Prevention of Ischemic Stroke

Clinical Snapshot

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]

Recognize the Condition

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.

Ischemic stroke mechanism — the categorization that determines antithrombotic choice

Cardioembolic

An embolus arising from the heart. Atrial fibrillation (paroxysmal, persistent, or permanent) is the dominant cause, followed by a mechanical prosthetic valve, a recent (within 3 months) anterior MI with left ventricular thrombus, dilated cardiomyopathy, and rheumatic mitral valve disease. Treated with an anticoagulant, not an antiplatelet.

Large-artery atherosclerotic

Atherosclerotic plaque in a major extracranial or intracranial artery — most often the carotid bifurcation — causing artery-to-artery embolism or in-situ thrombosis. Treated with an antiplatelet, a high-intensity statin, and evaluation for carotid revascularization.

Small-vessel (lacunar)

Occlusion of a single deep penetrating arteriole, producing a classic lacunar syndrome — pure motor, pure sensory, ataxic hemiparesis, or dysarthria-clumsy hand. Treated with an antiplatelet; blood pressure control is especially important in this group.

Cryptogenic / embolic stroke of undetermined source

No cardioembolic, large-artery, or small-vessel cause is identified despite an adequate workup. Treated with an antiplatelet by default; in selected patients aged 60 or under with a right-to-left shunting patent foramen ovale and no other identified cause, PFO closure is considered.

Other determined etiology

Cervical artery dissection, vasculitis, a hypercoagulable state, moyamoya disease, or fibromuscular dysplasia. Treatment targets the specific cause and is usually managed with specialist input.

Risk Factors

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.

Red Flags & Refer

Any of the following changes the urgency of assessment from routine outpatient workup to same-day or emergency evaluation:

Crescendo TIA — 2 or more TIAs within 72 hours, or TIAs increasing in frequency, duration, or severity — needs same-day assessment by a clinician with stroke expertise.
High ABCD2 score (6-7), or any high-risk feature regardless of total score (motor or speech symptoms lasting more than 10 minutes, known atrial fibrillation) — needs urgent same-day investigation and treatment.
New or worsening neurologic symptoms in a patient already on secondary-prevention therapy — treat as a possible recurrent ischemic event or hemorrhagic transformation, not as breakthrough TIA to be managed by watchful waiting.
Sudden, severe focal neurologic deficit with a clear time-of-onset — assess immediately for hyperacute reperfusion eligibility (thrombolysis/thrombectomy) rather than routing directly into a secondary-prevention pathway.
Neck pain, headache, or Horner syndrome accompanying the neurologic deficit — raises suspicion for cervical artery dissection, which needs urgent vascular imaging and specialist input.
Recurrent ischemic event despite adequate, adherent antithrombotic therapy — needs re-investigation of the stroke mechanism rather than an empirical medication switch.
Stroke or TIA in pregnancy or the postpartum period — needs a combined stroke and maternal-fetal medicine assessment.

Assessment & Diagnosis

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]

Criterion	Points
Age >= 60 years	1
Blood pressure >= 140/90 mmHg at first assessment	1
Clinical feature: unilateral weakness (with or without speech disturbance)	2
Clinical feature: speech disturbance without weakness	1
Clinical feature: neither of the above	0
Duration >= 60 minutes	2
Duration 10-59 minutes	1
Duration < 10 minutes	0
Diabetes mellitus	1

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]

Criterion	Points
Congestive heart failure or left ventricular dysfunction	1
Hypertension	1
Age >= 75 years	2
Diabetes mellitus	1
Prior stroke, TIA, or systemic thromboembolism	2
Vascular disease — prior MI, peripheral artery disease, or aortic plaque	1
Age 65-74 years	1
Sex category — female	1

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.

Treatment Targets

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.

Choose Initial Treatment

Direct treatment rule

Step 1 — match antithrombotic class to mechanism

Cardioembolic mechanism — atrial fibrillation is the dominant cause use an oral anticoagulant, not an antiplatelet, for secondary prevention after a stroke/TIA and for primary prevention in a patient with atrial fibrillation who has not yet had a stroke.

