UNCONTROLLED WHEN PRINTED

Result of Sinoatrial Node (SA) dysfunction resulting in abnormal impulse formation or disruption. The remainder of the conduction system is normal (normal PR & QRS interval).

A normal sinus rhythm is a regular rhythm with rate of 50 to 100bpm with a P-wave before every QRS complex and P-wave positive in Lead II.

Sinus Bradycardia (Slow Heart Rate)

1

Has characteristics of a sinus rhythm, however the SA node fires at < 60bpm – Resulting in slower rate – Risk for reduced cardiac output. Can occur in fit & healthy people.

Treatment is required if the patient is symptomatic.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Present0.12 – 0.20s (3 – 5 small boxes) 40 – 60bpm
Causes
  • Sick Sinus Syndrome
  • Sleep Apnoea
  • Drugs
  • Thyroid Disease
  • Reperfusion
  • Hypothermia
  • AMI
  • Vomiting & Straining
  • Head Injury
Signs & Symptoms
  • Syncope (fainting from low HR & BP)
  • Dizziness
  • Chest Pain
  • Shortness of Breath
  • Cold & Clammy Skin
Sinus Tachycardia (Fast Heart Rate)

2

3

Has characteristics of a sinus rhythm, however the SA node fires at > 100bpm – Resulting in faster rate.

Treatment is based on the cause.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Present 0.12 – 0.20s (3 – 5 small boxes) 100 – 160 bpm
Causes
  • Excitement &/or physical exertion
  • Fever
  • Pain
  • Infection &/or Fever
  • Hypoxia
  • Hypovolemia &/or Anaemia
  • AMI
  • Heart Failure
  • Anxiety
  • Drugs that decrease Parasympathetic tone
  • Drugs that increases sympathetic tone
  • Stimulant ingestion
  • Hyperthyroidism
Signs & Symptoms
  • Dizziness & light-headedness
  • Shortness of breath
  • Rapid pulse
  • Heart palpation
  • Chest pain
  • Syncope
  • Depending on causes
Sinus Arrhythmias

4

Has characteristics of a sinus rhythm, however the SA node fires at an irregular rate – Normal in children & young adults; can associate with bradycardia. Elderly can lead to ‘sick sinus syndrome.’

Do not require treatment – not clinically significant.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes) Present 0.12 – 0.20s (3 – 5 small boxes) 60 - 100 bpm
Causes
  • Heart disease
  • Stress
  • Excessive stimulant consumption
  • Medication intake
  • Respiratory cycle in children & young adults
Signs & Symptoms
  • Nil – Asymptomatic
Sinus Arrest / Sinus Pause

5

When SA node has failed to generate an impulse resulting in timing disruption - Diagnosed when the cardiac cycle does not resume normally after an irregular pattern.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes)
Otherwise absent during pause
Present
Otherwise absent during pause
0.12 – 0.20s (3 – 5 small boxes)
Otherwise absent during pause
40 - 70 bpm
Causes
  • Drug toxicity
  • Electrolyte disturbance
  • SA node ischemia
  • Vagal enhancement (e.g. Vomiting)
  • Hypoxia
  • Sick sinus syndrome
Signs & Symptoms
  • Syncope
  • Loss of consciousness
  • Dizziness
  • Bradycardia
Sinus Block

6

When SA node generates an impulse, but it has been blocked from leaving the node - Diagnosed when the cardiac cycle does resume normally after an irregular pattern.

QRS Complex P Wave PR Interval Rate (bpm)
0.08 – 0.10s (2 – 2.5 small boxes)
Otherwise absent during pause
Present
Otherwise absent during pause
0.12 – 0.20s (3 – 5 small boxes)
Otherwise absent during pause
40 - 70 bpm
Causes
  • Drug toxicity
  • Electrolyte disturbance
  • SA node ischemia
  • Vagal enhancement (e.g. Vomiting)
    Hypoxia
  • Sick sinus syndrome
Signs & Symptoms
  • Syncope
  • Loss of consciousness
  • Dizziness
  • Bradycardia
Pulseless Electrical Activity (PEA)

9

When there is a semi or fully organised electrical activity of the heart – However the heart does not pump enough for a detectable pulse.

Commence CPR – NOT SHOCKABLE RHYTHM

QRS Complex P Wave PR Interval Rate (bpm)
Variable Nil Nil Variable but undetected Pulse
Causes
  • Hypovolemia
  • Hypoxia
  • Hypokalaemia or Hyperkalaemia
  • Electrolyte disturbances
  • Hypothermia or Hyperthermia
  • Toxicity
  • Tension Pneumothorax
  • Cardiac Tamponade
  • AMI
Signs & Symptoms
  • Absent Pulse
  • Loss of consciousness (GCS 3)
  • Absent or irregular respirations
Asystole

10

No ventricular activity – clinically dead. Consider Resuscitation or termination of resuscitation of criteria is met.

Commence CPR – NOT SHOCKABLE RHYTHM

QRS Complex P Wave PR Interval Rate (bpm)
Absent Absent Absent Nil
Causes
  • Cardiac Arrest
  • Death
Signs & Symptoms
  • Loss of consciousness
  • No palpating pulses
  • No signs of life
Agonal Rhythm

11

12

13

Last organised rhythm of the heart’s electrical activity prior to death (asystole).

Commence CPR – NOT SHOCKABLE RHYTHM

QRS Complex P Wave PR Interval Rate (bpm)
Wide & abnormal Absent Undetermined < 20bpm
Causes
  • 4 H’s & 4 T’s causes of Cardiac Arrest
  • Natural progression towards death
Signs & Symptoms
  • Loss of consciousness
  • No palpating pulses
  • No signs of life

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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