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PR interval

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PR interval

In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200ms in duration. If a Q wave is measured by EKG, the PR interval is sometimes termed the PQ interval.

Interpretation

Variations in the PR interval can be associated with certain medical conditions:

  • Duration
  • A long PR interval (of over 200 ms) may indicate a first degree heart block. Prolongation can be associated with hypokalemia, acute rheumatic fever, or carditis associated with Lyme disease.
  • A short PR interval (of less than 120ms) may be associated with Wolff–Parkinson–White syndrome, Lown–Ganong–Levine syndrome, or Junctional rhythms.
  • A variable PR interval may indicate other types of heart block.
  • PR segment depression may indicate atrial injury or pericarditis.
  • Variable morphologies of P waves in a single EKG lead is suggestive of an ectopic pacemaker rhythm such as wandering pacemaker or multifocal atrial tachycardia.

    • References

    PR interval Wikipedia
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