Bradycardia: Slow Heart Rate, Symptoms, Causes, and Treatment
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is bradycardia?
Bradycardia is a resting heart rate below 60 beats per minute, which may be harmless or may stop the body from getting enough oxygen. Symptoms include dizziness, chest pain, confusion, shortness of breath and fainting. Causes include aging heart tissue, heart disease, heart block and some medicines. Severe cases may need a pacemaker. [1] [2]
What the research says
According to PubMed:
Lithium can slow the heart, even at normal doses. A systematic review of 121 case reports (135 cases) found sinus bradycardia was the most common presentation (64.4%), it occurred at any age, dose, and duration, even within the therapeutic range, and 51.9% of the 27 re-challenge cases had recurrent bradycardia (Huh et al., DOI).
Slow heart rates are common in dengue. A meta-analysis of 35 studies (6,948 patients) estimated that arrhythmias occurred in 24.48% of patients with dengue, with sinus bradycardia the most frequent abnormality (11.84%) and atrioventricular block uncommon (1.33%) (López-Delgado et al., DOI).
Some heart block recovers on its own. In a systematic review of 50 case reports of high-grade atrioventricular block in Takotsubo cardiomyopathy, 30% had complete recovery of conduction, and an identifiable stressor predicted recovery — information that may guide the timing of a permanent pacemaker (Hussein et al., DOI).
Study details are from PubMed abstracts.
Key facts at a glance
Fact | Detail |
Definition | Resting heart rate below 60 beats per minute |
Normal adult resting rate | 60 to 100 beats per minute |
Normal in some people | 40 to 60 beats a minute in athletes, healthy young adults, and during sleep |
Main test | Electrocardiogram (ECG or EKG) |
Common outcomes | Often no symptoms or complications; severe cases may need a pacemaker |
Serious complications | Frequent fainting, heart failure, sudden cardiac arrest or death |
How does the heart keep its rhythm in bradycardia?
The heart has four chambers: two upper chambers called the atria and two lower chambers called the ventricles. In the upper right chamber sits a small group of cells called the sinus node — the heart's natural pacemaker — which creates the electrical signal that starts each heartbeat [1].
The signal travels through the atria to the atrioventricular (AV) node, then passes into the ventricles, making the lower chambers squeeze and pump blood out to the body. Bradycardia happens when these signals slow down or become blocked [1].
When is a slow heart rate (bradycardia) not a problem?
A resting rate between 40 and 60 beats a minute is common in some people, particularly healthy young adults and trained athletes, and it is quite common for the heart rate to drop during sleep [1].
Bradycardia becomes a serious problem only when the rate is very slow and the heart cannot pump enough oxygen-rich blood to the body. Then you may feel dizzy, very tired or weak, and short of breath. Sometimes bradycardia causes no symptoms or complications at all [1].
What are the symptoms of bradycardia?
If the slow beat stops the brain and other organs from getting enough oxygen, symptoms may include [1]:
Symptom | What it means |
Dizziness or lightheadedness | The brain is not getting enough oxygen from the slow beat |
Fainting or near-fainting | A warning sign that blood flow has dropped; call emergency services if you faint |
Feeling very tired | Especially noticeable during physical activity |
Shortness of breath | The slow pump struggles to meet the body's oxygen demand |
Chest pain | A serious symptom that needs urgent attention |
Confusion or memory problems | Low oxygen flow can affect thinking and memory |
When to get help
Many things can cause symptoms of bradycardia, so a fast, accurate diagnosis matters. Make an appointment for a health checkup if you are worried about a slow heart rate. If you faint, have difficulty breathing, or have chest pain lasting more than a few minutes, call 911 or your local emergency medical services [1].
What causes bradycardia?
Causes fall into two groups: damage or disease affecting the heart itself, and outside factors that slow the heart's signaling [1].
Cause | How it slows the heart |
Heart tissue damage from aging | The signal-making cells wear out over time |
Heart disease or heart attack damage | Scarred tissue disrupts the electrical pathways |
Congenital heart defect | A heart condition present from birth affects rhythm |
Myocarditis | Inflammation of the heart tissue interferes with beating |
Heart surgery complication | The surgery can damage the heart's wiring |
Hypothyroidism | An underactive thyroid gland slows the body down, including the heart |
Mineral imbalances | Changes in potassium or calcium levels affect heart signals |
Obstructive sleep apnea | Breathing pauses during sleep can change the heartbeat |
Inflammatory disease | Conditions such as rheumatic fever or lupus can inflame the heart |
Certain medicines | Sedatives, opioids, and some heart and mental health medicines slow the rate |
Two electrical signaling problems deserve special attention. In bradycardia-tachycardia syndrome, problems in the sinus node cause alternating slow and fast heart rates. In heart block (atrioventricular block), the heart's electrical signals do not move correctly from the upper chambers to the lower chambers [1].
What are the risk factors?
