Erfan Bashar
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Stroke Secondary Prevention

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Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.

Secondary prevention means preventing the next stroke after an ischemic stroke or transient ischemic attack. The strategies are the same for both presentations. Prevention combines a mechanism-specific treatment with control of the risk factors that built the disease.

Antiplatelet therapy

Antiplatelets are the foundation after non-cardioembolic ischemia. Platelet aggregation at plaque or injured endothelium starts thrombus formation, and these drugs interrupt that cascade. Aspirin irreversibly blocks platelet cyclooxygenase-1 and thromboxane A2 production; clopidogrel blocks the ADP P2Y12 receptor and the downstream glycoprotein IIb/IIIa activation. Because the targets differ, combined treatment inhibits platelets more broadly than either drug alone.

Standard single agents are aspirin 50–325 mg daily, clopidogrel 75 mg daily, or aspirin 25 mg plus extended-release dipyridamole 200 mg twice daily. Short-term dual aspirin and clopidogrel for 21 to 90 days is reserved for acute minor stroke or high-risk transient ischemia, defined by an ABCD2 score of 4 or above. The studied regimen behind this window is clopidogrel 300 mg load then 75 mg daily with aspirin 75 mg daily for the first 21 days. Long-term dual therapy is not recommended for most patients because bleeding rises without proportional stroke benefit. In lacunar stroke, adding clopidogrel to aspirin did not reduce recurrence and increased bleeding and death, so long-term dual therapy has no place there either.

For stroke or transient ischemia within 30 days from severe 70–99% intracranial stenosis, dual aspirin and clopidogrel for up to 90 days with aggressive medical management is preferred over first-line angioplasty and stenting. Embolic stroke of undetermined source should not be treated empirically with anticoagulation or ticagrelor.

When anticoagulation replaces antiplatelets

Cardioembolic stroke needs anticoagulation rather than antiplatelets alone. Clots forming in stagnant cardiac blood, most often the left atrial appendage in atrial fibrillation, are fibrin-rich, and antiplatelets cannot reliably prevent them; anticoagulants block the coagulation cascade that builds fibrin. The same switch applies to mural thrombus after myocardial infarction, valvular disease, and intracardiac thrombus. Most patients with atrial fibrillation should be anticoagulated, with prolonged rhythm monitoring to find occult fibrillation.

Timing respects hemorrhagic transformation. After a large infarct with injured endothelium, anticoagulation may be delayed up to about 14 days before starting long-term therapy. Otherwise timing is individualized by infarct size and hemorrhagic-transformation risk, balancing early recurrence against intracranial bleeding. Early heparin bridging is reserved for selected high-relapse settings such as dissection, cerebral venous thrombosis, or intracardiac thrombus.

Carotid endarterectomy: thresholds and timing

Endarterectomy removes the carotid plaque itself rather than suppressing clotting. Symptomatic stenosis of 70–99% after a carotid-territory transient attack or stroke is an established indication, and endarterectomy is recommended for transient ischemia or non-disabling stroke with ipsilateral severe 50–99% stenosis. Symptomatic stenosis below 50% is generally not operated because surgical risk outweighs benefit; 50–69% is decided case by case. Asymptomatic stenosis of 60–99% in patients roughly 40–75 years old may be reasonable when surgical risk, life expectancy, and center quality favor it, with a smaller absolute benefit than in symptomatic disease.

Timing matters because the plaque is most unstable early: benefit is maximal within 2 weeks of the index event, and guidance converges on symptom-to-intervention within 14 days. Perioperative aspirin is given before and for at least several months after surgery to reduce perioperative stroke, myocardial infarction, and death.

Stenting and risk-factor control

Carotid stenting through percutaneous access is the endovascular alternative, generally considered when open surgery carries high risk from comorbidity, prior neck surgery or radiation, or unfavorable anatomy. Choice between endarterectomy and stenting rests on patient comorbidities and vascular anatomy.

Underneath every mechanism sits the same foundation with explicit targets. Blood pressure below 130/80 mmHg suits most hypertensive stroke patients. Atorvastatin 80 mg daily with LDL below 70 mg/dL reduces recurrence and cardiovascular events. Hemoglobin A1c at or below 7% suits most diabetic patients. Supervised physiotherapist-led exercise is the safe-activity model for patients with mobility deficits. Hypertension is the single most important modifiable driver across ischemic and hemorrhagic disease. Adequate control, not merely prescribed treatment, is what prevents the next event.

Evidence anchors

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