Carotid and Cerebrovascular Disease

Background

Carotid artery stenosis is a leading cause of ischemic stroke, accounting for approximately 15–20% of all ischemic events worldwide ^[1]. Stroke remains the second most common cause of death globally and the primary cause of long-term disability in adults.

• Asymptomatic carotid stenosis (ACS): highly prevalent in aging populations, affecting ~5–10% of men >65 years ^[2].
• Symptomatic carotid stenosis (SCS): presents with TIA, minor stroke, or amaurosis fugax. The risk of stroke recurrence is highest in the first 2 weeks after a symptomatic event.
• Intervention: Carotid endarterectomy (CEA) and carotid artery stenting (CAS) reduce stroke risk in selected patients.
• Modern evolution: improvements in medical therapy (statins, antiplatelets, antihypertensives) have lowered the absolute benefit of surgery in ACS ^[3].

Atherosclerosis (most common)

• Progressive lipid accumulation and plaque formation.
• Hemodynamic stress at bifurcations promotes turbulence → plaque localization.

Non-atherosclerotic causes

• Carotid dissection (spontaneous or traumatic).
• Fibromuscular dysplasia (FMD): string-of-beads appearance, often in young women.
• Vasculitis: Takayasu arteritis, giant cell arteritis.
• Radiation-induced stenosis: after neck irradiation.

Risk factors

• Non-modifiable: age, male sex, genetics.
• Modifiable: smoking, hypertension, diabetes, dyslipidemia, obesity, CKD.
• Systemic association: many patients with carotid disease also have 10PAD or CAD.

Pathophysiology

1. Plaque development
2. * Endothelial injury → LDL infiltration → oxidation → foam cell formation.
3. * Plaque composition: lipid-rich necrotic core, fibrous cap, calcification.
4. Plaque vulnerability
5. * Thin fibrous cap, neovascularization, intraplaque hemorrhage.
6. * “Vulnerable plaques” are more prone to rupture and embolization.
7. Hemodynamic consequences
8. *Moderate stenosis (50–69%):** may be compensated.
9. *Severe stenosis (>70%):** turbulent flow, risk of thrombus formation, distal embolization, cerebral hypoperfusion.

Clinical Presentation

• Asymptomatic stenosis: discovered by bruit or imaging.
• TIA: transient focal neurological deficit <24 h (usually <1 h).
• Stroke: persistent neurological deficit >24 h.
• Amaurosis fugax: transient monocular blindness, classic sign of ipsilateral carotid disease.

Stroke Risk by Category

• Symptomatic ≥70% stenosis: ~25% 2-year risk without treatment ^[4].
• Asymptomatic ≥60% stenosis: annual stroke risk ~0.5–1% with modern therapy ^[5],[6].

Clinical assessment

• Full neurological exam (NIHSS, modified Rankin scale).
• Cardiovascular risk evaluation.
• Risk stratification: asymptomatic vs symptomatic is the key determinant of management.

Duplex Ultrasound

Duplex ultrasound is the first-line modality for screening and surveillance. Laboratory-validated velocity criteria should be used; the Society for Radiologists in Ultrasound (SRU) consensus suggests peak systolic velocity (PSV) ≥230 cm/s as a guide to ≥70% NASCET stenosis, though thresholds should be validated locally and interpreted in conjunction with end-diastolic velocity (EDV) and ICA/CCA ratios ^[7]. Stenosis should always be reported using the NASCET method to align with clinical trial and guideline thresholds.

Advantages: Non-invasive, repeatable, and inexpensive.

Limitations: Operator-dependent interpretation and artifacts from heavy calcification.

CT Angiography

• Gold standard for anatomic assessment.
• Defines stenosis, plaque morphology (calcified vs soft vs mixed), and intracranial vessels.
• Provides surgical/endovascular planning.

MR Angiography

• Alternative when CTA contraindicated (renal dysfunction, contrast allergy).
• CE-MRA provides high-resolution images.

Digital Subtraction Angiography

• Historically reference standard.
• Now reserved for intervention.
• Risk: 0.5–1% stroke.

