ATHEROSCLEROSIS OR ARTERIOSCLEROSIS
Atherosclerosis or arteriosclerosis refers to the simultaneous developmentof an atheroma in an artery and the sclerosis of its wall. An atheroma (from the Greek word for porridge) is a hard yellow plaque that gradually builds up on the inside of medium-sized arteries. The plaque consists of a necrotic (dead) core rich in cholesterol, surrounded by fibrous tissue. Sclerosis (from the Greek word for hard) means an abnormal hardening or fibrosis, which is the formation of excess fibrous material within a tissue. Sufferers may experience a sudden heart attack or stroke, but this belies the fact that in most cases the arteries of the victims have gradually become blocked by atherosclerosis.
Initially atheromatous plaques start at the site in an artery where the smooth muscle layer has thickened and been infiltrated with fibrous connective tissue (fibrosis) when cholesterol and other lipids have been deposited, and may become calcified. This condition is commonly referred to as hardening of the arteries. During the course of the disease, the affected artery expands as the plaque becomes larger so as to allow a more or less normal flow of blood. However, as the plaque increases in size this becomes less possible and the lumen of the artery becomes narrower and a ballooning of the arterial wall causes it to weaken. Also, there is more likelihood of an embolus becoming trapped in the narrowed artery making the blockage worse. Healthy arteries are lined with endothelial cells, but the rough lining of a plaque-damaged artery seems to encourage the adhesion of platelets which means they are common sites for the formation of a clot (thrombus).
The progresses of atheromatous disease means the arteries become increasingly occluded and the threat of a heart attack or stroke increases. Some patients may receive warning in the form of chest pains if, for example, a coronary artery is partially blocked. The condition known as angina pectoris (see below) is a signal that the heart is not receiving sufficient oxygen. This is most likely to occur when the heart is working hard because of physical or emotional stress. However, for many people there are no symptoms and they are completely unaware of their condition until the catastrophic event occurs. Some individuals have an inherited tendency to develop hypertension, which promotes atherosclerosis and increases the risk of heart attack or stroke and can cause chronic damage to the endothelium lining the arteries promoting atherosclerosis.