CARDIAC ARRHYTHMIAS

Epidemiology

• Less common than in adults
• Peak age is in infancy or late childhood

Causes

The causes of tachy-arrhythmias in children include:

• Re-entrant congenital conduction pathway abnormality (most common) eg. Wolf Parkinson White Syndrome
• Post cardiac surgery
• Cardiomyopathy
• Long QT syndrome
• Metabolic / electrolyte disturbance
• Poisoning

The causes of brady-arrhythmias in children include:

• Pre-terminal event in hypoxia or shock/acidosis
• Raised intracranial pressure
• After conduction pathway damage during cardiac surgery
• Congenital heart block
• Long QT syndrome
• Following vagal stimulation eg. passing NG tube

Recognition

Presentation can include

• Palpitations (verbal child)
• Poor feeding (pre-verbal child)
• Shock
• Heart failure

• Assess vocalisations (crying / talking)
• Assess airway patency by looking for breath sounds, listening for breath sounds and stridor and feeling expired air

• Assess effort of breathing, saturations, breath sounds (signs of heart failure)

• Check for a central pulse (carotid or femoral)
• Heart rate – this is the defining observation for this presentation. An abnormal heart rate would be that which falls outside of the normal range for the given age

Table:  Normal vital signs in children
	Infant	1-2 years	2-5 years	5-12 years	Adolescent
Pulse rate (bmp)	110-160	100-150	95-140	80-120	60-90
Respiratory rate (rpm)	30-40	25-35	25-30	2-25	14-18
Blood pressure Systolic mmHg	80-90	85-95	85-100	90-100	100-140
Temperature (define if oral etc)	35-37oC				36-37.5 oC
Saturations	94-98%

• Pulse volume
• Capillary refill time
• Blood pressure

A thready pulse, with hypotension and delayed capillary refill suggests haemodynamic instability.

• Conscious level – reduced GCS suggests haemodynamic instability
• Pupils – dilated pupils may point to a poisoning cause eg. tricyclic antidepressants cause dilated pupils and cardiac arrhythmias.
  Unequal pupils and a bradycardia suggest raised intracranial pressure.

• Assess for fever – may suggest simple sinus tachycardia rather than a pathological arrhythmia as heart rate tends to increase alongside an increase in temperature
• Look for clues for the cause for arrhythmia – eg. signs of head injury to explain a bradycardia due to raised intracranial pressure / any evidence of poisoning

Response

All cardiac arrhythmias, particularly if unstable, require the same initial response:

• Open the airway (head tilt / chin lift)
• Apply oxygen 15L/min via a reservoir mask
• Call for anaesthetic help – may need intubation

• Monitor oxygen saturations

• Attach ECG monitor or defibrillator
• Assess cardiac rhythm
• Evaluate if the rhythm is slow or fast for the child's age
• Evaluate if the rhythm is regular or irregular
• Evaluate if the QRS complex is narrow or broad
• Obtain IV access – obtain bloods for FBC, U&E, Calcium, Magnesium and a venous gas (electrolyte abnormalities can triggers arrhythmias)

The treatment options will depend on the above and the child's stability

• If any deterioration in the child's conscious level – treat the child as haemodynamically unstable (see below)

• Treat any cause that is identified by further examination – eg. Refer to Toxbase for antidotes if poisoning is suspected

Essentially, there are a series of questions you need to ask yourself when you see a child with a cardiac arrhythmia

Question 1- Is there a central pulse and signs of life?

Question 2 - Is the patient haemodynamically stable?

Question 3 - What is the heart rate? Is it fast or slow?

This will help you identify the cause of the arrhythmia and narrows down your treatment options.

If the heart rate is fast you need to ask yourself the following question:

Question 4 - Is the QRS complex narrow or broad?

Narrow complex tachycardias

• Sinus tachycardia.

Sinus tachycardia has a number of causes. The treatment needs to be tailored to the cause. For example, a 20mg/kg bolus of 0.9% normal saline would be a sensible first line management if hypovolaemia was thought to be the cause. IV antibiotics would be needed if sepsis were suspected.

• Supraventricular Tachycardia (SVT)

Image courtesy of https://www.acls.net

If SVT is the likely rhythm (very fast heart rate, no p waves seen):

In a haemodynamically stable patient:

• Perform vagal manoeuvres (i.e. applying iced water onto face, one-sided carotid sinus massage or older children can try a Valsalva manoeuvre like blowing hard through a straw)
• Give IV Adenosine if the above does not work
• Further doses can be given every 2 minutes if no improvement (increasing dose each time)

In a haemodynamically unstable patient:

• Perform vagal manoeuvres only if they can be performed quickly
• Give IV Adenosine if IV access can be obtained quickly (100mcg/kg)
• Give a synchronous DC Shock 1 J/kg if the patient has difficult IV access or if access cannot be obtained quickly
• Further shocks (2J/kg) can be administered if there is no improvement

Click below for the algorithm which explains the management very clearly

Broad complex tachycardias

Broad complex tachycardias are considered to be ventricular tachycardias until proven otherwise. They are uncommon in children, mostly occurring in those with underlying heart problems. It is imperative that blood electrolytes (U&E, Calcium and Magnesium) are checked, as electrolyte disturbances are also a cause.

Image: Ventricular tachycardia

Image courtesy of www.practicalclinicalskills.com

In the haemodynamically unstable patient:

Give a synchronised DC Shock (1J/kg), and repeat if needed (2J/kg). Consider amiodarone if no improvement.

In the haemodynamically stable patient:

Early consultation with a paediatric cardiologist would be advised. They may suggest using IV amiodarone or IV procainamide.

There are many different types of arrhythmias which are beyond the scope of this course but if you are able to answer the key 4 questions we have discussed, you will be able to start some life saving interventions before your help arrives:
So remember to ask yourself:   

1. Is there a central pulse?
2. Is the patient haemodynamically stable?
3. Is the heart rate too fast or too slow?
4. Is the QRS complex narrow or broad?

The diagram on the below helps to summarise these points.

Figure: Management of arrhythmias
Q1 – Presence of central pulse?
Q2 – Clinical status – compensated or decompensated?
Q3 – Is the heart rate fast or slow?
Q4 – Are the QRS complexes narrow or broad?