Transient ischemic attack: Omen and opportunity
ABSTRACTA transient ischemic attack (TIA) is not a benign event; it is often the precursor of stroke. As such, every TIA deserves to be taken seriously, and patients who present with a TIA should be promptly evaluated and, if appropriate, started on stroke-preventive therapy.
KEY POINTS
- Modifiable risk factors for stroke and TIA include cigarette smoking, hypertension, diabetes, lipid abnormalities, atrial fibrillation, carotid stenosis, and dietary and hormonal factors.
- The three major mechanisms of stroke and TIA are thrombosis, embolism, and decreased systemic perfusion.
- Typical symptoms of TIA include hemiparesis, hemisensory loss, aphasia, vision loss, ataxia, and diplopia. Three clinical features that suggest TIA are rapid onset of symptoms, no history of similar episodes in the past, and the absence of nonspecific symptoms.
- In suspected TIA, magnetic resonance imaging is clearly superior to noncontrast computed tomography (CT) for detecting small areas of ischemia; this test should be used unless contraindicated.
- Imaging studies of the blood vessels include CT angiography, magnetic resonance angiography, conventional angiography, and extracranial and transcranial ultrasonography.
TREAT THE UNDERLYING DISORDER
Treatment depends on the mechanism that is thought to be responsible for the ischemic event. Vascular risk factors are important to identify and modify for all stroke subtypes.
Illustrating the importance of treating TIA and minor stroke, one study72 found that for antiplatelet therapy (aspirin, dipyridamole, or aspirin plus dipyridamole), the number needed to treat for 2 years was around 18.
Anticoagulation for cardioembolism
Atrial fibrillation, especially following a cerebrovascular ischemic event, should be treated with long-term anticoagulation with warfarin (Coumadin), dabigatran (Pradaxa), rivaroxaban (Xarelto), or apixaban (Eliquis).73 If the patient cannot tolerate anticoagulation, aspirin is recommended, and if he or she cannot tolerate aspirin, clopidogrel (Plavix) is recommended.
Antiplatelet therapy for large-vessel atherosclerosis and small-vessel disease
In the acute phase, aspirin 81 mg to 325 mg orally can be given. If the patient is allergic to aspirin, a loading dose of clopidogrel 300 mg and then 75 mg daily may be given.
A pilot study of loading with aspirin 325 mg or clopidogrel 375 mg in acute ischemic stroke and TIA patients showed that these treatments were safe when given within 36 hours and decreased the risk of neurologic deterioration.74 The patient should continue on aspirin 81 mg or clopidogrel 75 mg, as suggested by the Fast Assessment of Stroke and Transient Ischaemic Attack to Prevent Early Recurrence (FASTER) trial.75 In the long term, an antiplatelet drug such as aspirin or clopidogrel or the combination of aspirin and extended-release dipyridamole is reasonable.76
Cilostazol (Pletal) is not inferior and is possibly superior to aspirin in preventing noncardioembolic ischemic stroke. It is used off-label for secondary prevention of stroke of noncardioembolic origin.77
Statins
In the Stroke Prevention by Aggressive Reduction in Cholesterol Levels (SPARCL) trial, high-dose atorvastatin (Lipitor)—80 mg daily—was found to reduce the risk of subsequent stroke and other cardiovascular events in patients with recent stroke irrespective of low-density lipoprotein cholesterol (LDL-C) level, but there was a small increase in the risk of hemorrhagic stroke.78
In patients with hyperlipidemia, current recommendations suggest a target LDL-C level lower than 100 mg/dL in patients with atherosclerotic stroke or TIA, and lower than 70 mg/dL in those with concomitant diabetes.79
Antihypertensive therapy
In the acute period, ie, the first 24 hours after symptoms, guidelines have advocated allowing high blood pressure to remain high (“permissive hypertension”) unless the systolic pressure is greater than 200 mm Hg or the diastolic pressure is greater than 120 mm Hg or the patient is receiving thrombolytic therapy.80 However, this has recently been challenged by findings in randomized trials.81 Permissive hypertension and avoidance of dehydration with intravenous normal saline may improve cerebral perfusion, which is especially important in patients with high-grade intracranial or extracranial stenosis. Within the parameters outlined above, we recommend against aggressively treating high blood pressure in the acute phase.
In the long term, antihypertensive therapy reduces the risk of recurrent stroke or TIA.82 The goal is to keep blood pressure lower than 140/90 mm Hg, or lower than 130/80 mm Hg in patients with diabetes. A study of patients with ischemic noncardioembolic stroke showed a higher risk of recurrent stroke if the systolic blood pressure was lower than 120 or higher than 140 mm Hg.83
Some classes of antihypertensive medication may be more beneficial than others. There is some evidence that angiotensin-converting enzyme (ACE) inhibitors alone or in combination with a diuretic or an angiotensin receptor blocker are superior to other regimens, possibly because of neuroprotective mechanisms.84 A recent meta-analysis found angiotensin receptor blockers to be more effective than either ACE inhibitors or beta-blockers in stroke prevention; however, calcium channel blockers were superior to renin-angiotensin system blockers (ACE inhibitors and angiotensin receptor blockers).85
Lifestyle modifications
Smoking cessation and cardiovascular exercise for more than 10 minutes more than 3 times per week is strongly recommended.
For patients with diabetes, the goal is to keep the fasting blood glucose level lower than 126 mg/dL.
Moderate alcohol intake has been shown to decrease stroke risk compared with excessive intake or none at all.86
Carotid endarterectomy
Carotid endarterectomy has been recommended within 2 weeks of cerebral or retinal TIA in those cases attributable to high-grade internal carotid artery stenosis in patients who have low surgical risk.87 This risk can be estimated on the basis of patient factors, surgeon factors, and hospital volume. The specific recommendations are as follows:
- 70% to 99% carotid stenosis: carotid endarterectomy recommended
- 50% to 69% carotid stenosis: carotid endarterectomy recommended in select patients with a perioperative complication rate < 6%
- < 50% carotid stenosis: carotid endarterectomy not routinely recommended.
Carotid artery angioplasty and stenting with distal embolic protection device
Data from the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST) and European stenting trials indicate that in patients over age 70, carotid endarterectomy appears to be superior to carotid artery stenting, whereas in younger patients the periprocedural risks of stroke and death are similar. Hence, carotid artery stenting performed by an interventionist with a low complication rate is a reasonable alternative to carotid endarterectomy.88,89
