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Slow Heart Rate (Bradycardia)

by | Jun 28, 2024 | Info | 0 comments

Bradycardia Overview

Bradycardia refers to a resting heart rate that is slower than usual. A heart rate of fewer than 60 beats per minute may indicate an underlying health issue, but this is not always the case.

According to the American Heart Association (AHA), a person’s resting heartbeat is generally between 60⁠ and 100 beats per minute (bpm).

However, people who are physically active or athletic may have resting heartbeats that are as low as 40 bpm. A person’s resting heart rate can also drop during deep sleep. Additionally, a slow resting heart rate can be a result of certain health conditions.

What is a Heart Rate?

A person’s heart is responsible for pumping blood throughout the body. The heart consists of four chambers:

  • Right atrium
  • Left atrium
  • Right ventricle
  • Left ventricle

The top two chambers,  the atria, receive blood. The bottom two chambers, the ventricles, pump blood from the heart.

Blood has many functions, such as:

  • Bringing waste products to the kidneys and liver, which then filter and clean the blood
  • Transporting oxygen and nutrients to tissues and organs
  • Regulating body temperature
  • Creating blood clots to stop bleeding
  • Transporting antibodies to fight infections

According to the AHA, generally, a resting heart rate of less than 60 bpm means that a person has bradycardia.

An individual who has bradycardia may not get enough oxygen-rich blood to certain areas of their body. If left untreated, bradycardia can lead to life threatening complications, such as syncope.

However, a person may naturally have a slower resting heart rate due to physical fitness or age. If an individual is concerned about their slow resting heart rate, they should seek guidance from a doctor.

Signs and Symptoms of Bradycardia

Some people who have bradycardia do not experience any symptoms other than a slow heart rate. Other individuals with bradycardia may have symptoms such as:

If a person’s bradycardia is due to a serious medical condition, it can cause life threatening complications if left untreated.

Complications of Untreated Bradycardia

Complications of untreated bradycardia include:


Measuring Heart Rate

A person can find out their heart rate by taking their pulse.

If a person wants to accurately measure their resting heart rate, they should take their pulse when sitting or lying down. A person should also make sure they feel calm and relaxed before checking their resting heart rate.

A person can take their pulse from different locations on their body, including:

  • Inside of the elbows
  • Side of the neck
  • Top of the feet
  • Wrists

Using two fingers, a person can check each of these areas to find where their pulse is easiest to feel. They should not use their thumb to take their pulse,  the thumb has a pulse of its own and may interfere with the results.

Once a person has found their pulse, they can count the number of beats they feel over 60 seconds. They may want to set a stopwatch or look at a clock while they count their heartbeats.

If a person has a heartbeat lower than 60 bpm, they have bradycardia. Bradycardia does not always mean that an individual has an underlying health condition. However, they should contact a doctor to determine the cause of their bradycardia.

Children and young people have more rapid heart rates than adults. A typical heart rate for an infant is around 140 bpm, whereas an older child or teenager should have a resting heart rate of about 70 bpm.

Causes and Risk factors of Bradycardia

A person may experience mild bradycardia or only have symptoms from time to time. If they notice that they have a slow heart rate, they should speak with a doctor to determine the cause.

Bradycardia will not always require treatment. If a person does not have any other symptoms and has a structurally normal heart, their bradycardia may be due to an additional factor, such as physical fitness.

People who engage in high amounts of physical activity tend to have more efficient hearts. This may slow their pulse because their heart does not have to pump as hard or as fast to supply blood to the rest of the body.

Certain medical conditions can cause bradycardia. These conditions include:

Sick Sinus Syndrome

Also known as sinus node dysfunction (SND), this condition affects a person’s sinoatrial (SA) node, a structure in the top of a person’s right atrium that generates the electrical impulse that starts a heartbeat. This can mean a person’s heart rate speeds up, slows down, or does a combination of both.

Other symptoms of SND include:

  • Palpitations where a person’s heart feels like it is fluttering, pounding, or pausing
  • Tiredness
  • Feeling faint or fainting
  • Lightheadedness

Although SND can develop at any time, the average age of someone who has it is 68 years old. SND is a common cause of bradycardia.

Other Heart Electrical Issues

If the heart is unable to send electrical signals due to a blockage or heart disease, this can lead to bradycardia.

Complete heart block is when there is a total loss of communication between a person’s atria and the ventricles. This occurs when the SA node is unable to pass a signal to the AV node.

Complete heart block results in a person’s atria and ventricles activating independently of each other. It can be fatal if a person does not receive treatment for complete heart block quickly.

Metabolic Problems

Some metabolic disorders can slow the heart rate. One of the most common is hypothyroidism, which is when the thyroid gland does not produce enough hormones. Hypothyroidism can affect the health of the blood vessels, which may slow the heart rate.

Thyroid disorders are common and may affect young and otherwise healthy people. Between 4 and 10% of individuals in the United States have hypothyroidism.

