Bradycardia

What is bradycardia?

Bradycardia means that your heart beats very slowly. For most people, their resting heart rate is between 60 and 100 beats per minute (bpm).

Low heart rate

A low heart rate (fewer than 60 bpm) may sometimes be normal and can be a sign of being very fit. This normal slow heartbeat doesn't cause any problems and does not need any treatment. This is called sinus bradycardia, with a reduced rate of the electrical signal that controls the heart beat. Sinus bradycardia is common, particularly in well-conditioned athletes. Bradycardia is also normal during sleep.

What causes bradycardia?

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 impulses. It means that the heart's natural pacemaker isn't working right (eg, sick sinus syndrome) or that the electrical pathways of the heart are disrupted (eg, heart block).

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.

When to worry about low heart rate

A low heart rate is often harmless but the causes of bradycardia include various heart conditions or other conditions such as hypothyroidism. Symptoms associated with a low heart rate that need to be assessed and investigated by a healthcare professional include:

• Lack of energy.

• Tiredness.

• Dizziness.

• Fainting or loss of consciousness.

• Weakness.

• Chest pains.

• Confusion/memory problems.

• Heart palpitations.

Bradycardia symptoms

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.

Risk factors

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).

• Rheumatic fever.

• 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, using a Holter monitor.

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.

Complications

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).

• Death.

Bradycardia prevention

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).

• Taking regular exercise.

See the separate leaflet called Cardiovascular disease (Atheroma) for more details.