What Is Bradycardia?

Bradycardia is a condition when the heart’s rhythm is slower than it should be. In general, an adult human should have a resting heart rate ranging between 60-100 beats per minute (bpm), so a heart rate lower than 60 bpm is considered bradycardia (40-60 bpm). It can be normal for heart rate to fall below 60 bpm when the person is asleep;⁵ and when awake, it is also not unusual for people in certain age groups and circumstances to have bradycardia.⁴

Bradycardia is a common occurrence in people over 65, as well as in young and healthy individuals, or to be more precise, someone in a great physical state (e.g., athletes, physically active people etc.).⁴ A slow heart rate in physically active people is mostly harmless and usually these individuals show no symptoms, but in the instance where the individual is not as physically active, it may indicate that there are problems with the heart and symptoms may appear,with the possibility of further complications depending on their underlying conditions.^1,5,12 At the same time, for many people, even when bradycardia occurs, it does not necessarily mean that there are problems with the heart nor is it a sign of something serious.⁴

Treatment of Bradycardia depends on the cause of it.  Bradycardia can create life threatening situations in extreme cases.^5,12

Signs and symptoms

There may not be any signs or symptoms for some people with bradycardia, but when symptoms do develop, individuals may experience:

• Dizziness or light-headedness
• Fainting episodes
• Shortness of breath (especially during physical movements)
• Fatigue
• Angina (Chest pain)
• Confusion or concentration problems¹²

Types of bradycardia, who is at risk, how common is it

There are different types of bradycardia, each causing their own set of complications.⁶

Sinus Bradycardia

• Heart rate lower than 60 bpm
• Can be a normal occurrence
• Common in young, healthy and physically very active people (6)

Sinus pause/ sinus arrest

• Occurs when the heart’s natural pacemaker (SA node) fails to discharge an impulse; causing the heartbeat to pause for a few seconds
• Can be a normal occurrence
• Further investigation is not required if the pause is no longer than 3 seconds
• Investigation and treatment is required when the pause goes on for longer than 3 seconds^6,13

Sick sinus syndrome

• Heart rhythm disorder usually due to scar-like damage in the heart tissue
• Uncommon
• Can develop at any age, but people aged 70+ are more at risk 
• Can cause arrhythmias (irregular heart rhythm). Individuals with sick sinus syndrome may experience slow heart rate, a fast heart rate, or a combination of both at the same time^{6, 8}

Complications

As previously mentioned, for most individuals, having a slow heart rate does not necessarily indicate  a  serious issue, or the occurrence of  complications, but when there are complications, it can differ depending on the underlying cause of bradycardia.¹²

Sinus bradycardia 

• Unlikely to cause complications, unless the heart rate becomes lower than 40 bpm⁶
• Most likely won’t require treatment unless there are symptoms^6,7

Sinus pause/sinus arrest

• May have complications depending on what is causing it. When the cause is identified, the underlying condition may be treated before bradycardia⁶

Sick sinus syndrome

• Some complications sick sinus syndrome can cause include atrial fibrillation, heart failure, stroke, and cardiac arrest⁸

If bradycardia is left untreated, it can lead to fainting, low blood pressure, and heart failure. It can also lead to cardiac arrest, or even death in extreme cases.^1,5,12

Causes and risk factors

Causes of Bradycardia can include:

• Metabolic disorders (i.e., Hypothyroidism) 
• Abnormality in the electrical conduction system of the heart, such as sinoatrial node (SA node) dysfunction , and arrhythmias^1,2
• Congenital heart defects (congenital means a condition that someone is born with) (12) 
• Certain heart conditions, for example, myocarditis (heart muscle infection/ inflammation), myocardial infarction (heart attack) etc^1,5,12
• Side effects of certain medications such as beta-blockers, calcium channel blockers, sedatives and opioids^5,12
• Complications after a heart surgery¹
• Electrolyte imbalances in blood — too high or too low calcium, potassium levels etc¹
• Inflammatory disorders (i.e., lupus, rheumatic fever)
• Obstructive sleep apnoea (OSA) 
• Anorexia Nervosa (may potentially cause sinus bradycardia)

Risk factors

Any factors that increase the risk of heart disease can lead to an increased risk of bradycardia. That includes:

• Aging. As the person ages, changes can occur in the heart and blood vessels. When a person gets older, heart rate can be naturally slower^4,9
• High Blood Pressure⁷
• Smoking⁷ 
• Anxiety⁷ 
• Stress⁷ 
• Heavy use of alcohol⁷

