PR Interval — ECG/EKG Terminology

Definition: The time from the onset of atrial depolarization (P wave) to the onset of ventricular depolarization (QRS). Normal is 0.12–0.20s.

Key Facts

• Measured from P-wave onset to QRS onset and reflects AV conduction time.
• Normal adult range is about 120 to 200 ms.
• Prolonged PR suggests first-degree AV block; short PR can indicate pre-excitation or junctional origin.

ECG Connection: PR trend is key for identifying AV nodal delay and conduction disease progression.

Why It Matters: Early recognition of AV conduction changes supports timely escalation before high-grade block develops.