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MBBS QUESTION #10239
Question 1
The PR interval on a surface ECG represents:
  • The time for ventricular depolarization alone
  • The time from the onset of atrial depolarization to the onset of ventricular depolarization, reflecting conduction delay through the AV node✔️
  • The time for ventricular repolarization
  • The total duration of one complete cardiac cycle
Correct Answer Explanation
The PR interval spans atrial depolarization (P wave) through the physiological delay at the AV node, ending at the start of ventricular depolarization (QRS onset); its prolongation reflects delayed AV conduction, as in first-degree heart block.