Understanding Bradycardia: Causes, Symptoms, Treatment & Prevention

Bradycardia is a type of abnormal heart rhythm (arrhythmia) that occurs when the heart beats slower than normal, generally under 60 beats per minute (bpm) at rest. For most adults, a normal resting heart rate falls between 60 and 100 bpm.

A slow heart rate is not uncommon and not always a cause for concern, especially in a well-conditioned athlete. Regular exercise can improve the body’s cardiovascular efficiency by strengthening the heart muscle, allowing it to pump a larger volume of blood with each beat. For this reason, physically fit individuals often have a naturally slow heart rate.

That said, bradycardia can be serious if it interferes with the heart’s ability to pump sufficient oxygen-rich blood to meet the needs of the body’s organs and tissues. Therefore, understanding the condition is essential to promote overall heart health.

What Are the Types of Bradycardia?

The heart consists of two upper chambers (atria) and two lower chambers (ventricles). Bradycardia is classified based on the origin of the abnormal heart rhythm. The types include:

Sinus Node Dysfunction

Typically, the rhythm of the heart is controlled by the sinus (sinoatrial) node, an area of specialized cells in the right atrium. An important part of the heart’s electrical signaling system, the sinus node serves as a natural pacemaker, generating and conducting electrical signals that stimulate the heart to beat. If the sinus node is damaged or malfunctions, its electrical impulses may become erratic, leading to an irregular or abnormally slow heartbeat. Also known as sick sinus syndrome, sinus node dysfunction can result from an underactive thyroid gland (hypothyroidism) or an illness. However, in many cases the cause is unknown.

Tachycardia-Bradycardia Syndrome

A variant of sinus node dysfunction, tachycardia-bradycardia (tachy-brady) syndrome is also caused by a malfunction of the sinus node. In the case of tachy-brady syndrome, the sinus node triggers alternating episodes of slow and fast heart rhythms, often with long pauses between heartbeats. An example is atrial fibrillation (Afib), a subtype of bradycardia-tachycardia syndrome.

Heart Block

A heart block occurs when the electrical signals that control the heart’s rhythms are delayed, interrupted or blocked as they travel from the atria to the ventricles. This disruption can slow the heart rate and impair the heart’s ability to pump blood effectively. Heart block can vary in severity, ranging from a mild delay (first-degree heart block) to a moderate delay (second-degree heart block) to a complete signal blockage (third-degree heart block). Each degree of heart block may require a different treatment approach.

What Are the Causes of and Risk Factors for Bradycardia?

Bradycardia can develop for many reasons, including:

• Advanced age – The heart’s electrical system naturally degenerates over time.
• Heart disease – Cardiac conditions, such as coronary artery disease and heart attack, can damage the heart muscle and disrupt its electrical signals.
• Medication – Certain drugs, such as beta blockers, calcium channel blockers and antiarrhythmics, may slow the heart rate.
• Electrolyte imbalance – Abnormal levels of potassium, calcium or magnesium can interfere with the heart’s electrical activity.
• Hypothyroidism – Thyroid hormones affect the heart by increasing the expression of beat receptors, which increases the heart rate. An underactive thyroid gland can reduce the level of thyroid hormones in the bloodstream, leading to bradycardia.
• Sleep apnea – During sleep, episodes of interrupted breathing can intermittently stress the heart and lead to rhythm irregularities, including bradycardia.
• Infectious disease – Heart infections, such as myocarditis and endocarditis, can damage the heart’s electrical pathways.
• Congenital heart defect – A condition present at birth, such as congenital atrioventricular block (CAVB), may affect the heart’s rhythms.
• Athletic conditioning – Physically fit individuals may have bradycardia due to enhanced heart efficiency.

What Are the Symptoms of Bradycardia?

The warning signs of bradycardia can vary based on the severity of the slowed heart rate and its impact on effective blood circulation. Common symptoms include:

• Fatigue – Persistent tiredness, physical weakness, lack of energy and exercise intolerance may occur due to insufficient oxygen delivery to the body’s organs and tissues.
• Dizziness – Lightheadedness can result from reduced blood flow to the brain.
• Shortness of breath – Breathing may become difficult if the heart cannot pump fast enough to keep up with the body’s demand for oxygen, especially during physical activity.
• Syncope – Fainting or near-fainting episodes can result from a sudden drop in blood pressure.
• Palpitations – Chest pain or discomfort may accompany an awareness of the heart beating abnormally slow.
• Cognitive issues – Mental confusion or memory problems can result from decreased oxygen supply to the brain.

Bradycardia symptoms warrant a medical evaluation, especially if they occur frequently or disrupt daily activities. Early detection and treatment (if needed) can help prevent complications.

How Is Bradycardia Diagnosed?

