Bradycardia refers to a slower than normal resting heart rate. Resting heart rate is how fast a person’s heart beats when they are at rest. A person’s heart rate may lower due to age or physical health. Bradycardia can also be a symptom of certain medical conditions.
According to the American Heart Association (AHA), a person’s resting heartbeat is generally
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.
Read on to learn more about slow heart rate, its causes, and treatment options.
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:
- transporting oxygen and nutrients to tissues and organs
- creating blood clots to stop bleeding
- transporting antibodies to fight infections
- bringing waste products to the kidneys and liver, which then filter and clean the blood
- regulating body temperature
The AHA states that, generally, a resting heart rate of less than
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.
Sinus bradycardia is a form of slow heart rate that begins in a person’s sinoatrial (SA) node. The SA node is a structure in the top of a person’s right atrium that generates the electrical impulse that starts a heartbeat.
If a person 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.
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 a problem with their SA node that causes the AV node to take over. Additionally, physically athletic individuals, young children, and people in a deep sleep
Some people who have bradycardia do not experience any symptoms other than a slow heart rate. Other individuals with bradycardia may have symptoms
- feelings of exhaustion and weakness
- fainting or dizziness
- shortness of breath
- exercise intolerance or trouble breathing when working out
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 include:
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 they are
A person can take their pulse from different locations on their body, including:
- their wrists
- the side of the neck
- the inside of the elbows
- the top of the feet
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, as the thumb has a pulse of its own, and it may therefore 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 stop watch or look at a clock while they count their heartbeats.
If a person has a heartbeat count that is 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 normal heart rate for an infant is around
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.
People who engage in high amounts of physical activity tend to have more efficient hearts. This may slow their pulse, because their heart
Certain medical conditions can cause bradycardia. These conditions include:
Sick sinus syndrome
Sick sinus syndrome, also known as sinus node dysfunction (SND), is a condition that affects a person’s SA node, causing it to fire impulses at irregular rates. 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
- feeling faint or fainting
Although SND can develop in people of any age, the average age of someone who has it is 68 years old. SND is a
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
Complete heart block results in a person’s atria and ventricles activating independently of each other. If a person does not receive treatment for complete heart block quickly, it can be fatal.
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
Other metabolic conditions that can cause bradycardia include:
- 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
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:
- congestive heart failure
- coronary artery disease
- heart attack
- myocarditis, which is inflammation of the heart muscle
- Lyme disease
- thickened heart muscle
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.
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 it can occur when a person is choking or having a severe asthma attack. Chronic medical conditions, such as chronic obstructive pulmonary disease, may also cause hypoxia.
If hypoxia lowers a person’s heart rate, it is essential to treat the underlying cause.
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
- have heart disease and bradycardia
- experience bradycardia and other symptoms, such as fainting spells
- experience episodes of bradycardia and tachycardia, which is a rapid heartbeat
If a person is concerned about their slow heart rate, they should also consult a doctor.
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.
- physical tests
- questions about medical history
- blood tests
- heart monitors
- imaging tests
If a person has a condition that interferes with the electrical impulses of their heart, they
Depending on the cause, a doctor might also recommend:
- changing heart medications
- taking medication to treat thyroid or other metabolic disorders
- making lifestyle changes, such as eating a low fat diet, getting more exercise, or quitting smoking
- monitoring heart rate or blood pressure frequently
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 be an indication 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.