Ischemic stroke is an acute onset of focal neurological deficit that involves permanent infarction of central nervous system tissue. A transient ischemic attack (TIA) is similar to ischemic stroke but is caused by focal brain, spinal cord, or retinal ischemia without acute infarction. Cranial occlusions result from an embolus formed in the carotid arteries or the ventricles of the heart. Atherosclerosis of the carotid arteries leads to plaque formation and if plaque ruptures, collagen is exposed resulting in platelet aggregation and thrombus formation. The clot may break off and cause cranial vessel occlusion (decreased blood flow to the brain region it supplies) resulting in ischemia. Strokes originating from a cardioembolic source are presumed to originate from thrombus formation in the left ventricle. Clinical presentation includes weakness on one side of the body, visual impairment, and inability to speak. Diagnosis is confirmed via computed tomography (CT) scanning and magnetic resonance imaging (MRI). Risk factors for an ischemic stroke include hypertension, dyslipidemia, diabetes, cigarette smoking, and atrial fibrillation (Table 6-1).
TABLE 6-1Risk Factors for Ischemic Stroke ||Download (.pdf) TABLE 6-1 Risk Factors for Ischemic Stroke
|Age ||Younger age groups (25-44 y) are at lower risk |
|Low birth weight ||Low-birth weight patients have a higher mortality rate |
|Race/ethnicity ||Blacks and some Hispanic/Latino Americans are at higher risk |
|Genetics ||Positive family history increases risk |
|Gender ||Men have a greater risk than women |
|Hypertension || |
Most important modifiable risk factor
Treat to a goal of <140/90 mm Hg
|Dyslipidemia ||Use of statin therapy in addition to lifestyle changes decreases risk in high-risk patients (coronary heart disease or diabetes) |
|Diabetes ||There is no correlation with glycemic control; however, risk is reduced when blood pressure is controlled |
|Cigarette smoking ||Abstention from cigarette smoking by nonsmokers and smoking cessation by current smokers decreases risk |
|Atrial fibrillation ||Risk is decreased with concomitant use of antithrombotic therapy |
Primary prevention against ischemic stroke focuses on the reduction of modifiable risk factors (see Table 6-1).
The immediate goal of therapy is to reduce neurologic injury and long-term disability. Once the patient is through the hyperacute period, the goal of therapy is to prevent reoccurrence and decrease mortality.
The treatment for acute ischemic stroke has a narrow therapeutic window; therefore, a timely evaluation and diagnosis is essential. Pharmacologic agents recommended by the American Heart Association Stroke Council for acute stroke treatment are recombinant tissue plasminogen activator (rtPA/Activase®), aspirin, and the combination of aspirin plus clopidogrel.
rtPA is a fibrinolytic agent able to achieve early reperfusion and improve neurological outcomes. rtPA exerts its effects via the initiation of local fibrinolysis. It binds directly to fibrin thereby causing plasminogen to convert to plasmin. Plasmin is the enzyme ...