2.7 Pathology of Cardiovascular Disease (CVD) Flashcards
Atherosclerosis
The accumulation of fatty material (consisting mainly of cholesterol, fibrous material and calcium) forming an atheroma or plaque beneath the
endothelium.
Atherosclerosis is the root cause of various cardiovascular diseases (CVD) —
angina, heart attack, stroke and peripheral vascular disease.
Cause of increased Blood Pressure
As the atheroma grows the artery thickens and loses its elasticity. The diameter of the lumen becomes reduced and blood flow becomes restricted resulting in increased blood pressure.
Rupture of Atheroma
Atheromas may rupture damaging the endothelium. The damage releases clotting factors that activate the following cascade of reactions:
1. The clotting factors result in the conversion of the enzyme prothrombin to its active form thrombin.
2. Thrombin causes molecules of the plasma protein fibrinogen to form threads of fibrin.
3. The fibrin threads form a meshwork that clots the blood, seals the wound and
provides a scaffold for the formation of scar tissue.
Thrombosis
The process releasing clotting factors results in the formation of a clot (thrombus) and is referred to as thrombosis.
A thrombus may break loose forming an embolus which travels through the bloodstream until it blocks a blood vessel.
Action of Thrombosis
A thrombosis in a coronary artery may lead to a myocardial infarction (MI), commonly known as a heart attack.
A thrombosis in an artery in the brain may lead to a stroke.
Death of Tissues
In both heart attacks and strokes, cells are deprived of oxygen leading to death
of the tissues.
Peripheral Vascular Disease
Peripheral vascular disease is narrowing of the arteries due to atherosclerosis
of arteries other than those of the heart or brain.
The arteries to the legs are most commonly affected. Pain is experienced in the leg muscles due to a limited supply of oxygen.
Deep Vein Thrombosis (DVT)
DVT is a blood clot that forms in a deep vein, most commonly in the leg. This can break off and result in a pulmonary embolism in the lungs (if the clot blocks the pulmonary artery).
Cholesterol
A type of lipid found in the cell membrane. It is also used to make
the sex hormones — testosterone, oestrogen and progesterone.
Cholesterol is synthesised by all cells, although 25% of total production takes
place in the liver. A diet high in saturated fats or cholesterol causes an increase in
cholesterol levels in the blood.
High Density Lipoproteins (HDL)
Transports excess cholesterol from the body cells to the liver for elimination. This prevents accumulation of cholesterol in the blood.
Low Density Lipoproteins (LDL)
Transports cholesterol to body cells.
Most cells have LDL receptors that take LDL into the cell where it releases
cholesterol.
Once a cell has sufficient cholesterol a negative feedback system inhibits the
synthesis of new LDL receptors and LDL circulates in the blood where it may deposit cholesterol in the arteries forming atheromas.
Ratio of HDL to LDL
A higher ratio of HDL to LDL will result in lower blood cholesterol and a reduced
chance of atherosclerosis.
Regular Physical Activity & Dietary Changes
Regular Physical Activity tends to raise HDL levels and dietary changes aim to reduce the levels of total fat in the diet and to replace saturated with unsaturated fats.
Drugs
Drugs such as statins reduce blood cholesterol by inhibiting the synthesis of
cholesterol by liver cells.