Non-cardioembolic mechanism — large-artery atherosclerotic, small-vessel/lacunar, or cryptogenic use an antiplatelet agent, not an anticoagulant.

Do not combine a DOAC or warfarin with an antiplatelet for stroke prevention unless there is a separate, specific cardiac indication (e.g. a recent coronary stent) — combination therapy increases bleeding without a clear stroke-prevention benefit in this setting.^[2]

Step 2 — antiplatelet selection for non-cardioembolic stroke/TIA

1st line, long-term monotherapy ASA 80-325 mg PO daily, clopidogrel 75 mg PO daily, or ASA / extended-release dipyridamole 25 mg/200 mg PO BID — all 3 are appropriate with broadly similar efficacy; ASA is the usual starting choice given cost and tolerability, clopidogrel is preferred when ASA is not tolerated, and ASA/dipyridamole is generally reserved as a second-line choice given twice-daily dosing and a higher headache-related discontinuation rate.^[2]

Short-course dual antiplatelet therapy — use only for acute high-risk TIA (ABCD2 >= 4) or minor ischemic stroke (NIHSS 0-3) of non-cardioembolic origin, without high bleeding risk clopidogrel 300-600 mg PO loading dose then 75 mg PO daily, plus ASA 160-325 mg PO loading dose then 81 mg PO daily, started within 24 hours of symptom onset (ideally within 12 hours) and continued for 21 days, then stepped down to single-agent antiplatelet therapy.^[5]^[6] Aspirin plus ticagrelor 180 mg PO loading dose then 90 mg PO BID for 30 days is an alternative short-course regimen in suitable patients.^[7]

Do not continue dual antiplatelet therapy beyond 21-30 days for routine secondary prevention — the excess bleeding risk of prolonged dual therapy is not offset by any further reduction in ischemic events beyond this window, unless a separate indication for longer dual therapy exists (e.g. a recent coronary stent, or symptomatic intracranial atherosclerosis under specialist direction).^[2]

Step 3 — anticoagulant selection for cardioembolic stroke and atrial fibrillation

1st line a direct oral anticoagulant — apixaban, dabigatran, edoxaban, or rivaroxaban — is preferred over warfarin for most patients with non-valvular atrial fibrillation, given comparable or superior efficacy and a better intracranial hemorrhage profile.^[1]^[2]

Use warfarin instead when the patient has a mechanical prosthetic heart valve or moderate-to-severe mitral stenosis — DOACs are not validated or are inferior in these populations — or when the patient is already stable on warfarin with a time-in-therapeutic-range above 70% and prefers to continue it.

Step 4 — timing of anticoagulation initiation after an acute ischemic stroke with atrial fibrillation

Balance recurrent-embolism risk against hemorrhagic-transformation risk using stroke severity as the practical guide: start at approximately 1 day for a TIA with no visible infarct, 3 days for a minor stroke/small infarct, 6-7 days for a moderate stroke/moderate infarct, and 12-14 days for a severe stroke/large infarct — obtain repeat brain imaging before starting if initiation is delayed beyond 24 hours, to confirm no hemorrhagic transformation has occurred.^[2]

Recent randomized trial evidence supports earlier initiation than this traditional schedule — within 48 hours for a minor or moderate stroke, and by day 6-7 even for a major stroke — without an increase in the composite of recurrent ischemic event or major bleeding; use this evidence to lean toward the earlier end of the ranges above when repeat imaging shows no hemorrhagic transformation, rather than defaulting rigidly to the longer, traditional intervals.^[8]

Do not routinely bridge with heparin while awaiting a therapeutic INR in a patient starting warfarin after an acute ischemic stroke with atrial fibrillation — bridging increases hemorrhagic transformation risk without a demonstrated reduction in recurrent stroke; low-dose ASA until the INR is therapeutic is a reasonable interim approach instead.^[2]

Step 5 — statin therapy

Every patient with an atherosclerotic-mechanism ischemic stroke or TIA — regardless of baseline LDL-C — should be started on a high-intensity statin (atorvastatin 40-80 mg or rosuvastatin 20-40 mg PO daily); add ezetimibe if LDL-C remains >=1.8 mmol/L (70 mg/dL) on maximally tolerated statin, then a PCSK9 inhibitor (evolocumab or alirocumab) if still above target.^[1]

