Stenosis in Carotid Circulation Treatment by Stent or CEA

Flow

Flow occurs primarily because of energy gradients but observed as pressure gradient or differences in pressures.

an energy gradient

higher pressure  to lower pressure

greater the pressure gradient, the greater the flow rate.

the relationship among...

Pressure, viscosity and flow

the radius

Direct

Both increase together.

Inverse relationship

When one decrease, the other increases.

Inverse

When one decreases the other increases.

• Radius decreased?    YES
• Resistance?              YES
• Pressure gradient?    YES
• Velocities?                YES

Diameter reduction of =   50%

Area reduction of =     75%

diameter reduction

• That's why Doppler measuring velocities is important. Can get velocity measurements after stenosis. If higher velocities than larger stenosis. If lower velocities smaller stenosis.
• Still there even if can't visual see well.

B-mode is the most appropriate method to see degree of narrowing

1st- visualize the plaque in the transverse section.

It is possible to overestimate and underestimated eccentric disease when imaging in longitudinal section.

• ICA/CCA PSV ratio
• ICA/CCA EDV ratio

• ICA PSV- use the highest PROX, MID, DIST
• ICA EDV-
• CCA PSV- use DIST CCA

Need to document.

• 1.) the PSV and EDV don't fall in the same category.
• 2.) Presence of tandem lesions.
• 3.) Contralateral high-grade stenosis
• 4.) Discrepancy between visual assessment of the plaque and ICA PSV.
• 5.) Elevated CCA velocities- from older age.
• 6.) Hyperdynamic cardiac states
• 7.) A person may have poor CO, therefore have a low CCA velocities

Always do a bilateral carotid so you have both sides to compare.

Check hospital or clinic protocol.

1.) North American Symptomatic Carotid Endarterectomy Trial (NASCET)

2.) Asymptomatic Carotid Atherosclerosis Study (ACAS)

Have changed the way many interpret and report carotid duplex examinations.

ECST

European Carotid Surgery Trialists' Collaborative GRoup

1.) NASCET- North American Symptomatic Carotid Endarterectomy Trail

2.) ECST- European Carotid Surgery Trailists' Collaborative Group

Stenosis or occlusion in PROX Lt. Subclavian A. before Vertebral A takeoff.

In the Vertebral A. - May see To-Fro flow or Retrograde flow.- Need to do exercise like reactive hyperemia.

Waveform will be monophasic in subclavian

• Symptoms? Usually asymptomatic.
• If symptoms- Vertebrobasilar

1.) Supraorbital A.

2.) Frontal A.

3.) Nasal A. - Angular A. - Facial A. - ECA

Towards

1.) Supraorbital A.

2.) Frontal A.

MCA is more dominate.

ICA and CCA

1.) crypts

2.) overhanging

3.) swirling color flow

High resistance flow

1.) How long?

2.) How far is the dissection?

3.) How is the flow in both the lumens?

when carotid arteries have an unusual shape.

• 1.) looped or coiled
• 2.) Kinked
• 3.) C-shaped
• 4.) S-shaped

• 1.) Atherosclerosis
• 2.) History
• 3.) Increased cholestrol
• 4.) Smoking/tobacco use
• 5.) Age
• 6.) Sedentary lifestyle
• 7.) Unhealthy diet

• 1.) movement of blood
• 2.) velocity of blood
• 3.) turbulence
• 4.) direction of blood flow
• 5.) amplitude

pressure and velocity have inverse relationship

Pressure- decrease

Velocity- increases

Pressure- increase

Velocity- decrease

May not have velocity changes.

Need to go off appearance to get percentage of stenosis and not velocities for classification.

• Used instead of CEA when...
• 1.) Patients are a high risk with coronary, pulmonary or renal diseases.

2.) Used when the atheroma extends beyond the accessible surgical field.

Prox stent

Mid stent

Dist stent

Can be normal.

• 1.) Clamping off ICA, ECA, and CCA.
• 2.) Sense cerebral circulation can be compromised a temporary plastic shunt can be used.
• 3.) Use of TCD to measure MCA blood velocity to see if shunt is failure.
• 4.) Vein or prosthetic patch may be used to close the site of the endart.

1.) slightly dilated bifurcat

A prosthetic patch will appear brighter.

Rupture

infection