What is the likely diagnosis for a patient who cannot move their left arm immediately after a complex cardiac surgical procedure, including mitral valve repair, left atrial appendage removal, and maze procedure, with a normal CT head scan?

Perioperative Stroke After Complex Cardiac Surgery

Most Likely Diagnosis

This patient has suffered an acute perioperative ischemic stroke, most likely involving the right hemisphere, which is the predominant pattern after cardiac valve surgery. 1, 2

Clinical Presentation Pattern

The immediate postoperative presentation with left-sided weakness (arm initially, with leg involvement that partially resolved) following mitral valve repair, left atrial appendage removal, and maze procedure strongly suggests:

• Right hemispheric ischemic stroke is the most common pattern after cardiac valve surgery, occurring in approximately 61% of post-cardiac surgery strokes (right hemisphere predominance with p=0.034) 2
• Embolic mechanism is the primary pathophysiology, related to surgical manipulation, cardiopulmonary bypass, and intraoperative factors 1, 2
• Normal CT head does not exclude acute ischemic stroke, particularly in the hyperacute phase (first 6-12 hours), as CT has poor sensitivity for early ischemic changes 1

Timing and Risk Factors

The immediate postoperative presentation is typical:

• Valve surgery carries the highest stroke risk among cardiac procedures, with mean onset at 1.3 days post-operatively for hemispheric strokes 1, 2
• 40% of strokes occur intraoperatively, with 60% occurring postoperatively, peaking at 40 hours after surgery 1
• Prolonged cardiopulmonary bypass time is strongly associated with increased stroke risk, particularly with large vessel occlusion (ELVO occurred in 10.9% of post-cardiac surgery strokes) 1
• The combination of mitral valve repair, left atrial appendage removal, and maze procedure represents a complex, prolonged operation with extended bypass time, increasing embolic risk 1, 3

Immediate Diagnostic Approach

Urgent CT angiography and perfusion imaging should be obtained immediately, as the patient is in the critical window for potential intervention 1:

• Non-contrast CT head alone is inadequate for excluding acute stroke or guiding treatment decisions 1
• CT angiography is essential to identify large vessel occlusion (ELVO), which occurs in approximately 10.9% of post-cardiac surgery strokes 1
• Perfusion imaging helps determine salvageable brain tissue and guides intervention decisions in the extended window 1

Mechanism-Specific Considerations

The embolic source in this case likely involves:

• Procedure-related right hemispheric embolism from surgical manipulation, aortic cannulation, or air embolism during cardiopulmonary bypass 2
• Atrial manipulation during maze procedure and left atrial appendage removal increases thromboembolic risk 1, 4
• Aortic atherosclerosis with embolization during aortic cross-clamping or cannulation 1

Treatment Considerations

Mechanical thrombectomy should be strongly considered if ELVO is identified, despite the recent cardiac surgery 1:

• Post-cardiac surgery patients with ELVO show a trend toward improved functional outcomes with mechanical thrombectomy 1
• Individualized perfusion imaging data should guide the decision for expanded window thrombectomy 1
• Communication with the cardiothoracic surgical team is essential before administering anticoagulation or thrombolytics, as patients with open thoracic approaches are generally not candidates for intravenous thrombolysis 1

Access Site Selection

If thrombectomy is pursued:

• Check for existing arterial access from the cardiac surgery, which may expedite revascularization 1
• If bilateral femoral cutdowns were performed, consider transradial approach 1
• If radial artery was harvested during surgery, use transfemoral approach 1

Prognosis

Despite the concerning initial presentation:

• Most hemispheric stroke patients after cardiac surgery become functionally independent (mean modified Rankin Scale <2), even those with initial severe deficits 2
• Right hemispheric strokes after cardiac surgery have relatively fair outcomes compared to other stroke etiologies 2
• The partial recovery of leg function already observed is an encouraging prognostic sign 2

Critical Pitfall to Avoid

Do not delay imaging or intervention based on the normal initial CT head—this is inadequate for diagnosis and treatment planning in acute stroke after cardiac surgery 1. The patient requires immediate CT angiography with perfusion imaging to determine if mechanical thrombectomy is indicated.