Bradycardia classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:


Bradycardia is a decrease in the heart rate due to abnormalities in the atria, AV node or ventricles.


Classification of Bradycardia According to The Origin of Impulse

The origin of the impulse:
The origin of the impulse:
AV junction
The origin of the impulse:
Sinus node dysfunction:
Respiratory sinus arrhythmia
Sinus bradycardia
Sinoatrial block
Sinus arrest
Sick sinus syndrome

Normal variant:
Respiratory sinus arrhythmia
Abnormality in the atria:
Low atrial focus bradycardia
Atrial bigeminy
AV node dysfunction:
First degree AV block
Second degree AV block
Complete or third-degree AV block
Junctional escape rhythm
Junctional bigeminy
Isorhythmic A-V dissociation
Slow VT (idioventricular rhythm)
Ventricular escape rhythm
Escape capture bigeminy

Classification of Bradycardia According to The Location of the Abnormality


Respiratory Sinus Arrhythmia

Sinus Bradycardia

  • Sinus bradycardia is a sinus rhythm of less than 60 bpm. It is a common condition found in both healthy individuals and those who are considered well-conditioned athletes.
  • Studies have found 50-85% of conditioned athletes have benign sinus bradycardia, as compared to 23% of the general population studied.
  • The heart muscle of athletes has become conditioned to have a higher stroke volume, so it requires fewer contractions to circulate the same volume of blood.[1]

Sick Sinus Syndrome

AV Junction


  • Ventricular bradycardia, also known as ventricular escape rhythm or idioventricular rhythm, is a heart rate of less than 50 bpm.
  • This is a safety mechanism when there is a lack of electrical impulse or stimuli from the atrium. Impulses originating from or below the His bundle, also known as ventricular, will produce a wide QRS complex with heart rates between 20 and 40 bpm.[1]
  • Those above the His bundle, also known as junctional, will typically range between 40 and 60 bpm with a narrow QRS complex.
  • In a third degree heart block, approximately 61% take place at the bundle branch-Purkinje system, 21% at the AV node, and 15% at the His bundle.
  • AV block may be ruled out with an EKG indicating "a 1:1 relationship between P waves and QRS complexes. Ventricular bradycardias occurs with sinus bradycardia, sinus arrest, and AV block."
  • Treatment often consists of the administration of atropine and cardiac pacing.[1]

Infantile Bradycardia

  • For infants, bradycardia is defined as a heart rate of less than 100 bpm (normal is around 120-160).[4][5]
  • Premature babies are more likely than full-term babies to have apnea and bradycardia spells; their cause is not clearly understood.
  • Some researchers think the spells are related to centers inside the brain, that regulate breathing, which may not be fully developed.
  • Touching the baby gently or rocking the incubator slightly will almost always get the baby to start breathing again, which increases the heart rate.
  • Medications (theophylline or caffeine) can be used to treat these spells in babies if necessary.
  • NICU standard practice is to electronically monitor the heart and lungs for this reason.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Allan B. Wolfson, ed. (2005). Harwood-Nuss' Clinical Practice of Emergency Medicine (4th ed.). p. 260. ISBN 0-7817-5125-X.
  2. "CrossRef Listing of Deleted DOIs". CrossRef Listing of Deleted DOIs. 2008. doi:10.1007/BF00400429. ISSN 0000-0000.
  3. Sharma, Sanjay (2003). "Physiological Society Symposium - the Athlete's Heart". Experimental Physiology. 88 (5): 665–669. doi:10.1113/eph8802624. ISSN 0958-0670.
  4. Rein AJ, Simcha A, Ludomirsky A, Appelbaum A, Uretzky G, Tamir I (November 1985). "Symptomatic sinus bradycardia in infants with structurally normal hearts". J. Pediatr. 107 (5): 724–7. doi:10.1016/s0022-3476(85)80400-5. PMID 4056971.
  5. Fleming S, Thompson M, Stevens R, Heneghan C, Plüddemann A, Maconochie I, Tarassenko L, Mant D (March 2011). "Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies". Lancet. 377 (9770): 1011–8. doi:10.1016/S0140-6736(10)62226-X. PMC 3789232. PMID 21411136.