Atherosclerosis — often called hardening of the arteries — is the buildup of fatty substances in the arteries, which can lead to heart disease and stroke. It’s a slow, complex disease that typically starts in childhood and progresses with age.
Deposits of fatty substances, cholesterol, cellular waste products, calcium and other substances build up in the inner lining of an artery. They cause the formation of blood clots that can block blood flow or break off and travel to another part of the body. View a detailed animation of atherosclerosis.
If a clot blocks a blood vessel that feeds the heart, it causes a heart attack. If it blocks a blood vessel that feeds the brain, it causes a stroke. If blood supply to the arms or legs is reduced or blocked, it can cause difficulty walking and eventually gangrene.
Males and people with a family history of premature cardiovascular disease have an increased risk of atherosclerosis. Other risk factors include:
- High blood cholesterol
- Cigarette smoking and exposure to tobacco smoke (the chemicals in cigarettes can cause damage to blood vessels accelerating the development of atherosclerosis)
- High blood pressure (it damages the lining of blood vessels making them susceptible to atherosclerosis)
- Diabetes mellitus
- Physical inactivity
How it progresses
The inner lining of the artery, called the endothelium, can be damaged due to high cholesterol and triglyceride levels, cigarette smoke, high sugar levels and other factors. High blood pressure can also cause damage. Once the damage is done, atherosclerosis begins and a plaque forms.
Fats, cholesterol, platelets, cellular debris and calcium begin to deposit in the artery walls. These substances may stimulate the cells of the artery wall to produce still other materials. More cells accumulate, and many divide. At the same time, fat builds up within and around these cells, and connective tissue forms. This buildup is called plaque. It usually affects large and medium-size arteries. These cells and surrounding material thicken the endothelium significantly. The artery’s diameter shrinks and blood flow decreases, reducing oxygen supply.
How atherosclerotic plaque causes damageMost of the damage occurs when plaques become fragile and rupture. Plaques that rupture cause the formation of blood clots that can block blood flow or break off and travel to another part of the body. In either of these cases, if a clot blocks a blood vessel that feeds the heart, it causes a heart attack. If it blocks a blood vessel that feeds the brain, it causes a stroke. If blood supply to the arms or legs is reduced or blocked, it can cause difficulty walking and eventually gangrene.
Stroke and atherosclerosis
There are two types of ischemic stroke caused by blood clots, narrowing of blood vessels to the brain caused by atherosclerosis or other particles.
Atherothrombotic stroke is the most common. It occurs when a blood clot forms on an atherosclerotic plaque within a blood vessel in the brain and blocks blood flow to that part of the brain.
A cerebral embolism happens when a wandering clot or some other particle, called an embolus, is carried by the bloodstream. It lodges in an artery leading to or in the brain and blocks the flow of blood. The embolism could be due to a piece of clot or plaque that broke off from an atherosclerotic plaque. However, most embolic strokes are due to blood clots that form in people with atrial fibrillation and enter the bloodstream.