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PR Interval (Pediatric)

Overview:

  • PR interval: period from beginning of P wave to beginning of QRS (ie, P wave + PR segment)
  • Cardiac event: transmission from atrium (adjacent to sinus node) to ventricle (adjacent to Purkinje-network fibers)

PR interval duration:

  • In general: ↑ PR interval with ↑ age [1]
  • Average based on age:
    • 18-22 weeks GA: 102 ms
    • Term: 110 ms
    • Birth: 107 ms
    • 1 month: 98 ms
  • ↓ PR interval from birth-to-1 month primarily due to autonomic factors [1]
  • ↑ PR interval after 1-month due to slowing of AV nodal conduction related to intrinsic changes in AV node & ↑ in atrial size
  • Lower limit of normal:
    • Children: 90 ms
    • Adults: 120 ms
  • Upper limit of normal:
    • Young infants: 140 ms
    • Adolescents: 180 ms
    • Adults: 200 ms

Short PR interval:
Ventricular preexcitation

  • Due to conduction over (1) accessory AV connection (more common) or (2) fasciculoventricular pathway [3]
  • May be difficult to recognize with short PR interval
  • Suspect if: [2]
    • PR interval <100 ms
    • No Q waves in left-lateral precordial leads (V5-V6)
    • LAD (QRS in frontal plane)

Prolonged PR interval:
1st-degree AV block

  • Due to conduction slowing at atrium, AV node, or His-Purkinje system in children [4]
  • Occurs at only one of these sites in children with heart disease [5]

REFERENCES

1. Chia EL, Ho TF, Rauff M, et al. Cardiac time intervals of normal fetuses using noninvasive fetal electrocardiography. PrenatDiagn 25:546, 2005.

2. Perry JC, Giuffre, Garson A Jr. Clues to the electrocardiographic diagnosis of subtle Wolff-Parkinson-White syndrome in children. J Pediatr 117:871, 1990.

3. Sallee D III, Van Hare GF. Preexcitation secondary to fasciculoventricular pathways in children: a report of three cases. J Cardiovasc Electrophysiol. 10:36, 1999.

4. Sarubbi B, Mercurio B, Ducceschi V, et al. A “multisite” atrioventricular block. Ital Heart J 5:64, 2004.

5. Sherron P, Torres-Arraut E, Tamer D, et al. Site of conduction delay and electrophysiologic significance of first degree atrioventricular block in children with heart disease. Am J Cardiol 55:1323, 1985.

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Dr. Anthony Kashou (The EKG Guy) is a physician resident at the Mayo Clinic in Rochester, Minnesota. He is on a mission to transform ECG education and filling the gap exists around the world. Dr. Kashou has taught and developed curriculum for medical students, including 500+ lectures and 100+ hours of adult and pediatric ECG lessons.

At the Mayo Clinic, he pursues innovative ECG research and was awarded first place for his research at the Minnesota American College of Cardiology Conference 2018. His passion for medical education and innovation led to the development of EKG.MD, which provides a convenient and accessible forum to learn the fundamentals and foundations of ECG interpretation. He has also authored dozens of peer-reviewed articles for medical journals and textbooks, along with multiple ECG books for learners at all levels.

Dr. Kashou continues to lead and teach weekly ECG sessions and weekend seminars for residents, nurses, ECG interpreting technicians, and physician assistants at the Mayo Clinic. He has been asked and is currently developing an ECG board review course for cardiology fellows. He has an online following of over 275,000 individuals and is the founder of the largest, fastest growing ECG community in the world. His clinical research focuses on developing innovative ECG algorithms that can be integrated and implemented into clinical practice.

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