Carotid Artery DiseaseCarotid Artery Disease

Lenore C. Ocava, MD

Vascular Neurology

AECOM/Jacobi Medical Center

Anatomy: Transverse Aortic Arch

Brachiocephalic trunk or Innominate Artery (1) R common carotid artery R subclavian artery

Vertebral artery Left common carotid Artery (2) Left subclavian artery(3)

L vertebral artery

True in about 70% Common variant: L CCA

originating from innominate artery

12 3

Anatomy: Common Carotid Artery

Located anterolaterally in the neck and medial to the jugular vein

The carotid artery, jugular vein, and vagus nerve are enclosed in connective tissue - carotid sheath

Terminates as the carotid bifurcation Internal carotid artery (ICA) and External carotid artery (ECA) At the vicinity of the superior

border of the thyroid cartilage or approximately at the level of C4

Bifurcation has been described to be as low as T2 and as high as C1.

External Carotid Artery smaller of the two terminal

branches of the CCA Has 8 branches : the superior

thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, and the terminal branches, the superficial temporal, and the internal maxillary artery.

The abundant number of anatomoses between the branches of the ECA and the intracranial circulation provides important collateral pathway for cerebral perfusion when significant disease is present in the ICA

Internal Carotid Artery

The larger of the CCA terminal branches

Divided into 4 main segments: Cervical

begins at the CCA bifurcation and extends to the base of the skull

normally has a slight dilation, termed the carotid bulb and/or the carotid sinus

usually does not have branches

Petrous - inside the petrous part of the temporal bone

Internal Carotid Artery Cavernous

invested within the cavernous sinus

situated between the layers of the dura mater of the cavernous sinus, but covered by the lining membrane of the sinus

Cerebral – begins after the artery perforates the dura matter, passes between the optic and oculomotor nerves, then proceeds to the terminal bifurcation into

The Circle of Willis

Formed by branches from paired carotid (anterior circulation) and vertebral (posterior circulation) arteries the posterior cerebral,

posterior communicating, internal carotid, anterior cerebral, and anterior communicating arteries on each side

Allows for “collateral flow” in the setting of atherostenosis or occlusive disease

Carotid Artery Disease

Vascular layers: adventitia, intima, media

Carotid disease is mostly due to atherosclerosis buildup of cholesterol and fibrotic tissue in the arterial wall

results from both genetic and environmental influences

Caucasians – cervical carotid disease

Ethnic minorities – intracranial atherostenosis

Other uncommon causes: dissection, vasculitis, fibromuscular dysplasia

Evaluation of Patients with Carotid Disease - History

Useful information: vascular risk factors focal neurologic deficits transient monocular blindness

Likely unrelated events Syncope headache or pain*

*except in dissection

Evaluation of Patients with Carotid Disease – Carotid Artery Bruit

Classic recommendation: assess for the presence of a bruit (CAB – carotid artery bruit)

Questions: Does a detectable CAB indicate the presence

of a significant lesion? Does the absence of a CAB preclude the

presence of a significant lesion? Will the presence of a CAB change further

investigation and disposition?

Evaluation of Patients with Carotid Disease – Carotid Artery Bruit

Hemodynamically significant stenotic lesions may exist in the absence of an audible bruit.

The absence of CAB may also signify complete occlusion of the carotid artery.

CAB assessment has a sensitivity of 63%-76% and specificity of 61%-76% for clinically significant stenosis*

Irrespective of the detection of a CAB in patients with possible vascular events, most authorities would still recommend imaging studies.

