Atherosclerotic pathology and supra-aortic stenosis

The stenosis of the supra-aortic arteries are common, with their incidence being directly related to age and cardiovascular risk factors.

Their main complications are the occurrence of ischemic strokes. They are also an important marker of coronary artery disease risk.

Occlusive lesions of the internal carotid arteries

Complications and risks

• Ipsilateral stroke: causes ~10% of strokes
• Indicate a major risk of cardiovascular events. Therefore, a full cardiovascular assessment is justified in the event of their discovery, even incidentally.

Determining factors: symptomatic nature and degree of stenosis

Symptomatic nature

The definition of symptomatic stenosis is solely based on the clinical occurrence of vascular events in the ipsilateral carotid territory (not on silent infarcts incidentally detected by imaging):

• Strokes in the territories of the MCA, ACA, and anterior choroidal arteries
• Retinal vascular events (amaurosis fugax ++)

Additional examinations to assess the degree of stenosis

This assessment requires two concordant non-invasive methods. In case of discrepancy and possible surgery, conventional arteriography is necessary.

Doppler ultrasound = duplex of the neck vessels

Good sensitivity for detecting stenosis > 70%, operator-dependent, no accepted criteria to specify the degree of stenosis, the presence of calcifications can underestimate stenoses → good for screening and follow-up.

Magnetic resonance angiography (MRA)

→ request time-of-flight imaging and gradient-echo imaging with gadolinium injection → sensitivity/specificity comparable to angiography. Possible overestimation of stenoses (turbulence causing excessive signal loss), does not visualize calcifications/surface lesions of plaques.

Spiral computed tomography (angio-CT scan)

Alternative to MRA if unavailable. Less reliable for mild stenoses, does not assess the impact on intracranial flow.

Conventional arteriography

Former gold standard. Still indicated in case of discrepancy among other tests.

Treatments

Medical

• Short-term prevention:
  • Aspirin 160-300 mg/day + statin in case of stroke reduces the risk of recurrence.
  • No evidence-based medicine (EBM) for anticoagulation… however, heparin at isocoagulant doses (100 UI/kg/day) is sometimes used in case of stenosis with TIA/minor stroke before surgery.
• Long-term prevention:
  • Asymptomatic stenosis → no EBM, but aspirin 80-160 mg/day + statin (proven effective for coronary event prevention).
  • Symptomatic stenosis → see stroke

Surgical / endovascular

Indications to be considered on a case-by-case basis (stroke risk vs. surgical risk).

• Theoretical indication (NASCET study): symptomatic stenosis > 70%
• Uncertain indications (to discuss): symptomatic stenosis 50-69% and asymptomatic stenosis > 60% with a life expectancy greater than 5 years.
• A (sub)-occluded carotid artery is generally not surgical (possible bypasses to be discussed case-by-case if the Willis polygon has poor compensation with hemodynamic incidents).
• Endovascular treatment can be considered an alternative to surgery in specialized centers (if the mortality and stroke rate is < 3% for asymptomatic patients and 6% for symptomatic patients).
• For symptomatic patients, the intervention should take place as soon as possible, within 2 weeks.

A cerebral event rather than a retinal event and the presence of a carotid occlusion are factors that favor surgery.

Prefer locoregional anesthesia (superficial and deep cervical blocks + maxillary branch of V). Surgical techniques: conventional endarterectomy/eversion/with ICA reimplantation, ACP/ICA bypasses (exceptional).

Occlusive lesions of the brachiocephalic trunk

Uncommon. An occlusive lesion may result in transient vertebrobasilar ischemia (++ nonspecific balance disorders). An ulcerated lesion may result in strokes/retinal events. In case of intervention, prioritize endovascular stenting for trunk lesions (consider surgery - ascending Ao bypass/distal part of the BCA - for ostial lesions).

Occlusive lesions of the common carotid artery

Usually juxta-ostial (extension of atherosclerosis from the aortic arch) and rarely symptomatic (++ incidentally discovered during screening). When treatment is considered, it is usually endovascular.

Occlusive lesions of the subclavian arteries

Typically located in the pre- or juxtavertebral segment of the subclavian artery. Variable symptoms: significant blood pressure asymmetry, rare ischemia of the upper limb, vertebrobasilar ischemia if bilateral lesions,… Embolic strokes are rare but require rapid intervention. Intervention is indicated only if symptomatic (spontaneous evolution of asymptomatic lesions is generally favorable) → surgery (prevertebral subclavian reimplantation onto the ACP) >> endovascular treatment.

Occlusive lesions of the vertebral arteries

These lesions are very common… but there is currently no evidence of the effectiveness of intervention. Ostial lesions are considered generally benign, whereas distal lesions pose a higher risk of vertebrobasilar strokes. There is a risk of progressively disabling vertebrobasilar ischemia (++ hemodynamic) in case of bilateral lesions or lesions with hypoplasia (considered a physiological variant) of the contralateral vertebral artery.

It is important to note that vertebral artery caliber asymmetry or a hypoplastic vertebral artery are common "normal variants" often confused with stenotic lesions on radiological grounds.

Endovascular treatment is recommended for vertebral artery stenosis > 50% and ischemic stroke related to the lesion, recurring despite optimal medical treatment.

Bibliography

EMC, traité de chirurgie vasculaire, Elsevier, 2018