Risk of Stroke After the International Classification of Diseases-Ninth Revision Discharge Code Diagnosis of Hypertensive Encephalopathy.

Abstract

Although chronic hypertension is a well-established risk factor for stroke, little is known about stroke risk after hypertensive encephalopathy (HE), when neurologic sequelae of hypertension become evident. Therefore, we evaluated the risk of stroke after a diagnosis of HE. We identified all patients discharged from California, New York, and Florida emergency departments and acute care hospitals between 2005 and 2012 with a primary International Classification of Diseases, Ninth Edition, Clinical Modification discharge diagnosis of HE (437.2). Patients discharged with a primary diagnosis of seizure (345.x) served as negative controls, whereas patients with a primary diagnosis of transient ischemic attack (435.x) were positive controls. Our primary outcome was the composite of subsequent ischemic stroke or intracerebral hemorrhage. Kaplan-Meier survival statistics were used to calculate cumulative outcome rates, and Cox proportional hazard analysis was used to examine the association between index disease types and outcomes while adjusting for vascular risk factors. We identified 8233 patients with HE, 191 091 with seizure, and 308 680 with transient ischemic attack. The 1-year cumulative rate of ischemic stroke or intracerebral hemorrhage after HE was 4.90% (95% confidence interval [CI], 4.45-5.40) when compared with 0.92% (95% CI, 0.88-0.97) after seizure and 4.49% (95% CI, 4.42-4.57) after transient ischemic attack. The risk of intracerebral hemorrhage was significantly elevated in those with HE (hazard ratio, 2.0; 95% CI, 1.7-2.5) but not in those with transient ischemic attack (hazard ratio, 1.0; 95% CI, 0.9-1.1), when compared with seizure patients. Patients discharged with a diagnosis of HE face a high risk of future cerebrovascular events, particularly intracerebral hemorrhage.