* Using 70%-99% stenosis on a carotid angiogram as a gold standard threshold

Evaluation of Patients with Carotid Disease – Imaging Studies

Available Options Carotid duplex US

Non invasive, virtually without complications

Readily available and quick to do

Sensitivity ~70% when compared with angiography

CT angiogram – CT with IV contrast, very thin sections

Good resolution but requires expertise for interpretation

Readily available and quick to do

Complications associated with IV dye

MR angiogram Good resolution but requires

expertise for interpretation Readily available (except in

Jacobi) and relatively quick to do

Claustrophobia-inducing machine patient required to lie still for about 20-30 minutes

Digital subtraction angiography gold standard Invasive Complications related to IV

dye 1% stroke risk associated with

the procedure

Carotid Duplex Ultrasound

The degree of stenosis is determined by the velocity of blood flow through the artery

the higher the velocity, the greater the degree of stenosis

Carotid Duplex Ultrasound

Color doppler can demonstrate the area of stenosis with increased flow ( blue/ yellow flow

pattern in this image)

B-mode can demonstrate the walls of the vessel and the area of stenosis

Carotid Duplex Ultrasound

Can identify other pathology.

Carotid artery dissection - the "false“ channel (yellow-orange) is show, distinct from the normal lumen (red).

Carotid Duplex Ultrasound: Interpretation

Carotid Duplex Ultrasound: Interpretation

<50% stenosis PSV < 125 cm/sec

50-79% stenosis PSV>125 cm/sec

80-99% stenosis EDV>140 cm/sec

>70% stenosis ICA/CCA (PSV) >4

Occlusion Absence of flow

with contralateral ICA occlusion: ICA flow velocity may be falsely elevated

Other important information: extent of the plaque plaque

characteristics patency of the distal

ICA

CT Angioram

Using a 70% cutoff value for stenosis, CTA compared to DSA agreement in 96% of

cases sensitivity 100% specificity 63% negative predictive value

was 100% Interobserver agreement

was higher for CTA-measured stenosis than for DSA-measured stenosis

Neurology. 2004;63:412-413, 457-460

CT Angioram

MR Angiogram 70% to 99% ICA stenoses

Time-of-flight MRA

Sensitivity 91.2% Specificity 88.3%

Contrast-enhanced MRA

Sensitivity 94.6% Specificity 91.9% ICA occlusion

Time-of-flight MRA

Sensitivity 94.5% Specificity 99.3% Contrast-enhanced MRA

Sensitivity 99.4% Specificity 99.6% Moderate (50 to 69%) stenoses

Time-of-flight MRA

Sensitivity 37.9% Specificity 92.1% Contrast-enhanced MRA

Sensitivity 65.9% Specificity 93.5% Stroke. 2008;39:2237-2248

MR Angiogram

LR

Digital Subtraction Angiogram

Treatment Strategy #1 stabilize or halt the progression of the carotid plaque

Risk Factor Target Comment

Hypertension SBP <140 and DBP <90.For patients with diabetes, SBP<130 and DBP <85

Use of ACEIs should be encouraged

Diabetes FBS < 126 mg/dL Diet and oral hypoglycemic agents or insulin as needed

Elevated lipid levels LDL <100 mg/dL AHA step II diet (<30% fat, <7% saturated fat, < 200mg chol/d) Statin therapy if lipid levels remain elevated

Cigarette smoking Stop smoking Counseling, specific therapies

Alcohol use Eliminate excessive use Mild to moderate use (1-2 drinks per day)

Physical activity 30-60 minutes of exercise at least 3x per week

Treatment Strategy #2 eliminate or reduce carotid stenosis

Treatment Strategy #2 eliminate or reduce carotid stenosis Carotid endarterectomy (CEA) – treatment of

choice Other procedures

EC-IC bypass: not beneficial (1980’s) Currently being revisited - Carotid Occlusion Surgery

Study (COSS) • aims to identify a subgroup of patients with carotid occlusion

that may benefit from EC-IC bypass• ipsilateral increased oxygen extraction fraction (OEF) measured

by positron emission tomography (PET) Carotid angioplasty and stenting

trials and case series have shown that the outcomes of stenting are worse than or no different from those of carotid endarterectomy

Current use limited to patients with high surgical risk preventing the performance of CEA

