| Heart
Attacks
A heart attack (also known as a myocardial infarction)
is the death of heart muscle from the sudden blockage
of a coronary artery by a blood clot. Coronary arteries
are blood vessels that supply the heart muscle with
blood and oxygen. Blockage of a coronary artery deprives
the heart muscle of blood and oxygen, causing injury
to the heart muscle. Injury to the heart muscle causes
chest pain and pressure. If blood flow is not restored
within 20 to 40 minutes, irreversible death of the heart
muscle will begin to occur. Muscle continues to die
for 6-8 hours at which time the heart attack usually
is “complete.” The dead heart muscle is replaced
by scar tissue.
Many people in the world suffer a heart attack each
year. Four hundred thousand of them die as a result
of their heart attack.
What causes a heart attack?
Atherosclerosis
Atherosclerosis is a gradual process in which plaques
(collections) of cholesterol are deposited in the walls
of arteries. Cholesterol plaques cause hardening of
the arterial walls and narrowing of the inner channel
(lumen) of the artery. Arteries that are narrowed by
atherosclerosis cannot deliver enough blood to maintain
normal function of the parts of the body they supply.
For example, atherosclerosis of the arteries in the
legs causes reduced blood flow to the legs. Reduced
blood flow to the legs can lead to pain in the legs
while walking or exercising, leg ulcers, or a delay
in the healing of wounds to the legs. Atherosclerosis
of the arteries that furnish blood to the brain can
lead to vascular dementia (mental deterioration due
to gradual death of brain tissue over many years) or
stroke (sudden death of brain tissue).
In many people, atherosclerosis can remain silent (causing
no symptoms or health problems) for years or decades.
Atherosclerosis can begin as early as the teenage years,
but symptoms or health problems usually do not arise
until later in adulthood when the arterial narrowing
becomes severe. Smoking cigarettes, high blood pressure,
elevated cholesterol, and diabetes mellitus can accelerate
atherosclerosis and lead to the earlier onset of symptoms
and complications, particularly in those people who
have a family history of early atherosclerosis.
Coronary atherosclerosis (or coronary artery disease)
refers to the atherosclerosis that causes hardening
and narrowing of the coronary arteries. Diseases caused
by the reduced blood supply to the heart muscle from
coronary atherosclerosis are called coronary heart diseases
(CHD). Coronary heart diseases include heart attacks,
sudden unexpected death, chest pain (angina), abnormal
heart rhythms, and heart failure due to weakening of
the heart muscle. |
