100 - Transient Ischemic Attack and Acute Ischemic Stroke

The yearly incidence of TIA in the United States has been estimated to be approximately 200,000 to 500,000 but may be higher because of the high frequency of underreporting of these events by medical professionals. The annual incidence of TIA may be less and the annual incidence of stroke may be higher if the tissue-based definition were applied to all patients evaluated for TIA. It has been estimated that the overall incidence rate of TIA is 1.1 per 1000 U.S. population. This incidence increases with age from 0.1 per 1000 for patients younger than 50 years to 11.7 per 1000 for patients older than 80 years. The incidence of TIA also varies with race and gender: it is significantly greater in blacks and men than in whites and women. The greatest incidence of TIA occurred in black men older than 85 years, who had an incidence of 16 events per 1000. TIAs account for 0.3% of all emergency department (ED) visits, and it is estimated that 8.7% to 30% of patients will have a TIA before stroke. Only 28% of TIA patients arrive via ambulance, and 36% of patients arrive during daylight hours. Emergency physicians (EPs) obtain computed tomography (CT) scans on 56% to 70% of all TIA patients and magnetic resonance imaging (MRI) scans on 7% of TIA patients. Nearly half of all patients with TIA are admitted to the hospital, although there is geographic variability in this practice; another 20% of patients are referred for follow-up. Finally, patients seen in the ED with TIA receive preventive aspirin therapy in 18% of cases, other antiplatelet therapy in 7%, and no preventive therapy in an estimated 42%. Clearly defined risk factors for stroke and adverse events following a TIA are now well described in the literature, and several groups of investigators have independently developed short-term risk stratification methods applicable to TIA patients in the ED. These investigators reported a 10% rate of stroke in the 90 days following the TIA, with 50% of these strokes occurring in the immediate 48 hours after the TIA. Recently, the ABCD2 score, which combines elements from existing risk stratification systems, was devised to create a robust prediction standard for determining high-risk populations that will benefit from emergency investigation and therapy to prevent short-term adverse events (Table 100.1). Patients with the following characteristics were at high risk for having a stroke in the next 2 to 90 days: age older than 60 years, blood pressure higher than 140 mm Hg systolic or 90 mm Hg diastolic, clinical features such as unilateral • Transient ischemic attack (TIA) is a high-risk warning sign for stroke within 90 days, with the highest risk occurring in the first 2 days. • Patients with TIA can be accurately risk-stratified for recurrent stroke. • Large artery atherosclerosis, cardioembolism, and small vessel disease are the leading causes of TIA and acute ischemic stroke. • Magnetic resonance imaging is valuable in differentiating TIA from acute ischemic stroke. • The goal of management of patients with TIA is to prevent recurrent stroke with antiplatelet, anticoagulation, or surgical therapy. • The best outcomes for strokes treated with thrombolytic therapy are found with early delivery of recombinant tissue plasminogen activator (rt-PA) within established guidelines. • Recent evidence supports extending the time window for treatment of ischemic stroke with rt-PA to 4.5 hours for specific patient populations. • Stroke units and stroke teams provide comprehensive stroke care that improves patient outcomes. KEY POINTS