Atherosclerosis & Cholesterol

Learning Objectives

• Understand the types and function of lipoproteins.

• Review age-related changes within the circulatory system.

• Describe the role of cholesterol in the development of atherosclerosis.

• Describe the aetiology, pathophysiology, and clinical manifestations of atherosclerosis.

• Describe the role of atherosclerosis in acute coronary syndromes, stroke, and peripheral vascular disease.

Lipoproteins - Cholesterol

• Fats are not water-soluble; they need to be wrapped in protein for transport through the blood.

• Types of cholesterol: "bad" (LDL) and "good" (HDL) lipoproteins.

Blood cholesterol

• Cholesterol and triglycerides are transported in plasma by apoproteins.

• LDLs are "bad cholesterol" and are removed from the blood by receptors in the liver, tissues, and macrophages.

• HDLs are "good cholesterol" and transport cholesterol from tissues to the liver for excretion or reuse.

Sugar The 'new' cholesterol?

• Differing opinions and research on whether sugar is the main dietary factor in cholesterol and atherosclerosis.

• Excess glucose can be converted into fatty acids.

Arteriosclerosis

• Abnormal thickening and hardening of artery walls.

• Smooth muscle cells and collagen fibers enter the tunica intima, making it stiff and narrowing the lumen.

Atherosclerosis

• A specific form of arteriosclerosis with soft deposits of intra-arterial fat and fibrin in the vessel walls.

• Main cause of coronary heart disease and cerebrovascular disease.

• Endothelium cell injury is a risk factor.

• Inflammatory cells adhere to the injured endothelium, causing more damage to the vessel wall.

• LDL is oxidized by toxic oxygen radicals and engulfed by macrophages, forming foam cells.

• Foam cells increase in number and form fatty streaks.

• Fatty streaks produce more toxic oxygen radicals, further damaging the vessel wall.

• Macrophages release growth factors that stimulate smooth muscle cell proliferation.

• Smooth muscle cells and collagen migrate over the fatty streak, forming a fibrous plaque.

• Fibrous plaque may calcify, protrude into the vessel lumen, and obstruct blood flow.

• Fibrous plaque may rupture, leading to platelet adhesion, clotting cascade, and thrombus formation.

Atherosclerosis: main cause of CAD

• Atherosclerosis is responsible for about 33% of deaths in New Zealand.

• Associated with high obesity rates, lack of exercise, and unhealthy diets.

Complications of Atherosclerosis

• Coronary artery disease: plaque buildup in an artery, leading to angina or heart attack.

Myocardial ischaemia: Angina

• Stable or classic angina is common and comes on with increased myocardial oxygen demands.

• Sub-sternal constricting pain associated with a stable plaque.

• Silent ischemia may have no angina pain but may have dyspnea and fatigue.

Peripheral Vascular Disease

• Chronic progressive disease with partial or total arterial occlusion in the lower extremities.

• Affects older age group and younger persons with diabetes.

Stroke & TIA

• 75-80% of all strokes are ischemic, caused by occlusion of cerebral artery from atherosclerosis.

• May be preceded by TIA (transient ischemic attack), a short period of cerebral ischemia that resolves without infarction.

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• Reducing cholesterol

  • Increase exercise and physical activity

  • Smoking cessation

  • Eat a wide variety of plant-based foods