PR interval
Period in electrocardiography
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 200 ms in duration. The PR interval is sometimes termed the PQ interval.
01Interpretation
Variations in the PQ interval can be associated with certain medical conditions:
- Duration
- A long PR interval (of over 200 ms) indicates a slowing of conduction between the atria and ventricles, usually due to slow conduction through the atrioventricular node (AV node). This is known as first degree heart block. Prolongation can be associated with fibrosis of the AV node, high vagal tone, medications that slow the AV node such as beta-blockers, hypokalemia, acute rheumatic fever, or carditis associated with Lyme disease.
- A short PR interval (of less than 120ms) may be associated with a Pre-excitation syndromes such as Wolff-Parkinson-White syndrome or Lown-Ganong-Levine syndrome, and also junctional arrhythmia like atrioventricular reentrant tachycardia or junctional rhythm.
- A variable PR interval may indicate other types of heart block.
- PR segment depression may indicate atrial injury or pericarditis.
Sources and credits
This article is adapted from the Wikipedia article “PR interval”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- SinusRhythmLabels.svg by Created by Agateller (Anthony Atkielski), converted to svg by atom., Public domain
- Heart electrical conduction system (PQ segment).svg by ecgpedia, CC BY-SA 3.0
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