Historically, the main cause of death worldwide was infectious disease (communicable diseases) Today, infectious disease such as malaria and gastroenteritis remains the major cause of death in developing countries However, in developed countries, non-infectious diseases pose the greatest health challenges, with heart disease and cancers being significant causes of death Non-communicable diseases are emerging in countries where economic conditions have improved and rapid industrialisation is taking place, e.g. Singapore The lifestyle changes associated with greater affluence in our societies is a major contributor to the incidence of non-communicable diseases

Cardiovascular disease (CVD) is the main cause of death in the UK accounting for around 230,000 deaths a year: four out of ten of all deaths The main forms of CVD are coronary heart disease (CHD) and stroke, with around half of all deaths from CVD being from coronary heart disease and a quarter from stroke CHD causes around 114,000 deaths a year in the UK and is the most common cause of premature death Although death rates from CHD in the UK have been falling, they have not decreased as fast as in some other countries

Source: World Health Organisation: Death rates for those aged under 65 years Comment on the graph

Coronary heart disease (CHD) is a narrowing of the coronary arteries that supply blood and oxygen to the heart Coronary heart disease usually results from the build up of fatty material in the walls of the arteries; this is known as atherosclerosis and is usually accompanied by a loss of elasticity of the arteries involved

Atherosclerosis causes the coronary arteries to narrow and slows or stops the flow of blood to the cardiac muscle Chest pain (angina), shortness of breath, heart attack (myocardial infarction) and other symptoms, can result from the narrowing of the coronary arteries

Cardiac muscle will contract over 2.5 billion times during an average lifetime The heart is a fist-sized organ made up mainly of cardiac muscle The function of the heart is to circulate blood through the body and lungs through a double circulatory system Cardiac muscle relies on a sufficient supply of oxygen and nutrients to maintain its pumping action

Cardiac muscle cells are supplied with their nutrients and oxygen from the capillaries derived from the coronary arteries Left coronary artery Right coronary artery Aorta Coronary arteries branch from the aorta Any blockage of the coronary arteries reduces blood flow to the cardiac muscle cells Blockage of the coronary arteries reduces the supply of nutrients and oxygen to cardiac muscle cells, and interferes with their ability to contract Varying symptoms result from a lack of oxygen supply to cardiac muscle cells, and these correlate with the degree and the site of a blockage

A myocardial infarction occurs when areas of the myocardium (heart muscle) die due to an interruption of blood flow The usual cause of interrupted blood flow is a blockage where atherosclerosis has developed If the blockage occurs in one of the major branches of the coronary arteries, then the amount of myocardial damage is quite extensive If the blockage occurs in one of the smaller branches of the coronary arteries, then the amount of myocardial damage is more limited

Atherosclerosis is a progressive degenerative process in which fatty (lipid) material is deposited as plaques in the walls of the coronary arteries, and other arteries of the body; these plaques are inflamed and encased in a thin fibrous capsule As the lipid-like material (lipoproteins from blood plasma) accumulates, it bulges into the opening of the arteries, leading to varying degrees of obstruction of the blood flow to the cardiac muscle

Normal Artery Moderate Atherosclerosis Severe Atherosclerosis Outer layer Middle layer Endothelium As the plaque builds up, the lumen of the artery narrows and blood flow is reduced; damage to the endothelium results in blood clot formation (thrombosis) LUMEN Fat-laden cells form beneath the endothelium and produce an atheroma; fibres and muscle cells grow into this region and form a plaque Blood clot (thrombus) forming in the arterial lumen

Outer layer Middle layer Endothelium Atheromatous plaque The atheromatous plaque is a combination of cholesterol, triglycerides and blood components; as atheroma formation continues, the fat deposits become invaded by fibrous tissue, and then become calcified (arteriosclerosis) Atheromatous plaques roughen the lining of the artery and cause turbulent blood flow; this can lead to blood clot (thrombus) formation, and the potential danger of the clot breaking away from its site of origin to be carried to other other body areas; when a blood clot breaks away from its original site, it is called an embolus

A very common site for the development of atheromatous plaques is the first few centimetres of the coronary arteries

Atherosclerosis increases the risk of coronary heart disease and stroke, and together with high blood pressure, significantly increases the possibility of a potentially fatal aortic aneurysm An aortic aneurysm is the dilatation (or bulging) of a portion of the aorta usually at a site of weakness in the aortic wall Atherosclerosis, high blood pressure, smoking and genetic inheritance, are the major risk factors for developing an aortic aneurysm