Prevention of Ischemic Stroke

Secondary prevention of ischemic stroke is the coordinated program of antithrombotic therapy, high-intensity statin therapy, blood pressure control, and — in selected patients — carotid revascularization or patent foramen ovale (PFO) closure that begins once the acute diagnosis is established and any hyperacute reperfusion decisions have already been made; this chapter does not cover thrombolysis, thrombectomy, or other hyperacute management, which are addressed elsewhere. The single most important branch point in this chapter is stroke mechanism: a cardioembolic event — atrial fibrillation is by far the most common cause — is treated with an anticoagulant, while a non-cardioembolic event (large-artery atherosclerotic, small-vessel/lacunar, or cryptogenic) is treated with an antiplatelet.^[1] The same antithrombotic framework also governs primary stroke prevention in a patient who has never had a stroke but has a high-risk cardioembolic condition such as atrial fibrillation. Recurrence risk is highest in the first days to weeks after a TIA or minor stroke, which is why same-day risk stratification and prompt initiation of secondary prevention are routine, expected care rather than an exception.^[2]

How TIA and minor ischemic stroke present

Sudden-onset, focal neurologic deficit corresponding to a specific vascular territory: unilateral weakness or numbness, expressive or receptive language disturbance, dysarthria, monocular vision loss (amaurosis fugax), homonymous visual field loss, diplopia, ataxia, or vertigo accompanied by other posterior-circulation features. A transient ischemic attack (TIA) is a deficit that resolves completely, typically within an hour; a minor (non-disabling) stroke produces a deficit that persists but does not substantially limit activities of daily living. Both carry a high short-term risk of a second, potentially disabling event and both trigger the same urgent secondary-prevention workup.

• Prior TIA or ischemic stroke — the single strongest predictor of a recurrent event.
• Atrial fibrillation (paroxysmal, persistent, or permanent) or atrial flutter.
• Hypertension.
• Diabetes mellitus.
• Dyslipidemia.
• Current smoking.
• Carotid artery stenosis.
• Other cardiac disease: recent MI with left ventricular thrombus, dilated cardiomyopathy, valvular heart disease, or a mechanical prosthetic valve.
• Patent foramen ovale, particularly relevant in younger patients with cryptogenic stroke.
• Obesity and physical inactivity.
• Obstructive sleep apnea.
• Excess alcohol intake.
• Cocaine or other stimulant use.
• Hypercoagulable states — more relevant in younger patients without traditional vascular risk factors.
• Combined hormonal contraceptive or menopausal hormone therapy use, particularly when combined with smoking, migraine with aura, or another vascular risk factor.
• Family history of stroke, especially at a young age.

History

• Characterize nature, frequency, duration, and distribution of symptoms to localize the vascular territory.
• Review vascular risk factors systematically: hypertension, diabetes, dyslipidemia, smoking, atrial fibrillation or palpitations, prior cardiac disease.
• In younger patients, ask specifically about additional etiological factors not captured by standard risk-factor review: recent trauma or neck manipulation (dissection), cardiac abnormalities, recent infection, coagulation disorders, and illicit drug use.

Physical examination

• Complete neurologic assessment.
• Visual assessment: eye movements, visual fields, acuity, and funduscopy.
• Complete vascular examination: auscultation (cranium, neck, heart), palpation (temporal artery, peripheral pulses), and blood pressure measured in both arms.

Initial investigations — indicated in essentially every patient with TIA or minor stroke

• CT brain plus CT angiography (arch to vertex) to exclude a hemorrhagic process or a stroke mimic and to define vascular anatomy; cervical duplex ultrasonography is an acceptable alternative to CT angiography in some patients.
• CBC, coagulation parameters, blood glucose, renal function, fasting lipid profile, and hepatic enzymes.
• 12-lead ECG to exclude atrial fibrillation or another contributing arrhythmia.

