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Atherosclerosis, sometimes called "hardening of the arteries,"
occurs when fat (cholesterol) and calcium build up inside the lining of the artery wall, forming a substance called plaque. Over time, the fat and calcium
buildup narrows the artery and blocks blood flow through it.
Atherosclerosis can happen in all arteries. If you have atherosclerosis in
one of your arteries, there is a good chance that you have atherosclerosis in
other blood vessels throughout your body.
Coronary artery disease. When atherosclerosis affects the arteries that
supply blood to the heart, the coronary arteries, it can restrict blood flow to the heart muscle.
Heart attack. Plaque, caused by atherosclerosis, is surrounded by a fibrous cap. This fibrous cap may
tear or rupture if blood suddenly flows faster or if the artery suddenly narrows.
A tear or rupture tells the body to repair the injured artery lining, much as
it might heal a cut on the skin, by forming a blood clot to seal the area. A
blood clot that forms in an artery can completely block blood flow to the heart
muscle and cause a heart attack. See a picture of how atherosclerosis can cause a heart attack.
Stroke or transient ischemic attack (TIA). When
atherosclerosis affects the arteries that supply blood to the brain, it may
cause a transient ischemic attack (TIA) or stroke.
Peripheral arterial disease. Atherosclerosis
can affect arteries in other parts of the body, such as the pelvis and legs,
causing poor circulation.
aortic aneurysm. Atherosclerosis can make the walls of the aorta weak. The aorta is the large artery that carries blood from the heart to the rest of the body.
A major part of treating atherosclerosis and coronary artery
disease involves lifestyle changes (such as quitting smoking) and medicines
to help reduce high cholesterol, control high blood pressure, and manage other
things that increase a person's risk of heart attack, stroke, and other
If you think of atherosclerosis as a response to injury, the buildup
of fibrous plaque can be reversed by removing the source of injury. In the case
of high cholesterol, by reducing the amount of LDL cholesterol in your arteries
and increasing the amount of HDL—which removes cholesterol that is already in
your artery walls—you can actually reverse atherosclerosis. The ability to
reverse atherosclerosis helps explain why treating high cholesterol can reduce
the risk of further complications from atherosclerosis.
Although the exact process is not completely understood, scientists
have described three different stages of atherosclerosis that lead to clogged
arteries. These stages do not necessarily occur in order, nor is there always a
progression from one stage to the next.
The fatty streak. The "fatty streak" appears as a yellow streak running inside
the walls of the major arteries, such as the aorta. The streak consists of
cholesterol, white blood cells, and other cellular matter. The fatty streak by
itself does not cause symptoms of heart disease but can develop into a more
advanced form of atherosclerosis, called fibrous plaque.
The plaque. A plaque forms in the inner layer of the artery. Plaque is a buildup of cholesterol, white blood cells, calcium, and other substances in the walls of arteries. Over time, plaque narrows the artery, and the artery hardens.
Plaque sometimes reduces blood flow to the heart muscle, which can cause angina symptoms. Plaque in the large artery in the neck (carotid artery stenosis) may block blood flow to the brain and is a common cause of transient ischemic attack (sometimes called "mini-stroke") and stroke.
Plaques are covered with a fibrous cap, which may rupture if some trigger causes a surge in blood pressure or causes the artery to constrict. A person may have a heart attack if a plaque breaks open, creating a blood clot that completely blocks blood flow through the artery.
Complicated lesion. The last stage of atherosclerosis occurs when the plaque breaks
open, exposing the cholesterol and tissue underneath. Blood clots form in
response to this rupture and cause symptoms of a heart attack and unstable
Response-to-injury. This theory suggests that atherosclerosis
develops as a result of repetitive injury to the inner lining of the artery.
Injury may stimulate cells to grow and divide as part of the
inflammatory process. This normal, healing response to chronic injury may
actually result in the growth of atherosclerotic plaque.
This injury could be caused by any number of things, including:
Smoking plays a large role in the development of atherosclerosis. The
carbon monoxide and nicotine contained in tobacco smoke affect blood flow
through your arteries by:
Atherosclerosis is one of the major causes of
The wall of the aorta (and all blood vessels) is a dynamic tissue
made up of living cells that need nutrients and oxygen. Many of these
nutrients seep from the inside of the blood vessel through the walls to nourish
the rest of the blood vessel. When the inner lining of the vessel is covered
with an atherosclerotic plaque, nutrients can no longer seep through
sufficiently. The cells receive no oxygen, and some of them die. As the
atherosclerosis progresses and cells continue to die, the walls become weaker
At some point, a critical relationship is reached between the
pressure experienced in the center of the blood vessel, the wall tension, and
the strength of the wall itself. When this point is reached, the wall begins to
dilate (grow larger) in the area of the plaque. As the diameter of the vessel
grows, the wall tension increases, leading to even more dilation. The end
result is an aneurysm.
February 13, 2013
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
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