Vascular Disorders Flashcards
Intima
The innermost coating or membrane of a part or organ, especially of a vein or artery.
Atherosclerosis.
Primarily a progressive disease of intima involving large & medium-sized elastic and muscular arteries.
Atheroma.
Focal lipid-rich intimal lesions.
Major modifiable risk factors of Atherosclerosis.
- Hyperlipidemia
- Hypertension
- Smoking
- Diabetes mellitus
Major nonmodifiable (Constitutional) risk factors of atherosclerosis.
- Genetic abnormalities
- Family history
- Increasing age
- Male gender
Additional risk factors.
- Inflammation
- CRP level
- Hyperhomocystinemia
- Metabolic syndrome
- Lipoprotein (a)
- Raised procoagulant level
- Inadequate physical activity
- Stressful lifestyle
- Obesity
- Alcohol
CRP level
-Normal C-reactive protein level.
-Excellent marker for disrupted atheromatous
plaque.
Hyperhomocystinemia
- A medical condition characterized by an abnormally high level of homocysteine in the blood, conventionally described as above 15 μmol/L
- Homocysteine is a type of amino acid, a chemical your body uses to make proteins. Normally, vitamin B12, vitamin B6, and folic acid break down homocysteine and change it into other substances your body needs.
Major components of lipid in blood are.
- LDL
- HDL
- Serum cholesterol level
Low density lipoprotein
“Bad Cholesterol”
Serum cholesterol level
-Normal range (140-240 mg/dL)
-Strongly related to the dietary intake of saturated fat.
- Risk of atherosclerosis increases with increasing serum cholesterol concentrations and lowering serum
cholesterol concentrations reduce the risk.
Margarine.
Transaturated fats produced by artificial hydrogenation of polyunsaturated oils.
Cholesterol-Lowering Drug
Example:
- Statins, lower circulating cholesterol levels by inhibiting hydroxymethylglutaryl coenzyme A [HMG CoA] reductase.
- HMG CoA is a rate-limiting enzyme involved in cholestrol biosynthesis in Liver.
HDL
- Good cholesterol removes cholesterol from atheromatous plaque and transports to liver.
- From the liver, it is excreted in the bile.
Disorders associated with hypercholesterolemia.
- Nephrotic syndrome
- Alcoholism
- Hypothyroidism
- Diabetes mellitus
Increased very _______ leads to reduced HDL.
Very Low-Density Lipoprotein (VLDL)
Familial hypercholesterolemia
Mendelian disorders, such as familial hypercholesterolemia are associated with atherosclerosis.
Premenopausal women have lower incidence….
Premenopausal women have lower incidence of
atherosclerosis-related diseases compared to males of
the same age groups. However, after menopause this sex difference disappears. This may be due to protective role of estrogen.
*However, hormone replacement therapy has no role in the prevention of coronary heart disease.
Achilles’ tendon xanthoma
Pathognomonic of familial hypercholesterolemia.
Theories of pathogenesis of Atherosclerosis.
- Insudation hypothesis
- Encrustation hypothesis
- Monoclonal hypothesis
- Response-to-injury hypothesis
Insudation hypothesis
Here, the focal accumulation of lipid in a vessel wall is due to insudation (transport) of plasma lipoproteins across an intact endothelium.
Encrustation hypothesis
Here, small mural thrombi are formed at the site of endothelial damage.
These thrombi become organized and form plaque.
Monoclonal hypothesis
Here, a single clone (monoclonal) of smooth muscle migrate from underlying media into the intima and then proliferate.
The stimulus for monoclonal proliferation may be metabolites of cholesterol.
Response-to-injury Hypothesis.
Here, atherosclerosis develops as a chronic (inflammatory and healing) response of the arterial wall to the endothelial injury.
RTI sequence of pathogenic events.
- Endothelial injury and dysfunction.
- Migration of monocytes into the intima.
- Lipid accumulation in the intima.
- Formation of foam cells and activation of macrophages.
- Migration of smooth muscle cells into the intima.
- Smooth muscle cell proliferation in the intima and ECM production.
- Lipid accumulation.
Effect of endothelial injury or dysfunction.
- Monocyte & T-Lymphocyte adhesion to endothelium
- Increased vascular permeability.
- Platelet adhesion and thrombosis.
- Movement LDLs across the endothelium into the intima.
The monocytes migrate into the intima, where they are transformed into ____.
Macrophages.
Foam cells.
