What is the initial workup for a patient presenting with Amaurosis fugax, including the use of an event monitor?

Workup for Amaurosis Fugax Including Event Monitor

Amaurosis fugax requires immediate emergency department or stroke center evaluation within 24 hours, with carotid duplex ultrasound as the primary initial imaging test, and cardiac rhythm monitoring (including event monitoring) is appropriate when no clear embolic source is identified, given the significant risk of atrial fibrillation as an underlying cause. 1

Immediate Actions and Timeframe

• Treat as a medical emergency requiring referral to an emergency department or stroke center for neurological evaluation within 24 hours of symptom onset 1
• The risk of stroke is highest within the first 7 days and remains elevated for 30 days after the initial event 1, 2

Essential Diagnostic Workup

Vascular Imaging (First Priority)

• Carotid duplex ultrasound is the initial imaging modality of choice for all patients presenting with amaurosis fugax 3
• Up to 70% of patients with symptomatic ocular vascular events have clinically significant carotid stenosis 1, 2
• Patients with amaurosis fugax have a 53% likelihood of significant (>60%) carotid stenosis 4
• High-grade stenosis of the ipsilateral carotid artery should be identified rapidly with CT angiography, MR angiography, or cervical artery ultrasound 3

Brain Imaging

• Order diffusion-weighted MRI of the brain, as silent brain infarction is present in up to 24% of patients with acute ocular vascular events 1, 2
• Multiple small cerebral infarcts are found in up to 31% of cases with acute retinal ischemia, associated with ipsilateral atheromatous carotid stenosis 2

Cardiac Evaluation

Echocardiography

• Transthoracic echocardiography is reasonable to examine for evidence of a cardioembolic source, given the high rate of structural heart disease among patients with retinal artery occlusion 3
• Transesophageal echocardiography should be reserved for patients with high suspicion for occult structural cardiac lesion and an otherwise negative diagnostic workup 3

Cardiac Rhythm Monitoring (Event Monitor)

• Some duration of ambulatory cardiac rhythm monitoring is appropriate in patients without a clear other cause for the retinal ischemia 3
• The ideal screening regimen for atrial fibrillation has not yet been defined, but cardiac monitoring is justified given that AF is a significant cardioembolic source 3
• If episodes of symptoms are infrequent, an event recorder (which allows the patient to transmit the ECG when symptoms occur) may be more useful than 24-hour Holter monitoring 3
• When atrial fibrillation is detected, oral anticoagulation should be initiated in accordance with established guidelines for stroke secondary prevention 3

Age-Specific Testing

• For patients over 50 years of age, evaluate for giant cell arteritis by assessing for temporal tenderness, jaw claudication, weight loss, proximal myalgia, or fever 1
• Order C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), which are typically elevated in giant cell arteritis 1
• If giant cell arteritis is suspected, immediately initiate high-dose systemic corticosteroid therapy (40-60 mg/day prednisone equivalent) before awaiting biopsy results 1

Risk Stratification

The 3-year stroke risk varies significantly based on risk factors 1, 2:

• 0-1 risk factors: 1.8% stroke risk
• 2 risk factors: 12.3% stroke risk
• 3-4 risk factors: 24.2% stroke risk

Secondary Prevention Initiation

• Antiplatelet therapy (75-325 mg aspirin daily) should be initiated for patients with documented amaurosis fugax 1, 2
• In patients with presenting symptoms suggesting minor stroke (NIH Stroke Scale ≤3), an initial course of 21 days of dual antiplatelet therapy may be reasonable, followed by long-term single antiplatelet agent 3
• Statin therapy should be initiated as part of vascular secondary prevention 3

Common Pitfalls to Avoid

• Delaying referral beyond 24 hours to emergency services or stroke center 1, 2
• Failing to evaluate for giant cell arteritis in patients over 50 years of age 1
• Overlooking silent brain infarctions on imaging that may be present despite transient symptoms 1, 2
• Not performing carotid imaging, as even minor degrees of stenosis (0-50%) can be associated with atheroembolic events and subsequent stroke or blindness 5
• Assuming Hollenhorst plaques without symptoms require the same workup, as asymptomatic plaques have only 9% association with significant carotid stenosis compared to 53% with amaurosis fugax 4

Rationale for Event Monitor

The inclusion of cardiac rhythm monitoring (event monitor) in the workup is justified because:

• Cardioembolic sources, particularly atrial fibrillation, are important causes of retinal ischemia 3
• The high rate of structural heart disease necessitates cardiac evaluation 3
• When AF is detected, it fundamentally changes management to oral anticoagulation rather than antiplatelet therapy alone 3
• Event monitors are particularly useful when symptoms are infrequent, allowing capture of paroxysmal arrhythmias 3