The diagnostic process for bradycardia typically includes a medical history review, physical examination and medical testing, which can help the physician measure the heart rate and check for underlying conditions and contributing factors. Common diagnostic tests for bradycardia include:

• Electrocardiogram (ECG or EKG) – The primary test for bradycardia, an EKG involves placing several adhesive electrodes on the chest, arms and legs. While the patient relaxes, the electrodes will record the heart’s electrical impulses, which will be sent to a nearby EKG machine and displayed in graphical form on a nearby monitor or printout.
• Holter monitor – A portable EKG device, a Holter monitor is designed to be worn continually for 1 to 2 days to record the heart’s rhythms during a variety of daily activities.
• Cardiac event recorder – Similar to a Holter monitor, this compact device is designed to capture irregular heart rhythms for a few minutes at a time. To activate the recording, the patient will press a button whenever they experience heart-related symptoms, such as dizziness or palpitations. The device can be worn continually for up to 30 days.
• Echocardiogram – A type of ultrasound imaging test, an “echo” uses high-frequency sound waves to create detailed images of the heart, including its walls, chambers, valves and blood flow.
• Exercise tolerance test (ETT) – Also known as a cardiac stress test, an ETT involves monitoring the heart's activity with an EKG while the patient walks on a treadmill or pedals a stationary bicycle. For patients unable to exercise, medication may be used to simulate the effects of physical activity by increasing the heart rate.
• Tilt table test – To help the physician determine the cause of unexplained fainting or dizziness, the patient will be asked to lie flat on a specialized table that transitions from a horizontal position to a nearly vertical position, simulating a standing posture. Throughout the test, the patient’s heart rate, blood pressure and symptoms will be closely monitored, allowing the physician to assess the body’s cardiovascular response to changes in posture.
• Lab testing – The physician may order blood work to measure electrolyte levels, assess thyroid function or check for troponin and toxic substances that can cause bradycardia.

How Do You Treat Bradycardia?

Bradycardia treatment can vary depending on its underlying cause, severity and symptoms. The main approaches include:

• Observation – If bradycardia is mild and not causing symptoms, it might not require treatment. Regular monitoring may be sufficient.
• Lifestyle changes – In some cases, lifestyle modifications such as adjusting medications, consuming a balanced and nutritious diet, exercising regularly, losing excess body weight, managing stress, reducing caffeine intake and limiting alcohol consumption may be sufficient to normalize the heart’s rhythms.
• Treating other medical conditions – A slower-than-normal heart rate may be linked to heart disease, hypothyroidism, heart infection, electrolyte imbalance, sleep apnea or medication. In these instances, bradycardia may be resolved if the underlying health issue is addressed.
• Medication – If bradycardia is causing dizziness or fainting, atropine may be prescribed to accelerate the heart rate.
• Pacemaker – If a problem with the heart’s electrical system is slowing the heart rate, a pacemaker may be considered. This small, implantable device can send electrical impulses to help regulate the heart’s rhythms.

What Are the Potential Complications and Long-Term Effects of Bradycardia?

If left untreated, bradycardia can lead to several potentially serious complications and long-term effects, particularly if it causes insufficient blood flow to the body. These may include:

• Chronic fatigue and weakness – A slower-than-normal heart rate can reduce oxygen delivery to the body’s organs and muscles, resulting in persistent tiredness and low energy levels.
• Syncope – Bradycardia can lead to inadequate blood flow to the brain, increasing the risk of lightheadedness and fainting episodes, which can cause falls and injuries.
• Low blood pressure (hypotension) – A slow heart rate can contribute to abnormally low blood pressure, causing further symptoms, such as dizziness and mental confusion.
• Heart failure – Chronic bradycardia may strain the heart and impair its pumping efficiency over time.
• Other arrhythmias – Bradycardia can coexist with or lead to other irregular heart rhythms, such as tachy-brady syndrome.
• Cognitive impairment – Reduced blood flow to the brain can affect memory, focus and overall mental function.
• Sudden cardiac arrest – In severe cases, bradycardia can cause the heart to stop pumping altogether. Cardiac arrest is a life-threatening event that requires emergency medical intervention.

An accurate diagnosis and appropriate treatment of bradycardia are essential to reduce the risk of complications and maintain overall heart health.

How Do You Prevent or Reduce Your Risk of Bradycardia?

Although bradycardia cannot be prevented in every case, several proactive steps can be taken to help reduce the risk. These include:

• Promoting optimal heart health – It is important for everyone to maintain a heart-healthy lifestyle, which includes consuming a balanced diet, engaging in regular physical activity, achieving and maintaining a healthy body weight, managing stress, limiting alcohol consumption and avoiding tobacco use.
• Monitoring and managing health conditions – Several medical conditions have been linked to bradycardia, including heart disease, hypothyroidism, heart infection, electrolyte imbalance and sleep apnea. With the guidance of an experienced physician, these conditions can often be effectively managed.
• Being aware of medication side effects – Certain drugs, such as beta blockers and calcium channel blockers, can slow the heart rate. It is important for patients who take these medications to work with a physician who can adjust the doses or suggest alternatives if needed.
• Having regular medical checkups – Through routine health screenings, it may be possible to detect heart issues and other conditions early so they can be promptly addressed.

