PR interval
{{Short description|Period in electrocardiography}}
Image:SinusRhythmLabels.svg EKG wave|300x300px]]
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.
Interpretation
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).{{Cite book|title=Clinical cardiac electrophysiology in clinical practice|others=Huang, David T.,, Prinzi, Travis|isbn=978-1-4471-5433-4|location=Berlin|oclc=897466910|date = December 2014}} 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.{{cite journal |vauthors = Karacan M, Ceviz N, Olgun H |title=Heart rate variability in children with acute rheumatic fever |journal=Cardiol Young |volume=22 |issue=3 |pages=285–92 |year=2012 |pmid=21933462 |doi=10.1017/S1047951111001429 |s2cid=25845504 }}{{cite journal |doi=10.1542/peds.2008-3058 |pmid=19403477 |title=Lyme Carditis in Children: Presentation, Predictive Factors, and Clinical Course |journal=Pediatrics |volume=123 |issue=5 |pages=e835–41 |year=2009 |last1=Costello |first1=J. M. |last2=Alexander |first2=M. E. |last3=Greco |first3=K. M. |last4=Perez-Atayde |first4=A. R. |last5=Laussen |first5=P. C. |s2cid=25270378 }}
- 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.{{fact|date=May 2015}}
- PR segment depression may indicate atrial injury{{cite book |first1=B.N. Vijay Raghawa |last1=Rao |year=2009 |chapter=Evolution of ECG Changes |chapter-url=https://books.google.com/books?id=_IGGF2Etes8C&pg=PT575 |pages=561–2 |title=Clinical Examinations in Cardiology |isbn=978-81-312-0964-6}} or pericarditis.{{cite journal |pmid=11989495 |year=2002 |last1=Pedley |first1=D. K. |title=P-R segment depression: An early diagnostic feature in acute pericarditis: A telephone survey of UK accident and emergency departments |journal=European Journal of Emergency Medicine |volume=9 |issue=1 |pages=43–5 |last2=Brett |first2=C |last3=Nichol |first3=N |doi = 10.1097/00063110-200203000-00010|s2cid=22919251 }}
File:Heart electrical conduction system (PQ segment).svg|230x230px]]
See also
References
{{reflist}}
{{Cardiovascular physiology}}
{{DEFAULTSORT:Pr Interval}}