What are the possible causes of an acute‑to‑subacute ischemic stroke in a 70‑year‑old patient who recently underwent a guarded surgical excision?

Causes of Acute-to-Subacute Stroke After Guarded Endarterectomy

The most likely causes of stroke in this 70-year-old patient following guarded endarterectomy are thromboembolism (70-80% probability) from surgical manipulation of atherosclerotic plaque, postoperative atrial fibrillation, and hemodynamic hypoperfusion causing watershed infarcts (20-30% probability). 1

Primary Mechanism: Thromboembolism

Thromboembolism accounts for approximately 70-80% of perioperative strokes and represents the dominant mechanism in this clinical scenario. 1

Intraoperative Embolic Events

• Mechanical injury from surgical instruments disrupting atherosclerotic plaque during endarterectomy generates thromboembolic debris that travels to cerebral vessels 1
• Direct manipulation of the carotid artery during the procedure dislodges atherosclerotic material and calcific deposits, which are the most common source of emboli 2
• Air embolism can occur if aspiration or irrigation techniques are inadequate during the vascular procedure 1

Postoperative Thrombotic Events

• Thrombus formation at the surgical site occurs due to endothelial damage, tissue disruption, and activation of the coagulation cascade by surgical trauma 1
• The acute-to-subacute timing (likely within 7 days postoperatively) suggests early postoperative stroke, which is primarily attributable to postoperative arrhythmias—particularly atrial fibrillation—and hemodynamic factors 1

Secondary Mechanism: Hemodynamic Hypoperfusion

Hypoperfusion results in border zone or watershed strokes and comprises 20-30% of intraprocedural strokes. 1

• Prolonged hypotension during or after surgery reduces cerebral perfusion pressure, causing ischemia in watershed territories between major arterial distributions 1
• Shock or hemodynamic instability in the perioperative period exacerbates this mechanism 1
• Dehydration compounds hypoperfusion risk 1

Postoperative Arrhythmias

Atrial fibrillation is the leading cause of early postoperative stroke within the first 7 days after surgery. 1

• New-onset atrial fibrillation in the postoperative period generates cardiac thrombi that embolize to cerebral vessels 1, 3
• The 70-year-old age group has increased susceptibility to postoperative atrial fibrillation 1

Patient-Specific Risk Factors

Age-Related Risk

• Age >62 years is an independent risk factor for perioperative stroke 1
• Older adults (≥55 years) have growing prevalence of cardiovascular disease, cerebrovascular disease, and diabetes mellitus, which increase overall risk for major adverse cardiac events including stroke 1

Pre-existing Vascular Disease

• Previous cerebrovascular disease increases stroke risk with an adjusted odds ratio of 12.57 4
• Peripheral vascular disease increases risk with an adjusted odds ratio of 5.35 (or 14.70 when combined with stroke-related factors) 4
• Chronic obstructive pulmonary disease increases risk with an adjusted odds ratio of 7.51-10.04 4

Timing Considerations

The acute-to-subacute designation suggests stroke occurred within the first 7 days postoperatively, when thromboembolism and atrial fibrillation dominate. 1

• Approximately 40% of surgical strokes occur intraoperatively, while 60% occur postoperatively with a peak at 40 hours after surgery 1, 2
• Median procedure-to-stroke interval is 2 days (range 0-16 days) 4
• Late postoperative stroke (7 days to 1 month) would be more commonly associated with the patient's overall atherothromboembolic risk factors rather than the procedure itself 1

Less Common Mechanisms to Consider

Contrast-Induced Complications

• If angiography was performed perioperatively, contrast media can cause vasospasm of cerebral arteries and direct neurotoxicity 1

Hypercoagulable States

• Disseminated intravascular coagulation occurs in 6.6% of postoperative stroke patients versus 0% of controls 4
• Inherited or acquired hypercoagulable states (antithrombin III deficiency, protein C/S deficiency, antiphospholipid antibodies) are rare but recognized etiologies 3

Concurrent Myocardial Infarction

• Myocardial infarction occurs in 6.6% of postoperative stroke patients versus 0% of controls, suggesting a shared thrombotic mechanism 4

Critical Clinical Pitfalls

Hypotension rarely accounts for postoperative strokes despite common assumptions—major comorbidity of the patient at risk is more important than complicating events during surgery. 4

• Do not assume hypotension caused the stroke without evidence of watershed distribution on imaging 4
• Blood pressure and urea levels contribute only slightly to stroke risk (odds ratios of 1.05 and 1.04 respectively) 4
• The stroke likely occurred during an asymptomatic interval, making precise timing difficult to determine 4

Diagnostic Approach

Imaging Pattern Recognition

• Cortical or large subcortical infarctions suggest cardioembolic or artery-to-artery embolic mechanism 3
• Border zone or watershed infarcts suggest hemodynamic hypoperfusion 1
• Multiple territorial infarcts suggest embolic shower from surgical site or cardiac source 3

Cardiac Evaluation

• Immediate electrocardiogram and continuous telemetry to detect atrial fibrillation 1
• Echocardiography to identify cardiac thrombus or structural abnormalities 3
• Troponin measurement to exclude concurrent myocardial infarction 4

Vascular Assessment

• Imaging of the surgical site to assess for acute thrombosis or residual stenosis 3
• Evaluation of intracranial vessels to identify the occluded artery and guide potential intervention 3