Which term describes groups of waves that reflect contraction/relaxation in ECGs?

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

Answer: (B)

In ECG terminology, groups of waves that together represent a phase of heart muscle activity are called a complex. The deflections within a complex stack together to depict what’s happening mechanically—such as ventricular contraction during the QRS complex, which is formed by the Q, R, and S waves. The P wave and T wave are single deflections that relate to atrial depolarization (contraction) and ventricular repolarization (relaxation), respectively, but when you’re describing the set of waves tied to a single electrical event, you’re talking about a complex. An interval refers to time between two points on the tracing, and a segment is the flat baseline portion between waves, while a single wave is one deflection like a P or T wave. So, the term that describes the grouped waves reflecting contraction and relaxation is complex.