What Does ST Segment Depression Represent?

A normal electrocardiogram tracing (EKG or ECG) is made up of a "P" wave, a QRS complex and a "T" wave. The part of the tracing between the QRS complex and the "T" wave is known as the ST segment. Abnormalities in the ST segment can indicate serious disorders.

Identification

• The ST segment is normally a flatline segment running along the baseline of the EKG tracing. ST segment depression occurs when the line segment is below the baseline of the EKG tracing. It may be parallel to the baseline, or it may slope either up or down.

Causes

• According to the Diseases Database, a depressed ST segment may indicate the heart isn't getting enough oxygen, there's too much digoxin in the body, the ventricles of the heart are enlarged or there's a defect in the conduction system of the left ventricle. It may also mean the person's had a heart attack or a pulmonary embolus (blood clot in one of the arteries supplying the lungs).

Considerations

• According to the University of Utah, an EKG tracing may also show a depressed ST segment if there is poor contact between the person's skin and EKG electrodes.

Effect

• The ST segment depression doesn't cause symptoms. Instead, the person will have symptoms from his underlying disorder. Someone with a pulmonary embolus, for example, may experience shortness of breath, chest pain and cough.

Warning

• Because ST segment depression is associated with some serious cardiopulmonary disorders, it's important to follow up with a doctor to get a definitive diagnosis.