Select an option to reveal the explanation.
Explanation of Answer
Best answer and reason
Correct answer: Embolic stroke
A mechanical valve left without anticoagulation for almost a week allows thrombus to form on the prosthesis and embolise, and the abrupt deficit confined to the left middle cerebral artery territory fits an embolus exactly.
- Warfarin stopped without heparin cover, leaves a highly thrombogenic prosthesis unprotected before elective hernia surgery.
- Sudden onset, maximal at the start, is the signature of an embolus rather than a bleed.
- Right face and arm weakness with dysphasia, maps to the left middle cerebral artery, sparing the leg.
Why the other options are wrong
Amaurosis fugax
Amaurosis fugax is transient painless monocular visual loss, described as a curtain descending, lasting minutes and resolving fully. It causes no limb weakness or speech disturbance and reflects a retinal rather than hemispheric embolus.
Haemorrhagic stroke
Haemorrhagic stroke is the risk of continuing anticoagulation, not of stopping it. His international normalised ratio should be subtherapeutic after almost a week off warfarin, although a CT head remains mandatory before any treatment.
Prosthetic valve endocarditis
Prosthetic valve endocarditis develops over days to weeks with fever, malaise, a new or changed murmur and positive blood cultures. It can embolise to the brain, but no febrile subacute illness is described.
Subdural haematoma
A subdural haematoma follows head injury in an elderly or anticoagulated patient and evolves over days to weeks with headache and fluctuating conscious level. It does not give an abrupt single territory deficit.
Exam takeaway
- Ask what changed in the days before the event.
- Mechanical valve plus stopped warfarin, plus sudden hemiparesis equals cardioembolic stroke until imaging says otherwise.
- Mechanical valves are bridged, never simply stopped, and are never anticoagulated with a direct oral anticoagulant.
- Deficit maximal at onset, means embolus; a deficit building with headache suggests haemorrhage.
- Target international normalised ratio 2.5 to 3.5, for a mechanical prosthetic valve, higher than for atrial fibrillation.
- Fluctuating drowsiness weeks after a fall, is a subdural haematoma, not an embolic event.
Learn the Condition
Cardioembolic stroke after interrupted anticoagulation
Cardioembolic stroke after interrupted anticoagulation
Definitions
| Pattern | Onset | Distinguishing feature |
|---|---|---|
| Embolic ischaemic stroke | Abrupt, maximal at onset | Single arterial territory, cardiac or carotid source |
| Haemorrhagic stroke | Minutes to hours, progressive | Headache, vomiting, reduced consciousness, blood on CT |
| Transient ischaemic attack | Abrupt, then resolves | Deficit clears without infarction on imaging |
| Subdural haematoma | Days to weeks | Fluctuating consciousness after a fall, crescent collection |
- Cardioembolic source, a mechanical valve, atrial fibrillation, mural thrombus or infective vegetation.
Causes and risk factors
- Interrupted anticoagulation, the avoidable cause here, with warfarin stopped and no heparin bridging.
- Mechanical prosthetic valve, a highly thrombogenic surface requiring uninterrupted lifelong anticoagulation.
- Atrial fibrillation, the commonest cardiac source of embolism in unselected stroke patients.
- Conventional vascular risk factors, hypertension, smoking, diabetes and hyperlipidaemia, which compound the embolic risk.
Clinical features
- Abrupt maximal deficit, with no build up and no preceding headache or vomiting.
- Left middle cerebral artery occlusion, gives right face and arm weakness with expressive dysphasia.
- Right sided occlusion, gives left sided weakness with inattention and neglect instead.
- Leg sparing, because the leg area lies in the anterior cerebral artery territory.
- Valve thrombosis itself, breathlessness, a muffled prosthetic click, a new murmur or heart failure.
Investigation
- Immediate non-contrast CT head, within 1 hour, and certainly before any thrombolytic treatment is given.
- Capillary glucose and ECG, to exclude hypoglycaemia and identify atrial fibrillation at the bedside.
- Clotting screen with international normalised ratio, documenting how far anticoagulation had actually worn off.
- CT angiography, to identify a large vessel occlusion amenable to mechanical thrombectomy.
- Echocardiography with valve fluoroscopy, transthoracic then transoesophageal, where prosthetic valve thrombosis is suspected.
Management of the acute stroke
- Admit directly to a specialist acute stroke unit, after initial assessment, as NICE requires for every suspected stroke.
- Screen swallowing before oral intake, by a trained professional, before any food, fluid or medication.
- Alteplase within 4.5 hours, started as soon as possible, once intracranial haemorrhage has been excluded.
- Mechanical thrombectomy, where CT angiography confirms a proven large vessel occlusion.
- Decompressive hemicraniectomy within 48 hours, considered in selected patients after discussion with family or carers.
- Restarting anticoagulation, timed by the stroke team against infarct size and bleeding risk.
Management of anticoagulation around surgery
- Target international normalised ratio 2.5 to 3.5, for a mechanical valve, against 2.5 for atrial fibrillation.
- Write a bridging plan before warfarin stops, so the patient is never left without any anticoagulation.
- Therapeutic low molecular weight heparin, started as the international normalised ratio falls below target.
- Omit the dose on the morning of surgery, and restart both agents once haemostasis is secure.
- Never substitute a direct oral anticoagulant, which is not used for mechanical prosthetic heart valves.
UK guidance
NICE NG128 is the UK standard for imaging and initial management of a suspected acute stroke.
- Perform brain imaging immediately with a non-enhanced CT scan where the listed indications for suspected acute stroke apply.
- Immediate means the next available slot and definitely within 1 hour, whichever is sooner.
- For everyone else, scan as soon as possible and within 24 hours of symptom onset.
- Alteplase is recommended within 4.5 hours of onset, once intracranial haemorrhage has been excluded.
- Admit everyone with suspected stroke directly to a specialist acute stroke unit after initial assessment.
- Screen swallowing by a trained professional before any oral food, fluid or medication is given.
Clinical application
Every patient with a mechanical valve needs a written bridging plan before warfarin stops.
- Agree the plan with haematology preoperatively, rather than leaving the general practitioner to stop warfarin alone.
- Check the international normalised ratio on admission, and again on the morning of the planned operation.
- Get an immediate CT head, if any focal deficit appears, and call the stroke team.
- Do not adjust anticoagulation yourself, since restart timing depends on infarct size and bleeding risk.