Other metabolic conditions that can cause bradycardia include the following:

  • Acidosis, a condition where there is too much acid in bodily fluids
  • Hyperkalemia,, where a person’s potassium levels are too high
  • Hypokalemia, which is when a person’s potassium levels are too low
  • Hypothermia, which happens when the body temperature becomes too low

Heart-Damaging Conditions

Damage to the heart due to certain conditions can cause it to pump more slowly and less effectively. Conditions that can damage the heart include:

Heart Medication

Certain medications, including those for heart disease and high blood pressure, may lower heart rate.

Beta blockers or calcium channel blockers, which doctors prescribe for a rapid heart rate and some other heart conditions, may also slow heart rate.

Individuals taking a new medication who experience symptoms of bradycardia should contact a doctor.

Oxygen Deprivation

Hypoxia is a term that health experts use when a person is unable to get enough oxygen to the tissues of their body. Hypoxia is a medical emergency, and can occur when a person is choking or having a severe asthma attack. Chronic medical conditions, such as chronic obstructive pulmonary disease (COPD), may also cause hypoxia.

If hypoxia lowers a person’s heart rate, it is essential to treat the underlying cause.

Types of Bradycardia

There are different types of bradycardia, depending on which part of the heart they start in.

Sinus Bradycardia

Sinus bradycardia is a form of slow heart rate that begins in a person’s SA node.

If a patient has sinus bradycardia, their SA node is sending the impulses to start a heartbeat but is generating them at a slower rate. This leads to a slower heart rate.

The majority of people who have sinus bradycardia will have no symptoms. Sinus bradycardia can occur in individuals who are physically active or athletic or during deep sleep. However, sinus bradycardia can also develop due to various health conditions, such as heart disease.

Junctional Bradycardia

Junctional bradycardia occurs when the electrical impulse to start the heartbeat begins in the atrioventricular (AV) node rather than in the SA node.

The AV node is a structure at the bottom of the right atrium that can be a pacemaker when the SA node does not function properly.

It is also the location of the pause of the impulse generated from the SA node. This pause provides time for the atria of the heart to finish beating, which causes blood to pool inside the ventricles of the heart.

Once the ventricles have filled with blood, the impulse passes to the His-Purkinje system, which causes the ventricles to contract and pump blood out of the heart.

If a person has junctional bradycardia, they may have an issue with their SA node that causes the AV node to take over.

Additionally, physically athletic individuals, young children, and people in deep sleep may also experience junctional bradycardia.

When to Seek Medical Help for Bradycardia?

If a baby has a low pulse, a parent or caregiver should take them to the emergency room.

Adults and children who have a low pulse and experience symptoms such as chest pain, fainting, or exercise intolerance should also go to the hospital.

A person should contact a doctor about bradycardia when they:

  • Experience an unexplained change in heart rate that lasts for several days
  • Have bradycardia and other heart health risk factors, such as diabetes or smoking
  • Experience bradycardia and other symptoms, such as fainting spells
  • Heart disease and bradycardia
  • Experience episodes of bradycardia and tachycardia, which is a rapid heartbeat


Treatment of Bradycardia

A doctor may not always need to treat a slow heart rate. However, when a slow heart rate causes serious health problems, it is essential that a person receives treatment.

The treatment an individual receives for their bradycardia will depend on the underlying cause. A doctor may use certain tests to diagnose the cause of a person’s bradycardia. These tests include:

  • Blood tests
  • Heart monitors
  • Imaging tests
  • Physical tests
  • Questions about medical history

If a person has a condition that interferes with the electrical impulses of their heart, they may require a pacemaker. This is a device that is implanted under a person’s skin and connected to their heart. The pacemaker then sends impulses to the heart that cause it to beat regularly.

Depending on the cause, a doctor might also recommend:

  • Changing heart medications 
  • Making lifestyle changes, such as eating a low fat diet, getting more exercise, or quitting smoking
  • Taking medication to treat thyroid or other metabolic disorders
  • Monitoring heart rate or blood pressure frequently


Common Questions about Bradycardia

Here are some common questions people often ask about bradycardia.

What is the main reason for bradycardia?

The main reason for bradycardia is an issue with the heart. These may be due to age, cardiovascular disease, an infection, or an inherited condition. Using heart medication can sometimes lead to bradycardia. It can also happen with diseases such as lupus, sleep apnea, and hypothyroidism.

When is bradycardia an emergency?

Bradycardia is not always serious, but it can have severe consequences in some cases. A person should seek immediate medical help if there are signs of cardiac arrest, heart failure, or a heart attack. They should contact a doctor as soon as possible if they are fainting frequently.

How low is too low for a heart rate?

The typical range for a heart rate is 60–100 beats per minute. A doctor will diagnose bradycardia if a person’s heart rate is below 60 beats per minute. However, during sleep, a heart rate can be lower than usual, and some physically active adults may regularly have a lower heart rate.

Summary

Heart disease can be fatal, so it is crucial that a person take any changes in heart health, blood pressure, or pulse seriously.

However, a slow heart rate is not always a cause for concern. Bradycardia can sometimes indicate that a person is in good physical condition.

Only a doctor can evaluate a person’s cardiovascular risk factors. If an individual is concerned about their slow heart rate, they should consult a doctor.

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