ECG Question #3


Use the ECG strip above to answer the following questions:

Time from SA node stimulation to ventricular contraction is represented by which area of the ECG strip.


  1. ST segment
    • Rationale:
  2. PR interval
    • Rationale:
  3. QRS complex
    • Rationale:
  4. P wave
    • Rationale:



The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex and represents the time needed for sinus node stimulation, atrial depolarization, and conduction through the AV node before ventricular depolarization. The ST segment lasts from the end of the QRS complex to the beginning of the T wave. The QRS complex represents ventricular depolarization and is normally less than 0.12 seconds in duration. The P wave represents atrial depolarization and lasts 0.11 seconds or less.

Learning Outcomes

Test Taking Tip

Video Rationale