Abstract WP235: Risk of Arterial Ischemic Events After Non-Traumatic Subdural Hemorrhage

Abstract

Introduction: To study the risk of arterial ischemic events after non-traumatic subdural hemorrhage (SDH). Methods: We performed a retrospective cohort study using inpatient and outpatient claims data from 2008-2015 from a nationally representative 5% sample of Medicare beneficiaries. The exposure was diagnosis of SDH. Our primary outcome was an arterial ischemic event defined as a composite of acute ischemic stroke and acute myocardial infarction (MI). Secondary outcomes were ischemic stroke alone and MI alone. We used validated ICD-9-CM diagnosis codes to identify our predictor and outcomes. We excluded patients who had an arterial ischemic event prior to SDH diagnosis. Using Cox regression and corresponding survival probabilities, adjusted for demographics and vascular comorbidities, we computed the hazard ratio (HR) in each 4-week interval after discharge for SDH. We performed secondary analyses stratified by strong indications for antithrombotic therapy (composite of atrial fibrillation, peripheral vascular disease, valvular heart disease and venous thromboembolism). Results: Among 1.7 million Medicare beneficiaries, 2,939 were diagnosed with SDH. Compared to patients without SDH, those with SDH were more often older, male, and had more vascular risk factors. In the 4 weeks after SDH, patients’ risk of an arterial ischemic event was substantially increased (HR, 4.2; 95% CI, 2.2-6.7). There was no association between SDH diagnosis and arterial ischemic event risk beyond 4 weeks. In secondary analysis, during the 4 weeks after SDH, patients’ risk of ischemic stroke was increased (HR, 5.6; 95% CI, 3.6-9.7) but not their risk of MI (HR, 0.8, 95% CI, 0.2-1.7). Patients with strong indications for antithrombotic therapy had similarly increased risks for arterial ischemic events as compared to patients in the primary analysis; patients without strong indications for antithrombotic did not demonstrate an increased risk for arterial ischemic events. Conclusions: Among Medicare beneficiaries, we found a heightened risk of arterial ischemic events, particularly ischemic stroke, in the four weeks after SDH. This increased risk may be driven by withholding of antithrombotic therapy after SDH diagnosis.