The initial recognition of myocardial ischaemia is generally through the sensation of angina. Angina pectoris, pain of the chest, gnerally begins as a constricting pain in the chest, usually provoked by exercise. It is an indication that the oxygen demand of the heart is exceeding the rate at which it can be supplied. The immediate cause of this is the reduction in diameter of the coronary arteries. The prime cause of obstruction of coronary arteries, atherosclerosis, is generally agreed to be associated with an accumulation of cholesterol and other materials inside the arteries, resulting initially in reduced flow, but steadily increasing the risk that blood may clot at the obstruction, blocking the artery completely and leading to a heart attack.
Cholesterol occurs naturally in the body, but is taken in the diet in foods rich in animal fats.
Most of the cholesterol in the blood is carried round the body in combination with a protein as lipoproteins. There is now overwhelming evidence that reduction in LDL and total cholesterol by either diet or drugs can produce a significant decrease in coronary artery disease. Factors other than strict attention to diet can however have an important influence on the level of blood cholesterol, often in ways that are not entirely understood. Being overweight, smoking, excess sugar intake, alcohol consumption , and genetic factors may all significantly decrease HDL and increase the risk of heart disease. In contrast regular excercise and a healthy life style may increase HDL and significantly reduce the risk.