Extended cardiac investigations

Transthoracic or transesophageal echocardiography, and 24-48 hour Holter monitoring, are indicated when a cardioembolic source is suspected or the initial workup is otherwise unrevealing; yield is higher in patients with known cardiac disease or in older patients. In patients under investigation for cryptogenic stroke specifically, a prolonged (approximately 30-day) period of cardiac monitoring with a loop recorder substantially increases detection of paroxysmal atrial fibrillation compared with a short in-hospital telemetry strip and should be pursued rather than relying on a brief monitoring period alone.^[1] In patients under 60 with cryptogenic stroke and no other identified etiology, transesophageal echocardiography should specifically be pursued to look for a patent foramen ovale.

Selective and specialized testing — not routine

Reserve erythrocyte sedimentation rate, autoimmune/vasculitis workup, a hypercoagulable panel (protein C, protein S, antithrombin, factor V Leiden, antiphospholipid antibodies), and homocysteine testing for younger patients (generally under 50) or those whose clinical picture specifically suggests one of these causes — do not order a full hypercoagulable panel routinely in an older patient who already has a plausible atherosclerotic or cardioembolic mechanism identified. MRI and MR angiography can confirm the degree of arterial occlusion or exclude a mimicking condition; catheter cerebral angiography is reserved for confirming a vasculopathy (e.g. moyamoya disease, fibromuscular dysplasia) or vasculitis when non-invasive imaging is inconclusive.

TIA and minor stroke mimics to exclude

• Hypoglycemia.
• Focal (partial) seizure with post-ictal (Todd) paralysis.
• Migraine with aura.
• Peripheral vestibular disorder — benign paroxysmal positional vertigo, vestibular neuritis.
• Bell palsy.
• Syncope or presyncope.
• Functional neurologic symptoms.

Tempo of onset, positive versus negative symptoms, and associated features usually distinguish these from a true ischemic event; when the diagnosis is uncertain, neuroimaging helps confirm it. Treating a mimic as a TIA exposes the patient to antithrombotic bleeding risk without any benefit.

ABCD2 score — urgency of TIA investigation

A 7-point score used to estimate short-term stroke risk after a TIA and to decide how urgently to investigate and treat.^[3]

Maximum score is 7. Interpretation: 0-3 points is low risk, 4-5 points is moderate risk, and 6-7 points is high risk, with 2-day stroke risk climbing steeply in the high-risk band.^[3] A score of 4 or higher — or any high-risk clinical feature regardless of total score, such as crescendo TIA, a patient already on an antithrombotic, or known atrial fibrillation — should prompt same-day assessment and initiation of secondary prevention rather than a delayed outpatient work-up.

CHA₂DS₂-VASc score — the anticoagulation decision in atrial fibrillation

A point-sum used to estimate annual stroke risk in atrial fibrillation and to decide whether anticoagulation is indicated.^[4]

Maximum practical score is 9 (the two age tiers are mutually exclusive). Interpretation: a score of 0 in a man, or 1 in a woman where the only point is sex category, is low risk and anticoagulation is not usually indicated on stroke-risk grounds alone; a score of 1 in a man favours anticoagulation, weighed against bleeding risk; a score of 2 or higher in a man, or 3 or higher in a woman, is an indication for anticoagulation.^[4] In a patient presenting after an ischemic stroke or TIA with known atrial fibrillation, a qualifying stroke/TIA event alone already contributes 2 points, so the practical takeaway is that anticoagulation is indicated, not optional — CHA₂DS₂-VASc is most useful for identifying which patients with atrial fibrillation who have not yet had a stroke need primary-prevention anticoagulation.

• Prevent recurrent ischemic stroke and disabling neurologic deficit.
• Prevent cerebrovascular and cardiovascular mortality.
• Match antithrombotic drug class — antiplatelet versus anticoagulant — to the confirmed or presumed stroke mechanism.
• Achieve a blood pressure below 130/80 mmHg in most patients.
• Achieve an LDL-C below 1.8 mmol/L (70 mg/dL) in patients with an atherosclerotic mechanism, using high-intensity statin therapy started regardless of baseline LDL.
• Eliminate modifiable risk factors: smoking cessation, glycemic control, weight management, regular exercise.
• Identify and refer candidates for carotid revascularization or PFO closure promptly, since benefit is highly time-dependent for carotid intervention.

