What Is Bradycardia?
Cavan Images/Getty Images
Medically reviewed by Jeffrey S. Lander, MD
Bradycardia is an arrhythmia, or heart rhythm disorder. It is usually diagnosed when your resting heart rate—the number of times your heart beats in one minute when you're at rest—is slower than 60 beats per minute (BPM).
Heart rate is influenced by factors like age and physical condition, but it typically falls between 60 to 100 BPM. While some people might have a lower heart rate with no other symptoms, bradycardia can be a sign of an underlying medical condition.
Bradycardia Symptoms
A heart rate below 60 BPM isn't always a cause for concern, especially if you aren't experiencing any other odd or concerning symptoms. Heart rate can fluctuate; for example, your heart rate naturally slows during deep sleep.
Many people with bradycardia do not experience other symptoms. For example, athletes and physically active people often have lower heart rates because their hearts don't need to work as hard to maintain a steady beat. Their lower heart rate is generally considered a measure of strength.
However, a lower heart rate can decrease the amount of blood pumped from your heart to other parts of your body, particularly your brain. Complications from this are rare; although, insufficient blood flow can contribute to a variety of symptoms depending on your age, physical condition, and the underlying cause of bradycardia.
Possible symptoms of bradycardia include:
Fatigue or weakness
Lightheadedness or dizziness
Fainting or a feeling that you might faint
Chest pain
Confusion or difficulty in concentrating on a task
Tiring easily during exercise
Shortness of breath
Reach out to a healthcare provider if you experience any of these symptoms. They could be a sign of bradycardia or another condition such as arrhythmia, coronary artery disease, anemia (low red blood cell count), or hypoglycemia (low blood sugar).
Causes
Bradycardia can be caused by a variety of factors, including age, physical condition, and conditions that affect the heart's conducting tissues (the tissues that signal the heart to contract). It's more common in older adults due to cardiovascular disease and age-related cardiac changes.
The most common cause of bradycardia is a problem with the sinoatrial node, which is commonly called your sinus node. Your sinus node is your body's natural pacemaker: It produces electrical activity to set your heart rhythm. Sinus bradycardia is when your sinoatrial node generates a heart rate below 60 BPM.
Here are some medical conditions that can cause bradycardia:
Heart disease: A range of conditions that affect the heart or blood vessels
Congenital heart defect: A heart condition present at birth that can affect the structure and functionality of a baby's heart
Myocarditis: An infection of the heart tissue
Conduction system problem: Your heart's conduction pathway regulates your heart rate and rhythm. A problem with this pathway can cause the heart to beat too slowly. This includes medical conditions such as an atrioventricular block, also knows as heart block (a block in the electrical pathway that controls your heartbeat), and sick sinus syndrome (a heart rhythm disorder).
Heart damage: Heart damage can occur due to heart disease or a heart attack, as well as aging
Hypothyroidism: A condition in which the thyroid gland doesn't make and release enough thyroid hormone into your blood (also known as underactive thyroid)
Chemical imbalance: An imbalance of ions in your body, such as potassium and calcium
Sleep apnea: A sleep condition that can cause breathing problems during sleep, leading to a decrease in oxygen levels in the blood
Inflammatory condition: Conditions in which the body's immune system attacks its own tissues, such as rheumatoid arthritis and lupus
Anorexia nervosa: An eating disorder characterized by abnormally low body weight, a fear of gaining weight, and a distorted view of your body
Some medications can cause bradycardia, including:
Beta-blockers: A class of medications used to control heart rhythm and lower blood pressure, such as Tenormin (atenolol), Cardicor and Emcor (bisoprolol), and Lopresor and Betaloc (metoprolol)
Calcium channel blockers: A class of medications used to lower blood pressure, such as Verelan and Verelan PM (verapamil) and Cardiazem (diltiazem)
Lanoxin (digoxin): A medication used to treat abnormal heart rhythms and heart failure
Bradycardia in Athletes
Bradycardia is common with athletes and people who regularly engage in intense physical activity. Athletes often have a resting heart rate between 40 and 60 BPM. One theory is that this is due to a higher vagal tone, which is the activity of the vagus nerve.
Your vagus nerve is one of 12 cranial nerves that connect your brain with other areas of your body. It's responsible for functions like breathing and cardiac (heart) activity. Vagal tone is a measure of heart efficiency: It helps assess how well your vagus nerve regulates your heartbeat.
Vagal tone is typically measured by heart rate variability (HRV), or how much the time between your heartbeats varies. This measurement isn't perfect, but it can give a general sense of vagus nerve functioning. A high vagal tone reduces heart rate, which might explain the connection between vagal tone and bradycardia in athletes. However, research suggests that other factors might cause this type of bradycardia.
How Is Bradycardia Diagnosed?
Your healthcare provider will complete a thorough medical history and physical examination. An electrocardiogram (ECG or EKG) is generally necessary for diagnosis. An electrocardiogram measures the electrical activity of your heart. Every time your heart beats, an electrical impulse travels through your heart's four chambers and allows your heart to contract in proper rhythm so that blood can travel to other parts of your body.
Most people with bradycardia do not experience symptoms that let them know their heart rate is low. If your healthcare provider finds that you have bradycardia, they may recommend wearing a Holter monitor or event monitor. These are devices you would wear for at least 24 hours to monitor your heart's activity.
Other common tests include thyroid function testing and an echocardiogram, which is a type of ultrasound that shows detailed images of your heart's structure. Less common tests include a chest X-ray, urine testing, viral panel, and a blood culture. These tests all help to rule out potential underlying causes of the bradycardia.
Complications
Complications of bradycardia can arise if the bradycardia is left untreated. Common complications include:
Heart failure: A condition in which your heart does not pump enough to meet the body's oxygen and nutrient needs
Syncope: Fainting or dizziness due to reduced blood flow to the brain
Cardiac arrest: Sudden loss of heart function
Treatment
Treatment of bradycardia depends upon the severity of symptoms and the underlying cause. Some bradycardia—for example, if it's mild, occasional, or without symptoms—might not require treatment.
Your healthcare provider may begin by looking for any reversible causes of bradycardia. For example, they may ask which medications you're taking and recommend adjusting the dosage or discontinuing use altogether. However, this might not be an option depending on the reason you take the medication.
If the underlying cause of your bradycardia is a condition like thyroid dysfunction or sleep apnea, your healthcare provider will treat those conditions.
Medication is typically the initial treatment for a person with symptoms like low blood pressure, altered mental status, or difficulty breathing. For example, you might receive a medication called Atropen (atropine), which treats symptoms of low heart rate. This drug is given by inserting a needle through a vein with an intravenous (IV) drip.
Long-term treatment might include an implantable pacemaker. This electrical device sends electrical signals to your heart to keep it beating at a normal rhythm.
A Quick Review
Bradycardia is generally defined as a resting heart rate slower than 60 BPM. Heart rate is influenced by factors like age and physical condition, but it typically falls between 60 to 100 BPM.
Many people with bradycardia do not experience symptoms and do not require treatment. There are many potential causes of bradycardia. A diagnosis requires an electrocardiogram, as well as testing such as a thyroid profile, complete blood count, chest x-ray, blood culture, and a viral panel.
Treatment depends on the underlying cause and the severity of your symptoms. In extreme cases, the temporary pacemaker is the choice, while in asymptomatic cases no medication is recommended.
Related:What Your Resting Heart Rate is Telling You
For more Health news, make sure to sign up for our newsletter!
Read the original article on Health.