Bradycardia is often linked to damage to heart tissue from some type of heart disease. Anything that raises the risk of heart problems can raise the risk of bradycardia [1].
Risk factor | Why it matters |
Older age | Heart tissue naturally ages and signals slow |
High blood pressure | Long-term strain damages heart tissue |
Smoking | Tobacco harms the heart and its blood supply |
Heavy alcohol use | Excess drinking raises heart problem risk |
Illegal drug use | Drugs can damage the heart and disrupt its rhythm |
Stress and anxiety | Intense emotions may affect the heart rate |
What complications can follow?
When bradycardia is not managed, possible complications are serious: frequent fainting, heart failure, and sudden cardiac arrest or sudden cardiac death [1].
How is bradycardia diagnosed?
A healthcare professional examines you, listens to your heart with a stethoscope, and asks about your symptoms and medical history. If a standard ECG does not catch the slow rhythm, longer monitoring can: a Holter monitor is a portable ECG worn for a day or more, while an event recorder captures a few minutes at a time when you press a button after symptoms occur, worn for up to 30 days [2].
Test | What happens | What it finds |
Electrocardiogram (ECG/EKG) | Sticky sensor patches on the chest, arms, and legs connect by wires to a computer | The main test for bradycardia; shows how the heart is beating electrically |
Blood tests | A blood sample is analyzed | Infections, chemical changes such as potassium, and thyroid function |
Holter monitor | Portable ECG worn for a day or more | Slow rhythms that a brief ECG misses during daily activities |
Event recorder | Wearable device recording a few minutes at a time when you press a button | Rare episodes, worn up to 30 days |
Tilt table test | Heart rate and blood pressure are checked while the table tilts you to a standing position | The cause of fainting spells |
Stress exercise test | Heart is watched while walking a treadmill or riding a stationary bike | Irregular beats triggered or worsened by exercise; medicine substitutes if you cannot exercise |
Sleep study | Overnight monitoring of breathing and rhythm | Obstructive sleep apnea pauses that change the heartbeat |
How is bradycardia treated?
Treatment depends on how severe the symptoms are and what is causing the slow heart rate. If you have no symptoms, treatment might not be needed at all [2].
Approach | When it applies |
No treatment | Slow rate with no symptoms may simply be monitored |
Lifestyle changes | Heart-healthy habits to protect the heart and its rhythm |
Medicine change | Lowering the dose or switching a medicine that causes the slow rate |
Treating the underlying condition | Fixing thyroid disease or sleep apnea may correct the slow rate |
Pacemaker | A device for severe symptoms when other treatments are not possible |
Medicines
Many medicines can affect the heartbeat, and some might cause bradycardia. Always tell your healthcare team about every medicine you take, including those bought without a prescription. If a medicine is causing the slow rate, your healthcare professional may suggest a lower dosage or a switch to a different medicine [2].
Pacemaker
If you have severe symptoms and other treatments are not possible, a pacemaker may be suggested. It is placed under the skin near the collarbone during a minor surgery. When the heart beats too slowly, the pacemaker sends electrical signals to the heart to speed up the beat [2].
How can you protect your heart and lower bradycardia risk?
Preventing heart disease may help lower the risk of bradycardia [1]:
Get regular exercise, asking your healthcare team how much and what type is best for you
Eat nutritious foods low in salt and solid fats and rich in fruits, vegetables, and whole grains
Keep a healthy weight, since being overweight raises heart disease risk
Control blood pressure and cholesterol through lifestyle changes and medicines taken as directed
Do not smoke or use tobacco, and limit alcohol to up to one drink a day for women and two for men, or avoid it entirely
Manage stress through exercise, mindfulness, and support groups
Aim for 7 to 9 hours of sleep daily on a consistent schedule
Keep up with regular health checkups; if you already have heart disease, follow your treatment plan and tell your care team whenever symptoms change
How should you prepare for a bradycardia appointment?
You may be referred to a cardiologist, a doctor trained in heart conditions [2].
Ask about any pre-appointment restrictions, such as not eating or drinking before a cholesterol test [2]
Write down all your symptoms, even ones that seem unrelated, plus family history of heart disease, stroke, high blood pressure, or diabetes, and recent life changes [2]
List all medicines, vitamins, and supplements with dosages, and take someone with you if possible [2]
Questions to ask: what is likely causing my slow heart rate, what tests do I need, what is the most appropriate treatment, what are the possible complications, and how will other conditions or medicines affect my heartbeat [2]
Expect to be asked whether you have fainted, whether exercise worsens symptoms, whether you smoke, and whether you are being treated for heart disease or high blood pressure [2]
What is the bottom line on bradycardia?
Bradycardia simply means the heart beats fewer than 60 times a minute at rest, and for athletes, young adults, and sleepers that pace can be perfectly normal. It only becomes a health problem when the slow pump withholds oxygen from the brain and body, bringing on dizziness, fainting, and extreme fatigue [1]. Blood tests, ECGs, and wearable monitors pinpoint the cause, medicines can often be adjusted, and a small pacemaker can keep the rhythm steady when the heart's own wiring fails [2].
