Pathoma- Arteriosclerosis, Aortic Dissection, Aneurysm Flashcards
What is aortic dissection?
Intimal tear with dissection of blood through media layer of aortic wall
What are the modifiable risk factors for atherosclerosis? (4)
Modifiable risk factors:
1) HTN
2) Hypercholesterolemia (high LDL)
3) Smoking
4) DM
Where does aortic dissection most commonly occur? Why?
Proximal 10 cm of aorta because this is a high stress region, in which there is lots of pressure for the blood to rip through the media.
What are the 4 complications of atherosclerosis?
1) Stenosis of medium sized vessels (that supply end organs) → imapired blood flow and ischemia resulting in: peripheral vascular disease, angina, ischemic bowel disease.
2) Plaque rupture with thombosis → atherosclerotic emoboli
3) Weakening of vessel wall → aneurysm
4) Plaque rupture with thombosis → MI (coronary arterier) and stroke (eg middle cerebral artery)
What are the 2 types of arteriolosclerosis?
Hyaline arteriolosclerosis, Hyperplastic arteriolosclerosis
What is the gross appearance of glomerular scarring?
Shrinkage of kidney with scarring on the surface
In hyaline arteriolosclerosis, what is seen on microscopy and why
Vascular thickening with pink hyaline, which are the proteins that have leaked into the vessel wall
How do Monckeberg Medial Calcific sclerosis present clinically and why
Bc the calcification is nonobstructive, it doesn’t alter lumen caliber and doens’t alter blood flow; as a result, is not clinically significant
Common arteries that are most susceptible to atherosclerosis (4)
Abdominal aorta, coronary artery, popliteal artery, internal carotid artery
What is seen in gross aorta that has thoracic aneurysm and why
Tree bark appearance due to scarring and fibrosis from endarteritis
What are common causes of weakness of media in kids?
Inherited Connective Tissue disorders:
1) Marfan syndrome- defect of fibrillin which affects elastin → weakning of media
2) Ehlers-Danlos syndrome: defective formation of collagen→ weakening of media
What is hyperplastic arteriolosclerosis?
Thickening of vessel wall by hyperplasia of smooth muscle
How does a thrombus form when plaque ruptures?
Plaque ruptures usually at the necks, exposing the necrotic lipid core. This activates coagulation cascade → thrombus formation. This can occlude a vessel leading to infarction of an organ.
What are fatty streaks and when do they appear?
They are flat yellow lesions of intima consisting of lipid-laden macrophages. They arise early in life (present in most teenagers)
How does atherosclerosis lead to weakening of a vessel and aneurysm?
Blood vessel wall components (intima, media, adventitia) need O2 from the blood via diffusion. Formation of atherosclerosis creates a diffusion barrier, weakning the wall, and increasing the risk of ballooning (aneurysm).
Result of hyperplastic arteriolosclerosis and what are two classic findings?
Results in reduced vessel caliber with end-organ ischemia.
2 classic findings:
1) Acute renal failure- due to acute damage due to high blood pressure to kidney
2) Flea bitten appearance of kidney- on surface of kidney, get pinpoint hemorrhages from blowing out of BVs.
What is arteriolosclerosis and what type of vessels (small/medium/large) are affected?
It is the narrowing of small arterioles.
What causes weakness of media layer of aorta in older adults before aortic dissection occurs?
HTN: in proximal 10 cm of aorta, the wall is very thick and therefore O2 cannot diffuse sufficiently to provide I, M, and A all with O2. As a result, there is vasa vasorum that provides the outer half of aortic wall with oxygen. However, in hypertensive patients, there is hyaline arteriolosclerosis of vasa vasorum, decreasing blood flow to the outer 1/2 of aortic wall. This causes atrophy of SM of the medial layer and weakning of media, increaisng the likelihood of a dissection.
What two disease processes cause hyaline arteriolosclerosis and how?
1) Long-standing benign HTN- high blood pressure forces proteins into the vessel wall → hyaline arteriolosclerosis
2) DM- nonenzymatic glycosylation of basement membrane of blood vessel causes BV to become leaky → protein leaks in → hyaline arteriolosclerosis
How is Monckeberg medial calcific sclerosis seen in x-ray/mammography?
It is usually seen on x-ray or mammography as cacification of blood vessels.
What is arteriolonephrosclerosis and how is it formed?
AKA glomerular scarring; this is when hyaline arteriolosclerosis affects afferent arteriole of glomerulus, slowly decreasing the amount of blood to the glomerulus over time. This ultimately results in glomerular scarring.
Major complication of AAA and how does it present?
Rupture- presents with triad of hypotension, pulsatile abdominal mass, flank pain.
