Vascular Surgery — Carotid Endarterectomy

• Atherosclerotic plaque formation and composition: Carotid stenosis develops through progressive accumulation of lipid-laden macrophages, smooth muscle cells, and extracellular lipid within the arterial intima and media. In response to endothelial injury (induced by hypertension, hyperlipidemia, smoking, and diabetes), oxidized low-density lipoprotein (oxLDL) accumulates subintimally, triggering CD4+ and CD8+ T-cell infiltration and macrophage foam cell formation. The lipid core becomes surrounded by a fibrous cap composed of collagen and smooth muscle cells; rupture of this cap exposes the thrombogenic lipid core to circulating blood, precipitating in situ thrombosis. Heterogeneous plaques with large lipid cores, thin fibrous caps, and intraplaque hemorrhage ("vulnerable plaques") are at highest risk for rupture and are associated with symptomatic disease despite similar degree of stenosis compared to homogeneous, fibrotic plaques.

• Hemodynamic effects and critical stenosis: Carotid stenosis causes hemodynamic compromise according to Bernoulli's principle, where flow velocity increases and pressure drops across a narrowed segment. Critical stenosis (typically ≥70% by angiography or equivalent by ultrasound criteria: peak systolic velocity >230 cm/s) impairs distal perfusion pressure sufficiently to compromise regional cerebral blood flow, particularly during periods of decreased cardiac output or hypotension. The relationship between stenosis degree and stroke risk is nonlinear: stenosis >70% carries exponentially higher stroke risk due to combined effects of reduced perfusion pressure and increased thromboembolism. Cerebral autoregulation normally maintains constant cerebral blood flow across a wide range of systemic pressures (50–150 mmHg mean arterial pressure), but in the setting of critical stenosis, autoregulation becomes exhausted and cerebral perfusion becomes pressure-dependent, increasing vulnerability to hypotensive episodes or contralateral carotid occlusion.

• Thromboembolism and plaque embolization: Symptomatic carotid stenosis frequently results from microembolization of thrombotic material or atherosclerotic debris rather than hemodynamic insufficiency alone. Platelets adhere to exposed collagen and tissue factor in ruptured plaques, activating the coagulation cascade and generating thrombin, which converts fibrinogen to fibrin and promotes platelet aggregation. These microthrombi either occlude distal cerebral arteries (causing TIA or stroke) or dissolve spontaneously. The high frequency of microemboli in symptomatic patients explains why antiplatelet therapy alone does not reliably prevent recurrent events and why CEA (removing the plaque source) provides superior stroke prevention compared to medical therapy alone. Advanced imaging (MRI of carotid plaque) demonstrates that plaque heterogeneity, lipid-rich necrotic core volume, and intraplaque hemorrhage independently predict symptom status and future ipsilateral stroke risk, suggesting that plaque morphology is as important as degree of stenosis.

• Collateral circulation and cerebral reserve: The adequacy of collateral blood flow through the circle of Willis, anterior communicating artery, and leptomeningeal collaterals determines whether a patient with carotid stenosis remains asymptomatic or develops symptoms. Patients with good collateral development (evident on cross-sectional imaging or transcranial Doppler studies showing robust flow in the anterior cerebral artery and middle cerebral artery) may tolerate even complete carotid occlusion without stroke, whereas those with inadequate collaterals may become symptomatic with moderate stenosis. Cerebral perfusion imaging (xenon CT, positron emission tomography) can quantify regional cerebral blood flow and identify areas of misery perfusion (low flow states), which identify high-risk asymptomatic patients who benefit most from CEA.

• Atherosclerotic carotid disease (primary etiology): The vast majority (>95%) of hemodynamically significant carotid stenosis results from atherosclerotic plaque accumulation at the bifurcation of the common carotid artery, where hemodynamic shear stress is lowest and plaque deposition is most favorable. The severity of atherosclerotic burden is determined by cumulative exposure to traditional cardiovascular risk factors including age (>65 years, with exponential increase in prevalence), male sex (2–3:1 male predominance), hypertension (present in 60–70% of patients with carotid stenosis), hyperlipidemia, diabetes mellitus (2–3-fold increased risk), and smoking (current smokers have 2–4-fold increased risk compared to never-smokers). Carotid stenosis frequently coexists with coronary artery disease and peripheral arterial disease, reflecting systemic atherosclerotic burden; approximately 10–15% of patients undergoing CEA have significant coronary disease.

