Coronary Heart Disease Arteries supplying the heart become narrowed and the blood supply to cardiac tissues is reduced Heart has to work harder to force blood through narrowed vessels / blood pressure increases Angina Chest pain due to severe shortage of blood to the heart muscle - cells do not die Pain only occurs during activity but not at rest Caused by narrowing of coronary arteries (atherosclerosis) Heart attack (myocardial infarction) When a coronary artery is totally blocked by a thrombus/embolus No blood supply to heart muscle and cells die - often fatal Heart failure Blockage leads to damage of heart muscle and to gradual weakening of muscle Less efficient pumping Often accumulation of blood on right side → enlargement of heart Causes of Coronary Heart Disease The main cause is atherosclerosis Often called hardening of the arteries Inner layer of artery wall thickens with deposits of Cholesterol Fibrous (scar) tissue Dead muscle cells Blood platelets Fats, in the form of lipoproteins, accumulate beneath the endothelium Form plaque on the wall of arteries, also called atheroma Arteries become less elastic and partially narrowed Accelerated by high blood pressure Arterial endothelium damage is more likely but also leads to further weakening Aneurysm: weak walls may burst leading to severe loss of blood (haemorrhaging) Brain aneurysm is called a stroke Atheroma increases the risk of blood clotting Thrombus (blood clot) may break away and lodge elsewhere in the circulation (e.g. brain, heart) Circulating thrombus is called an embolus Cholesterol and Atherosclerosis Cholesterol has important functions and is needed for Vitamin D production in skin Sex hormone production in gonads and adrenal glands Making cell membranes Make bile acid (salts) Cholesterol is an alcohol, not a fat but has properties similar to fats - soft, waxy, and insoluble (difficult to remove if deposits form) Cholesterol is transported in the blood stream from the liver to tissues Safe transport is needed due to its insolubility This is achieved by lipoproteins, which are soluble fatty proteins These are wrapped around the cholesterol Usually, only small amounts of free cholesterol escape Fatty streaks adhere to wall of arteries - Atheroma/atherosclerosis/plaque forms Narrows lumen of artery Damages endothelium Can lead to formation of thrombus/blood clot Lipo-Proteins Low density lipo-proteins LDL's Carry cholesterol from the liver to the tissues Normal levels: some cholesterol 'leaks' from the lipoprotein and is absorbed to build cell membranes High levels: too much cholesterol leaks out Cholesterol is deposited on the arterial walls White blood cells are trapped within the cholesterol Free radicals are released by white blood cells and react with cholesterol This damages artery wall which allows further cholesterol deposits (i.e. Atherosclerosis) Blood platelets are activated and stick to damaged areas releasing clotting factors (thromboxanes) Healthy arteries produce anti-clotting factors (prostaglandins) Normally a balance between these two. Healthy vessels do not form clots High density lipo-protein HDL's Carry cholesterol away from tissues, including artery walls Travels to liver, is broken down and removed with bile Smoking Reduces levels of antitoxidants (vitamins), more damage due to release of free radials by phagocytes Nicotine constricts arteries causes platelets to stick together → vasoconstriction → heart must work harder to force blood through → increases blood pressure [EXAM] Raises conc. of fibrinogen (in blood) → increased risk of clotting Higher blood pressure causes damage to blood vessel lining/endothelium/collagen [EXAM] Leads to rise on blood platelets and makes them more sticky/form a plug/adhere to collagen fibres Release of thromboplastin/thrombokinase Fibrinogen converted to insoluble fibrin Platelet plug trapped by fibrin mesh Raises blood cholesterol by causing a rise in LDLs in blood Carbon monoxide reduces the efficiency of the blood in terms of carrying oxygen Haemoglobin combines with CO more readily than with oxygen → forms carboxyheamoglobin Associated with plaque formation Principle CHD = heart muscle receives inadequate amount of blood or oxygen/(coronary) blood supply reduced Treatment Lower blood pressure Drugs which regulate heart rate/beat - prevent abnormal rhythms (beta blockers) Drugs which prevent blood clotting making thrombosis less likely (warfarin) Heart by-pass Vein from the leg is used to by-pass the blocked region of the coronary artery Involves open heart surgery Angioplasty Deflated balloon-like device is passed up to the heart via the aorta Guided into damaged coronary artery and inflated to stretch the artery Transplant Need to find a suitable donor Need to prevent rejection → drugs that suppress immune system needed for rest of life Prevention is more cost effective then treatment Screen the population for High blood pressure High cholesterol Stop smoking, healthier diet, more exercises Men over 35 are at highest risk Monitor the behaviour of the heart during exercise Difficult but encouraging the population to adopt a more healthy lifestyle from an early age is important Often leads to changes in diet and weight management Giving up smoking and reducing alcohol intake Reduces blood pressure Many people do not heed the advice until it is too late Coronary heart disease is a long-term degenerative disease, starts at birth