Vascular Pathophysiology Flashcards
What are the characteristics inside an artery with stenosis?
Arterial stenosis creates focal acceleration of flow and distal turbulence proportional to severity.
A tighter stenosis creates ____ turbulence.
More
What are the characteristics of critical stenosis?
Critical stenosis causes reduction of flow and pressure distally.
Plaque is a ____ disease, not localized.
Systemic
What is the true indicator of the severity of stenosis?
Area
Why do we use diameter reduction rather than area reduction when diagnosing a stenosis?
Because you use the diameter in Angiography, and angio is the gold standard.
In angiography you don’t see vessel walls, you just see ____.
Flow
50% stenosis by diameter = __% stenosis by area.
75%
80% stenosis by diameter= __% stenosis by area.
96%
Pressure and flow will maintain until about __% stenosis by diameter.
50%
Significant stenosis causes a loss of energy in the form of what?
Heat
Significant stenosis causes a loss of energy in the form heat due to what?
- Change from potential to kinetic energy and back
- Distal turbulence dissipating energy in the form of heat
- High resistance collaterals use up energy
What is turbulence?
Chaotic flow: has many directions and many velocities (especially lower velocities)
What is the characteristic of turbulence on spectral waveform?
Spectral broadening- filling in of the systolic window.
Degree of turbulence is ____ to the severity of stenosis.
Proportional
____ ____ of velocity suggests >50% stenosis.
Focal doubling
Any significant stenosis should have what 2 things?
- focal acceleration
2. distal turbulence
These are existing vessels that carry more flow than usual and/or flow in retrograde to compensate for loss of flow from a main line artery.
Collaterals
Collaterals are brought about by what?
Abnormal pressure gradients
What is a subclavian steal?
It occurs when the proximal subclavian artery is occluded, causing low pressure in the left arm. Thus flow is drawn retrograde down the vertebral artery.
If a 10 mm native artery was occluded how many 2.5 mm collaterals would it take to compensate for its loss?
256
What is edema and how is it caused?
Edema is a build up of fluid in interstitial space and it is caused by excess venous pressure.
Fluid flows from an area of ____ pressure to an area of ____ pressure.
High to low
How does abnormally high intravenous pressure cause edema?
The osmotic gradient at the venular end is upset, preventing resorption of fluid, so the fluid stays in the interstitial space causing edema.
Name the 2 big vascular enemies.
- plaque
2. clot
What could be a cause of too much pressure in the veins?
Prolonged standing/sitting- too much blood pools in LEs. It helps to some calf activities.
How many mmHg of hydrostatic pressure is at the bottom of the calfs, what helps to break up this pressure?
90-100 mmHg, venous valve help to break up the column of fluid.
Venous stasis and ulcers are secondary to what?
Venous hypertension
What is a common site for venous ulcers?
Gaiter area by the malleolus/ ankles
What is osmosis?
The diffusion across a semipermeable membrane from an area of low concentration to an area of high concentration.
The osmotic gradient is created by what?
Plasma proteins
Carotid disease can lead to ____, the 3rd leading cause of death.
Stroke
2 types of strokes
- Ischemic
2. Hemorrhagic
Ischemic Stroke
Lack of oxygen and blood flow (majority of strokes are ischemic)
Hemorrhagic Stroke
Bleeding out into cranium causing pressure to build. Caused by aneurism or injury.
2 Ischemic subcategories
- Hemodynamic lesion
2. Embolic lesion
Hemodynamic lesion
plaque is tight enough that it reduces blood flow at the site (severe stenosis at the site).
Embolic lesion
Erosion of plaque cause emboli to enter into cerebrocirculation.
Plaques are ____ tissue- can be thought of as a form of cancer.
Living tissue
Thrombus usually refers to ____, whereas plaque refers to ____.
Thrombus= veins Plaque= arteries
What are the 4 classifications of plaque?
- fatty streak
- fibrous (soft)
- dense (calcific)
- complicated
What are the characteristics of fatty streak plaque?
Foam cells/ cholesterol along the vessel wall.
What are the characteristics of fibrous plaque?
It is soft, and produces a dark echo.
What are the characteristics of dense plaque?
it is hard and calcific, producing bright echoes with acoustic shadowing.
What are the characteristics of complicated plaque?
It is heterogeneous, having a different composition throughout. It is more likely to ulcerate and cause stroke.
What are the common grades of stenosis?
80%) severe
Total occlusion
Amaurosis fugax
temporary blindness in one eye (carotid territory)
Hemiparesis
weakness in one side (carotid territory)
Hemiplegia
loss of function in one side (carotid territory)
Hemiparesthesia
one-sided tingling sensation (carotid territory)
Dysphagia/ Aphasia
slurred or absence of speech (carotid territory)
Homonymous Hemianopia
loss of 1/2 the visual field in both eyes (carotid territory)
Carotid territory Sx’s are ____, they are referable to ____ hemisphere.
They are lateralizing Sx’s referring to one hemisphere
Diplopia
binocular vision disturbance (vertebrobasilar territory)
Syncope
loss of consciousness (vertebrobasilar territory)
Vertigo
dizziness, spinning sensation (vertebrobasilar territory)
Nausea
uneasiness of the stomach, feeling queasy (vertebrobasilar territory)
Ataxia
loss of coordination (vertebrobasilar territory)
Vertebrobasilar territory Sx’s are more ____, non-lateralizing. They can often suggest ____ circulation problems.
Sx’s are more vague, can suggest posterior circulation problems.
What did the NASCET study suggest?
It suggested endarterectomy reduces stroke risk significantly in Pt’s with >70% stenosis.
Where the 4 common sites for lower extremity ASO (arteriosclerosis obliterans) ?
- Aortoiliac bifurcation
- CF bifurcation
- adductor canal
- origins of tibials
What is ASO?
An occlusive arterial disease most prominently affecting the abdominal aorta and the small- and medium-sized arteries of the lower extremities.
What is the most common site of ASO?
SFA (mid to distal thigh) in adductor canal
What are the stages of Sx for ASO?
Asymptomatic > claudication > rest pain > ischemic ulcer > gangrene
What is claudication?
Pain with exercise relieved by rest.
What is rest pain?
continuous, unrelenting ischemic pain. Usually at toes and feet. (similar to angina in the heart)
What causes ulceration?
usually caused by injury, it takes much more perfusion to heal tissue than just to sustain it. (Pts with ulcers tend to have thickened toe nails and flaky skin)
What is gangrene?
tissue death due to ischemia.
Claudication is ____ pain, whereas rest pain is ____ pain.
claudication is muscle pain.
rest pain is tissue pain.
Name some risk factors for atherosclerosis.
Age, hypertension, smoking, diabetes, family Hx, hypercholesterolemia, male sex, etc.
__% of diabetics die from atherosclerotic death.
75%. Diabetes is devastating to the circulatory system, especially small vessels.
