Stroke is the third most common overall cause of death and the leading cause of adult disability in the United States. New therapeutic interventions instituted in the period immediately after a stroke have revolutionized the approach to ischemic cerebrovascular disease. Recognition of a transient ischemic attack provides an opportunity to prevent a subsequent stroke. Specific stroke prevention treatment depends on the cause of the transient ischemic attack, its cerebrovascular localization and the presence of associated coexisting medical problems. Modification of stroke risk factors is the principal therapeutic approach. Antiplatelet agents and anticoagulants have been shown to be effective in reducing the occurrence of stroke in certain populations. Several well-designed studies have recently demonstrated the effectiveness of carotid endarterectomy in preventing strokes related to extracranial carotid artery disease.

Approximately 550,000 new strokes and 150,000 stroke-related deaths occur each year in the United States.1 About 80 percent of strokes are due to ischemic cerebrovascular disease, and the rest are attributable to hemorrhagic causes such as subarachnoid or intracerebral hemorrhage. Even though great strides have been made in the identification and treatment of risk factors for stroke and the development of new therapeutic interventions, ischemic stroke continues to be a significant public health problem.

A completed stroke is caused by irreversible brain injury secondary to the interruption of blood flow. In contrast, a transient ischemic attack (TIA) is a temporary focal neurologic deficit caused by the brief interruption of local cerebral blood flow. The prevalence of TIAs ranges from 1.6 to 4.1 percent, depending on gender and age. Stroke occurs in one third of patients who have a TIA.

Prevention of stroke may be classified as primary prevention if there is no previous history of stroke or transient ischaemic attack (TIA) and secondary prevention if there has been such an event.

The revised Joint British Societies’ (JBS 2) guidelines on prevention of cardiovascular disease (CVD) in clinical practice recommend that cardiovascular disease prevention should focus equally on the following three groups of patients who are at high risk of cardiovascular disease

- People with established atherosclerotic CVD
- People with diabetes mellitus (type 1 or 2)
- Apparently healthy individuals at high risk (CVD risk of 20% or greater over 10 years) of developing symptomatic atherosclerotic disease

Well-documented and modifiable risk factors for stroke include hypertension, exposure to cigarette smoke, diabetes, atrial fibrillation (AF), dyslipidaemia, carotid artery stenosis, sickle cell disease, postmenopausal hormone therapy, poor diet, physical inactivity, and obesity - especially truncal obesity.

Less well-documented or potentially modifiable risk factors include the metabolic syndrome, alcohol abuse, drug abuse, oral contraceptive use, obstructive sleep apnoea, migraine headaches, hyperhomocysteinaemia, elevated lipoprotein(a), elevated lipoprotein-associated phospholipase, and hypercoagulability.

After a stroke or TIA, there is a high risk of stroke and of other serious vascular events. Medical treatments with clear evidence of benefit include:

- Lowering blood pressure (BP) after all types of stroke or TIA.
- Lowering blood cholesterol with a statin after ischaemic stroke or TIA.
- Antiplatelet treatment after ischaemic stroke or TIA.
- Warfarin instead of antiplatelet treatment in patients with ischaemic stroke or TIA who have AF and no contra-indications to anticoagulation.

Survivors of a transient ischemic attack (TIA) or stroke have an increased risk of another stroke, which is a major source of increased mortality and morbidity. Among the estimated 700 000 people with stroke in the United States each year, 200 000 of them are among persons with a recurrent stroke. The number of people with TIA, and therefore at risk for stroke, is estimated to be much greater. Epidemiological studies have helped to identify the risk and determinants of recurrent stroke, and clinical trials have provided the data to generate evidence-based recommendations to reduce this risk. Prior statements from the American Heart Association (AHA) have dealt with primary and secondary stroke prevention. Because most strokes are cerebral infarcts, these recommendations focus primarily on the prevention of stroke among the ischemic stroke or TIA group. Other statements from the AHA have dealt with acute ischemic stroke, subarachnoid hemorrhage (SAH), and intracerebral hemorrhage (ICH).

The aim of this new statement is to provide comprehensive and timely evidence-based recommendations on the prevention of ischemic stroke among survivors of ischemic stroke or TIA. A writing committee chair and vice chair were designated by the Stroke Council Manuscript Oversight Committee. A writing committee roster was developed and approved by the Stroke Council with representatives from neurology, cardiology, radiology, surgery, nursing, and health services research. The committee met in person and had a number of teleconferences to develop the outline and text of the recommendations. The writing group conducted a comprehensive review of the relevant literature. Although the complete list of keywords is beyond the scope of this section, the committee reviewed all compiled reports from computerized searches and conducted additional searching by hand. Searches were limited to English language sources and to human subjects. Literature citations were generally restricted to published manuscripts appearing in journals listed in Index Medicus and reflected literature published as of December 31, 2004. Because of the scope and importance of certain ongoing clinical trials and other emerging information, published abstracts were cited when they were the only published information available. The references selected for this document are exclusively for peer-reviewed papers that are representative but not all inclusive. All members of the committee had frequent opportunities to review drafts of the document, comment in writing or during teleconference discussions, and reach consensus with the final recommendations.