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Source: Johnston SC, et al. Short-term prognosis after emergency department diagnosis of TIA. JAMA 2000;284:2901-2906.
This large cohort study from 16 hospitals in the kaiser permanente HMO of Northern California involved patients identified by emergency department (ED) physicians as having presented with an acute transient ischemic attack (TIA). The main objective was to determine the short-term risk of stroke during the 90 days after the index TIA. Other outcome measures included death, recurrent TIA, and hospitalization for other cardiovascular events. Patients were followed up by searching computerized databases, reviewing medical records, and checking a separate database for hospitalizations outside the system.
Of the 1707 patients with a TIA diagnosis, more than 99% arrived within one day of symptom onset. Mean age was 72 years and the mean symptom duration was 207 minutes. Strokes occurred in 180 patients (10.5%) within 90 days of the index TIA, 91 of which occurred during the first two days. The combined risk of stroke, recurrent TIA, hospitalization for cardiovascular events, and death during the 90-day follow-up period was 25.1%. More than 50% of the combined adverse events occurred within the first four days.
Five factors were independently associated with stroke: age older than 60 years (OR 1.8; 95% CI 1.1-2.7); diabetes mellitus (OR 2.0; 95% CI 1.4-2.9); symptom duration longer than 10 minutes (OR 2.3; 95% CI 1.3-4.2); weakness (OR 1.9; 95% CI 1.4-2.6); and speech impairment (OR 1.5; 95% CI 1.1-2.1). A simple index (1 point for each risk factor) showed that the 90-day stroke risk varied from 0% in patients with no risk factors to 34% in patients with all five.
If you have experienced concern for the TIA patients you’ve discharged from the ED, this study confirms your clinical instinct. A TIA appears to be an ominous sign, conveying a substantial (25%) short-term risk of stroke, recurrent TIA, hospitalization for other cardiovascular events, and death. A 10.5% risk of stroke within 90 days (5% risk within 2 days) is significant and certainly underscores the importance of either admission, neurology consultation, or close follow-up and good communication with the patient and family.
One criticism of the study, noted by the authors themselves, is that the patient cohort was recruited from the EDs of hospitals in a large HMO system. It is possible that disincentives to using the ED led to a selection bias in favor of patients with longer duration of symptoms (the mean was quite long at 207 minutes) and at greater risk for adverse outcomes. On the other hand, at least one other, smaller study found a similar stroke risk.1 In addition, it would have been interesting to know what percentage of the patients presented with their first TIA as opposed to a recurrent TIA, and if that was associated with the outcomes.
The problem for us, of course, is who to admit, who to hold for a neurology consultatation, and who to discharge. A prediction model based on risk factors would be helpful, and this study is a first step in creating such a tool. Unfortunately, until these risk factors are validated prospectively in an independent cohort, they are still in the development phase. In the meantime, having a low threshold for admission and/or consultation seems prudent.
1. Whisnant JP, et al. Transient cerebral ischemic attacks in a community. Rochester, Minnesota, 1955 through 1969. Mayo Clin Proc 1973;48:194-198.