Vascular Pathology Flashcards
What are the two main mechanisms of disease of the vasculature?
- narrowing or obstruction of the vessel lumen
2. weakening of the vessel wall making it prone to rupture
What are the three main vascular congenital anomalies?
- berry aneurysm
- arteriovenous fistulas
- fibromuscular dysplasia
What is a berry aneurysm?
A saccular outpouching of the vessel wall in the circle of Willis.
It can rupture and lead to hemorrhage and potentially death
What is an arteriovenous fistula?
In addition to being congenital, what are 3 other causes of AV fistulas?
What is it called if an AV fistula forms a mass?
Abnormal connection between an artery and vein that bypasses the capillaries and transport unused blood increasing work of the heart causing high-output heart failure.
They can be congenital or due to:
- inflammation
- trauma
- dialysis
If the AV fistula forms a mass, it is called a AV malformation.
What is fibromuscular dysplasia?
What are the two main arteries where it occurs?
What are the outcomes?
Segmental thickening of the muscular layer of medium and large muscular arteries (renal and carotid) due to fibrosis and hyperplasia of the intima and media.
It can lead to secondary hypertension if it occurs in the renal arteries.
What are the6 major products of endothelium?
- anticoagulants (prostacyclin) and antithrombotics (thrombomodulin)
- PROthrombotic- thromboxane, vWF
- ECM
- substances to modulate flow (vasoconstrictors like endothelin and dilators like NO)
- factors that regulate immunity (VCAM, IL1 ICAM)6. factors that inhibit and stimulate growth
It also oxidizes LDL
What are things that can damage endothelium?
In the case of endothelium damage or dysfunction, what is stimulated to migrate from the media into the intima? What is the result?
Infection, trauma, inflammation, immune injury, toxic exposure
Smooth muscle cells migrate into the intima, become proliferative and synthetic and make ECM thickening the intima.
What is arteriosclerosis?
What are the 3 main forms (using the old classification scheme)?
It is the hardening of the arteries (thickening and loss of elasticity of the vessel wall).
- atherosclerosis
- arteriosclerosis
- Monckeberg medial calcification
What is Monckeberg medial calcification?
What are the 2 arteries it affects most?
Who does it affect?
When the media of the muscular arteries is filled with calcified deposits 1. Radial 2. Ulnar In individuals over the age of 50. It RARELY causes stenosis
What are the two main types of arteriosclerosis?
- Hyaline
2. hyperplastic
What are the 5 classifications of arteriosclerosis according to Robbins?
- atherosclerosis
- primary arterial calcification (Monckeberg and internal lamina calcifications)
- fibrinomuscular intimal thickening (dysplasia and hyperplastic)
- arterial hyalinosis
- oxalosis and amyloidosis
4.
What is atherosclerosis?
What is it composed of?
Where in the world is it seen most frequently?
formation of atherosclerotic plaques in the intima.
The plaque is an eccentric mass composed of fibrous cap and lipid/necrotic core.
It protrudes into the lumen and blocks blood flow
It is seen in developed nations
What are the three categories of risk factors for atherosclerosis?
- major and modifiable
- major and non-modifiable
- uncertain risk
What are the 3 major non-modifiable risk factors for atherosclerosis?
- Age- plaques present around 40-60yrs
- Sex- males are at greater risk until females reach menopause and then the risk is relatively equal (or females may surpass)
- Genetics- multifactorial disease but associated with familial hypercholesterolemia (atherosclerosis sequelae by 20 years)
What are the 4 major modifiable risks for atherosclerosis?
- Diabetes- hypercholesterolemia to increase risk of ischemic heart disease by 2x
- Hyperlipidemia- LDL(eggs/animal fats) delivers cholesterol to tissue and is bad. HDL(exercise/alcohol) removes it from tissue.
- Smoking - ischemic heart disease by 200%
- Hypertension - increase risk of ischemia by 60%
What are “other risks” for atherosclerosis (5)?
