Which term describes the interval from the end of the P wave to the start of the QRS complex?

• A. QT interval
• B. PR interval
• C. QRS duration
• D. P-R segment

Answer: (D)

In an ECG, different parts of the tracing correspond to specific electrical events. The P wave marks atrial depolarization, and the QRS complex marks ventricular depolarization. The time from the end of the P wave to the start of the QRS complex is the PR segment. That portion reflects conduction through the AV node and His-Purkinje system, where the signal travels without any additional wave of depolarization visible on the surface leads. The full PR interval, by contrast, runs from the start of the P wave to the start of the QRS and includes the P wave plus this AV delay. The QT interval spans from the start of the QRS to the end of the T wave, and the QRS duration is just the width of the QRS complex. So the interval described is the P-R segment.