• Symptomatic status and plaque vulnerability: Recent ipsilateral transient ischemic attack (TIA) or ischemic stroke indicates plaque rupture with thromboembolism or hemodynamic compromise and defines "symptomatic carotid stenosis." Symptoms must occur within 6 months of diagnosis to classify stenosis as symptomatic (most randomized trials used this criterion). Symptoms ipsilateral to the contralateral carotid stenosis (amaurosis fugax, hemispheric TIA, stroke) predict markedly higher subsequent stroke risk (4–13% annual risk in untreated symptomatic patients with ≥70% stenosis) compared to asymptomatic stenosis. Plaque surface characteristics on imaging (ulceration, irregularity, heterogeneity) correlate with symptom status and future stroke risk independent of stenosis severity.

• Degree of stenosis: Stenosis ≥70% by NASCET criteria (North American Symptomatic Carotid Endarterectomy Trial) is the primary anatomic threshold guiding CEA decisions. NASCET defines degree of stenosis as [(1 − minimal lumen diameter/distal internal carotid artery diameter) × 100]. Stenosis 50–69% represents an intermediate-risk group where CEA may be beneficial, particularly in symptomatic patients with favorable anatomy and low perioperative risk. Stenosis <50% does not justify CEA in symptomatic or asymptomatic patients, as the procedural risk exceeds the benefit. Contralateral carotid occlusion increases both perioperative stroke risk and long-term stroke risk if the ipsilateral stenosis is left untreated, making CEA relatively more beneficial in this subset.

• Asymptomatic carotid stenosis (ACAS/ACST definitions): Asymptomatic carotid stenosis ≥60% (ACAS trial definition) or ≥70% (ACST trial definition) identified by screening (typically carotid ultrasound) in patients without ipsilateral cerebrovascular symptoms carries lower annual stroke risk (1–2% annually if untreated with optimal medical therapy) compared to symptomatic disease. Asymptomatic patients with excellent expected lifespan (>5 years) and low perioperative risk may still benefit from CEA, though the absolute risk reduction is smaller. Progression of asymptomatic stenosis to complete occlusion occurs in approximately 1–2% of asymptomatic cases annually, and once occlusion develops, stroke risk increases markedly; some advocate CEA in asymptomatic patients to prevent this risk.

• Contralateral carotid status and cerebral reserve: Contralateral carotid occlusion substantially increases perioperative stroke risk during CEA (due to reliance on ipsilateral blood flow for cerebral perfusion) and increases long-term stroke risk if the stenotic artery is left untreated. Conversely, contralateral stenosis (without occlusion) increases perioperative risk modestly and alters the risk-benefit ratio for CEA.

• Transient ischemic attack (TIA): TIA represents transient focal neurological deficit from cerebral ischemia that resolves completely within 24 hours (though most resolve within 1 hour). Amaurosis fugax (transient monocular blindness) is the classic TIA presentation specific to carotid disease, occurring when microemboli lodge in the ophthalmic artery (first branch of the internal carotid artery). Patients describe sudden onset of painless monocular vision loss that progresses from superior to inferior visual field (curtain-like), lasting minutes to hours, then completely resolving. Hemispheric TIAs present with contralateral motor weakness (arm more than leg, face sparing), sensory loss, speech disturbance (if dominant hemisphere), or gaze deviation (contralateral). The ABCD² score predicts early stroke risk after TIA: age ≥60 (1 point), blood pressure ≥140/90 (1 point), clinical features of motor weakness or speech disturbance without weakness (2 points for weakness, 1 point for speech disturbance), duration ≥60 minutes (2 points), diabetes (1 point). Score ≥4 indicates high early stroke risk (>4% at 2 days) and warrants urgent carotid imaging.

