ST Segment Depression (4-Codes) and Negative T-Waves (5-Codes)

Toward the end of ventricular excitation (QRS), the earliest part of the heart to be excited begins to recover or recharge to produce the T-wave. If the heart muscle is injured or short of oxygen, the electrical recovery starts prematurely, and this may produce a sizable current. The trace between QRS and T is then displaced up or down, depending on the location of the injury and on the lead. The ST segment is continuous with the T-wave and both are often coded together; thus, they are learned together.