In a 65‑year‑old man post‑mitral valve repair with left atrial appendage excision and Maze procedure who now has three brief episodes of lower‑field visual loss in the left eye (amaurosis fugax) with a normal right carotid artery and less than 50 % stenosis of the left carotid artery, what is the most likely cause and how should it be managed?

Recurrent Embolic Events from Cardiac Source Despite Maze Procedure and LAA Excision

This patient is experiencing recurrent embolic events from a cardiac source despite the maze procedure and left atrial appendage excision, most likely due to inadequate anticoagulation, incomplete LAA closure, or thrombogenic surgical lesions in the early post-operative period. 1, 2

Most Likely Etiology

The three episodes of transient monocular visual loss (amaurosis fugax) at 90 days post-operatively represent embolic events from the heart, not carotid disease, given:

• Less than 50% carotid stenosis does not cause amaurosis fugax – only one-third of patients with amaurosis fugax have treatable carotid lesions, and significant stenosis (>75%) is required for embolic symptoms 3, 4, 5
• The maze procedure creates thrombogenic surgical lesions that remain high-risk for thrombus formation for at least 3 months post-operatively 1, 2
• Incomplete LAA closure occurs in 26-57% of cases and is a documented source of ongoing thromboembolism 2, 6
• Device-related thrombus formation occurs in 2-5% of cases within 180 days post-procedure 2, 6
• Atrial fibrillation persists in 80% of patients who had pre-operative AF ≥3 months, maintaining thromboembolic risk despite the maze procedure 1, 2

Immediate Diagnostic Workup

Brain Imaging

• Obtain urgent brain MRI with diffusion-weighted imaging (DWI) immediately – CT scans miss 58-100% of new embolic brain lesions after cardiac valve procedures 2, 6
• Standard CT has poor sensitivity for acute ischemic stroke within the first 24 hours, which is precisely when post-cardiac surgery complications occur 2, 6
• MRI will detect acute embolic infarcts in the retinal or posterior circulation territories 2

Cardiac Source Evaluation

• Transesophageal echocardiography (TEE) to assess:
  • Completeness of LAA closure/excision (incomplete closure in 26-57% of cases) 2, 6
  • Presence of left atrial thrombus on surgical lesion lines from the maze procedure 1
  • Device-related thrombus formation 2, 6
  • Valvular function and any new regurgitation 1

Rhythm Monitoring

• 30-day continuous cardiac monitoring to detect paroxysmal atrial fibrillation, which persists in 80% of patients with pre-operative AF ≥3 months 1, 2

Anticoagulation Management

The patient requires immediate therapeutic anticoagulation with warfarin targeting INR 2.5-3.5 for at least 3 months post-maze procedure, regardless of rhythm status. 1, 7

Critical Anticoagulation Principles

• Anticoagulation for at least 3 months after maze procedure and LAA excision is a Class 2a recommendation from ACC/AHA guidelines 1
• The maze procedure does not eliminate the need for anticoagulation in the immediate post-operative period 2, 6
• Surgical ablation creates endocardial thrombogenic lesions that require anticoagulation coverage 1
• Discontinuation of oral anticoagulation has been associated with late stroke, highlighting that the LAA is not the exclusive source of all thrombi 1

Specific Warfarin Dosing

• Target INR 2.5 (range 2.0-3.0) for bioprosthetic mitral valve repair 7
• Target INR 3.0 (range 2.5-3.5) if mechanical valve or persistent AF 7
• For patients with recurrent systemic embolism, maintain INR 2.0-3.0 7

Common Pitfalls to Avoid

Do Not Attribute Symptoms to Carotid Disease

• Less than 50% carotid stenosis is not hemodynamically significant and does not cause embolic symptoms 3, 4, 5
• Only 53% of patients with amaurosis fugax have significant (>60%) carotid stenosis 5
• Patients with amaurosis fugax from carotid disease require 75% or greater stenosis at the bifurcation 3

Do Not Assume the Maze Procedure Eliminated Thromboembolic Risk

• Success rates for sinus rhythm conversion are only 75-95% with maze, and 80% of patients with pre-operative AF ≥3 months remain in AF 1, 2, 6
• The maze procedure creates a prothrombotic state from surgical trauma, blood stasis, and loss of atrial contraction 2

Do Not Delay Anticoagulation

• The immediate post-operative period (first 3 months) carries the highest thromboembolism risk due to inadequate anticoagulation, inflammatory state, and atrial stunning 1, 2
• Nonrandomized registry data show that stroke in the first 3 months after ablation is driven by discontinuation of oral anticoagulation 1

Long-Term Management Strategy

If TEE Shows Incomplete LAA Closure or Thrombus

• Continue indefinite anticoagulation with warfarin targeting INR 2.5-3.5 1, 7
• Consider percutaneous LAA closure device if surgical closure was incomplete 2

If TEE Shows Complete LAA Closure and No Thrombus

• Continue warfarin for minimum 3 months post-maze (currently at 90 days, so continue at least another month) 1
• Reassess rhythm status with 30-day monitor at 6 months 2, 6
• If in sinus rhythm at 6 months with no AF recurrence, consider transitioning to aspirin 75-100 mg daily 1
• If persistent AF, continue indefinite anticoagulation 1, 7

Stroke Risk Stratification

• Bioprosthetic mitral valves carry 2.4% per patient-year thromboembolism risk, higher than aortic prostheses at 1.9% 2, 6
• Freedom from stroke with successful maze is 100% at 2 years versus 90% in controls 2