Plaque Imaging

In asymptomatic carotid stenosis (ACS), high-risk plaque features identify patients at elevated ipsilateral stroke risk and may support consideration of revascularization in otherwise borderline cases. These features include MRI-detected intraplaque hemorrhage, plaque ulceration, echolucency on ultrasound, and transcranial Doppler (TCD) microembolic signals ^[6].

Optimal Medical Therapy

Antiplatelet therapy: For carotid endarterectomy (CEA), single antiplatelet therapy (aspirin 75–325 mg daily) should be administered preoperatively and continued indefinitely. For carotid artery stenting (CAS) and transcarotid artery revascularization (TCAR), dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 1 month (often extended to 3 months), followed by single antiplatelet therapy ^[6]. In patients with high-risk TIA or minor stroke, short-term dual antiplatelet therapy reduces early stroke recurrence (CHANCE, POINT trials) ^[8],[9].

Lipid management: High-intensity statin therapy is indicated for all patients with atherosclerotic carotid disease. The SPARCL trial demonstrated that intensive statin therapy reduces stroke recurrence ^[10]. Consider adding ezetimibe or PCSK9 inhibitors if LDL cholesterol remains above target ^[6].

Blood pressure control: Target blood pressure <130/80 mmHg in most patients with prior stroke or TIA if tolerated ^[11].

Diabetes management: Individualized glycemic control (often HbA1c <7%) with comprehensive cardiovascular risk reduction ^[11].

Lifestyle modifications: Smoking cessation, weight management, Mediterranean-style diet, and regular physical activity are essential components of secondary prevention ^[11].

Carotid Endarterectomy

Carotid endarterectomy is the gold standard surgical treatment for symptomatic carotid stenosis. Landmark trials established its efficacy: NASCET (1991) demonstrated that 7Carotid reduced stroke risk in patients with symptomatic stenosis ≥70% ^[4], and ECST (1998) confirmed this benefit ^[12]. In asymptomatic patients, ACAS (1995) and ACST (2004) showed a small benefit for stenosis ≥60%, though this advantage is less pronounced with modern medical therapy.

7Carotid is recommended for symptomatic stenosis of 50–99% when performed within 14 days of TIA or non-disabling stroke, provided the perioperative stroke or death risk is <6% ^[6]. In asymptomatic carotid stenosis (ACS), routine 7Carotid is not indicated. However, it may be considered in highly selected patients with ≥60% stenosis who have a life expectancy >3–5 years, low perioperative risk (<3%), and high-risk imaging features ^[6].

Acceptable perioperative complication rates are crucial: <6% stroke or death for symptomatic patients and <3% for asymptomatic patients.

Carotid Artery Stenting

• Minimally invasive alternative.
• CREST (2010): 7Carotid vs 7Carotid → no difference in long-term stroke/MI/death, but 7Carotid had higher peri-procedural stroke, lower MI ^[13].
• ICSS (2010): higher peri-procedural stroke with 7Carotid.
• Indications: high surgical risk, restenosis after 7Carotid, radiation-induced stenosis.
• Embolic protection devices strongly recommended.

Transcarotid Artery Revascularization

• Hybrid technique: surgical exposure of common carotid + stent via direct puncture + flow reversal neuroprotection.
• ROADSTER trial (2019): low peri-procedural stroke rates ^[14].
• Emerging alternative in high-risk patients.

Follow-up

Post-procedure surveillance: Duplex ultrasound surveillance should be tailored to individual risk factors, including early residual stenosis, periprocedural complications, and contralateral severe disease. A common surveillance schedule includes imaging at 1, 6, and 12 months, followed by annual examinations if findings remain stable ^[6].

Medical therapy: Lifelong secondary prevention with optimal medical therapy is mandatory regardless of revascularization, including antiplatelet agents, statins, blood pressure control, and lifestyle modifications ^[6],[11].

