What does the term "Isoelectric" refer to in a normal ST segment?

The term "Isoelectric" in the context of the normal ST segment refers to a segment that aligns with the baseline on the electrocardiogram (ECG). This means that during the ST segment, the electrical activity of the heart is stable and there are no significant changes in voltage. When the ST segment is isoelectric, it serves as a reference point that helps in determining if there are deviations or abnormalities in other segments of the ECG.

In a healthy heart, the ST segment ideally doesn't show any elevation or depression from the baseline, which is crucial for correctly interpreting heart activity and diagnosing potential issues. An isoelectric ST segment indicates that the heart is not experiencing ischaemia or other conditions that could result in ST segment changes, enabling clinicians to assess cardiac health more accurately.