Bradycardia classification

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

Overview

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

Classification

Classification of Bradycardia According to The Origin of Impulse

 
 
 
 
 
 
 
 
 
 
Bradyarrhythmia
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The origin of the impulse:
Atria
 
 
 
 
 
The origin of the impulse:
AV junction
 
The origin of the impulse:
Ventricles
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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

Atria

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

Ventricles

  • 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.

References

  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.