Pathogenesis of atherosclerotic plaque formation
1) Damage to endotehlium allows lipid to leak into intima
2) Lipids are oxidized and consumed by macrophages via scavanger receptors → foam cells
3) Inflammation and healing → more deposition of lipids into intima → thickening of lipid layer w/ necrotic core
4) More inflammation and healing leads to deposition of extracellular matrix and proliferation of smooth muscle → fibromuscular cap
What is Monckeberg medial calcific sclerosis?
Calcification of media of mediumsized arteries
Why do patients with long-standing HTN or DM get chronic renal failure?
Bc they get hyaline arteriolosclerosis → glomerular scarring → chronic renal failure.
What causes hyperplastic arteriolosclerosis?
Malignant hypertension- in response to high blood pressure, smooth muscle becomes hyperplastic (proliferates) to try to contain high BP
Obstruction/ stenosis of which arteries cause peripheral vascular disease, angina, and ischemic bowel disease?
Peripheral vascular disease- due to lower extremity arteries (e.g. popliteal)
Angina- due to stenosis of coronary arteries
Ischemic bowel disease- due to stenosis of mesenteric arteries
What is the major complication of thoracic aneurysm? What are some complications?
Major complication: Dilation of aortic valve root due to balloon like dilation of aorta pulling on root of aortic valve →aortic valve insufficiency
Other complications:
1) Compression of mediastinal structures (airway or esophagus)
2) Thombosis/embolism: loss of laminar flow at the balloon like structure → clotting cascade → thrombus formation → embolization
What are the consequences of hyaline arteriolosclerosis and what is usually seen in the kidney?
Results in reduced vessel lumen caliber → end organ ischemia. A classic finding is glomerular scarring (arteriolonephrosclerosis) that slowly progresses to chronic renal failure.
What is the most common cause of abdominal aortic aneurysm?
Atherosclerosis- increases the diffusion barrier to the media, resulting in atrophy and weakness of vessel wall → increase risk for aneurysm
How is hyperplastic arteriolosclerosis seen in histology
Onion like appearance due to layering of smooth muscle.
What type of arteries are affected by atherosclerosis (large/medium/small)
Large and medium sized arteries
In aortic dissection, how do pts present?
Sharp, tearing chest pain that radiates to the back
What may happen to BV wall due to hyperplastic arteriolosclerosis?
Leads to fibrinoid necrosis vessel wall with hemorrhage
How are hyaline arteriolosclerosis formed?
It is caused by proteins leaking into the vessel wall, producing vascular thickening.
Where do abdominal aortas usually occur?
Below renal arteries but above aortic bifurcation
What is the structure of atherosclerotic plaque?
Necrotic lipid core (containing mostly cholesterol) with a fibromuscular cap
What are the nonmodifiable risk factors for atherosclerosis (3)
1) Age (number and severity of lesions increase with age)
2) Gender (increased risk in males and postmenopausal females; estrogen is protective)
3) Genetics (multifactorial but family history is highly predictive of risk)
Complications of aortic dissection (3)
1) Pericardial tamponade- dissection goes backwards, getting access to pericardium and filling the pericardium with blood
2) Rupture- blood can blow thorugh whole blood vessel and go into mediastnum → fatal hemorrhage
3) Obstruction of branching arteries- e.g. coronary or renal arteries, with resultant end-organ ischemia.
When do abdominal aortic aneurysms have greater chance of rupture?
When it’s greater than 5 cm
Where are the two most common locations of aortic aneurysms?
Thoracic and Abdominal
What is a typical patient with abdominal aortic aneurysm?
Same risk factors as atherosclerosis: Male smokers greater than 60 years old with HTN
What is arteriosclerosis and what are the three pathologic patterns?
Arteriosclerosis is global term for 3 mechanisms that creates thickening of BV wall.
3 pathologic patterns of arteriosclerosis:
1) Atherosclerosis
2) Arteriolosclerosis
3) Monckeberg Medial Calcific Sclerosis
What is the most common cause of death in people with aortic dissection?
Pericardial tamponade
How much stenosis has occur by atherosclerosis for complication sx to occur?
Complication sx don’t occur until there is a greater than 70% of stenosis to the arteries that supply end organs.
What infection is commonly seen with thoracic aneurysms and why?
Tertiary syphilis; because this causes endarteritis of the vasa vasorum, resulting in lumenal narrowing, decreased flow, and atrophy of vessel wall.
What is needed to happen to the vessel in order for aortic dissection to occur?
There has to be weakness of the media layer.
What is required of the aortic wall for aneurysms to occur?
Needs weakness of aortic wall.
In atherosclerosis, which layer of blood vessel is thickened?
Intimal layer
What are the 2 morphologic stages of atherosclerosis?
1) Fatty streaks
2) Atherosclerotic plaque
What is the main feature of an atherosclerotic emboli on histology?
Presence of cholesterol clefts
