Myocardial infarction, commonly known as a heart attack,
is essentially synonymous with the acute coronary syndrome spectrum classification for STEMI.
It occurs when a large part of the heart muscle is deprived of oxygen
after a sudden and complete, or nearly complete, blockage of a coronary artery.
If the flow of blood is not restored quickly, the affected heart muscle becomes damaged
from lack of oxygen and begins to die.
The patient will most likely complain of chest pain, nausea, sweating, and difficulty breathing.
However, as many as 20% of myocardial infarctions may go unrecognized
because they are silent and do not cause any pain.
Myocardial infarction is a medical emergency.
Among those patients who actually survive long enough to make it to the hospital,
about 10% will die within a year.
Approximately half of all deaths from a myocardial infarction
occur within the first 3 to 4 hours after the onset of symptoms.
The rapid reestablishment of coronary circulation is critical to preventing
or minimizing damage to the myocardium.
In fact, prompt reperfusion may limit the extent of the infarction
and minimize the risk of major cardiac complications,
such as pump failure and abnormal heart rhythms.
Thus, patients who are having a myocardial infarction
are frequently given aspirin to thin the blood,
or antithrombolytic drugs, such as Heparin,
to prevent the formation of additional clots.
Diagnoses of myocardial infarction is based on ECG findings and blood tests
to evaluate the presence of myocardial proteins
and enzymes which are released into the circulation when myocardial cells die.
Although the ECG usually reveals an ST segment elevation,
occasionally a negative result can be obtained.
Therefore, serial ECG tracing are important for the diagnosis
of acute myocardial infarction.
Blood tests will show cardiac biomarkers,
or enzymes, within 12 hours of heart muscle damage.