Restenosis: Patch closure during CEA reduces restenosis rates compared with primary closure. Clinically significant restenosis after CEA or CAS is uncommon, occurring in approximately 10–15% after CEA and 5–10% after CAS. Symptomatic or high-grade (≥70%) restenosis, including in-stent restenosis (ISR), should be managed with reintervention (repeat CEA, CAS, TCAR, or endovascular treatment for ISR) in experienced centers ^[6].

Tables

Table 8.1. Indications for Carotid Revascularization (Guidelines)

Table 8.2. CEA vs CAS – Comparative Outcomes

Asymptomatic carotid stenosis (ACS): contemporary selection for intervention vs best medical therapy (BMT)

Best medical therapy (BMT) is the first-line approach for most patients with asymptomatic carotid stenosis (ACS) in the contemporary era. Intervention may be considered for patients with ≥60% ACS only when perioperative risk is <3%, life expectancy exceeds 3–5 years, and one or more high-risk features are present. These high-risk features include rapid stenosis progression, ipsilateral silent cerebral infarcts, intraplaque hemorrhage or ulceration on imaging, echolucent plaque characteristics, microembolic signals on transcranial Doppler (TCD), or contralateral internal carotid artery (ICA) occlusion.

For procedure selection in patients deemed appropriate for revascularization, CEA is preferred in average-risk patients, while CAS or TCAR may be favored when anatomic considerations or surgical risk factors support an endovascular approach. The ACST-2 randomized controlled trial demonstrated that CEA and CAS provide similar medium-term outcomes in asymptomatic patients selected for revascularization. The ongoing CREST-2 trial is evaluating BMT alone versus revascularization plus BMT in patients with asymptomatic carotid stenosis.

Modern CEA vs CAS evidence synthesis and patient selection (ACT-1/ACST-2; age/anatomy modifiers)

Recent evidence has refined the comparative outcomes of CEA versus CAS. In asymptomatic patients, the ACST-2 trial demonstrated similar medium-term non-procedural stroke rates for CEA versus CAS, with acceptably low rates of procedural disabling stroke or death for both approaches. In mixed symptomatic and asymptomatic cohorts, the CREST trial showed similar long-term composite outcomes, though with important differences in perioperative events: CAS was associated with higher periprocedural stroke rates, while CEA had higher myocardial infarction rates. Patient age significantly modifies these outcomes, with older patients generally achieving better results with CEA compared to CAS.

These findings inform contemporary patient selection for revascularization strategy. CEA remains preferred for most average-risk patients, particularly those of advanced age. CAS or TCAR may be favored in patients with high surgical risk, unfavorable neck anatomy for surgery, prior neck irradiation, or recurrent stenosis after previous CEA.

Timing of carotid intervention after TIA/minor stroke and after thrombolysis

The timing of carotid revascularization after neurological events is critical to balancing stroke prevention against procedural risk. For symptomatic stenosis of 50–99%, CEA should be performed as soon as feasible within 14 days of the index TIA or non-disabling stroke, with an ideal window of within 7 days. In experienced centers, urgent CEA (<48–72 hours) may be considered for patients with crescendo TIA or neurologically unstable symptoms.

Special considerations apply after acute stroke treatment or in the setting of large cerebral infarction. Following intravenous thrombolysis or in cases of large infarction with hemorrhagic transformation, carotid intervention should be deferred until the patient is neurologically and radiographically stable. While CAS timing follows similar principles, hyperacute CAS is generally avoided due to elevated periprocedural stroke risk in this setting.

Imaging criteria: stenosis grading standards and plaque vulnerability features

Standardized stenosis grading is essential for consistent clinical decision-making and comparison with clinical trial evidence. Carotid stenosis should be reported using the NASCET (North American Symptomatic Carotid Endarterectomy Trial) method. If alternative grading methods are employed, they should be explicitly specified, and direct cross-conversion between methods should be avoided due to inherent measurement differences.

Duplex ultrasound velocity thresholds should follow laboratory-specific validation protocols. The Society for Radiologists in Ultrasound (SRU) consensus suggests peak systolic velocity (PSV) ≥230 cm/s as a guide for identifying ≥70% NASCET stenosis, though local validation with correlation to other imaging modalities is recommended.

