Abstract WP223: Ischemic Stroke After Emergency Department Discharge for Symptoms of Transient Neurological Attack

Abstract

Introduction: Compared to transient ischemic attack (TIA), little is known about the risk of ischemic stroke after the nonspecific symptoms of a transient neurological attack (TNA). Methods: Using administrative claims data, we identified patients discharged from emergency departments (ED) in New York State between 2006 and 2012 with a primary discharge diagnosis of a TNA symptom, defined as in prior work as altered mental status, generalized weakness, and sensory changes. The primary outcome of ischemic stroke was identified using validated ICD-9-CM diagnosis codes. We used Kaplan-Meier survival statistics to calculate cumulative rates, and Cox regression to compare stroke risk after TNA versus after TIA (positive control) or renal colic (negative control) while adjusting for demographics and vascular risk factors. We performed subgroup analyses stratified by age. In sensitivity analyses, TNA was limited to cases of altered mental status or sensory changes, as these were more commonly associated with stroke in prior work, or limited to discharges without neuroimaging, to assess whether limited evaluation was associated with increased risk. Results: Of 499,369 patients diagnosed with a TNA symptom and discharged from the ED, 7,756 were hospitalized for ischemic stroke over 4.7 (±1.9) years. At 90 days, the cumulative stroke rate was 0.29% (95% confidence interval [CI], 0.28-0.31%) after TNA symptoms versus 2.08% (95% CI, 1.89-2.28%) after TIA and 0.03% (95% CI, 0.02-0.04%) after renal colic. The hazard of stroke was higher after TNA than after renal colic (hazard ratio [HR], 2.13; 95% CI, 1.90-2.40). However, the risk was lower than after TIA (HR, 0.47; 95% CI, 0.44-0.50). Compared to TIA, TNA was less strongly associated with stroke among patients under 60 years of age (HR, 0.22; 95% CI, 0.19-0.25) than in those over 60 years of age (HR, 0.50; 95% CI, 0.47-0.53) ( P <0.001 for interaction). Our results were unchanged in sensitivity analyses limiting TNA diagnoses to patients with altered mental status or sensory changes or to those who did not undergo neuroimaging. Conclusions: Patients discharged from the ED with TNA symptoms faced a higher risk of ischemic stroke than low risk controls, but the magnitude of stroke risk was low, particularly in comparison to TIA.