Bradycardia In Paediatric Patients 

Introduction

In adult humans, a normal heart rate (HR) is between 60 and 100 beats per minute (bpm) at rest. The normal range of HR in children varies:

• Neonates:  the resting HR is between 90 and 180 bpm
• Infants:  110-160 bpm  
• 1-5 years old: 100-150 bpm
• 6-12 years old: 80-120 bpm
• 12 years old and above:  60-100 bpm 

A doctor can determine whether your child has an abnormal HR depending on their situation. A slow heart rate is called bradycardia and a child can show symptoms associated with it if their HR drops below 50 bpm. However, a well-trained child athlete may have a HR below 50 and not show any signs or symptoms. In general, athletes have a lower HR so a low resting HR may not be a cause for concern if no symptoms are evident. 

Bradycardia can affect your child’s ability to pump blood effectively around their body and blood flow to the brain and other organs may be disrupted. Your child may experience symptoms as a result. If you are worried about your child’s health, seek medical assistance as soon as possible. This article will outline the causes, symptoms, diagnosis, and management of bradycardia in paediatric patients.

Causes of bradycardia in paediatric patients

Bradycardia in paediatric patients typically manifests as either sinus bradycardia, junctional bradycardia or atrioventricular block.¹ 

Sinus bradycardia

The sinoatrial node (SA) is the primary pacemaker responsible for setting the heart's rhythm. Sinus bradycardia may be caused by a range of extrinsic and intrinsic factors that can affect the integrity of the SA. 

Junctional bradycardia

A junctional bradycardia occurs when the atrioventricular node (AV) or Bundle of His acts as the primary pacemaker. This type of bradycardia may be caused by a blockage of the electrical activity to the SA or the automaticity of the SA falls below that of the AV. 

Atrioventricular block

Normally, the electrical impulses of the heart originate in the upper chambers (atria) and are then conducted to the lower chambers (ventricles). An AV block is a type of bradycardia that occurs due to the improper movement of electrical signals in the heart. 

AV block bradycardia is categorised into three groups:

• First-degree heart block: This is the mildest form of AV block and manifests itself in a delay of the electrical impulses that reach the ventricles²
• Second-degree heart block: Not all of the electrical signals from the atria reach the ventricles, resulting in  some beats being absent and leading to a lower and irregular HR
• Third-degree heart block: None of the electrical signals are reaching the ventricles, meaning the ventricles may beat on their own but at an incredibly reduced rate 

Extrinsic and intrinsic factors

Here is a list of some of the possible causes of bradycardia:

• Chest trauma
• Ischemic heart disease
• Myocarditis
• Radiation therapy
• Calcium channel blockers
• Beta-blockers

This is not an exhaustive list of all the possible causes of bradycardia. Many more factors can contribute to delays in conduction and overall a lower HR. 

Clinical presentation 

Symptoms 

In milder cases of bradycardia, it is likely that no symptoms are present. However, if symptoms are present they may manifest themselves through the following:

• Excessive fatigue and tiredness
• Exercise intolerance
• Dizziness
• Syncope and fainting episodes due to changes in cerebral perfusion (blood flow to the brain)

• Poor feeding in young children
• Frequent and worsening nightmares in young children

In severe cases of bradycardia, a greatly reduced cardiac output can lead to cardiorespiratory arrest. A child exhibiting bradycardia accompanied by severe hypotension and poor perfusion (poor circulation) requires emergency care.³

Physical examination

A healthcare professional will perform a physical examination of your child to help determine whether your child’s symptoms are a result of an arrhythmia. They will be looking for abnormalities in heart rhythm and abnormal heart sounds.³

Diagnostic evaluation 

Electrocardiogram (ECG)

An ECG is a test, carried out by healthcare professionals, to record the electrical activity in your heart. It involves attaching sticky pads to various parts of the body which will send the electrical activity of your heart to the ECG machine. It is completely painless and very quick. 

On an ECG, sinus bradycardia will exhibit a sinus rhythm below the normal range. The ECG will show a heartbeat in the shape of a ‘wave’ consisting of the P wave, QRS complex and T wave. They will be normal in sinus bradycardia.⁴ 

Junctional bradycardia will be shown as inverted P waves on an ECG.⁴ This is because the SA node isn’t acting as the primary pacemaker in this type of bradycardia. 

A first-degree AV block will show an increased PR interval on an ECG. Second-degree AV blocks may show increased PR intervals and sometimes a P wave which is not followed by a QRS complex. A third-degree AV block will show no conduction of atrial impulses to the ventricles.⁴

Holter monitor

Your doctor may suggest the use of a Holter monitor to diagnose bradycardia. Similarly to an ECG, the Holter monitor records the electrical activity of your heart but over a longer period of time. Sticky pads are used to hold the electrodes in place to provide a continuous rhythm recording over roughly 24 hours.³

Echocardiogram

An echocardiogram uses sound waves to form an image of the heart. This allows doctors to evaluate the structure, function, and blood flow through the heart. A gel is put on the chest and a special probe is used to send and receive sound waves. Overall, the procedure is painless and lasts roughly an hour. 

Management

Acute management

A child in cardiorespiratory arrest requires urgent attention. Including:

• CPR
• Medicine to increase HR such as adrenaline and atropine

Chronic management

Chronic pharmacological intervention is not recommended due to side effects and a variable response.³ In some cases your cardiologist may suggest the fitting of a permanent pacemaker. 

Fitting a pacemaker is not risk-free so be aware of the following complications:⁵

• Wound infection
• Pneumothorax 
• Pacemaker syndrome
• Lead dislodgement 
• Pericarditis 

Summary

To summarise: 

• Bradycardia is an average HR below the normal range
• Many children won’t show symptoms of bradycardia 
• If symptoms are present they can include: fatigue, tiredness, dizziness and syncope
• The three most common types of bradycardia in children are sinus bradycardia, junctional bradycardia, and AV block 
• An ECG and Electrocardiogram can be used to diagnose bradycardia 
• Severe bradycardia may need immediate attention if cardiac output and perfusion are compromised 
• A permanent pacemaker can be used to manage chronic bradycardia 

FAQs

What is a normal heart rate for my child? 

• In babies: 90-180 bpm
• In infants:  110-160 bpm  
• 1-5 years old: 100-150 bpm
• 6-12 years old: 80-120 bpm
• 12 years old and above:  60-100 bpm 

What are the symptoms of mild bradycardia?

Symptoms may include: tiredness and fatigue, exercise intolerance, syncope and fainting, frequent nightmares in young children, and difficulty feeding in younger children.

My child’s HR is below the range at rest what should I do?

Highly athletic children will generally have a low resting HR which is not a cause for concern. If your child experiences symptoms such as fainting, tiredness and fatigue, you should consider seeking medical advice from your GP.

What can cause bradycardia?

Chest trauma, ischaemic heart disease, myocarditis, and some medications can increase the risk of bradycardia.

Why does my child have bradycardia?

Improper conduction of electrical signals in the heart can result in poor pacemaking and a lower HR. 

How will a doctor perform a diagnosis?

They may perform an ECG, an ambulatory ECG or an echocardiogram. All three methods are pain-free. 

When do I need to go to the hospital?

A severely reduced cardiac output and poor perfusion can lead to cardiorespiratory arrest. This is an emergency and requires urgent care.