• This study aims to assess the prevalence of aspirin resistance in patients with acute ischemic stroke and its importance in secondary stroke prevention.
• Effect of aspirin resistance on short and long term mortality and detection of its relationship with recurrence of stroke.

Stroke is the rapidly developing loss of brain functions due to disturbance in the blood supply to the brain. It is the leading cause of adult disability in the United States and Europe and currently the second leading cause of death, ranking after heart disease and before cancer, accounting for 10% of deaths worldwide . About 80-90% of strokes are caused by ischemia, and the remainder by hemorrhage . Arterioarterial micro thromboembolism is an important etiological factor in the pathogenesis of ischemic stroke. Platelet activation in cerebrovascular disease is associated with recurrent stroke and death, while inhibition of platelet function by antiplatelet drugs including aspirin lowers the risk of ischemic stroke. Aspirin is an effective antiplatelet agent, exhibiting its action by irreversibly inhibiting platelet cyclooxygenase-1 enzyme, thus preventing the production of thromboxane A2 (TXA2). It has been used in the primary and secondary prevention of thromboembolic vascular events. Yet, some patients experience recurrent ischemic events despite optimal antiplatelet therapy. This has raised the possibility that these patients may be resistant to aspirin and generated much interest in identification of such patients with laboratory tests of platelet function. Although many studies have demonstrated aspirin resistance in cardiovascular disorders including coronary artery disease, metabolic syndrome , and diabetes by certain tests of aspirin resistance, there are still concerns that these tests have not correlated closely with subsequent recurrent events, and have not reliably identified non-responders to antiplatelet therapy . In addition to the absence of any standardized approach to the diagnosis, there is currently no proven effective treatment for aspirin resistance. Although aspirin resistance has been demonstrated as a possible risk factor for recurrent cardiovascular ischemic events, there is a lack of data correlating aspirin resistance and risk of cerebrovascular ischemic events

Inclusion Criteria:

1. At least 7 days of aspirin therapy (acetylsalicylic acid, 100 mg daily) prior to stroke onset
2. Within 24 h of experiencing a new focal or global neurological deficit.
3. Evidence of new or old ischemic infarct on CT brain or magnetic resonance imaging (MRI).
4. With informed consents.
5. Presence or not previous cerebrovascular event as previous history of transient ischemic attack (TIA) before the onset of stroke.

Exclusion Criteria:

1. Patients with other neurological deficits due to stroke mimics or hemorrhagic insult.
2. Patients is subjected to anticoagulant treatment (atrial fibrillation, valve replacement, others).

Patients presenting consecutively to the Department of Neurology of Assiut university Hospital with acute ischemic stroke whether new onset or recurrent. Acute ischemic stroke was defined as focal neurological deficit persisting for more than 24 h with evidence of cerebral infarction on neuroimaging (MRI brain). The time between stroke occurrence and admission to the hospital was 1-48 h.