• Acute ischemic stroke: Symptomatic carotid stenosis can precipitate acute ischemic stroke due to complete thrombotic occlusion of the internal carotid artery or thromboembolic occlusion of distal intracranial vessels. Stroke presentation depends on vascular territory: middle cerebral artery distribution (most common with carotid disease) causes contralateral motor and sensory deficits (arm > leg), facial droop, and expressive or receptive aphasia (if dominant hemisphere). The presence of acute stroke symptoms (onset within 4.5 hours for IV thrombolysis eligibility) mandates urgent head CT to exclude hemorrhage, followed by CT angiography or MR angiography to assess carotid status. Patients presenting with acute stroke and severe carotid stenosis present a challenge: if symptom onset is within 24 hours, thrombolysis may be contraindicated due to concern for hemorrhagic transformation in penumbral tissue, yet CEA in the acute setting carries higher perioperative stroke risk; most guidelines recommend medical management initially with delayed CEA once acute phase resolves (typically 2–6 weeks).

• Asymptomatic carotid stenosis: Approximately 80% of patients with carotid stenosis ≥70% are asymptomatic at the time of detection, identified through screening (carotid ultrasound in high-risk patients or as incidental finding on cross-sectional imaging). These patients have no history of TIA, amaurosis fugax, or stroke. The natural history of asymptomatic stenosis is slow progression to higher degrees of stenosis or eventual occlusion; approximately 1–2% per year progress to complete occlusion, and the annual ipsilateral stroke risk without intervention is 1–2%.

• Hemodynamic stroke ("watershed stroke"): Rarely, critical carotid stenosis causes stroke through hemodynamic insufficiency rather than thromboembolism, particularly when collateral circulation is inadequate. These patients develop stroke during hypotensive episodes, after initiation of aggressive antihypertensive therapy, or in the setting of contralateral carotid occlusion. Hemodynamic stroke classically affects watershed zones between major arterial territories (middle cerebral artery/anterior cerebral artery junction, middle cerebral artery/posterior cerebral artery junction).

• Physical examination findings: The carotid bifurcation atherosclerosis may generate audible turbulent flow. A carotid bruit (systolic or systolic-diastolic) is heard best with the bell of the stethoscope at the angle of the mandible; bruits are present in approximately 50% of patients with significant stenosis (>70%) but also occur with lesser degrees of stenosis or increased flow states. Absence of bruit does not exclude significant stenosis. A unilateral bruit may be more specific for ipsilateral disease than bilateral bruits. Diminished carotid pulse or pulsatility on palpation may indicate severe stenosis or occlusion. Signs of acute stroke (facial droop, arm weakness, speech abnormality) represent established cerebral ischemia requiring urgent evaluation.

• Carotid duplex ultrasonography (B-mode and Doppler): Duplex ultrasound is the first-line imaging modality for detecting and quantifying carotid stenosis due to availability, lack of radiation, lack of contrast requirement, and operator-dependent but generally excellent sensitivity (85–95%) and specificity (80–95%) for stenosis ≥70%. B-mode imaging visualizes the plaque morphology (hypoechoic, hyperechoic, heterogeneous), surface characteristics (smooth, irregular, ulcerated), and echolucency. Doppler interrogation measures peak systolic velocity (PSV) in the internal carotid artery and the internal carotid artery/common carotid artery PSV ratio to estimate degree of stenosis. Standard criteria for ≥70% stenosis are PSV ≥230 cm/s or ICA/CCA ratio ≥4.0; criteria for 50–69% stenosis are PSV 130–230 cm/s or ICA/CCA ratio 2.0–4.0. Peak diastolic velocity (reflecting distal resistance) is also measured; markedly elevated diastolic velocities favor higher-grade stenosis. End-diastolic velocity (EDV) >100 cm/s indicates ≥70% stenosis with high specificity. Spectral broadening (turbulent flow) appears on the velocity tracing. Complete carotid occlusion appears as absence of Doppler signal with no flow detected. Criteria vary slightly among laboratories, and operator dependency is a limitation; concordance with other imaging modalities (CTA or MRA) strengthens the diagnosis.

