Alternative
names
myocardial infarction; MI; heart attack
Definition
A disorder in which damage to an area of heart muscle
occurs because of an inadequate supply of oxygen to that
area.
Common
causes, incidence, and risk factors
Causes
include clot formation or spasm in one of the arteries
that supply the heart muscle (a coronary artery).
These and other similar conditions block the supply of oxygen
to an area of the heart, leading to damage or death of the
cells in that area. Most often, this occurs in a coronary
artery that has been narrowed from changes related to atherosclerosis.
The damaged tissue results in a permanent loss of contraction
of this portion of the heart muscle.
Risk factors for MI include smoking, hypertension,
diabetes mellitus, high fat diet, high
blood cholesterol (LDL) levels, obesity,
male gender, age over 65, and heredity. A personal or family
history of coronary artery disease, cerebrovascular
disease, peripheral vascular disease, angina
(particularly unstable angina), or kidney failure
requiring hemodialysis indicates increased risk for
MI. Occasionally, sudden overwhelming stress can
trigger an MI, but this is rare. In older persons, straining
to have a bowel movement can be a risk factor.
Chest pain is the cardinal symptom of MI, but in
many cases the pain may be subtle or even completely absent,
especially in the elderly and diabetics. Other symptoms
such as weakness, shortness of breath, nausea,
or vomiting may predominate.
Acute MI occurs in approximately 2 out of 1,000 people per
year. It is a major cause of sudden death in adults.
Prevention
Control cardiac risk factors whenever possible. Control
blood pressure and total cholesterol levels,
reduce or avoid smoking, modify diet (increase high
density lipoproteins & decrease low density lipoproteins)
if necessary, control diabetes, lose weight if obese.
Follow an exercise program to improve cardiovascular
fitness. (Consult the health care provider first.)
After an MI, followup care is important to reduce the risk
of developing a new MI. Often, a cardiac rehabilitation
program is recommended to aid in gradual return to a "normal"
lifestyle. Follow the exercise, diet, and/or medication
regimen prescribed by your doctor.
Symptoms
- chest
pain below the sternum (breastbone)
- back
pain
- abdominal
pain
- pain
may radiate
- to
the chest, arms, shoulder
- to
the neck, teeth and jaw
- to
the back
- pain
is prolonged, typically greater than 20 minutes
- pain
similar to angina but not relieved by
rest or nitroglycerin
- any
prolonged chest pain, back pain, or abdominal pain
- pain
that may be described as:
- "bad
indigestion".
- intense,
severe, subtle, or absent
- squeezing
or heavy pressure
- a
tight band on the chest
- "an
elephant sitting on my chest"
- shortness
of breath
- sudden
- may
or may not be accompanied by pain
- cough
- lightheadedness
- dizzy
- fainting
- nausea
- vomiting
- sweating,
may be profuse (diaphoresis)
- dry
mouth
- feeling
of "impending doom"
- anxiety
Additional
symptoms that may be associated with this disease:
- seizures
- fatigue
- breathing,
absent temporarily
- breathing
difficulty, lying down
- blood
pressure, low
- behavior,
unusual or strange
Signs
and Tests
Examination often reveals a rapid pulse. Blood
pressure may be normal, high, or low. Listening to the
chest with a stethoscope (auscultation) may show
crackles in the lungs, heart murmur, or other abnormal sounds.
- An
ECG, single or repeated over 2 to 3 days, often
shows MI.
Indications
of MI and extent of heart damage may show on the following
tests:
- coronary
angiography
- nuclear
ventriculography (MUGA or RNV).
- echocardiography
- treadmill
Byproducts
of heart damage and factors indicating high risk for MI
may show on the following tests:
- LDH
- LDH
isoenzymes
- CPK
- CPK
isoenzymes
This
disease may also alter the results of the following tests:
- aldolase
- apolipoprotein
B100
- apolipoprotein
CII
- AST
- BUN
- chem-20
- cholesterol
test
- heart
MRI
- lipids
- serum
- myoglobin
- serum
- myoglobin
- urine
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