Collateral Circulation Flashcards
____% of cardiac output supply the brain
15%
___% CCA blood goes to the ICA
80%
*The most common collateral pathway involves (1)
The circle of Willis
*What is the second most important route of collateral flow?
Peri-orbital circulation
Peri-orbital branches of the ICA (3)
Can communicate with (2)
Peri-orbital branches:
- Frontal A
- Supraorbital A
- Nasal artery A
Communicate with:
- Superficial temporal A
- Facial A
The intracranial-extracranial anastomoses occur between (2)
Orbital branch of superficial temporal (ECA branch)
+
Opthalmic A (ICA branch)
Only ____% of patients have complete Circle of Willis
50%
What are the 3 major collateral routes
Circle of Willis
Posterior cerebral circulation
ECA branches
Some patients don’t reveal any symptoms of cerebrovascular disease even with total occlusion of both ICAs
True -
How do collaterals develop?
Because of a change in pressure gradient between the vessels caused by a stenosis
Cellular death can occur in _____ mins
3-8 mins
In hemodynamics, what is the most limiting?
Width - poiseuille’s law
Will blood take a long wide path or a short narrow path?
Long & wide
Adequate arterial perfusion relies on (3)
Blood pressure
Cardiac output
Blood volume
The vertebral-basilir system provides how much cerebral blood flow
20-30%
Normal Vertebral A flow:
velocity & waveform
Low resistant, monophonic, large EDV
20-60 cm/s
What is the least likely level for VA to be diseased?
Mid portion
What side VA is more commonly larger?
Left more common than right
Vertebral flow:
Abnormal traits &
What can this imply (2)
High resistant flow with no diastolic waveform
Implies: distal VA stenosis/occlusion, hypoplastic VA
S/S VA disease (2)
Dizziness & unsteady walking
What side is SSS most commonly seen?
Left side
what arteries can SSS involve? (3)
RT subclavian A
LT subclavian A
INN A
What will you see with SSS? (Describe SCA, Brachial A, VA)
-SCA high PSV >500 cm/s Short low-resistant path becomes high resistant due to narrowing Loss of tri-phasic signal Aliasing Damped flow distally (monophonic)
- Decreased ipsilateral (same side) brachial artery systolic BP - (20-40 mmHg pressure difference between arms)
- Reversed flow ipsilateral VA to supply the arm
