Carotid Disease

A

History

• 1.

  Characteristics of neurologic symptoms—can localize a circulatory impairment (see Table 56.1 for a more complete review)

  • a.

    Onset—left leg weakness and speech difficulty

  • b.

    Provoking factors—none, onset is sudden and unexplained

  • c.

    Palliative factors—none, resolves with time

  • d.

    Timing differentiates between TIA and stroke—majority of TIAs last less then 6 hours.

  • e.

    Associated symptoms

  • f.

    Pertinent negatives—denies nausea, vomiting, fevers, chest pain, or chest palpitation

  TABLE 56.1

  Relation of Neurologic Impairment with Vascular Lesion

  Symptoms	Vascular Distribution	Neurologic Distribution
  Transient monocular blindness (amaurosis fugax)
  Visual field disturbances	Retinal artery	Limited to the ipsilateral retina/eye
  Altered mental status
  Impaired judgment
  Contralateral motor weakness	Anterior cerebral artery	Cerebral hemisphere
  Loss of sensation
  Speech/language deficits
  Visual field deficits	Middle cerebral artery	Cerebral hemisphere
  Hemianopsia
  Impaired memory	Posterior cerebral artery	Cerebral hemisphere
  Dysarthria, dysphagia, diplopia
  Limb or gait ataxia
  Simultaneous motor, sensory, and visual loss	Vertebrobasilar	Brainstem, cerebellum, cerebrum

• 2.

  Medical history—risk factor assessment including hypertension, diabetes, and coronary disease

• 3.

  Surgical history

  • a.

    Three-vessel coronary artery bypass grafting 2 years ago

  • b.

    Guidelines recommend carotid evaluation in the preoperative work-up of selected high-risk potential coronary bypass patients.

• 4.

  Allergies/medications—no known drug allergies; currently taking atenolol, metformin, lisinopril, and aspirin

• 5.

  Social history—nonsmoker, quit 10 years ago; drinks alcohol socially; no recent travel

B

Physical Examination

• 1.

  HEENT (head, eyes—presence of Hollenhorst plaque does not increase the risk of TIA or stroke, ears, nose, and throat)

  • a.

    There are no carotid bruits bilaterally.

  • b.

    The presence of a carotid bruit has low sensitivity for detecting more than 70% stenosis.

  Amaurosis fugax alone is associated with the same stroke risk as a TIA.

• 2.

  Cardiovascular

  • a.

    Rate and rhythm are regular, with no murmurs.

  • b.

    Evaluate pulse and murmurs for possible cardiac sources of emboli.

• 3.

  Pulmonary—clear bilaterally

• 4.

  Abdomen—no palpable masses or audible periumbilical bruits

• 5.

  Vascular

  • a.

    Two plus carotid, radial, femoral, popliteal, and dorsalis pedis pulses bilaterally

  • b.

    A full vascular examination is important to diagnose other possible pathologic conditions, including aneurysms.

• 6.

  Neurologic

  • a.

    Cranial nerves II–XII intact. 5 of 5 strength in all upper and lower extremity muscle groups. No evidence of hyperreflexia

  • b.

    A full neurologic examination may help to identify symptoms in active stroke and localize a lesion.

C

Imaging

• 1.

  Carotid duplex ultrasound ( Fig. 56.1 )

  • a.

    Advantages

    • (1)

      Noninvasive

    • (2)

      Can give information on velocities, anatomy, and plaque morphology

    • (3)

      Can achieve high sensitivity (>75%) and specificity (>95%) if combinations of parameters are measured ( Table 56.2 ).

      • Contralateral stenosis/occlusion can falsely elevate velocities; low cardiac output can influence velocities

      TABLE 56.2

      Carotid Stenosis Velocity Criteria by Carotid Duplex Ultrasound

      Degree of Stenosis of the Internal Carotid Artery	Peak Systolic Velocity	End-Diastolic Velocity	Internal Carotid Artery/Common Carotid Artery Ratio
      Normal <50%	<125	<40	<2.0
      Between 50%–70%	125–230	40–100	2.0–4.0
      >70%	>230	>100	>4.0
      Occluded	Undetectable	N/A	N/A

  • b.

    Disadvantages: Ultrasound is limited by the following factors:

    • (1)

      Operator dependence

    • (2)

      Tortuous vessels

    • (3)

      Visualizations of proximal common carotid or intracranial branches

    • (4)

      Arterial calcification

  

• 2.

  Computed tomographic angiography

  • a.

    Advantages

    • (1)

      Anatomy of the arch—important planning for carotid stenting

    • (2)

      Demonstrates relative position of calcifications and stenosis near the carotid bifurcation

    • (3)

      Provides an estimate of the residual lumen and less likely to overestimate stenosis

  • b.

    Disadvantage—requires a contrast bolus comparable to that of angiography

• 3.

  Magnetic resonance angiography

  • a.

    Advantages

    • (1)

      Avoids nephrotoxic contrast agents

    • (2)

      May allow characterization of plaque morphology

  • b.

    Disadvantages

    • (1)

      Can overestimate stenosis

    • (2)

      Incompatible with implanted metallic devices

    • (3)

      Claustrophobia

• 4.

  Angiography—no longer the gold standard

  • a.

    Advantages

    • (1)

      Used mostly in the case of conflicting results between two other imaging techniques

    • (2)

      Evaluation of entire carotid system including collaterals and the aortic arch

    • (3)

      Necessary for patients undergoing carotid artery stenting (CAS)

  • b.

    Disadvantages

    • (1)

      Invasiveness and cost

    • (2)

      Neurologic and vascular morbidity (risk of stroke or TIA can be as high as 1.3%)

    • (3)

      Limited views

A

Atherosclerotic Disease

• 1.

  Comprises 90% of carotid occlusive disease cases

• 2.

  Anatomy influences hemodynamics—formation of plaque on lateral walls

• 3.

  Pathophysiology

  • a.

    Hyperlipidemia, hypertension, diabetes, and so on, lead to endothelial injury.

  • b.

    Monocytes driven by more low-density lipoproteins adhere to and invade the damaged endothelium.

  • c.

    Plaque size increases.

  • d.

    Increased platelet activity furthers endothelial damage.

  • e.

    Platelets stimulate intimal smooth muscle cells to secrete extracellular matrix.

  • f.

    Muscle cells accumulate lipids, and the plaque center becomes necrotic.

  • g.

    Plaque ulceration and rupture are similar to acute coronary syndrome.

B