Atherosclerosis

Atherosclerosis is the process in which fatty or fibrous deposits build up in the arterial wall to form atheromatous plaques. The build-up of plaques causes the artery to narrow which can reduce the blood supply to vital organs such as the heart and brain, depriving them of oxygen and vital nutrients. This is called ischaemia.

Damage to the arterial wall due to factors such as hypertension or smoking, allows cholesterol in the blood to enter the artery wall. This starts a chain of events that leads to a narrowing within the artery wall due to cholesterol accumulation, known as a ‘plaque’.

Figure 1: This diagram shows the build up of cholesterol in the arterial wall to cause a plaque. The cholesterol arrives as part of LDL (LDL-cholesterol, or ‘bad’ cholesterol) and can be removed as part of HDL (HDL-cholesterol, or ‘good’ cholesterol).

Atherosclerosis is a progressive disease and the main cause of cardiovascular disease – the number one killer worldwide.^1,2 An atherosclerotic plaque can cause complications in a number of ways:

• By growing in size, it leads to a narrowing of the blood vessel and a gradual reduction of blood flow. Many parts of the body can compensate by developing alternative routes of blood supply by collateral blood vessels, but only to a certain extent.  If these tissues receive a less-than-adequate blood supply, symptoms occur, i.e.:
  • heart: chest pain on exercise, known as angina
  • brain: can lead to transient ischaemic attack (mild stroke, temporary impairment of vision, speech, sensation or movement caused by a brief interruption in the blood supply to the brain)
  • Legs: intermittent claudication.
• By rupturing, the cholesterol and other parts of the vessel wall, are exposed to the blood leading to blood clotting activation, platelet activation, thrombus formation and subsequently, complete blockage of the blood flow, or a ruptured thrombus that blocks a blood vessel further downstream. In the coronary arteries, this can cause a myocardial infarction (heart attack) and in the carotid arteries leading to the brain, this can cause a stroke
• By weakening and widening the vessel wall, leading to an aneurysm, a bulging or ballooning of the vessel wall. When an aneurysm ruptures, it can result in massive internal bleeding.

References:
1. Lusis AJ. Atherosclerosis. Nature 2000;407:233-41.
2. World Health Report 2004. World Health Organization. http://www.who.int.

^ Top