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.

How is a heart attack treated?

Treatment of heart attacks include: