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Source: Johnston SC, et al. Short-term prognosis after emergency department diagnosis of TIA. JAMA 2000;284: 2901-2906.
The evaluation and treatment of patients with acute transient ischemic attacks (TIA) is variable depending upon the clinical judgement of the physicians involved. Some clinicians routinely hospitalize all TIA patients while others proceed with an outpatient evaluation. Johnston and colleagues sought to define the 90-day prognosis and risk factors for stroke after TIA in order to determine which patients needed urgent evaluation and therapy.
They studied more than 1700 patients (mean age 72) identified as having a TIA by Emergency Department (ED) physicians. Patients were followed for 90 days after presentation. Strokes, TIA, deaths, and hospitalizations for cardiovascular events were identified. Within 90 days of TIA presentation, strokes occurred in 180 patients (11%), more than half of which occurred during the first two days. Strokes were disabling in 64% and fatal in 21% of the patients.
The following factors were independently associated with an increased risk of stroke in univariate analysis: age older than 60 years, diabetes mellitus, symptom duration longer than 10 minutes, weakness or gait disturbance, and speech impairment. Symptoms of numbness were associated with reduced risk and medications taken prior to TIA did not influence prognosis. When analysis was limited to 918 patients who were not previously taking an anticoagulant or antiplatelet agent, those who initiated antiplatelet therapy (n = 775) tended to have a lower stroke risk than those not receiving prophylactic medication (n = 143) (9% vs 13%; P = NS). Stroke or other adverse events occurred in 25% of patients within 90 days of the index TIA and included recurrent TIA (13%), death (3%), and cardiovascular event (3%). More than 50% of adverse events occurred within the first four days.
The short-term risk of stroke and other adverse events among patients presenting to the ED with acute TIA was significant. The TIAs in this study are notable because they were both long (mean symptom duration was 207 minutes) and acute (half of the patients were symptomatic on arrival in the ED). The timing of presentation after TIA was important since more than half of strokes occurred within two days of the index TIA. This means that a patient evaluated more than two days after a TIA has already passed through the period of greatest stroke risk.
Treatment did not seem to matter much before or after TIA: patients presented with TIA who were taking prophylactic antiplatelet or anticoagulant medications, and post TIA initiated these same medications did not reduce stroke risk significantly. The present study, however, was observational and should not be used to provide data on the efficacy of medical therapies.
Johnston et al have identified risk factors that stratify TIA patients into subgroups with a low and a high short-term risk of stroke. Clinicians will find these useful in practice to select patients for acute stroke prevention interventions. —John J. Caronna