Bradycardia (low heart rate): what you need to know
Bradycardia (pronounced "bra-dee-KAR-dee-uh") means that your heart beats very slowly. A slow heart rate can be normal and healthy – for example, many fit people and young adults have a slow heart rate because the organ is so fit and strong – and for most people, a heart rate of between 60 to 90 beats a minute while at rest is considered normal. If your heart beats fewer than 60 times a minute, it is said to be slower than normal.
What is bradycardia?
Occasionally, bradycardia can be a sign of a problem with the heart's electrical system – this can mean the organ's natural pacemaker isn't working as it should, or that the complex electrical pathways are disrupted. In very severe forms of bradycardia, the heart beats so slowly that it doesn't pump enough blood to meet the body's needs, and this can be a life-threatening problem.
It is virtually impossible to give accurate figures on how common bradycardia is in the UK, as for most young people, bradycardia is physiological and normal, although the incidence of the condition rises with age as underlying possible causes become more frequent. For most people, symptoms do not arise unless the heart rate drops below 50 beats per minute, and absolute bradycardia is defined as being fewer than 40 beats per minute. Some types of bradycardia produce no symptoms, and others may cause dizziness, weakness or fainting.
Bradycardia causes
If not due to fitness or youth (physiological bradycardia), there are a number of pathological causes as to why a bradycardia may occur, with the most common ones being;
Sick sinus syndrome
This occurs when the heart's natural pacemaker (called the sino-atrial node), does not work properly, causing an irregular heartbeat. Patients with sick sinus syndrome may experience bradycardia or a fast heartbeat (tachycardia), or heartbeats that swap between fast and slow. Most common in elderly people, this can also occur in children, sometimes after heart surgery.
Heart block (atrioventricular block or AV block)
This occurs when electrical impulses are slowed or blocked as they travel from the atria chambers of the heart, through the AV node, into the ventricles of the heart. There are different types of heart block:
First–degree heart block occurs when the electrical impulses slow as they pass through the AV node. First–degree heart block rarely causes any symptoms, and is often found in athletes. No treatments are generally necessary.
Type I second–degree heart block occurs when the electrical impulses are delayed to a greater extent with each heartbeat until a beat is skipped entirely and the cycle then repeats itself.
Type II second–degree heart block occurs when some of the electrical impulses from the SA node are unable to reach the ventricles, usually because of underlying disease.
Third–degree heart block (complete heart block) occurs when no electrical impulses reach the ventricles at all. This is usually as a result of underlying disease or medications.
Bradycardia symptoms
Some people don't have symptoms, or their symptoms are so mild that they think they are just part of getting older. If symptoms do occur due to a very slow heart rate these include:
Dizzy spells, and feeling faint (because a slow heart rate causes a drop in blood pressure)
Shortness of breath and finding it harder to exercise
Feeling tired
Chest pain or a feeling that your heart is pounding or fluttering (palpitations).
Feeling confused, or having trouble concentrating
The symptoms of someone in heart block depend on its severity and the type of heart block present.
Bradycardia diagnosis
Your doctor will take your pulse and often be able to diagnose bradycardia on the spot but will also do a physical examination and arrange an electrocardiogram (ECG). This measures the electrical signals that control the heart rhythm and can show not only if bradycardia is present but also if heart block is a problem. Sometimes a basic ECG done in the surgery may not pick up a problem and a portable (ambulatory) electrocardiogram may be required in order to make an accurate diagnosis. This is a lightweight device - also called a Holter monitor – that is worn for 24 hours or more, and records your heart rhythm while you go about your daily routine. You may also have blood tests to find out if another problem is causing your slow heart rate such as problems with the thyroid gland or electrolyte imbalances.
Most cases of pathological bradycardia are due to problems with the heart electrical system although occasionally can be due to medication such as beta blockers or digoxin.
Your GP may refer you to a heart specialist (a cardiologist) for a more detailed assessment of your heart and treatment.
Bradycardia treatment
Once diagnosed and treated, bradycardia tends to cause few problems for most people. The usual treatment options for treating symptomatic bradycardia are:
Discontinuing any medications that slow the heartbeat
Treating any underlying medical conditions
Implanting a permanent pacemaker into the heart
A pacemaker is a small device, approximately the size of a fifty pence piece used to detect and treat slow heart rhythms. It is implanted beneath the skin below the collarbone and connected to a pacing wire placed inside the heart. The pacemaker fires a small electrical impulse to stimulate the heart to beat when it detects that the heart rate/pulse is going too slow. People older than 65 are most likely to have a type of bradycardia that requires pacemaker treatment but most people who get pacemakers lead normal, active lives.
Living with bradycardia
Because bradycardia is often the result of another heart condition, taking steps to improve heart health also usually improves your overall health. The best steps to take for this include:
Controlling your cholesterol and blood pressure
Eating heart-healthy foods
Getting regular exercise – your doctor can tell you what level of exercise is safe for you
If you smoke – quit. If you find this difficult ask your doctor about smoking cessation help available in your area.
Last updated: 01-04-2020
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