Step 6 — blood pressure

Target a blood pressure below 130/80 mmHg for most patients once past the acute phase of stroke or TIA.^[1] A combination of an ACE inhibitor or ARB plus a thiazide-type diuretic (e.g. perindopril/indapamide) is the best-studied regimen specifically for stroke-recurrence reduction and is a reasonable default when initiating new antihypertensive therapy in this population; consult current hypertension management guidance for full titration across all antihypertensive drug classes.

Step 7 — carotid revascularization

Symptomatic carotid stenosis 70-99%, ipsilateral to the qualifying event refer for carotid endarterectomy, performed as early as possible — within 2 weeks of the qualifying event, and within 7 days when feasible in a patient who is otherwise stable — combined with ongoing antithrombotic therapy.^[1]

Symptomatic carotid stenosis 50-69% consider carotid endarterectomy in selected patients — greater benefit in men, age over 75, hemispheric (rather than retinal) symptoms, and recent (within 2 weeks) symptom onset; the benefit is smaller than with severe stenosis, and shared decision-making is appropriate.

Carotid stenting reserve as an alternative to endarterectomy for patients at elevated surgical risk — significant coronary disease, prior neck surgery or radiation, contralateral carotid occlusion, or anatomically difficult surgical access — rather than as a routine first choice.

Step 8 — patent foramen ovale closure

Cryptogenic stroke, age 60 or under, with a PFO and no other identified stroke etiology after a complete workup refer for cardiology assessment for percutaneous PFO closure — closure plus antiplatelet therapy reduces recurrent stroke compared with antiplatelet therapy alone in this specific population.^[9]

Do not refer for PFO closure once an alternative stroke mechanism has been identified (the PFO is then an incidental finding), or in a patient over 60, without first obtaining specialist input — evidence for benefit is much weaker outside the age-60-and-under, no-alternative-cause population.

Non-Pharmacologic Treatment

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.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
ASA Preferred	1st-line antiplatelet, non-cardioembolic stroke/TIA	80-325 mg PO daily	GI upset, bleeding	Usual starting choice given cost and tolerability; continue indefinitely unless switched for intolerance.
Clopidogrel Preferred	Antiplatelet monotherapy alternative, or short-course DAPT partner	75 mg PO daily (monotherapy); loading 300-600 mg then 75 mg PO daily for 21-day DAPT	Bleeding, rash	Use as monotherapy when ASA not tolerated; use as the DAPT partner for high-risk TIA/minor stroke.
ASA / dipyridamole (extended-release) Alternative	2nd-line antiplatelet monotherapy	ASA 25 mg + dipyridamole (extended-release) 200 mg PO BID	Headache (common, dose-limiting), bleeding	Reserve for when ASA and clopidogrel are both unsuitable, given twice-daily dosing and headache-related discontinuation.
Ticagrelor Special situation	Alternative short-course DAPT partner with ASA	Loading 180 mg, then 90 mg PO BID for 30 days	Bleeding, dyspnea	Alternative to clopidogrel for short-course DAPT in high-risk TIA/minor stroke.
Apixaban Preferred	1st-line DOAC, cardioembolic stroke prevention (atrial fibrillation)	5 mg PO BID (2.5 mg PO BID if 2 of: age >=80, weight <=60 kg, SCr >=133 umol/L)	Bleeding	Preferred DOAC option; no routine coagulation monitoring needed.
Dabigatran Preferred	1st-line DOAC, cardioembolic stroke prevention (atrial fibrillation)	150 mg PO BID (110 mg PO BID if age >80 or elevated bleeding risk)	Bleeding, dyspepsia	Contraindicated at ClCr under 30 mL/min.
Rivaroxaban Preferred	1st-line DOAC, cardioembolic stroke prevention (atrial fibrillation)	20 mg PO daily with the evening meal (15 mg if ClCr 30-49 mL/min)	Bleeding	Take with food to maximize absorption.
Edoxaban Preferred	1st-line DOAC, cardioembolic stroke prevention (atrial fibrillation)	60 mg PO daily (30 mg if ClCr 30-50 mL/min, weight <=60 kg, or select P-gp inhibitors)	Bleeding	Not recommended at ClCr under 30 mL/min.
Warfarin Alternative	Mechanical valve, moderate-severe mitral stenosis, or patient already stable on it	Dose to INR 2-3 (2.5-3.5 for a mechanical mitral valve)	Bleeding, skin necrosis, many drug interactions	Requires regular INR monitoring; target time-in-therapeutic-range above 70%.
Atorvastatin (high-intensity) Preferred	Atherosclerotic-mechanism stroke/TIA, all patients regardless of baseline LDL	40-80 mg PO daily	Myalgia, transaminase elevation	Start before or shortly after discharge; target LDL-C below 1.8 mmol/L (70 mg/dL).

