What does the ST segment indicate in an ECG?

The ST segment on an ECG represents a critical phase in the cardiac cycle, specifically indicating the time between the end of ventricular depolarization and the beginning of ventricular repolarization. During this segment, the ventricles are in their plateau phase, meaning they are fully contracted and actively pumping blood. This is a crucial moment as it is when the heart is supposed to be in a stable state before the myocardial cells start to repolarize and prepare for the next heartbeat.

In a healthy individual, the ST segment typically appears as a flat line at the baseline of the ECG, and deviations from this baseline can indicate underlying heart conditions, such as ischemia or infarction. Understanding the significance of the ST segment is vital for interpreting ECG results accurately, as changes in this segment can provide essential insights into the heart's electrical activity and overall health.