Diagnosis

To diagnose bradycardia, a doctor or health care provider may ask questions about the patient’s family and medical history. An electrocardiogram (ECG) is the main physical test used to diagnose bradycardia. But during ECG, slow heart rate may not occur, so portable ECG devices such as Holter monitor and cardiac event recorder may be recommended to be worn by the patient to detect bradycardia or irregular heart rate.⁷ 

• Holter monitor: a small and wearable device that records the rhythm of the heart continuously for 24 to 72 hours⁸ 
• Cardiac event recorder: similar to holter monitors. A wearable device that records abnormal heart rhythm^7,8 

The doctor may also ask for blood tests to be performed to check for other problems that may be causing the bradycardia.⁷ 

Treatment 

Treatment for bradycardia varies depending on the cause and symptoms. If there are no symptoms, treatment may not be required. But if there is an underlying condition that is causing bradycardia, treatment will be focused on the underlying problem.¹² 

Here are the various treatments available for bradycardia::

• If hypothyroidism is the underlying cause, treating it might return the heart rate back in the normal range⁵ 
• If bradycardia is caused as a side effect of certain medications, your doctor may change the dose or medication, or your usage may be discontinued¹ 
• In cases of severe bradycardia, pacemaker implantation may be needed. A pacemaker is a small device that is implanted in the chest or abdomen.³ Having a pacemaker implanted can aid in maintaining a regular heart rhythm. The procedure is usually very safe with little risk of further complications¹⁰

Preventing bradycardia

Depending on the cause, slow heart rate can’t always be prevented. But making good lifestyle choices will help reduce the risk of heart disease. For example:

• Doing the recommended 150 minutes of moderate physical activity a week 
• Eating a balanced diet 
• Maintaining a healthy weight 
• Reducing stress 
• Getting the optimal amount of sleep every night
• Stop smoking
• Keep levels of cholesterol and blood pressure within the normal range 
• Go for regular health checkups 
• Keep track of the changes in your body 

When should I see a doctor?

See your doctor or a health care provider if you notice and are concerned by any changes with your heart rhythm, or you experience any of the symptoms listed above.

Who should I call for help and advice?

Dial 111 (for medical advice) if you experience symptoms such as shortness of breath, chest pain, dizziness and near-faint. 

Dial 999 for life-threatening situations only. 

Read on: Additional facts about bradycardia to look out for in  infants and children

Symptoms

Sinus bradycardia in children is mostly asymptomatic however, symptoms will appear depending on the severity of the condition. Some symptoms include:

• Refusing to eat (while feeding)
• Excessive fatigue (in older children)
• Fainting (in extreme situations)
• Growth arrest (in infants)¹¹ 

When the condition is on the severe side, cardiac shock may be present; its characteristics include:

• Weak pulse
• Mental fatigue
• Low blood pressure
• Low urine output¹¹ 

Causes

• Hypoxemia (a condition when oxygen levels in blood are abnormally low; most common cause of sinus bradycardia)
• Metabolic disorders (see causes and risk factors)
• Medication
• Postoperative complications (heart surgery)¹¹ 

Treatment

Similar to adults, treatment depends on how severe the condition is in children and infants with bradycardia. You should consult a healthcare professional as soon as any symptoms are noticed.

Summary

Bradycardia is a condition that causes slower heart rate than normal. But it is common for certain groups of people such as athletes and in older adults over 65. Having a slow heart rate is not necessarily serious unless symptoms start to develop. There are many factors that can cause slow heart rate, so if symptoms start to show, a prompt diagnosis is important in order to receive appropriate care depending on the underlying cause.^{4, 7}

Treatment may not be required for some people with bradycardia; but when there is an underlying condition, and if it has been identified, early diagnosis and prompt treatment is important for a good prognosis .⁴ Bradycardia usually cannot be prevented, but changing your lifestyle choices can reduce the risk of heart disease, which may help decrease the risk of bradycardia.⁵

Further reading

Arrhythmia: Read more at: https://www.bhf.org.uk/informationsupport/conditions/arrhythmias

Obstructive sleep apnoea (OSA): Read more at: https://www.nhsinform.scot/illnesses-and-conditions/lungs-and-airways/obstructive-sleep-apnoea

Electrocardiogram (ECG): Read more at: https://www.nhs.uk/conditions/electrocardiogram/

Infantile Bradycardia: Read more at: https://www.news-medical.net/health/Infantile-Bradycardia-Causes-Diagnosis-Symptoms-and-Treatment.aspx

Why bradycardia can be dangerous: Read more at: https://emcrit.org/ibcc/bradycardia/