• CT angiography (CTA): CTA provides rapid, high-resolution imaging of the carotid bifurcation and intracranial circulation, useful for confirming ultrasound findings, evaluating anatomy relevant for surgical planning (identifying heavily calcified plaques, severe tortuosity, or anomalous anatomy), and identifying intracranial stenosis or occlusion. CTA uses iodinated contrast (renal function must be assessed beforehand) and involves radiation exposure. Sensitivity and specificity for ≥70% stenosis are >95% when performed with modern multidetector technology. CTA is particularly valuable for excluding intracranial pathology (occlusive stroke, aneurysm) in patients presenting with acute stroke and carotid stenosis.

• MR angiography (MRA): MRA offers high sensitivity (>95%) and specificity (>90%) for significant stenosis without radiation or iodinated contrast, making it ideal for patients with contrast allergy or renal insufficiency. Contrast-enhanced MRA (using gadolinium) provides superior resolution to non-contrast MRA and is preferred when renal function permits (gadolinium is contraindicated in severe renal insufficiency due to risk of nephrogenic systemic fibrosis). MRA may overestimate degree of stenosis due to signal loss from turbulent flow; this is more pronounced with older non-contrast techniques but less problematic with modern contrast-enhanced sequences.

• Digital subtraction carotid angiography: Conventional angiography is reserved for situations where noninvasive imaging is equivocal, discordant between modalities, or when intervention is planned via endovascular approach (carotid artery stenting). Angiography provides the highest spatial resolution and allows assessment of collateral circulation and intracranial anatomy. However, angiography carries procedural stroke risk (0.5–1% depending on age and atherosclerotic burden

Immediate stabilisation (acute symptomatic presentation)

• Acute stroke pathway first: non-contrast head CT to exclude hemorrhage, then IV thrombolysis (alteplase or tenecteplase) if within the window and thrombectomy for large-vessel occlusion, per the AHA/ASA acute ischemic stroke guideline. Revascularization of the neck lesion is deferred, not emergent.
• Permissive hypertension in the acute infarct: aggressive BP lowering can convert a pressure-dependent, autoregulation-exhausted hemisphere into a watershed infarct.

First-line medical therapy (every patient, regardless of whether surgery is planned)

• Antiplatelet: aspirin monotherapy; after minor stroke or high-risk TIA, short-course dual antiplatelet therapy with aspirin plus clopidogrel for roughly the first 3 weeks then single-agent, per the AHA/ASA secondary stroke prevention guideline. Anticoagulation is not therapy for atherosclerotic carotid disease.
• High-intensity statin: atorvastatin or rosuvastatin, per the ACC/AHA cholesterol guideline — plaque stabilization, not just LDL lowering.
• Antihypertensives, smoking cessation, glycemic control (ADA Standards of Care) as risk-factor modification.

Definitive revascularization

• Symptomatic 70–99% stenosis: CEA is indicated (AHA/ASA and Society for Vascular Surgery), ideally within 2 weeks of the index TIA/minor stroke — recurrence risk is front-loaded.
• Symptomatic 50–69%: CEA reasonable in men with low perioperative risk and reasonable life expectancy.
• Asymptomatic ≥70%: CEA reasonable only if perioperative stroke/death risk is low and life expectancy exceeds ~5 years; contemporary medical therapy is a legitimate alternative.
• Acceptable perioperative stroke/death rate: under 6% symptomatic, under 3% asymptomatic.
• Carotid artery stenting (with embolic protection) for hostile neck, prior neck irradiation, restenosis after CEA, high lesions, or prohibitive cardiac risk. CREST showed more periprocedural stroke with stenting and more MI with CEA; stenting is less favorable in older patients.

Contraindicated / not indicated

• Stenosis <50% — procedural risk exceeds benefit.
• Chronic total occlusion — there is no lumen to endarterectomize.
• Large disabling infarct or altered consciousness — high hemorrhagic transformation risk.
• Routine population screening for asymptomatic stenosis (USPSTF grade D).