Symptomatic Carotid Stenosis

>70% stenosis 2 rate of ipsilateral stroke: 26% in the medical

group and 9%in the surgical group* Relative risk reduction 65%* Absolute risk reduction 17%* NNT 7-8 (# patients who would need to

undergo endarterectomy to prevent one stroke in a 5-year period)**

*,**North American Symptomatic Carotid Endarterectomy Trial (NASCET), the **European Carotid Surgery Trial (ECST), and the trial by the Veterans Affairs Cooperative Studies Program

Symptomatic Carotid Stenosis

<50% stenosis trials showed that there was no significant

benefit of surgery. in NASCET, there was no significant difference

in the risk of ipsilateral stroke between those who were treated with endarterectomy and those who were treated medically

North American Symptomatic Carotid Endarterectomy Trial (NASCET), the European Carotid Surgery Trial (ECST), and the trial by the Veterans Affairs Cooperative Studies Program

Symptomatic Carotid Stenosis

Moderate stenosis, 50 to 69% In ECST, there was no significant benefit of

surgery for those with moderate stenosis.

In NASCET, the 5-year risk of fatal or nonfatal ipsilateral stroke among patients was 22.2% in the medical group and 15.7% in the surgical group

Absolute risk reduction 6.5% NNT 15

North American Symptomatic Carotid Endarterectomy Trial (NASCET), and the European Carotid Surgery Trial (ECST)

Patients with symptomatic moderate grade stenosis with greatest benefit from CEA

more severe stenosis 75 years of age and older men patients with a recent (within 3 months) history of stroke

(rather than transient ischemic attacks) as the qualifying event

patients with hemispheric TIAs rather than transient monocular blindness

radiographic factors: the presence of intracranial stenosis, the absence of microvascular ischemia, and the presence of collateral vessels

operative risk experience of the surgeon

Asymptomatic Carotid Stenosis

the risk of stroke is lower than that associated with symptomatic disease

In observational studies, the rate of ipsilateral stroke was 1 to 3% per year among patients with asymptomatic stenosis of greater than 50%

the risk in NASCET was 3.2% per year for asymptomatic stenosis of 60 to 99%

Asymptomatic Carotid Atherosclerosis Study (ACAS) - >60% stenosis

The risk of ipsilateral stroke or any perioperative stroke or death was 5% during 5 years of follow-up in surgically treated patients and 11% in medically treated patients. Absolute risk reduction (ARR) 6% NNT 17

Because of the lower ARR, a rate of perioperative complications (stroke or death) of more than 3% would eliminate the potential benefit of the operation

The benefit of surgery was greater for men than women (reduction in risk, 66% vs. 17%)

The rate of perioperative complications was higher among women than men (3.6% vs. 1.7%).

Risk and Benefit of CE in Women With Symptomatic Carotid Artery Disease

With 70% stenosis, the 5-year absolute risk reduction (ARR) in stroke from CE was similar between women (15.1%) and men (17.3%). 30-day perioperative risk of death was higher in women

than in men (2.3% versus 0.8%) Higher perioperative risk of stroke and death was also

observed in women (7.6% versus 5.9%) but not statistically significant.

With 50% to 69% stenosis CE was not beneficial in women (ARR=3.0%), contrary

to men (ARR=10.0%). Medically treated women had low risk for stroke

Stroke. 2005;36:27 Data from NASCET and ACAS

Challenging the Results From ACAS and NASCET Observational study

(Southern Illinois University School of Medicine ) 21-year period 1,204 CEAs performed

464 (39%) in women

739 (61%) in men Complete follow-up

was available in 70% of patients.

Results Surgical death rates were

nearly identical for asymptomatic and symptomatic patients.

Perioperative stroke rates were similar for asymptomatic and symptomatic patients.

Life-table stroke-free rates at 1, 5, and 8 years were similar for asymptomatic women and men and symptomatic women and men.

Ann Surg. 2001 October; 234(4): 438–446

stroke-free survival rates at these follow-up intervals were greater for asymptomatic women compared with men, and for symptomatic women compared to men

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