Cardiovascular Disease

Learning outcomes Atherosclerosis is the accumulation of fatty material (consisting mainly of cholesterol), fibrous material and calcium forming an atheroma or plaque beneath the endothelium. As the atheroma grows the artery thickens and loses its elasticity. The diameter of the artery becomes reduced and blood flow becomes restricted resulting in increased blood pressure. Atherosclerosis is the root cause of various cardio vascular diseases including angina, heart attack, stroke and peripheral vascular disease.

Atheromas may rupture damaging the endothelium. The damage releases clotting factors that activate a cascade of reactions resulting in the conversion of the enzyme prothrombin to its active form thrombin. Thrombin then causes molecules of the plasma protein fibrinogen to form threads of fibrin. The fibrin threads form a meshwork that clots the blood, seals the wound and provides a scaffold for the formation of scar tissue. The formation of a clot (thrombus) is referred to as thrombosis. In some cases a thrombus may break loose forming an embolus and travel through the bloodstream until it blocks a blood vessel. A thrombosis in a coronary artery may lead to a heart attack (myocardial infarction). A thrombosis in an artery in the brain may lead to a stroke. Cells are deprived of oxygen leading to death of the tissues.

Peripheral vascular disease is narrowing of the arteries due to atherosclerosis of arteries other than those to the heart and brain. The arteries to the legs are most commonly affected. Pain is experienced in the leg muscles due to a limited supply of oxygen. A deep vein thrombosis (DVT) is a blood clot that forms in a deep vein most commonly in the leg. If the clot breaks off and travels through the bloodstream it may result in a pulmonary embolism.

Atherosclerosis Atherosclerosis is the formation of plaques, or atheromas, beneath the inner lining in the wall of an artery Atheromas are originally composed of fatty material, cholesterol, but in time they become enlarged by the addition of fibrous materials, calcium and more cholesterol

Atheromas form beneath the inner lining of the blood vessel

Atheroma

Larger atheromas lead to - Reduction in the diameter of the artery lumen Restriction of blood flow to capillary bed served by the artery An increase in blood pressure Larger plaques may become hardened by calcium deposits and this causes arterial walls to become thicker and lose their elasticity – often called ‘hardening of the arteries’ In summary, atherosclerosis can lead to – Coronary heart disease Strokes Heart attack Peripheral vascular disease

Coronary heart disease Coronary heart disease refers to any disease that results in the restriction or blockage of the coronary blood supply Angina Angina is caused by the coronary arteries becoming narrowed by atherosclerosis It causes pains in the centre of the chest radiating out into the left arm and up into the neck and jaw

Clotting of blood In the presence of damaged cells, an inactive plasma enzyme called prothrombin becomes an active enzyme called thrombin Thrombin promotes the conversion of a soluble plasma protein called fibrinogen into insoluble fibrin threads – eventually becomes a blood clot Fibrinogen --- thrombin --- > Fibrin threads

Thrombosis Thrombosis is the formation of a blood clot in a blood vessel How does this happen? As an atheroma becomes enlarged it may burst through the inner lining of the blood vessel and this ‘wound’ gets sealed by a blood clot, thrombosis If the thrombosis breaks loose it is called an embolus An embolus is carried along by the blood until it blocks a narrow blood vessel

Coronary thrombosis This is the blockage of the coronary artery by a thrombosis It deprives the heart muscle of oxygen and may lead to a heart attack (myocardial infarction) Stroke A thrombosis that causes a blockage in an artery in the Brain may lead to a stroke

Peripheral Vascular Disorders Peripheral arteries are arteries except the Aorta, Coronary and Carotid Peripheral vascular disease happens when peripheral arteries are affected by atherosclerosis PVD most commonly affects leg arteries Pain is felt in the leg muscles because they are receiving an inadequate supply of oxygen

Deep Vein Thrombosis This is the formation of a thrombosis (blood clot) in a vein, commonly in the calf muscle of the lower leg Pulmonary Embolism A clot may block a small arterial branch of the Pulmonary Artery This results in chest pain and breathing difficulties

Summary Atheroma present in blood vessel wall Atheroma enlarges Atheroma bursts through lining causing ‘wound’ Wound sealed by blood clot, thrombosis Thrombosis breaks loose and is called embolus Embolus is carried in blood and can cause a blockage....

Now try these questions What is atherosclerosis? 2. Describe the composition of an atheroma 3. What is ‘hardening of the arteries’? 4. Name some problems associated with atherosclerosis 5. Explain how a thrombosis forms 6. What is ‘Deep Vein Thrombosis’? 7. What is a ‘Pulmonary Embolism’?

1. What is atherosclerosis? Atherosclerosis is the formation of plaques, or atheromas, beneath the inner lining in the wall of an artery 2. Describe the composition of an atheroma Atheromas are originally composed of fatty material, cholesterol, but in time they become enlarged by the addition of fibrous materials, calcium and more cholesterol 3. What is ‘hardening of the arteries’? Larger plaques may become hardened by calcium deposits and this causes arterial walls to become thicker and lose their elasticity – often called ‘hardening of the arteries’ 4. Name some problems associated with atherosclerosis Coronary heart disease Strokes Heart attack Peripheral vascular disease

5. Explain how a thrombosis forms As an atheroma becomes enlarged it may burst through the inner lining of the blood vessel and this ‘wound’ gets sealed by a blood clot, thrombosis If the thrombosis breaks loose it is called an embolus An embolus is carried along by the blood until it blocks a narrow blood vessel 6. What is ‘Deep Vein Thrombosis’? This is the formation of a thrombosis (blood clot) in a vein, commonly in the calf muscle of the lower leg 7. What is a ‘Pulmonary Embolism’? A clot may block a small arterial branch of the Pulmonary Artery, this results in chest pain and breathing difficulties