Next steps: If your resting heart rate is low or you feel dizzy, unusually tired, or short of breath, book a checkup and bring a list of everything you take. Call 911 or your local emergency number if you faint, have trouble breathing, or have chest pain lasting more than a few minutes.
Frequently asked questions
What heart rate is too slow?
A resting heart rate below 60 beats per minute is called bradycardia, since most adults at rest beat between 60 and 100 times a minute. However, 40 to 60 beats a minute can be normal for healthy young adults, trained athletes, and during sleep [1].
Can bradycardia go away on its own?
It depends on the cause. If a medicine or a condition such as thyroid disease or sleep apnea is slowing the heart, treating that cause may correct the slow rate. If the heart's own signaling tissue is damaged, the slow rate usually needs medical care [2].
Is a slow heart rate dangerous while sleeping?
Heart rate commonly drops during sleep, and a slow rate with no symptoms or complications is often not a concern. The danger arises when the rate is very slow and the heart cannot pump enough oxygen-rich blood to the body [1].
When should I seek emergency help for a slow heart rate?
Call 911 or emergency services if you faint, have difficulty breathing, or have chest pain lasting more than a few minutes [1].
What does a pacemaker do for bradycardia?
A pacemaker is a small device placed under the skin near the collarbone during a minor surgery. When the heart beats too slowly, it sends electrical signals to the heart to speed up the beat [2].
This article is educational and is not a substitute for professional medical advice, diagnosis, or treatment.
What are the symptoms of bradycardia?
Many people with a slow heart rate have no symptoms. When the heart cannot pump enough blood, you may feel dizzy, tired, short of breath, confused, or have chest pain or fainting.
Can medicines cause a slow heart rate?
Yes. Some heart and blood pressure medicines, sedatives, opioids, and certain mental health medicines can slow the heart. Tell your provider about every medicine you take, and do not stop a prescribed medicine without talking to them.
Is a slow heart rate normal for athletes?
Often, yes. Well-trained athletes and healthy young adults can have a resting heart rate between 40 and 60 beats a minute without any problem. A slow rate that comes with dizziness or fainting should still be checked.
How is bradycardia diagnosed?
An electrocardiogram (ECG) is the main test, showing how the heart's electrical signals work. If the slow rhythm comes and goes, you may wear a Holter monitor or event recorder at home, and blood tests can check thyroid and potassium levels.
Can a thyroid problem cause bradycardia?
Yes. An underactive thyroid (hypothyroidism) can slow the body down, including the heart. Treating the thyroid problem may bring the heart rate back to normal.
Related Reading
Learn more in our guide to Heart Rate (Pulse): Normal Ranges by Age, How to Check It and Target Heart Rate.
Learn more in our guide to Holter Monitor: What It Detects, How It Works and Results.
Electrocardiogram (EKG or ECG): Why It's Done, How to Prepare, What Happens and Results explains how an EKG records your heart rhythm and what the results can show.
Heart Rate Monitors: How They Work, Types, Accuracy and When to See a Doctor explains how heart rate monitors work, how accurate they are and when a reading needs a call to your doctor.
References
Mayo Clinic Staff. Bradycardia - Symptoms and causes. Mayo Clinic. December 13, 2024. https://www.mayoclinic.org/diseases-conditions/bradycardia/symptoms-causes/syc-20355474
Mayo Clinic Staff. Bradycardia - Diagnosis and treatment. Mayo Clinic. December 13, 2024. https://www.mayoclinic.org/diseases-conditions/bradycardia/diagnosis-treatment/drc-20355480
Huh S, et al. Lithium-associated bradycardia: A systematic review of 121 case reports. Prog Neuropsychopharmacol Biol Psychiatry. 2026;149:111831. PMID 42425479. https://doi.org/10.1016/j.pnpbp.2026.111831
López-Delgado DS, et al. Arrhythmias in Dengue: A Systematic Review and Meta-Analysis. Pathogens. 2026;15(5). PMID 42198623. https://doi.org/10.3390/pathogens15050497
Hussein H, et al. Predictors of high-grade atrioventricular block recovery in Takotsubo cardiomyopathy: a systematic review of case reports. Open Heart. 2026;13(1). PMID 42173561. https://doi.org/10.1136/openhrt-2026-004035
National Heart, Lung, and Blood Institute. Arrhythmias - What Is an Arrhythmia?. NHLBI, NIH. Last updated March 24, 2022. https://www.nhlbi.nih.gov/health/arrhythmias
American Heart Association. Bradycardia: Slow Heart Rate. American Heart Association. Last reviewed September 25, 2024. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate
National Heart, Lung, and Blood Institute. Arrhythmias - Conduction Disorders. NHLBI, NIH. Last updated March 24, 2022. https://www.nhlbi.nih.gov/health/conduction-disorders
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