PR interval
Image:SinusRhythmLabels.svg|right|thumb|Schematic representation of a normal sinus rhythm EKG wave|300x300px
In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave until the beginning of the QRS complex ; it is normally between 120 and 200 ms in duration.
The PR interval is sometimes termed the PQ interval.
Interpretation
Variations in the PQ interval can be associated with certain medical conditions:- Duration
- * A long PR interval indicates a slowing of conduction between the atria and ventricles, usually due to slow conduction through the atrioventricular 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 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.