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.
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) | Present | 0.12 – 0.20s (3 – 5 small boxes) | 40 – 60bpm |
- Sick Sinus Syndrome
- Sleep Apnoea
- Drugs
- Thyroid Disease
- Reperfusion
- Hypothermia
- AMI
- Vomiting & Straining
- Head Injury
- Syncope (fainting from low HR & BP)
- Dizziness
- Chest Pain
- Shortness of Breath
- Cold & Clammy Skin
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 |
- 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
- Dizziness & light-headedness
- Shortness of breath
- Rapid pulse
- Heart palpation
- Chest pain
- Syncope
- Depending on causes
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 |
- Heart disease
- Stress
- Excessive stimulant consumption
- Medication intake
- Respiratory cycle in children & young adults
- Nil – Asymptomatic
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 |
- Drug toxicity
- Electrolyte disturbance
- SA node ischemia
- Vagal enhancement (e.g. Vomiting)
- Hypoxia
- Sick sinus syndrome
- Syncope
- Loss of consciousness
- Dizziness
- Bradycardia
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 |
- Drug toxicity
- Electrolyte disturbance
- SA node ischemia
- Vagal enhancement (e.g. Vomiting)
Hypoxia - Sick sinus syndrome
- Syncope
- Loss of consciousness
- Dizziness
- Bradycardia
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 |
- Hypovolemia
- Hypoxia
- Hypokalaemia or Hyperkalaemia
- Electrolyte disturbances
- Hypothermia or Hyperthermia
- Toxicity
- Tension Pneumothorax
- Cardiac Tamponade
- AMI
- Absent Pulse
- Loss of consciousness (GCS 3)
- Absent or irregular respirations
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 |
- Cardiac Arrest
- Death
- Loss of consciousness
- No palpating pulses
- No signs of life
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 |
- 4 H’s & 4 T’s causes of Cardiac Arrest
- Natural progression towards death
- Loss of consciousness
- No palpating pulses
- No signs of life
Page contributors:
 | Thanh Bui, AP60825 Event Medic, Emergency Medical Technician & Volunteer Development Officer
|
 | Andrew Moffat, AP16790 |
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