Bradycardia is a low heart rate and often occurs in people who are very fit, such as athletes. However, it may also occur because of an underlying condition such as a heart problem or an underactive thyroid gland.
What is bradycardia?
Bradycardia means that your heart beats very slowly. For most people, that heart rate is between 60 and 100 beats per minute (bpm) when resting.
A low heart rate (fewer than 60 bpm) may sometimes be normal and can be a sign of being very fit. Top athletes may have a pulse rate of fewer than 40 bpm. This normal slow heartbeat doesn't cause any problems and does not need any treatment. Bradycardia may also occur in older endurance athletes and may then need treatment with a pacemaker.
However, sometimes bradycardia is caused by an underlying medical condition and does cause symptoms. Bradycardia may be a sign of a problem with the heart's electrical system. It means that the heart's natural pacemaker isn't working right or that the electrical pathways of the heart are disrupted. In severe forms of bradycardia, the heart beats so slowly that it doesn't pump enough blood to meet the body's needs. This can cause symptoms and can be life-threatening.
What are the symptoms of bradycardia?
Bradycardia may not cause any symptoms. However, bradycardia may cause you to feel:
- Dizzy or light-headed. You might even experience faints or sudden collapse.
- Short of breath, especially with exercise.
- Very tired.
- A pain in your chest or a thumping or fluttering feeling in your chest (palpitations).
- Confused or that you are having trouble concentrating.
There are many possible causes. Bradycardia may be normal, especially in young very fit people. Otherwise the possible causes include:
- Abnormal conduction of the electrical impulse that stimulates the heart to pump blood around your body. Read more about abnormal heart rhythms (arrhythmias).
- Damage to the heart caused by a heart attack (myocardial infarction).
- High blood pressure (hypertension).
- Congenital heart disease. (A congenital condition is a condition that you are born with.)
- Infection of heart tissue (myocarditis).
- A complication of heart surgery.
- Underactive thyroid gland (hypothyroidism).
- Medications - eg, beta-blockers or digoxin.
How is bradycardia diagnosed?
- Taking your pulse rate reveals a very slow heartbeat.
- The first tests will include blood tests and a tracing of your heart (electrocardiogram, or ECG).
- Bradycardia often comes and goes, so you may need a portable (ambulatory) ECG.
Bradycardia treatment and management
The treatment depends on the underlying cause and the symptoms. If the bradycardia isn't causing any symptoms there is no need for any treatment unless treatment is needed for the underlying cause of the bradycardia.
If damage to the heart's electrical system causes your heart to beat too slowly, you may need to have a pacemaker. A pacemaker is a device placed under your skin that helps correct the low heart rate. People who have a pacemaker can lead normal, active lives; however, this will also depend on the underlying condition.
If another medical problem, such as hypothyroidism or an imbalance of salts (electrolytes), is causing a low heart rate then treating the cause will often cure the bradycardia.
If a medicine is causing your heart to beat too slowly, your doctor may lower the dose of the medicine or change it to a different medicine.
Always obtain emergency help (in the UK, call 999) if you, or someone near you, have collapsed or if you have symptoms of a heart attack, such as severe chest pain or severe shortness of breath.
Also seek emergency help if your heart rate is slower than usual and you feel like you might pass out, or if you notice increased shortness of breath.
For most people, bradycardia will not cause any complications. Any complications will depend on the underlying cause of the slow heart rate.
If severe bradycardia isn't treated, it can lead to serious problems. These may include sudden collapse, fits (seizures) or even death.
Bradycardia can be caused by heart disease, so healthy lifestyle advice is very important. This includes healthy eating, not smoking, reducing body weight (if overweight) and taking regular exercise. See the separate leaflet called Cardiovascular Disease (Atheroma) for more details.
Further reading and references
Checking your pulse; British Heart Foundation
Sidhu S, Marine JE; Evaluating and managing bradycardia. Trends Cardiovasc Med. 2020 Jul30(5):265-272. doi: 10.1016/j.tcm.2019.07.001. Epub 2019 Jul 9.
Mason KP, Lonnqvist PA; Bradycardia in perspective-not all reductions in heart rate need immediate intervention. Paediatr Anaesth. 2015 Jan25(1):44-51. doi: 10.1111/pan.12584. Epub 2014 Nov 20.
Cinier G, Haseeb S, Bazoukis G, et al; Evaluation and Management of Asymptomatic Bradyarrhythmias. Curr Cardiol Rev. 202117(1):60-67. doi: 10.2174/1573403X16666200721154143.
Da Costa D, Brady WJ, Edhouse J; Bradycardias and atrioventricular conduction block. BMJ. 2002 Mar 2324(7336):535-8.
Adult Bradycardia Algorithm; Resuscitation Council UK, 2021
British National Formulary (BNF); NICE Evidence Services (UK access only)