Special Populations

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.

Monitoring & Follow-Up

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.

Treatment Failure / Next Step

Confirm adherence to the prescribed antithrombotic and statin regimen before assuming the therapy itself has failed.
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.
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".
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.
Reassess statin adequacy with a repeat lipid panel and escalate through the ezetimibe/PCSK9 inhibitor pathway if LDL-C remains above target.
Reassess blood pressure control and carotid stenosis progression.
Refer to stroke neurology for any recurrence despite confirmed adherence and optimized therapy, or for any presentation where the mechanism remains unclear.

Common Errors to Avoid

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.

Clinical Decision Algorithm

Algorithm A — Matching antithrombotic therapy to stroke mechanism

Confirmed or strongly suspected ischemic stroke or TIA; hyperacute reperfusion decisions already addressed

Determine stroke mechanism: cardioembolic source (atrial fibrillation, mechanical valve, LV thrombus, cardiomyopathy) versus non-cardioembolic (large-artery atherosclerotic, small-vessel/lacunar, cryptogenic)

Cardioembolic — most often atrial fibrillation

Select an anticoagulant: DOAC (apixaban, dabigatran, edoxaban, or rivaroxaban) preferred; warfarin for a mechanical valve or moderate-to-severe mitral stenosis

Determine timing of initiation using stroke severity — see Algorithm B^[2]

Non-cardioembolic

Calculate the ABCD2 score for TIA, or assess stroke severity (NIHSS) for a completed minor stroke

High-risk TIA (ABCD2 4-7) or minor stroke (NIHSS 0-3), no high bleeding risk, within 24 hours of onset

Short-course DAPT: clopidogrel plus ASA (or ticagrelor plus ASA) for 21-30 days, then step down to single antiplatelet^[5]

Lower-risk TIA/stroke, or presenting beyond the DAPT window

Single antiplatelet: ASA, clopidogrel, or ASA/dipyridamole (extended-release)

Start a high-intensity statin, target blood pressure below 130/80 mmHg, and assess for carotid stenosis and — if cryptogenic and age 60 or under — a PFO; see Algorithm C

Algorithm B — Timing of anticoagulation after acute ischemic stroke with atrial fibrillation

Atrial fibrillation confirmed as the stroke mechanism

TIA, no visible infarct

Start anticoagulation at approximately 1 day

Minor or moderate stroke

Start at approximately 3 days (minor) or 6-7 days (moderate); repeat brain imaging first if starting beyond 24 hours^[2]

Severe stroke or large infarct

Start at approximately 12-14 days; repeat brain imaging first to exclude hemorrhagic transformation

Randomized trial evidence supports leaning toward the earlier end of each range — within 48 hours for minor/moderate stroke, day 6-7 for severe stroke — when repeat imaging shows no hemorrhagic transformation^[8]

Algorithm C — Carotid stenosis and patent foramen ovale referral

Carotid duplex/CT angiography completed; transesophageal echocardiography also completed if cryptogenic and age 60 or under

Symptomatic carotid stenosis 70-99%, ipsilateral to the event

Refer for carotid endarterectomy within 2 weeks (within 7 days if feasible); carotid stenting as an alternative if surgical risk is high^[1]

Symptomatic carotid stenosis 50-69%

Consider carotid endarterectomy in selected patients (male, age over 75, hemispheric symptoms, recent event); shared decision-making

Cryptogenic stroke, age 60 or under, PFO found, no other cause identified

Refer to cardiology for percutaneous PFO closure plus antiplatelet therapy^[9]

Drug Tables

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.

