What is the best next step for a 75-year-old woman with sudden left-sided weakness and atrial fibrillation?

Emergency Evaluation for Suspected Cardioembolic Stroke in a Patient with Atrial Fibrillation

The best next step in evaluating this patient is to perform an immediate emergency computed tomography (CT) scan of the brain. 1

Clinical Reasoning

This 75-year-old woman presents with classic signs of an acute stroke:

• Sudden onset left-sided weakness (focal neurological deficit)
• Symptoms began 1 hour prior to arrival (within the acute stroke window)
• Irregularly irregular heart rhythm with tachycardia (pulse 105 bpm)
• Likely undiagnosed atrial fibrillation (AF)

Diagnostic Algorithm

1. Immediate brain CT scan

   • Essential to differentiate between ischemic and hemorrhagic stroke
   • Must be performed urgently to determine eligibility for reperfusion therapies
   • The European Society of Cardiology guidelines explicitly state: "Patients with stroke or TIA require immediate stroke diagnosis, usually via emergency computed tomography (CT)" 1

2. Concurrent assessment for AF-related stroke risk

   • Document the irregularly irregular rhythm with 12-lead ECG
   • The patient's presentation strongly suggests cardioembolic stroke from AF
   • Her CHA₂DS₂-VASc score is at least 3 (age ≥75 [2 points] + female [1 point])

3. After CT confirmation (if ischemic stroke)

   • Assess eligibility for thrombolysis/thrombectomy based on time window
   • Initiate appropriate cerebral revascularization 1

Evidence Strength and Rationale

The recommendation for immediate CT is strongly supported by multiple guidelines. The ESC guidelines specifically address this clinical scenario, stating that patients with stroke or TIA require immediate stroke diagnosis via emergency CT 1. This approach allows for:

1. Time-critical intervention decisions: The patient is within the potential thrombolysis window (symptoms started 1 hour ago)

2. Proper risk stratification: The patient has multiple risk factors for cardioembolic stroke:

   • Age ≥75 years (increases stroke risk 5.28-fold) 1
   • Female sex (increases risk 1.17-fold) 1
   • Probable atrial fibrillation

3. Prevention of harm: CT will rule out hemorrhagic stroke before any antithrombotic therapy is initiated

Common Pitfalls to Avoid

1. Delaying neuroimaging to perform echocardiography first

   • While echocardiography is valuable for AF patients, it should not delay emergency CT in suspected acute stroke

2. Focusing only on the cardiac arrhythmia and neglecting the urgent neurological evaluation

   • The immediate threat is the evolving stroke, not the AF itself

3. Administering anticoagulation before neuroimaging

   • Could be catastrophic if the patient has a hemorrhagic stroke

4. Assuming TIA due to lack of other symptoms

   • The persistent left-sided weakness suggests an evolving stroke, not a TIA

Follow-up Considerations

After the immediate CT scan and appropriate acute stroke management:

• Perform comprehensive cardiac evaluation including echocardiography
• Assess for thrombus in the left atrial appendage
• Initiate appropriate anticoagulation if ischemic stroke is confirmed
• Consider direct oral anticoagulants (DOACs) over warfarin for long-term stroke prevention 2, 3

This patient's presentation represents a medical emergency requiring immediate neuroimaging to guide time-sensitive treatment decisions that will significantly impact morbidity, mortality, and quality of life outcomes.