Heart Attack (cont.)
How is a heart attack diagnosed?
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.
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.
Next: What about heart attacks in women? »
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