Drug	Dosage	Adverse effects	Drug interactions	Comments
ASA	Monotherapy: 80-325 mg PO daily	Gastritis, GI ulceration/hemorrhage, rare bronchospasm, tinnitus at high dose	Increased bleeding with anticoagulants, other NSAIDs	1st-line monotherapy given cost and tolerability. Continue indefinitely.
Clopidogrel	Monotherapy: 75 mg PO daily DAPT loading dose: 300-600 mg PO once, then 75 mg PO daily for 21 days total	Bleeding, rash, purpura	PPI use may reduce antiplatelet effect; caution with NSAIDs	Alternative monotherapy when ASA is not tolerated. Also the standard DAPT partner for high-risk TIA/minor stroke.
ASA / dipyridamole (extended-release)	Usual: ASA 25 mg / dipyridamole (extended-release) 200 mg PO BID	Headache (common, often dose-limiting), bleeding, GI upset	Increased bleeding with anticoagulants	2nd-line monotherapy given twice-daily dosing and a higher headache-related discontinuation rate than ASA or clopidogrel alone. No fixed-dose combination monograph exists in this database for this product; the individual components are ASA and dipyridamole — note the database's existing dipyridamole monograph is the unrelated intravenous stress-testing formulation, not this oral extended-release product, so it is deliberately left unlinked here.
Ticagrelor	DAPT loading dose: 180 mg PO once, then 90 mg PO BID for 30 days total	Bleeding, dyspnea, bradyarrhythmias	Avoid strong CYP3A4 inhibitors/inducers	Alternative to clopidogrel as the DAPT partner with ASA for high-risk TIA/minor stroke, for a shorter 30-day course.

Direct oral anticoagulants (DOACs)

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

Drug	Dosage	Adverse effects	Drug interactions	Comments
Apixaban	Usual: 5 mg PO BID Dose reduction (2 of: age 80+, weight 60kg or less, SCr 133 umol/L or more): 2.5 mg PO BID	Bleeding	Avoid combined strong CYP3A4 and P-glycoprotein inhibitors (e.g. ketoconazole, ritonavir); avoid combined strong inducers of both (e.g. rifampin) where possible	Not recommended at ClCr under 15 mL/min or in patients on dialysis.
Dabigatran	Usual: 150 mg PO BID Reduced dose (age over 80, or increased bleeding risk): 110 mg PO BID	Bleeding, dyspepsia	Strong P-glycoprotein inhibitors (e.g. ketoconazole) contraindicated in combination; caution with other P-gp-active drugs and agents that raise gastric pH	Contraindicated at ClCr under 30 mL/min.
Rivaroxaban	Usual: 20 mg PO daily with food Reduced dose (ClCr 30-49 mL/min): 15 mg PO daily with food	Bleeding	Avoid combined strong CYP3A4 and P-glycoprotein inhibitors/inducers	Not recommended at ClCr under 30 mL/min. Take with the evening meal to maximize absorption.
Edoxaban	Usual: 60 mg PO daily Reduced dose (ClCr 30-50 mL/min, weight 60kg or less, or select P-gp inhibitors): 30 mg PO daily	Bleeding	Avoid combined strong P-glycoprotein inducers (e.g. rifampin); reduce dose with P-glycoprotein inhibitors (e.g. ketoconazole)	Not recommended at ClCr under 30 mL/min.

Vitamin K antagonist

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

Drug	Dosage	Adverse effects	Drug interactions	Comments
Warfarin	Most cerebrovascular indications: Dose to INR 2-3 Mechanical heart valve, high-risk: Dose to INR 2.5-3.5	Bleeding, skin necrosis	Many clinically significant interactions — consult a reliable interaction reference before adding or stopping any concurrent drug	Requires regular INR monitoring; target time-in-therapeutic-range above 70%. Contraindicated in pregnancy.

