Carotid Artery Stenosis

Narrowing of the lumen of the carotid arteries, usually caused by atherosclerosis

Incidence:

May be asymptomatic
TIA (neurological deficit lasting < 24hrs)
- Amaurosis Fugax = Temporary monocular vision loss caused by a microembolus to the ophthalmic artery
Pulsatile tinnitus
Hollenhorst Plaques = Small bright flecks in field of vision, due to emboli lodged in arterial bifurcations in the retina
Stroke
Compared with Vertebrobasilar disease → Emboli in posterior circulation → Vertigo, diplopia, dysphagia & dysequilibirum

Origin of the ICA & Carotid Sinus is prone to atherosclerosis (change in flow, turbulence & dilatation at this point)
Plaques can undergo acute disruption → Thrombus formation & 2° thromboembolism
Trigger for acute change in plaque morphology is unknown, but may be related to increased expression of MMP
High Risk Features:
- 90 - 94% Stenosis
- Irregular / ulcerated plaque

Duplex USS - 94% sensitive and specific for detecting severe stenoses
- Flow ratio (velocity) estimates stenosis
MRA
CTA
Angiography = Gold standard – 1 - 4% risk of stroke
- Absolute indications
  - Technically inadequate duplex
  - Lesion beyond carotid bulb
  - Anatomic variants
- Relative
  - Unusually high bifurcation
  - Recurrent stenosis
  - Severe fixed neurological deficit
- Other complications
  - Allergy to contrast < 2%
  - Contrast-induced nephropathy
  - Puncture site problem

Symptomatic lesions > 70%
Asymptomatic lesions > 60% if operative risk is < 3% & life expectancy is > 5%
Decreases stroke risk for symptomatic patients with > 70% stenosis from 26% → 9% at 2 years
- Some benefit in symptomatic patients with 50-69% stenosis: 22% → 15.7% risk of stroke at 5 yrs
- NNT= 6 to prevent one stroke / death
Asymptomatic lesion
- Small risk reduction for asymptomatic pts with > 70% stenosis (12% → 6%)
- ACAS North America & the European ACST
  - NNT=19 to prevent one stroke / death (*)
  - Overall: ≈ 30% risk reduction for stroke over three years (Cochrane 2005)
Semi-acute OT – after small TIA / stroke
- After small stroke in pts ASA I/II: surgery within 2-4 weeks → perioperative stroke risk = 2-7%;
but if big stroke / unstable neurological deficit / ASA III or IV → ↑ perioperative stroke risk therefore best to delay surgery by ≈ 6 weeks

Thromboendarterectomy cannot be performed when the ICA completely occluded
Coexistent coronary disease treated first
Most strokes during cardiac procedure are from atheroma in aortic arch, not low flow through carotids
Stroke risk within 30 days = 3%; death rate < 1%
- May be higher if contralateral occlusion
Possible with regional anaesthesia (superficial & deep cervical plexus block – at posterior aspect of SCM) + awake neurological monitoring with selective shunting (only use intra-op shunt in the people who start to develop neurological Sx after cross-clamping)
- Regional anaesthesia may ↓ strokes, deaths & AMIs
Shunting everyone → ↑ complication rates
Patch angioplasty (cf primary closure) may ↓ stroke & re-stenosis rates
Post-op lose cerebral autoregulation – Keep BP 100-140 Systolic – nitroprusside/ GTN
- ± Post-op dextran (500mL dextran 40 over 4-6hrs) to ↓ platelet adhesiveness
- Dextran: Polysaccharide that decreases blood viscosity

CAVATAS trial = Carotid artery & vertebral artery transluminal angioplasty & stenting: 500 symptomatic pts RCT
Stroke rate ≈ 10% in both arms
Trial also not useful because no protection device was used
SAPPHIRE = Stenting and angioplasty with protection in pts at high risk for endarterectomy: >300pts; 2/3 were asymptomatic with >80% stenosis
Similar results for high risk pts undergoing stenting vs endarterectomy – for death & stroke & for stroke rates at 3yrs
Fewer immediate peri-op complications after stenting
Results improving (esp. since the intro of cerebral protection devices)
Useful for lesions that recur after surgical treatment
CREST study: similar results as surgery; higher morbidity in pts >80yrs

Rarely used for: long segment atherosclerosis, aneurysm disease, traumatic arterial disruption, re-stenosis after endarterectomy, as part of neck resections