• Smoking cessation counselling and pharmacotherapy — one of the highest-yield modifiable interventions.
• Reduce alcohol intake; heavy alcohol use raises both ischemic and hemorrhagic stroke risk.
• Reduce dietary sodium and saturated fat intake; a Mediterranean-pattern diet is a reasonable general approach.
• Regular aerobic exercise as tolerated, once medically stable.
• Weight reduction toward a healthy body weight.
• Optimize diabetes management.
• Screen for and treat obstructive sleep apnea when suspected.
• Refer for physiotherapy, occupational therapy, and speech-language therapy within 24-48 hours for any residual neurologic deficit.
• Advise against combined hormonal contraceptives or menopausal hormone therapy in a patient with a history of stroke or TIA (see Special Populations).
• In a patient with a documented PFO and no other identified cause for a cryptogenic stroke, refer to cardiology to assess candidacy for PFO closure.

Pregnancy

Choice of antithrombotic depends on the presumed etiology: an anticoagulant for a cardioembolic mechanism, or an antiplatelet for any other mechanism. Low molecular weight heparin is preferred over warfarin when anticoagulation is needed in pregnancy — warfarin is potentially teratogenic, and safety data for the DOACs in pregnancy are insufficient to recommend their use. If an antiplatelet is needed, low-dose ASA 81 mg PO daily is preferred, since evidence supporting the safety of other antiplatelets in pregnancy is more limited. For blood pressure control in pregnancy (target below 140/90 mmHg — a different, pregnancy-specific target from the 130/80 mmHg secondary-prevention target used outside pregnancy), labetalol, methyldopa, or long-acting nifedipine are the preferred agents.^[2] Statins are not recommended in pregnancy given insufficient safety data — manage dyslipidemia with diet and exercise instead, and resume statin therapy postpartum once breastfeeding status is confirmed.

Breastfeeding

Low-dose ASA is considered safe during breastfeeding; safety data for clopidogrel and ASA/dipyridamole are more limited. Warfarin is considered safe during breastfeeding. DOAC safety during breastfeeding has not been established — avoid unless no suitable alternative exists and specialist input supports it. The same antihypertensive agents used in pregnancy (labetalol, methyldopa, long-acting nifedipine) remain reasonable choices. Statins are not recommended during breastfeeding.

Older adults

Bleeding risk with any antithrombotic — antiplatelet or anticoagulant, and especially short-course dual antiplatelet therapy — rises with age; weigh this carefully but do not withhold indicated therapy on age alone. Confirm renal function before selecting a DOAC or its dose, since several dose-reduction criteria are age-triggered (see Pharmacologic Treatment Options).

Renal impairment

Apixaban is not recommended at ClCr under 15 mL/min or in patients on dialysis. Dabigatran is contraindicated at ClCr under 30 mL/min. Edoxaban and rivaroxaban are not recommended at ClCr under 30 mL/min. Warfarin has no direct renal dosing requirement, but bleeding risk is elevated in renal impairment and monitoring should be more frequent.

Hormonal contraception and menopausal hormone therapy

Avoid combined hormonal contraceptives in a patient with a history of stroke or TIA — use a non-hormonal or progestin-only method instead. Avoid initiating menopausal hormone therapy for cardiovascular protection in this population; it does not reduce recurrent stroke risk and increases it. If hormone therapy is being considered for severe vasomotor symptoms despite counselling on alternatives, use the lowest effective dose only after specialist discussion of the added risk.

Reassess adherence to antithrombotic and statin therapy at every follow-up visit — early nonadherence, particularly to a short-course dual antiplatelet regimen or to a newly started DOAC, is common and is something community pharmacists are well positioned to catch. Check renal function at least annually in any patient on a DOAC, and more frequently (every 6 months) if age is over 75, ClCr is 30-60 mL/min, or the patient is on an interacting medication — renal function directly changes DOAC dosing. For warfarin, follow INR per institutional protocol with a target time-in-therapeutic-range above 70%. Recheck a lipid panel 4-12 weeks after starting or adjusting statin therapy, then annually, and escalate through ezetimibe/PCSK9 inhibitor therapy if LDL-C remains above target. Check blood pressure at every visit, with home monitoring encouraged, and titrate therapy toward the below-130/80 mmHg target. Confirm smoking-cessation progress and reinforce other lifestyle measures at each visit. Confirm that prolonged cardiac monitoring was completed and reviewed in any patient investigated for cryptogenic stroke — if atrial fibrillation is later detected, switch from an antiplatelet to an anticoagulant. Patients managed medically for carotid stenosis below the revascularization threshold should have periodic carotid duplex surveillance to detect progression.