Lipid-lowering therapy

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

Drug	Dosage	Adverse effects	Drug interactions	Comments
Atorvastatin (high-intensity)	Usual: 40-80 mg PO daily	Myalgia, transaminase elevation	Diltiazem and other CYP3A4 inhibitors increase levels
Rosuvastatin (high-intensity)	Usual: 20-40 mg PO daily	Myalgia, transaminase elevation	Fewer CYP3A4 interactions than atorvastatin
Ezetimibe	Usual: 10 mg PO daily	Myalgia (mild), GI upset	None significant	Add if LDL-C remains 1.8 mmol/L (70 mg/dL) or above on maximally tolerated statin.
Evolocumab (PCSK9 inhibitor)	Usual: Per current lipid-management dosing guidance	Injection-site reaction	None significant	Add if LDL-C remains 1.8 mmol/L (70 mg/dL) or above despite maximally tolerated statin plus ezetimibe. Alirocumab is an alternative agent in the same class.

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.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Perindopril / indapamide	Usual: Per current hypertension dosing guidance	Cough, hypotension, hyponatremia, hypokalemia	Hyperkalemia risk with potassium-sparing diuretics; avoid with lithium	The best-studied fixed-dose combination specifically for stroke-recurrence reduction; a reasonable default when starting new antihypertensive therapy in this population.
Candesartan	Usual: Per current hypertension dosing guidance	Hyperkalemia, hypotension	Hyperkalemia risk with potassium-sparing diuretics	Alternative when an ACE inhibitor is not tolerated (e.g. cough).
Amlodipine	Usual: Per current hypertension dosing guidance	Peripheral edema, flushing, headache	None significant	Reasonable add-on or alternative agent, particularly for isolated systolic hypertension.

References

2021 Guideline for the Prevention of Stroke in Patients With Stroke and Transient Ischemic Attack: A Guideline From the American Heart Association/American Stroke Association — Stroke, American Heart Association/American Stroke Association (Kleindorfer DO, Towfighi A, Chaturvedi S, et al.). Stroke 2021;52(7):e364-e467
Canadian Stroke Best Practice Recommendations: Secondary Prevention of Stroke Update 2020 — Canadian Journal of Neurological Sciences (Gladstone DJ, Lindsay MP, Douketis J, et al.). Can J Neurol Sci 2022;49(3):315-337
Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack — The Lancet (Johnston SC, Rothwell PM, Nguyen-Huynh MN, et al.). Lancet 2007;369(9558):283-292
Refining Clinical Risk Stratification for Predicting Stroke and Thromboembolism in Atrial Fibrillation Using a Novel Risk Factor-Based Approach: The Euro Heart Survey on Atrial Fibrillation — Chest (Lip GYH, Nieuwlaat R, Pisters R, Lane DA, Crijns HJGM). Chest 2010;137(2):263-272
Clopidogrel with Aspirin in Acute Minor Stroke or Transient Ischemic Attack — New England Journal of Medicine (Wang Y, Wang Y, Zhao X, et al., CHANCE investigators). N Engl J Med 2013;369(1):11-19
Clopidogrel and Aspirin in Acute Ischemic Stroke and High-Risk TIA — New England Journal of Medicine (Johnston SC, Easton JD, Farrant M, et al., POINT investigators). N Engl J Med 2018;379(3):215-225
Ticagrelor and Aspirin or Aspirin Alone in Acute Ischemic Stroke or TIA — New England Journal of Medicine (Johnston SC, Amarenco P, Denison H, et al., THALES investigators). N Engl J Med 2020;383(3):207-217
Early versus Later Anticoagulation for Stroke with Atrial Fibrillation — New England Journal of Medicine (Fischer U, Koga M, Strbian D, et al., ELAN investigators). N Engl J Med 2023;388(26):2411-2421
Patent Foramen Ovale Closure or Anticoagulation vs. Antiplatelets after Stroke — New England Journal of Medicine (Mas JL, Derumeaux G, Guillon B, et al., CLOSE investigators). N Engl J Med 2017;377(11):1011-1021

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.