What immediate actions should be taken if a patient experiences a severe stroke during a mitral valve repair?

Intraoperative Stroke During Mitral Valve Repair: Mechanisms and Immediate Management

How Severe Stroke Can Occur Undetected Intraoperatively

Intraoperative stroke during mitral valve repair can occur through multiple mechanisms that may not be immediately apparent during surgery, including air embolism from inadequate de-airing, thromboembolism from atrial thrombus or prosthetic material, aortic dissection from cannulation, and particulate debris from the surgical field. 1

Primary Mechanisms of Intraoperative Stroke

Embolic causes:

• Air embolism is the most common preventable cause, occurring when air enters the left heart chambers during valve manipulation and is not adequately evacuated before restoring cardiac ejection 1
• Thromboembolism can originate from undetected left atrial thrombus, particularly in patients with atrial fibrillation, or from acute thrombus formation on prosthetic annuloplasty rings 2, 3
• Particulate debris from calcium deposits, valve tissue, or atherosclerotic material dislodged during surgical manipulation can embolize to cerebral vessels 1

Vascular complications:

• Aortic dissection from endoaortic balloon placement, transaortic clamping, retrograde perfusion cannulation, or antegrade cardioplegia needle insertion can compromise cerebral perfusion 1
• Hypoperfusion during cardiopulmonary bypass, particularly in patients with pre-existing cerebrovascular disease, may cause watershed infarcts that are not immediately symptomatic 1

Why Stroke May Go Unrecognized During Surgery

The patient is under general anesthesia with neuromuscular blockade, making neurological assessment impossible until emergence from anesthesia. 1

• Stroke symptoms cannot manifest while the patient is anesthetized and paralyzed 1
• Hemodynamic parameters may remain stable despite cerebral ischemia, as the stroke itself does not necessarily cause cardiovascular instability 1
• Standard intraoperative monitoring (ECG, blood pressure, oxygen saturation) does not detect cerebral ischemia unless cerebral oximetry is used, which is not universally employed 1

Immediate Actions When Stroke is Discovered Post-Operatively

Acute Recognition and Assessment (First 30 Minutes)

Immediately obtain non-contrast head CT to differentiate ischemic from hemorrhagic stroke, as this determines all subsequent management, particularly regarding anticoagulation reversal. 1

• Perform rapid neurological examination documenting specific deficits (motor, sensory, speech, visual fields) to establish baseline severity 1
• Check coagulation parameters (PT/INR, aPTT, platelet count) and complete blood count immediately 1
• Obtain stat neurology consultation for stroke protocol activation 1

Determining Stroke Mechanism (First 1-2 Hours)

Order emergent transesophageal echocardiography to identify residual air in cardiac chambers, new thrombus formation, or valve dysfunction that could indicate ongoing embolic source. 1, 2

• Assess for intracardiac air, particularly in left atrium and left ventricle, which may require urgent intervention 1
• Evaluate mitral valve repair integrity for new regurgitation or stenosis 1
• Examine for left atrial thrombus or prosthetic ring thrombus formation 2
• Assess left ventricular function, as severe dysfunction may indicate need for mechanical support 4

Review operative details systematically:

• De-airing technique and duration used before weaning from bypass 1
• Cannulation sites and any difficulties encountered (potential dissection) 1
• Cardiopulmonary bypass time and adequacy of perfusion pressures 1
• Presence of atrial fibrillation or other arrhythmias during procedure 5

Anticoagulation Management Decision Tree

If hemorrhagic stroke on CT:

• Immediately reverse all anticoagulation with prothrombin complex concentrate and vitamin K, accepting the risk of prosthetic valve thrombosis as secondary to preventing hemorrhage expansion 1
• Hold all antiplatelet agents 1
• Maintain INR <1.5 during acute hemorrhagic phase 1

If ischemic stroke on CT:

• Continue therapeutic anticoagulation with unfractionated heparin (aPTT 1.5-2.0 times control) to prevent thrombus propagation and recurrent embolism 1, 3
• Transition to oral anticoagulation (warfarin INR 2.5-3.0) once patient is stable and able to take oral medications 1, 3
• Do NOT use intravenous vitamin K for supratherapeutic INR in prosthetic valve patients due to rapid reversal increasing thrombosis risk 1

Specific Interventions Based on Mechanism

For suspected air embolism:

• Place patient in Trendelenburg position with left lateral decubitus to trap air in cardiac apex 1
• Consider hyperbaric oxygen therapy if available and patient is stable for transport 1
• Maintain high FiO2 (100%) to maximize nitrogen washout 1

For suspected ongoing embolic source:

• Urgent return to operating room may be necessary if TEE reveals large mobile thrombus, significant residual air, or acute valve dysfunction 1, 2
• Initiate therapeutic anticoagulation immediately if no contraindication 3

For aortic dissection:

• Obtain emergent CT angiography of chest, abdomen, and pelvis 1
• Strict blood pressure control (systolic <120 mmHg) with beta-blockade 1
• Emergent vascular surgery consultation for potential intervention 1

Neuroprotective Measures

Maintain cerebral perfusion pressure >70 mmHg with vasopressors if needed, avoiding hypotension which extends ischemic injury. 1

• Keep head of bed elevated 30 degrees to reduce intracranial pressure 1
• Maintain normoglycemia (glucose 140-180 mg/dL), as hyperglycemia worsens stroke outcomes 1
• Avoid hyperthermia; maintain normothermia or mild hypothermia (36°C) 1
• Ensure adequate oxygenation (SpO2 >94%) and normocarbia (PaCO2 35-45 mmHg) 1

Prevention Strategies for Future Cases

Meticulous de-airing technique with CO2 insufflation throughout the procedure, combined with TEE confirmation of air evacuation before weaning from bypass, significantly reduces air embolism risk. 1

• Use continuous CO2 flooding of operative field during all left heart procedures 1
• Perform systematic de-airing maneuvers including left ventricular venting, needle aspiration of cardiac apex, and Trendelenburg positioning 1
• Confirm absence of intracardiac air by TEE before discontinuing bypass 1

Preoperative CT angiography of aorta and femoral vessels identifies patients at high risk for cannulation-related dissection. 1

Initiate oral anticoagulation (warfarin INR 2.0-3.0) for minimum 3 months post-mitral valve repair, even without other indications, as this reduces stroke risk by 72% (HR 0.28) without increasing major bleeding. 1, 3

Critical Pitfalls to Avoid

• Never assume hemodynamic stability means absence of stroke—neurological injury can occur with normal vital signs 1
• Do not delay neuroimaging to "wait and see" if symptoms improve, as time-sensitive interventions may be missed 1
• Avoid rapid INR reversal with IV vitamin K in prosthetic valve patients unless life-threatening hemorrhage, as this dramatically increases thrombosis risk 1
• Do not attribute post-operative confusion solely to anesthesia emergence—perform focused neurological examination on all patients 1