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Carotid Stenosis

Basics

  • Narrowing of carotid artery lumen mostly due to atherosclerosis.
  • Responsible for 90% of extracranial carotid lesions and up to 30% of ischemic strokes.
  • Hemodynamically significant stenosis defined as internal carotid artery peak systolic velocity (PSV) >125 cm/s on duplex US.
  • Classification by symptom status and degree of stenosis:
  • Asymptomatic: homogenous, stable plaques.
  • Symptomatic: heterogeneous, unstable plaques presenting with stroke or TIA.
  • Degrees:
    • Total occlusion: no patent lumen
    • Near occlusion: markedly narrowed lumen
    • High grade: PSV >230 cm/s (70-99% stenosis)
    • Moderate grade: PSV 125-230 cm/s (50-69% stenosis)
    • Low grade: PSV <125 cm/s with plaque (<50% stenosis)
    • Normal: PSV <125 cm/s without plaque

Epidemiology

  • More common in men, increases with age.
  • Moderate stenosis prevalence:
  • Men <50 years: 0.2%, women: 0%
  • Men >80 years: 7.5%, women: 5%
  • Severe stenosis prevalence:
  • Men <50 years: 0.1%, women: 0%
  • Men >80 years: 3.1%, women: 0.9%

Etiology and Pathophysiology

  • Atherosclerosis begins in adolescence at carotid bifurcation due to disturbed flow and shear stress.
  • Plaques develop in vessel intima and inner media.
  • Genetic factors include polymorphisms (TNFSF4, PPARA, TLR4, ITGA2, HABP2).
  • Risk factors:
  • Nonmodifiable: age >65, male sex, family history, CAD, PAD, aortic aneurysm
  • Modifiable: smoking, diet, dyslipidemia, inactivity, obesity, HTN, DM
  • Infectious agents: Chlamydia pneumoniae, CMV (possible)

Risk Factors

  • Advanced age, male sex, family history of vascular disease
  • Hypertension, diabetes, hyperlipidemia, smoking, obesity

Prevention

  • Antihypertensive therapy to maintain BP <140/90 mmHg
  • Smoking cessation
  • Statin therapy for lipid control and plaque stabilization
  • Healthy lifestyle: diet, exercise, weight management

Associated Conditions

  • Transient ischemic attack (TIA), stroke
  • Coronary artery disease (CAD)
  • Peripheral vascular disease (PVD)

Diagnosis

History

  • Identify vascular risk factors (HTN, DM, smoking, CAD, PAD)
  • Symptoms suggestive of cerebral ischemia: TIA, stroke, amaurosis fugax, aphasia

Physical Exam

  • Neurologic deficits: contralateral motor/sensory loss
  • Amaurosis fugax: transient monocular visual loss
  • Carotid bruit (low sensitivity and specificity)

Differential Diagnosis

  • Aortic valve stenosis
  • Aortic arch atherosclerosis
  • Cardioembolic events from arrhythmias
  • Migraine, brain tumors
  • Metabolic or functional neurological disorders
  • Seizure

Diagnostic Tests

  • CBC, metabolic panel, ESR (if arteritis suspected), glucose/HbA1c, lipid profile
  • Duplex ultrasonography: first-line, 98% sensitivity and 88% specificity for ≥50% stenosis
  • CT angiography: 88% sensitivity, 100% specificity, requires IV contrast
  • MR angiography: 95% sensitivity, 90% specificity, may overestimate stenosis
  • Cerebral digital subtraction angiography (gold standard): invasive, risks include contrast nephropathy and embolism

Imaging Findings

  • Stenosis most frequent at carotid bifurcation and proximal internal carotid artery
  • Stable plaques: homogenous, fatty streak, fibrous tissue
  • Unstable plaques: heterogeneous with lipid-laden macrophages, necrotic debris, ulceration

Treatment

General Measures

  • Lifestyle modification: diet, weight loss, exercise
  • Smoking cessation

Medications

  • Blood pressure control (ACE inhibitors/ARBs preferred in diabetics)
  • Glycemic control using lifestyle and medications (metformin, SGLT2 inhibitors, GLP-1 agonists)
  • Statin therapy (maximally tolerated dose)
  • Antiplatelet therapy:
  • Aspirin 75-325 mg daily
  • Alternatives after stroke/TIA: clopidogrel or aspirin plus extended-release dipyridamole
  • Avoid clopidogrel plus aspirin combination within 3 months post-TIA/CVA

Surgery and Procedures

  • Carotid endarterectomy (CEA) for symptomatic stenosis:
  • Beneficial for 50-69% stenosis (some benefit)
  • Highly beneficial for 70-99% stenosis without near occlusion
  • No benefit for near occlusion or total occlusion
  • Recommended for life expectancy >5 years and perioperative stroke/mortality risk <6%
  • Aspirin perioperative and postoperative (≥3 months)
  • Carotid artery stenting (CAS):
  • Similar long-term outcomes as CEA
  • Higher risk of stroke but lower risk of MI compared to CEA
  • Preferred in patients with unfavorable anatomy or high surgical risk
  • Dual antiplatelet therapy for 30 days post-CAS
  • Transcarotid artery revascularization (TCAR):
  • Similar outcomes to CEA
  • Avoids some CAS pitfalls
  • For asymptomatic patients, CEA preferred over CAS if surgery chosen

Admission and Nursing Considerations

  • Hospitalize acute symptomatic stenosis patients for rapid evaluation
  • Discharge after 24-48 hours post-CEA if ambulatory, tolerating PO intake, neurologically intact

Follow-up

  • Duplex ultrasound 2-6 weeks post-op, then every 6-12 months
  • Reoperation considered for rapid restenosis
  • Intensive medical therapy and follow-up for patients with renal failure, heart failure, diabetes, or age >80

Diet

  • Heart-healthy diet low in saturated and trans fats

Patient Education

  • Refer to MedlinePlus carotid artery disease resources: https://medlineplus.gov/carotidarterydisease.html

Complications

  • Untreated: TIA/stroke risk ~1.68% per year ipsilateral
  • Post-CEA: perioperative stroke, death, cranial nerve injury, hemorrhage, MI, hemodynamic instability
  • Late post-CEA: restenosis, false aneurysm

Clinical Pearls

  • Atherosclerosis causes 90% of carotid stenosis cases
  • Duplex ultrasound is best initial diagnostic test
  • Aggressive vascular risk factor management and antiplatelet therapy essential
  • CAS increases stroke risk but decreases MI risk vs CEA
  • TCAR offers promising alternative with similar outcomes to CEA

References

  1. Krist AH, Davidson KW, Mangione CM, et al; US Preventive Services Task Force. Screening for asymptomatic carotid artery stenosis: USPSTF recommendation statement. JAMA. 2021;325(5):476-481.
  2. AbuRahma AF, Avgerinos ED, Chang RW, et al. Society for vascular surgery clinical practice guidelines for management of extracranial cerebrovascular disease. J Vasc Surg. 2022;75(1S):4S-22S.
  3. Columbo JA, Martinez-Camblor P, Stone DH, et al. Procedural safety comparison between TCAR, CEA, and CAS: perioperative and 1-year stroke or death rates. J Am Heart Assoc. 2022;11(19):e024964.
  4. Moresoli P, Habib B, Reynier P, et al. Carotid stenting versus endarterectomy for asymptomatic carotid stenosis: systematic review and meta-analysis. Stroke. 2017;48(8):2150-2157.