- Elevated C-reactive protein
- Lipoprotein A
- Elevated procoagulants
- Hyperhomocysteinemia
- Metabolic syndromes
What is C- reactive protein?
An acute phase reactant that is a marker for the role of inflammation in the development of atherosclerosis plaques.
(MI, stroke, peripheral vascular disease)
What is lipoprotein A?
It resembles plasminogen so competitively inhibits the activation of plasmin allowing thrombosis to occur
Describe the process of formation of an atherosclerotic plaque?
- Endothelium gets injured
- Increased permeability, leukocyte adhesion
- monocyte adhesion and migration to intima
- Macrophages engulf oxidized lipoproteins and form the lipid core of the plaque
- Platelets adhere and contribute to the thrombus
- Platelets, macrophages and endothelial cells recruit smooth muscle cells from the intima to proliferate and secrete ECM
What are the 2 major pieces of evidence for the role of hemodynamic disturbance in endothelial injury?
- Atherosclerotic plaques commonly form at points of bifurcation and Ostia where there are altered flow patterns
- non-turbulent laminar flow induces atherosclerotic-protective genes
What are the 4 major causes of hyperlipidemia?
- increased dietary LDL
- decreased serum HDL
- familial dyslipoproteinemias
- secondary to alcoholism or DM
What does hyperlipidemia lead to?
It increases production of ROS that can:
- inactivate NO (a vasodilator)
- oxidize LDL which will accumulate in the intima to be taken up by macrophages to accumulate in the clot and be toxic to endothelial cells and smooth muscle cells
What is the role of inflammation in endothelial cell injury and plaque formation?
When inflamed, endothelial cells express vascular cell adhesion molecules to bind monocytes which: 1. become macrophages in the intima to engulf lipid
2. produce ROS
3. increase production of oxidized LDL
They also bind T cells which :
1. secrete cytokines to activate macrophages, endothelial cells and smooth muscle cells
What infectious agents have been found in plaques but not normal vessels?
- herpesvirus
- CMV
- Chlamydia pneumoniae
What signals stimulate smooth muscle cells to migrate from the media to the intima to proliferate and secrete ECM?
What else do smooth muscle cells do besides thicken the intima?
PDGF, FGF, TGFa
They engulf LDL
Secretion of ECM, mainly ________ by smooth muscle cells, helps promote plaque growth and expansion from ______ to ____________.
mainly collagen
Fatty streak –> atherosclerotic plaque
Describe the morphology of a fatty streak.
Linear, slight intimal elevations filled with lipid-laden foam cells
They appear in the aorta as young as 1 year old
What are the three components of an atherosclerotic plaque?
- cells (macrophages, T cells, smooth muscle cells)
- ECM (collagen, elastic fiber, proteoglycans)
- lipid (intracellular and extracellular)
What are the three principal areas of the atherosclerotic plaque?
- fibrous cap
- shoulder (slightly more cellular)
- lipid/necrotic core
What do plaques have that make them especially susceptible to hemorrhage?
neovascularization that can hemorrhage, rupture and form thrombus
What are the acute changes in a plaque?
- rupture
- ulceration
- erosion
- hemorrhage
- embolism
If a plaque ruptures and exposes the necrotic core, why is this a problem?
The core is thrombogenic meaning that it will promote thrombogenesis and occlude the vessel more
If there is hemorrhage in the atherosclerotic plaque, what are two potential outcomes?
- acute expansion of the plaque can cause rupture and acute thrombosis
- the hemorrhage can resolve but contribute to the size of the plaque (chronic)
What are chronic changes that can occur to an atherosclerotic plaque?
pressure of the plaque on the intima causes atrophy and weakening of the media which can lead to:
- aneurysm
- rupture
- hemorrhage
Chronic changes in plaque size are due to what?
Acute changes in plaque size are due to what?
Chronic- increasing accumulation of LDL and continued collagen production and/or hemorrhage resolution
Acute- thrombosis or hemorrhage
What is the critical degree of stenosis that must occur for an atherosclerotic plaque to cause symptoms?
> 70-75% obstruction of the vessel