. Methods: Our institutional SAH outcomes registry was queried for all aSAH patients admitted 2016 - 2019 who underwent CTA brain between days 4-8 following ictus. We excluded patients who suffered DCI prior to this CTA study. All variables are prospectively entered into the registry, and outcomes including DCI and LVV are prospectively adjudicated. We evaluated the accuracy of moderate-severe LVV on CTA performed 4-8 days from ictus for the prediction of subsequent DCI, with a focus on the Negative Predictive Value (NPV). Results: A total of 243 aSAH patients were admitted during the study timeframe and 76 (31%) underwent CTA during the 4-8 day window following ictus. Of these, 22 were excluded for occurrence of DCI prior to the CTA study. Of 54 patients meeting eligibility criteria, 11 (20%) had moderate-severe LVV on the screening CTA study performed during the risk period. Seven of 11 (64%) patients with moderate-severe LVV on the day 4-8 screening CTA, vs 6 of 43 (14%) patients without, subsequently developed DCI. The NPV of CTA performed during days 4-8 for the subsequent development of DCI was 86% (95%CI 77-92%). Sensitivity was 54% (25-81%), Specificity 90% (77-97%) and Positive Predictive Value 64% (38-83%). Conclusions: The NPV of screening CTA performed between days 4-8 following SAH for the subsequent development of DCI was moderate, at 86%. The population studied likely represents a high-risk cohort, however, prospective studies of alternate risk-stratification strategies are necessary.