Heart Attack and Acute Coronary Syndrome

Tests
When a person presents with ACS, it is usually not clear whether the symptoms indicate that the patient is having an AMI or whether the blockage is only temporary. A number of tests are available to help evaluate whether AMI has occurred or not.

The diagnosis of a heart attack may be made by changes seen on an electrocardiogram (ECG or EKG) and by a number of blood tests. An ECG is performed within the first few minutes after a person with ACS arrives in the emergency room. It can recognize changes that prove that a severe heart attack has occurred, but this diagnostic change is only seen in the most severe AMI’s. More commonly, the ECG only confirms that the heart is not getting enough blood or has non-specific changes that do not prove that an AMI has occurred. Those with the most severe ECG changes (termed ST elevation, referring to increase in the height of the line on the ECG linking the S and T parts of the ECG tracing) usually have a major clot in an artery supplying the heart and should be treated rapidly with either drugs or cardiac catheterization to remove the clot.

In the remaining majority of patients with ACS, blood tests are needed to tell whether an AMI has occurred. The blood tests provide a measure of heart muscle damage. When some of the muscle dies, the dead cells release chemicals into the blood. These tests include CK-MB, myoglobin, and troponin. Measuring the levels of these cardiac biomarkers can detect a heart attack and provide a rough measure of how much muscle has been damaged. They are also used in the diagnosis, evaluation, and monitoring of patients with suspected ACS.

Other non-laboratory tests may be performed to diagnose a heart attack, including a nuclear scan and coronary angiography. For more information on these, visit the National Heart Attack Alert Program: Testing for a Heart Attack.