Macrophage engulfs lipoproteins and oxidized LDL from the extracellular space in the intima. Their cytoplasm becomes foamy and these cells are called
as foam cells
Foam cells and necrotic core.
Some foam cells may undergo apoptosis > release lipids > form lipid rich center called necrotic core in atheromatous plaques.
Oxidized LDL causes activated macrophages which produce:
- Cytokine (e.g. TNF); increases leukocyte adhesion.
- Chemokines (e.g. monocyte chemotactic protein 1); accumulation of monocytes.
- Reactive oxygen species; aggravate oxidation of LDL.
- GFs; stimulate smooth muscle cell proliferation and ECM synthesis.
Migration of smooth muscle cells into the intima.
Growth factor (e.g., platelet-derived growth factor) from activated platelets, macro phages, and endothelial cells causes migration of smooth muscle cells either from the arterial media or from circulating precursors.
Many growth
factors can cause smooth muscle cell proliferation.
These includes:
- PDGF
- Fibroblast growth factor (FGF)
- Transforming Growth Factor-Alpha (TGF-a)
_______cell may also engulf oxidized LDL and form foam cells.
Smooth muscle cell
Intracellular and Extracellular Lipid accumulation.
- Extracellular lipid is derived from insudation from vessel lumen (in hypercholesterolemia) and also from necrotic foam cells.
- Cholesterol in plaque is due to imbalance between influx and efflux, HDL transfers cholesterol from these lesions and leads to its excretion by liver.
Fatty Streak
- The earliest or precursor lesions of atherosclerosis.
- Found in children above 10 and adults.
- In the Intima.
- Multiple small (1mm) flat yellow lesions in the intima; may coalesce to form long streaks 1cm or more in length.
- Mildly elevated above intima without disturbing blood flow.
- Microscopy: Consist of lipid-filled foamy macrophages in the intima.
Major vessels involved in atherosclerosis in descending order are:
- Lower abdominal aorta > thoracic aorta.
- Coronary arteries.
- Popliteal arteries.
- Internal carotid arteries.
- Circle of Willis.
Gross features of atherosclerosis.
Color of Thrombus:
- White to yellow.
- Red-Brown if superimposed by thrombus.
Shape:
Irregular with well-defined boundaries.
Distribution:
-Patchy(focal)
On cross-section:
-Appears as an eccentric lesion.
Composition:
-Grumous core covered by a white fibrous cap.
Aortic lesion components.
- Superficial fibrous cap:
- Smooth muscle cells
- Collagen - Necrotic core:
- Lipid
- Debris from dead cells
- Foam cells
- fibrin, organized thrombus, plasma proteins. - Shoulder:
It is the peripheral region beneath and t the side of the cap.
- Macrophages
- SMC
- T-cells - Neuvascularization: My be seen at the periphery of the lesions near the shoulder.
Complications of atherosclerosis.
- Rupture
- Hemorrhage into the plaque
- Thrombosis
- Embolism
- Aneurysm
- Calcification; occurs in central necrotic area of the plaque.
Major clinical consequences of atherosclerosis.
- Myocardial infarction (heart attack)
- Cerebral infarction (stroke)
- Aortic aneurysms
- Peripheral vascular disease (gangrene of the legs).
Stable and Vulnerable plaques.
Stable plaque:
- Have thick densely collagenized fibrous cap.
- Minimal inflammation.
- Negligible lipid core.
Vulnerable plaque:
- Contain numerous foam cells.
- Abundant extracellular lipid.
- Many inflammatory cells.
- Thin fibrous cap.
- Few smooth muscle cells.
- High-risk to undergo rupture.
Atherosclerotic Stenosis
- Atherosclerotic plaques reduce the size of the lumen.
- Severe reduction of lumen may lead to ischema > the lesion resulting is termed as critical stenosis.
In the coronary artery, atherosclerotic lesion when produces a 70% decrease in luminal cross-sectional area____
The patient may develop chest pain with exertion. (stable angina)
Intermittent claudication.
Diminished perfusion of the extremities.
Collagen synthesis.
By Smooth muscle cells.
Collagen degradation.
By Inflammatory cells
Aneurysm
Defined as a congenital or acquired, localized, abnormal, permanent dilation of a blood vessel or the heart.
Classifying Aneurysm depending on gross appearance.
- Fusiform
- Saccular
- Cylindrical
- Arterial dissection/dissecting hematoma.
- Arteriovenous