In ECG terminology, what does the term segment refer to?

• A. Segment
• B. Complex
• C. Interval
• D. Wave

Answer: (A)

Segments are the portions of an ECG tracing that lie between two waves. They are the flat, isoelectric stretches you see between deflections, such as the PR segment (between the end of the P wave and the start of the QRS complex) and the ST segment (between the end of the QRS complex and the start of the T wave). This is why the term used to describe that part of the tracing is “segment.” It’s distinct from waves (the P, QRS, and T deflections themselves), from complexes (the QRS complex, for example), and from intervals (durations that start and end at different waves, including waves). Understanding that segment refers specifically to the straight portions between waves helps you identify settings like ST segment changes or PR segment characteristics on an ECG.