UNCONTROLLED WHEN PRINTED
Junctional Rhythm

1

When the SA node fails as main pacemaker – therefore AV node takes over whereas the P-wave indicates the depolarisation sequence;

  • P-wave in front of QRS = Atria depolarised before ventricles
  • P-wave after QRS = Ventricles depolarised before atria
  • P-wave hidden in QRS = Atria & ventricles depolarised together
QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Absent, inverted or after QRS Short if present 40 - 60 bpm
Causes
  • Damage to AV node
  • Cardiomyopathy
  • Drug toxicity
  • Electrolyte disturbance
  • Heart failure
  • Hypoxia
  • Myocarditis
  • Reperfusion
  • Valvular Heart Disease
Signs & Symptoms
  • Light-headedness
  • Palpations
  • Chest pain symptoms
  • Shortness of breath
  • Weakness
Junctional Escape Rhythm

2

Delayed impulse not from the atria but elsewhere in the AV junction – occurs when the SA node produces impulses slower than the AV node’s rate. This can due to a block.

QRS Complex P Wave PR Interval Rate (bpm)
< 0.10s (<2.5 small boxes) Absent, inverted or after QRS Short if present 40 - 60 bpm
Causes
  • Severe Sinus bradycardia
  • Sinus Arrest
  • Sino-atrial exit block
  • 2nd Degree AV block
  • 3rd Degree AV block
  • Hyperkalaemia
  • Drug Toxicity
Signs & Symptoms
  • Bradycardia
  • Light-headedness
  • Dizziness
  • Hypotension
  • Syncope
Accelerated Junctional Rhythm

3

When inherent junction pacemaker site is stimulated faster than the normal rate – This is an excited junction rhythm. Again P-wave behaviour indicates depolarising sequence.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Absent, inverted or after QRS Short if present 60 - 100 bpm
Causes
  • Damage to AV node
  • Cardiomyopathy
  • Drug toxicity
  • Electrolyte disturbance
  • Heart failure
  • Hypoxia
  • Myocarditis
  • Reperfusion
  • Valvular Heart Disease
Signs & Symptoms
  • Light-headedness
  • Palpations
  • Chest pain symptoms
  • Shortness of breath
  • Weakness
Junctional Tachycardia

4

5

When inherent junction pacemaker site is stimulated faster than the normal rate – This is an excited junction rhythm. The tachycardia is caused by re-entry circuit allowing repeat transmission of the impulse through the AV node and surrounding structures.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Absent, inverted or after QRS Short >100 bpm
Causes
  • AV node damage
  • Digitalis toxicity
  • Electrolyte disturbance
  • Heart failure
  • Post-cardiac Surgery
  • Valvular heart disease
Signs & Symptoms
  • Light-headedness
  • Palpations
  • Chest pain symptoms
  • Shortness of breath
  • Weakness
Premature Junctional Contraction (PJC)

6

Originate from ectopic sites closer to the AV node (cause absent P-waves) – Where little of this impulse is travelled through the atria tissue creating an inverted P-wave as impulse can travel backwards – Usually a precursor to other junctional rhythms.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Absent, inverted or after QRS Short Varying
Causes
  • Digoxin toxicity
  • Electrolyte imbalance
  • Heart failure
  • Hyperthyroidism
  • Stimulants
  • Pericarditis
  • Stress
  • Valvular Heart Disease
Signs & Symptoms
  • Bradycardia
  • Light-headedness
  • Dizziness
  • Hypotension
  • Syncope

References

College of Pre-Hospital Care. (2015). 12-Lead ECG Analysis: Self-Directed Learning Package. Version 3. St John Ambulance Ltd.  

Curtis, K., & Ramsden, C. (2016). Emergency and trauma care for Nurses and Paramedics (2nd ed.). Elsevier Australia.

DeLaune, S. C., Ladner, P. K., McTier, L., Tollefson, J., & Lawrence, J. (2016). Australian and New Zealand fundamentals of nursing (1st ed.). Cengage Learning Australia Pty Limited.

ECG & ECHO Learning. (2020). Clinical ECG Interpretation. https://ecgwaves.com/topic/ecg-normal-p-wave-qrs-complex-st-segment-t-wave-j-point/

Life in the Fast Lane. (2020). ECG Library. https://litfl.com/ecg-library/

St John WA Ltd. (2017). Electrocardiography (ECG). Clinical Resources. https://clinical.stjohnwa.com.au/clinical-skills/assessment/vital-signs/electrocardiography-(ecg)

WikiEM. 2020. The Global Emergency Medicine Wiki. https://www.wikem.org


Page contributors:

60825Thanh Bui, AP60825
Event Medic, Emergency Medical Technician &
Volunteer Development Officer

 

16790

Andrew Moffat, AP16790
Volunteer Training Manager & Volunteer Development Officer

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