1. Confirm adherence to the prescribed antithrombotic and statin regimen before assuming the therapy itself has failed.
2. Reassess whether the presumed stroke mechanism was correct: pursue extended cardiac monitoring for occult atrial fibrillation if not already completed, repeat carotid imaging, and consider a hypercoagulable workup in a younger patient without traditional risk factors.
3. Recurrent event on antiplatelet monotherapy: investigate for a missed cardioembolic or other specific source before simply escalating to indefinite dual antiplatelet therapy, which is not an evidence-based response to antiplatelet "failure".
4. Recurrent event on anticoagulation: confirm therapeutic dosing, adherence, and (for warfarin) that the INR has genuinely been in range before concluding the anticoagulant has failed; if confirmed, obtain specialist input on switching within or between DOAC and warfarin therapy rather than simply adding an antiplatelet.
5. Reassess statin adequacy with a repeat lipid panel and escalate through the ezetimibe/PCSK9 inhibitor pathway if LDL-C remains above target.
6. Reassess blood pressure control and carotid stenosis progression.
7. Refer to stroke neurology for any recurrence despite confirmed adherence and optimized therapy, or for any presentation where the mechanism remains unclear.

• Combining an anticoagulant and an antiplatelet for stroke prevention without a separate, specific cardiac indication.
• Continuing dual antiplatelet therapy beyond 21-30 days for routine secondary prevention.
• Defaulting to warfarin without considering a DOAC — DOACs are now preferred for most patients with non-valvular atrial fibrillation.
• Over-applying the longest anticoagulation-timing interval (12-14 days) to a patient with only a minor stroke or TIA — timing should scale with stroke severity, not default to the most conservative option for every patient.
• Ordering a full hypercoagulable workup routinely in an older patient who already has a plausible atherosclerotic or cardioembolic mechanism.
• Missing occult atrial fibrillation because only a brief in-hospital telemetry strip was obtained in a patient with cryptogenic stroke who actually needed prolonged loop-recorder monitoring.
• Withholding a high-intensity statin because the baseline LDL-C "looks fine" — every patient with an atherosclerotic-mechanism event gets a high-intensity statin regardless of baseline LDL.
• Treating asymptomatic carotid stenosis with the same urgency and intervention threshold as symptomatic disease.
• Referring for PFO closure without a genuinely complete workup excluding other causes, or in a patient over 60, without specialist input.
• Withholding all antithrombotic therapy in pregnancy out of excess caution when a clear indication for either an antiplatelet or an anticoagulant exists.
• Continuing combined hormonal contraception or starting menopausal hormone therapy for cardiovascular protection after a stroke or TIA.

How to use this table: Doses are adult doses and require patient-specific confirmation, including renal adjustment. Select any drug name to open its complete Pharmasist Drug Database page.

Antiplatelet agents

Preferred for non-cardioembolic (large-artery atherosclerotic, small-vessel/lacunar, or cryptogenic) ischemic stroke and TIA.

Direct oral anticoagulants (DOACs)

Preferred over warfarin for most patients with cardioembolic stroke/TIA due to non-valvular atrial fibrillation.

Vitamin K antagonist

Reserved for a mechanical prosthetic heart valve, moderate-to-severe mitral stenosis, or a patient already stable on it.

Lipid-lowering therapy

High-intensity statin for every patient with an atherosclerotic-mechanism ischemic stroke or TIA, started regardless of baseline LDL-C.

Antihypertensive therapy for stroke-recurrence reduction

Target blood pressure below 130/80 mmHg in most patients. This is a focused summary — consult dedicated hypertension management guidance for full agent selection and titration.