Complications of untreated disease

• Recurrent TIA / ipsilateral ischemic stroke: plaque rupture with artery-to-artery thromboembolism; risk is highest in the first days to weeks after the index event — this is why delay to surgery matters.
• Watershed (hemodynamic) infarction: exhausted autoregulation distal to a critical stenosis; signals itself as deficits provoked by hypotension, with border-zone infarcts on MRI.
• Progression to complete occlusion: converts a treatable lesion into an untreatable one.

Perioperative complications — emergencies in bold

• Perioperative stroke (EMERGENCY): embolization during dissection/clamping, or acute thrombosis of the endarterectomized surface. New contralateral deficit on emergence from anesthesia mandates immediate return to the operating room or urgent imaging — early thrombosis is surgically correctable.
• Expanding neck hematoma (EMERGENCY): arterial or venous bleeding into a closed space causing tracheal deviation and airway compromise. Stridor, dysphagia, and a tense neck are the tell. Open the wound at the bedside to decompress; do not wait for the OR.
• Cerebral hyperperfusion syndrome (EMERGENCY): chronically dilated, autoregulation-impaired distal vessels are suddenly exposed to normal pressure. Presents days after surgery with ipsilateral throbbing headache, seizures, and possible intracerebral hemorrhage. Treatment is strict blood pressure control.
• Cranial nerve injury: retraction or transection during exposure.
• Hypoglossal (XII): tongue deviates toward the injured side; dysarthria.
• Vagus / recurrent laryngeal: hoarseness, weak cough.
• Superior laryngeal (external branch): loss of high-pitched phonation, voice fatigue.
• Marginal mandibular branch of VII: asymmetric lower-lip depression.
• Glossopharyngeal (IX): dysphagia and aspiration — the most morbid of these.
• Baroreceptor dysfunction: carotid sinus manipulation causes labile hemodynamics — bradycardia and hypotension intraoperatively, hypertension postoperatively.
• Myocardial infarction: shared atherosclerotic burden; the dominant non-neurologic cause of perioperative death and more frequent after CEA than after stenting.
• Restenosis: myointimal hyperplasia within the first ~2 years; recurrent atherosclerosis later.

• Amaurosis fugax — painless, curtain-like transient monocular vision loss — localizes to the ophthalmic artery, the first branch of the internal carotid, and means symptomatic ipsilateral carotid disease until proven otherwise. Next best step: carotid duplex ultrasound.
• The two-week rule: for symptomatic 70–99% stenosis, CEA should be done within about 2 weeks of the index TIA/minor stroke (AHA/ASA, SVS). Stems that offer "schedule elective CEA in 3 months" are testing this.
• Tongue deviates toward the side of the lesion with hypoglossal nerve injury — the single most tested CEA complication. Hoarseness points to vagus/recurrent laryngeal instead.
• Postoperative day 2–7 unilateral pounding headache, then a seizure = cerebral hyperperfusion syndrome. The answer is aggressive blood pressure control, not more antiplatelet or thrombolysis.
• Stridor plus a tense, expanding neck after CEA is an airway emergency: open the incision at the bedside. Do not intubate blindly first and do not transport to CT.
• A 100% occluded internal carotid is not revascularized — a favorite distractor. So is offering CEA for <50% stenosis; the correct answer there is maximal medical therapy (high-intensity statin plus antiplatelet).
• CREST: stenting carried more periprocedural stroke, CEA more periprocedural MI; outcomes were otherwise comparable. Stenting is favored for a hostile/irradiated neck or prohibitive cardiac risk, CEA for older patients.
• A carotid bruit is neither sensitive nor specific — up to half of significant stenoses have no bruit. USPSTF recommends against screening asymptomatic adults for carotid stenosis (grade D), so an incidental bruit in an asymptomatic patient does not by itself justify a work-up in a screening-framed question.
• NASCET measures stenosis against the normal distal ICA diameter, not the estimated bulb — the reason ECST-style measurements read as more severe.