What is the likely cause of anisocoria in a patient post coronary angiogram (coronary artery angiography)?

Post-Coronary Angiogram Anisocoria: Likely Causes

The most likely cause of anisocoria following coronary angiography is inadvertent exposure to mydriatic agents (particularly phenylephrine or atropine) used during the procedure, though neurological complications including stroke must be urgently excluded.

Primary Diagnostic Consideration: Pharmacologic Mydriasis

Accidental contamination with ophthalmic mydriatic agents is the most common benign cause of post-procedural anisocoria 1. This occurs when:

• Healthcare personnel handling phenylephrine (used for hemodynamic support during catheterization) or atropine (used for bradycardia) inadvertently transfer these agents to the patient's eye 1
• The affected pupil will be dilated (mydriatic) and poorly reactive to light 1
• Phenylephrine causes maximal mydriasis within 20-90 minutes with recovery after 3-8 hours 1
• This is a diagnosis of exclusion after ruling out serious neurological causes 2

Critical Neurological Complications to Exclude Immediately

Ischemic Stroke

Stroke occurs in 0.05-0.1% of diagnostic coronary angiography procedures and represents a life-threatening cause of anisocoria 3. Key features include:

• Anisocoria may indicate posterior circulation stroke affecting the brainstem or third cranial nerve 4
• Stroke can present during the procedure or within 24 hours post-procedure 5
• Risk factors include advanced age, hypertension, diabetes, emergency procedures, history of stroke, renal failure, and use of intra-aortic balloon pump 3
• Immediate neuroimaging and neurological consultation are mandatory if stroke is suspected 4

Embolic Phenomena

• Catheter manipulation can dislodge atherosclerotic debris causing embolic stroke 3
• Posterior circulation involvement is more common than expected in catheterization-related strokes 4
• All neurological deficits occurring during or within 24 hours of angiography require urgent evaluation 5

Diagnostic Algorithm

Immediate Assessment (Within Minutes)

1. Perform focused neurological examination looking for:

   • Pupillary asymmetry: which pupil is abnormal (dilated vs constricted) 2
   • Extraocular movements and ptosis (third nerve palsy) 2
   • Other focal neurological deficits (weakness, speech changes, altered mental status) 5, 3
   • Timing of onset relative to procedure 5

2. If ANY focal neurological signs are present beyond isolated anisocoria:

   • Activate stroke protocol immediately 4
   • Obtain emergent brain imaging (CT or MRI) 4
   • Consider immediate neuroangiographic intervention with local thrombolysis, which shows favorable outcomes in catheterization-related stroke 4

3. If isolated anisocoria without other neurological findings:

   • Document which pupil is abnormal (larger pupil suggests mydriatic exposure; smaller pupil suggests Horner syndrome) 2
   • Test pupillary light reflex in both eyes 2
   • Review procedural medications and potential exposure routes 1

Risk Stratification

High-risk patients requiring heightened vigilance include those with 3:

• Age >70 years
• Arterial hypertension
• Diabetes mellitus
• Emergency/urgent procedure indication
• Prior stroke history
• Renal failure
• Congestive heart failure
• Intra-aortic balloon pump use

Common Pitfalls to Avoid

1. Never assume benign pharmacologic cause without excluding stroke - the 0.5% incidence of persistent neurological deficit from angiography means stroke must be ruled out first 5

2. Do not wait for symptom evolution - 50% of angiography-related strokes have delayed onset (not during procedure), so anisocoria appearing hours post-procedure still requires urgent evaluation 5

3. Recognize that contrast reactions can mimic stroke - both can present with posterior circulation symptoms, making clinical distinction difficult and necessitating imaging 4

4. Document the time course carefully - pharmacologic mydriasis from phenylephrine peaks at 20-90 minutes and resolves within 3-8 hours, whereas neurological causes persist 1

Management Based on Etiology

If Pharmacologic (After Stroke Excluded)

• Reassure patient that mydriasis will resolve spontaneously within 3-8 hours 1
• Protect eye from bright light during recovery period 1
• No specific treatment required 1

If Neurological

• Immediate neuroangiographic intervention with local thrombolysis appears most effective for catheterization-related ischemic stroke 4
• Mechanical embolectomy is a promising approach 3
• Mortality and disability rates are exceedingly high without prompt treatment 3