High-risk plaque features have emerged as important modifiers of stroke risk in asymptomatic carotid stenosis. These features include intraplaque hemorrhage (IPH) on MRI, plaque ulceration, echolucent plaque characteristics on ultrasound, microembolic signals on transcranial Doppler (TCD), rapid stenosis progression, and ipsilateral silent cerebral infarcts on imaging. The presence of these features increases stroke risk and may influence decision-making regarding revascularization in otherwise borderline cases.

Peri-procedural antithrombotic therapy for CEA/CAS/TCAR

Optimal periprocedural antithrombotic management is critical to preventing both thrombotic and hemorrhagic complications. For carotid endarterectomy (CEA), single antiplatelet therapy with aspirin (75–325 mg daily) should be administered preoperatively and continued indefinitely. For carotid artery stenting (CAS) and transcarotid artery revascularization (TCAR), dual antiplatelet therapy with aspirin plus clopidogrel is recommended for at least 1 month, with many centers extending this to 3 months, followed by single antiplatelet therapy thereafter.

High-intensity statin therapy should be initiated or optimized before the procedure in all patients. Patients on therapeutic anticoagulation require individualized management based on the specific procedure planned, indication for anticoagulation, and institutional protocols, with consideration of bridging strategies when appropriate.

Surveillance and restenosis management (including in-stent restenosis)

Surgical technique influences long-term outcomes after CEA. Patch closure reduces restenosis rates compared with primary arteriotomy closure and is widely employed in contemporary practice.

Post-procedure surveillance with duplex ultrasound should be tailored to individual risk profiles, with more intensive monitoring for high-risk subsets including patients with periprocedural complications, residual stenosis, or contralateral severe disease. Surveillance protocols typically include imaging at 1, 6, and 12 months, followed by annual examinations if stable.

In-stent restenosis (ISR) after CAS is diagnosed using duplex ultrasound criteria similar to those for native vessel stenosis, with PSV ≥230 cm/s generally corresponding to ≥70% stenosis, though stent type may influence velocity measurements. Reintervention is indicated for symptomatic ISR or high-grade (≥70%) asymptomatic ISR in selected patients. Treatment options include repeat angioplasty, drug-coated balloon angioplasty, or surgical revision, with choice dependent on anatomy, patient factors, and institutional expertise.

Role and Indications of TCAR Relative to CAS and CEA

Transcarotid artery revascularization (TCAR) represents a hybrid approach that combines direct surgical carotid access with endovascular stent placement. TCAR may be considered in patients at elevated risk for transfemoral CAS due to unfavorable aortic arch anatomy, severe arch tortuosity, hostile neck anatomy from prior surgery or radiation, or recurrent stenosis. Contemporary registry data suggest that TCAR achieves perioperative outcomes comparable to both CEA and transfemoral CAS.

TCAR employs flow reversal through extracorporeal circulation as a neuroprotection strategy during stent deployment, reducing the risk of cerebral embolization. As with standard CAS, dual antiplatelet therapy with aspirin and clopidogrel is required for at least 1 month (often 3 months) following TCAR, followed by indefinite single antiplatelet therapy.

Evidence-based carotid revascularization overview

The optimal approach to carotid revascularization—carotid artery stenting (CAS) versus carotid endarterectomy (CEA)—has been extensively studied. The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) demonstrated similar long-term composite outcomes for stroke, myocardial infarction, and death with both techniques ^[15].

However, CREST identified important age-related differences in procedural risk. CAS was associated with lower perioperative risk in younger patients (< 70 years), while CEA showed superior outcomes in older patients. The periprocedural hazard profiles also differed: CAS carried higher stroke risk, while CEA was associated with higher myocardial infarction risk.

For symptomatic carotid stenosis ≥ 50%, both techniques are effective when performed by experienced operators. In asymptomatic disease, indications for intervention continue to evolve. Optimal medical therapy has improved substantially since foundational trials (ACAS, ACST) were conducted, narrowing the benefit of prophylactic intervention. Current practice emphasizes patient selection based on stenosis severity (≥ 60–70%), life expectancy, surgical risk, and institutional expertise.