Heart Attack
Also known as: Myocardial
infarction
What is it?
A heart attack is damage to the heart caused by
lack of oxygen to the heart muscle as a result of
coronary artery disease.
Who gets it?
Heart attacks occur in about 1.5 million
American each year and is the leading cause of
death in this county. Risk factors include having
parents who have coronary artery disease, smoking,
high cholesterol (total cholesterol of 240 or
over), high blood pressure, obesity, diabetes,
lack of physical activity and high levels of
stress and anger.
In addition, African Americans are at a higher
risk because of their higher rates of blood
pressure. Men over the age of 45 and women over
the age of 55 are also considered at risk.
What causes it?
A heart attack is caused when one or more of
the coronary arteries that supply blood to heart
become completely blocked and blood to the heart
muscle is cut off. The blockage is usually caused
by the build-up of plaque over the years in the
artery walls or a blood clot in a coronary artery.
Rarely, a healthy coronary artery may have a
spasm, causing blood flowing to the heart to
decrease, resulting in a heart attack. An extreme
decrease in the amount of oxygen in the blood, as
with patients with severe lung disease, can also
trigger heart attacks. Sometimes a heart attack
will occur when the body’s organs need more oxygen
than usual, such as when a patient undergoes an
operation or fights a severe infection.
Recent research suggests that inflammation of
the heart can trigger the most powerful of heart
attacks. Inflammation is thought to weaken plaque,
making it more likely to burst. A piece of plaque
can then form a clot that can cause a heart
attack.
What are the symptoms?
Symptoms of a heart attack can occur days or
weeks leading up to the attack. Patients may not
recognize the symptoms, but usually they are
uncomfortable pressure, fullness, squeezing, or
pain in the center of the chest. This lasts more
than a few minutes, or may go away and return.
Other symptoms include pain that spreads to the
shoulders, neck, or arms and chest discomfort
accompanied by lightheadedness, fainting,
sweating, nausea, or shortness of breath.
Sometimes symptoms disappear and then reappear.
According to the American Heart Association, 63
percent of women and 48 percent of men who died
suddenly of coronary artery disease had no
previous symptoms. About one fifth of all heart
attacks are silent; the patient does not know one
has occurred. Silent heart attacks can damage the
heart, however.
How is it diagnosed?
A doctor can usually diagnose a heart attack by
simply looking at the patient. To confirm
diagnosis, the doctor may talk with the patient,
check heart rate and blood pressure, take a blood
sample and perform a test called an
electrocardiogram. The electrocardiogram will show
which coronary artery is blocked. The blood test
shows the leak of enzymes or other biochemical
markers from damaged cells in the heart muscle.
Using this information, the doctor can usually
determine the amount of damage to the heart. The
heart attack may be limited to a small part of the
inner wall of the heart (a
subendocardial MI) or may have destroyed the
entire depth of a section of heart muscle (a
transmural MI). Usually the longer treatment of a
heart attack is delayed, the more cells are
damaged.
The doctor may categorize the heart attack
according to which portion of the left ventricle
is damaged. The anterior refers to the front of
the heart, which is the part closest to the
breastbone. The inferior part of the heart is the
bottom, which rests on the diaphragm (the layer of
muscle that separates the abdomen from the chest).
The posterior heart is the back of the heart, and
the lateral portion is the side closest to the
left armpit.
Occasionally, a heart attack also involves the
right ventricle. The atria, however, are almost
never affected. These thin-walled chambers receive
a significant amount of their oxygen needs from
the blood contained within them because the use
less oxygen then the ventricles.
What is the treatment?
Once a heart attack has been diagnosed, the
doctor may perform cardiopulmonary resuscitation
(CPR) when necessary to start and keep the patient
breathing and the heart beating. An
electrical-shock device, called a defibrillator,
may be used to restore a normal rhythm if the
heartbeat is fluttering uncontrollably. The doctor
will usually prescribe clot-busting drugs and
other artery opening treatments that can stop a
heart attack in progress and limit damage to the
heart muscle. Treatments include drug therapy, re-vascularization
procedures, percutaneous transluminal coronary
angioplasty and coronary artery bypass surgery. To
be most effective, drug therapy should be given
within one hour of the start of heart attack
symptoms.
Once a zone of heart muscle has died, however,
it will not regenerate or return as functioning
muscle. After a heart attack, a tough scar forms
that may decreases the function of the ventricles
slightly. Sometimes, the portion of the heart
muscle that is still able to function is too weak
to meet all the needs of the body. As a result,
the patient may suffer from fatigue, shortness of
breath, and may develop congestive heart failure,
a condition in which the heart is unable to pump
enough blood to maintain normal circulation. The
scar may also lead to dangerous heart-rhythm
abnormalities (arrhythmias) or life-threatening
clots on the inner walls of the damaged heart
muscle, causing another heart attack or stroke. As
many as two-thirds of heart attack patients never
recover fully.
Self-care tips
To prevent a heart attack, the doctor may
recommend a healthy lifestyle to reduce the risk
of developing coronary artery disease. For
patients who have already had a heart attack, a
healthy lifestyle and carefully following doctor's
orders can prevent another heart attack. A heart
healthy lifestyle includes eating right, regular
exercise, maintaining a healthy weight, no
smoking, moderate drinking, no illegal drugs,
controlling hypertension, and managing stress.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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