In a patient who developed sudden left arm and leg weakness during open‑heart surgery, with MRI showing acute supratentorial cortical infarcts in the right frontal, parietal, and occipital lobes and the left pre‑ and post‑central gyri, is the intraoperative brain injury more consistent with air embolism or atheromatous plaque embolism, and how does the expected neurological recovery differ between these two mechanisms?

Intraoperative Stroke During Open-Heart Surgery: Air vs. Plaque Embolism

Direct Answer

The imaging pattern described—multiple cortical infarcts in a multivessel distribution with borderzone involvement—is most consistent with air embolism rather than atheromatous plaque embolism, and air embolism typically has better neurological recovery potential than plaque embolism.

Distinguishing Features Between Air and Plaque Embolism

Air Embolism Characteristics

The MRI findings in this case strongly suggest air embolism based on several key features 1:

• Gyriform (cortical ribbon) infarction pattern: Air emboli characteristically cause predominantly gyriform infarctions (86% of cases) rather than wedge-shaped territorial infarcts 2
• Multiple bilateral infarcts: Air embolism presents with multiple infarctions in 93% of cases and bilateral involvement in 79% 2
• Cortical borderzone predilection: The MRI description of "external border zone territory infarcts" is highly characteristic—cortical borderzone involvement occurs in 86% of air emboli versus only 25% in typical cardioembolic stroke 2
• Multivessel territory involvement: The right frontal, parietal, occipital lobes plus left pre- and post-central gyri distribution reflects the "shower" pattern typical of air emboli

Plaque Embolism Characteristics

Atheromatous plaque emboli from aortic manipulation typically present differently:

• Wedge-shaped territorial infarcts: Plaque emboli cause wedge-shaped infarctions in 71% of cases 2
• Single vessel territory: More commonly affects a single arterial territory
• Less frequent borderzone involvement: Only 25% show cortical borderzone patterns 2

Pathophysiology During Cardiac Surgery

During open-heart surgery, both mechanisms are possible 1:

Air embolism sources:

• Cardiopulmonary bypass circuit air bubbles
• Air from cardiothoracic suction entering bloodstream
• Inadequate de-airing during cardiac chamber procedures

Plaque embolism sources:

• Aortic cannulation and cross-clamping
• Manipulation of atherosclerotic aorta
• Detachment of calcific deposits or lipid-laden particles

The description of "multiple embolic showers with distal vessel occlusion" fits air embolism better, as air tends to fragment into multiple small bubbles causing widespread distal occlusions, while plaque fragments typically cause larger proximal occlusions.

Recovery Differences Between Mechanisms

Air Embolism Recovery

Better overall prognosis:

• Air is reabsorbed over 24-48 hours with appropriate treatment 3, 4
• Ischemia may be partially reversible if reperfusion occurs quickly
• The gyriform pattern suggests cortical surface involvement which may spare deeper structures
• Critical caveat: Delayed ischemia can occur—initial imaging may underestimate injury, with extensive infarction appearing 4 days later despite near-complete air resolution 3

Treatment-responsive:

• 100% fraction of inspired oxygen accelerates air reabsorption 3, 4
• Hyperbaric oxygen therapy (HBOT) is first-line treatment and may significantly improve outcomes 4

Plaque Embolism Recovery

Generally worse prognosis:

• Permanent arterial occlusion unless spontaneous recanalization occurs
• Larger territorial infarcts with deeper tissue involvement
• No specific treatment to remove embolic material
• Recovery depends on collateral circulation and infarct volume
• Thromboembolism accounts for 70-80% of intraoperative strokes and carries higher morbidity 1

Additional Prognostic Factors

Hypoperfusion contribution 1:

• Perioperative hypotension can transform subclinical embolic events into clinically evident lesions
• Prolonged cardiopulmonary bypass periods exacerbate injury
• This patient's "multiple embolic showers" may have been compounded by hemodynamic instability

Age and comorbidities:

• Younger patients (<60 years) have better recovery potential
• Pre-existing cerebrovascular disease worsens outcomes

Clinical Implications

Immediate Management Priorities

1. Maximize cerebral oxygenation: 100% FiO₂ immediately 3, 4
2. Consider hyperbaric oxygen therapy: First-line for confirmed air embolism 4
3. Optimize cerebral perfusion pressure: Avoid hypotension, maintain adequate MAP
4. Serial neuroimaging: Repeat MRI at 3-5 days to assess for delayed ischemia 3

Monitoring Requirements

• Close neurological monitoring for 72-96 hours minimum
• Watch for delayed cerebral edema development
• Serial imaging regardless of initial clinical stability 3

Common Pitfalls

Do not assume initial imaging shows full extent of injury—air embolism can cause delayed ischemia appearing days later despite near-complete air resolution on early CT 3. This patient requires intensive neurocritical care monitoring even if initial deficits seem stable.

Do not treat as typical cardioembolic stroke—the specific treatment (hyperbaric oxygen, high-flow oxygen) differs fundamentally from standard stroke protocols 4.

The combination of gyriform infarction pattern, bilateral multivessel involvement, and cortical borderzone predilection has 76.6% sensitivity and 96.4% specificity for air embolism 2, making this the most likely diagnosis with potentially better recovery if treated appropriately and promptly.