Living With Bradycardia

For many people, mild bradycardia does not cause noticeable symptoms or significantly impact their daily life. However, a slower-than-normal heart rate can lead to insufficient blood flow, which can cause fatigue, dizziness or shortness of breath. These effects can make even routine activities seem challenging.

Individuals with symptomatic bradycardia may benefit from making lifestyle adjustments, such as monitoring their heart rate and pacing their physical activities. In some cases, a pacemaker may be considered to help regulate the heart’s rhythms, improve energy levels and enhance quality of life.

Living with bradycardia often involves ongoing communication with a physician, who can monitor the condition, adjust medications if needed and address any complications. With proper management, many people with bradycardia can lead a full and active life.

Frequently Asked Questions (FAQs) About Bradycardia

The following FAQs and corresponding answers provide additional information about bradycardia:

What Is Bradycardia?

Bradycardia is a cardiac condition characterized by a slower-than-normal heart rate, typically fewer than 60 bpm in adults.

Is Bradycardia Always a Cause for Concern?

No. For some individuals, such as well-conditioned athletes, a low heart rate may be considered normal, efficient and healthy. However, bradycardia can be problematic if it causes symptoms or affects blood flow.

What Causes Bradycardia?

Bradycardia can result from athletic conditioning, aging, certain medications, electrolyte imbalances or sleep apnea. It is also associated with certain medical conditions that affect the heart’s electrical system, such as hypothyroidism, heart disease and heart infection.

What Are the Symptoms of Bradycardia?

Possible signs of a lower-than-normal heart rate include fatigue, dizziness, shortness of breath, syncope, palpitations and cognitive issues. However, it is important to note that bradycardia is sometimes asymptomatic.

How Is Bradycardia Diagnosed?

Typically, the diagnostic process for bradycardia involves a combination of tests, such as a medical history review, physical exam, ECG/EKG, echocardiogram, blood work, stress test, tilt table test and Holter monitoring or cardiac event recording to measure and monitor the heart’s rhythms over time.

Can Bradycardia Be Treated?

Yes. Bradycardia treatment can vary based on its cause and symptoms. Options may include observation, lifestyle modifications, medication and possibly a pacemaker to regulate the heart rate.

What Are the Potential Complications of Untreated Bradycardia?

If left untreated, bradycardia can lead to potentially serious complications, such as chronic fatigue and weakness, syncope, hypotension, heart failure, other arrhythmias, cognitive impairment and, in severe cases, sudden cardiac arrest.

Can I Prevent Bradycardia?

Although bradycardia cannot always be prevented, it may be possible to reduce the risk by maintaining a heart-healthy lifestyle, monitoring and managing health conditions, being aware of medical side effects and having regular medical checkups.

Is Bradycardia Common?

Bradycardia is relatively common, especially among older adults due to age-related changes in the heart’s electrical system. Additionally, many well-conditioned athletes have a lower-than-normal heart rate because regular exercise can make the heart more efficient, enabling it to pump more blood with every beat. As a result, its bpm may decline.

When Should I See a Physician About Bradycardia?

Bradycardia symptoms, such as fatigue, syncope and palpitations, should be promptly discussed with a physician, especially if the symptoms are severe or persistent.

Benefit From World-Class Care at TGH

The multidisciplinary team in TGH’s nationally renowned Heart & Vascular Institute and Electrophysiology Center of Excellence offers the latest diagnostic and treatment options for a comprehensive range of cardiac conditions, including bradycardia and other arrhythmias. As a leading academic health system, we collaborate with the University of South Florida (USF) Health Morsani College of Medicine to perform cutting-edge research and participate in groundbreaking clinical trials while prioritizing patient safety and comfort.

In acknowledgment of our commitment to delivering outstanding cardiac care, U.S. News & World Report has recognized TGH as one of the Nation’s Best Hospitals for Heart & Vascular Care for 2024-25. Additionally, Newsweek has ranked TGH as one of America’s Best Specialized Hospitals for Cardiac Care in 2024, and we are the only hospital in the Tampa Bay region to be included in the list of “100 Hospitals and Health Systems with Great Heart Programs” compiled by Becker’s Hospital Review.

If you would like to learn more about bradycardia, please contact us at (813) 844-3900 or email us at heart-vascular@tgh.org to request an appointment with a specialist in our Heart & Vascular Institute.