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When there is
severe chest pain, suspicion that a heart attack is occurring usually is high,
and tests can be performed quickly that will confirm the heart attack. A problem
arises, however, when the symptoms of a heart attack do not include chest pain.
A heart attack may not be suspected, and the appropriate tests may not be
performed. Therefore, the initial step in diagnosing a heart attack is to be
suspicious that one has occurred.
Electrocardiogram. An electrocardiogram (ECG) is a recording of the
electrical activity of the heart. Abnormalities in the electrical activity
usually occur with heart attacks and can identify the areas of heart muscle that
are deprived of oxygen and/or areas of muscle that have died. In a patient with
typical symptoms of heart attack (such as crushing chest pain) and
characteristic changes of heart attack on the ECG, a secure diagnosis of heart
attack can be made quickly in the emergency room and treatment can be started
immediately. If a patient's symptoms are vague or atypical and if there are
pre-existing ECG abnormalities, for example, from old heart attacks or abnormal
electrical patterns that make interpretation of the ECG difficult, the diagnosis
of a heart attack may be less secure. In these patients, the diagnosis can be
made only hours later through detection of elevated cardiac enzymes in the
blood.
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Blood tests.
Cardiac enzymes are proteins that are released into the blood by dying heart
muscles. These cardiac enzymes are creatine phosphokinase (CPK), special
sub-fractions of CPK (specifically, the MB fraction of CPK), and troponin, and
their levels can be measured in blood. These cardiac enzymes typically are
elevated in the blood several hours after the onset of a heart attack. A series
of blood tests for the enzymes performed over a 24 hour period are useful not
only in confirming the diagnosis of heart attack, but the changes in their
levels over time also correlates with the amount of heart muscle that has
died.
The most
important factor in diagnosing and treating a heart attack is prompt medical
attention. Rapid evaluation allows early treatment of potentially
life-threatening abnormal rhythms such as ventricular fibrillation and allows
early reperfusion (return of blood flow to the heart muscle) by procedures that
unclog the blocked coronary arteries.
The more rapidly
blood flow is reestablished, the more heart muscle that is
saved.
Large and
active medical centers often have a "chest pain unit" where patients suspected
of having heart attacks are rapidly evaluated. If a heart attack is diagnosed,
prompt therapy is initiated. If the diagnosis of heart attack is initially
unclear, the patient is placed under continuous monitoring until the results of
further testing are available.
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