Which statement correctly describes intervals in ECG context?

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

Answer: (A)

Intervals describe the time between two landmarks on the ECG tracing. This means they’re measuring how long something takes, not what the deflection or pattern looks like. For example, the PR interval spans from the start of the P wave to the start of the QRS complex, the QT interval runs from the start of the Q wave to the end of the T wave, and the RR interval is the time between successive R peaks. These are all expressed in milliseconds and reflect conduction timing and the duration of the cardiac cycle.

In contrast, a wave is a single deflection on the tracing, a complex is a group of waves that together represent a phase (like the QRS complex for ventricular depolarization), and a segment is a baseline portion between waves (such as the PR segment or the ST segment). So the term that correctly describes a measurement of time between two points is interval.