Heart block


Heart block
Heart block

Heart block is a condition where the heart beats more slowly or with an abnormal rhythm. It's caused by a problem with the electrical pulses that control the rhythm and rate of the heart.  

Symptoms depend on which type of heart block you have. First-degree heart block, the least serious type, may not cause any noticeable symptoms.

Second-degree heart block sometimes causes troublesome symptoms that need treatment, and third-degree heart block – the most serious type – can sometimes be a medical emergency.

Symptoms of heart block

First-degree heart block

First-degree heart block doesn't usually cause any noticeable symptoms. Most people only find out they have it when they're tested for an unrelated medical condition.

Second-degree heart block

Most people with the less serious type of second-degree heart block, known as Mobitz type 1, won't experience any symptoms.

But some people may experience:

  • mild light-headedness or dizziness
  • fainting

People with the more serious type of second-degree heart block, known as Mobitz type 2 heart block, are more likely to experience the above symptoms.

They may also experience:

  • chest pain
  • shortness of breath
  • feeling very dizzy suddenly when standing up from a lying or sitting position – this is caused by having low blood pressure (hypotension)

Third-degree heart block

Symptoms of third-degree or complete heart block include:

  • fainting – this can cause someone to collapse 
  • breathlessness
  • extreme tiredness (fatigue), sometimes with confusion
  • chest pain

If you experience severe symptoms or ones that come on very quickly, dial 999 to request an ambulance. These symptoms can be life threatening.

All types of heart block can increase your risk of developing other types of heart rhythm problems, such as atrial fibrillation (an irregular and abnormally fast heart rate).

Causes of heart block

Some people are born with heart block – known as congenital heart block.

But more commonly, heart block develops later in life. This is known as acquired heart block and can be caused by:

  • other heart conditions, such as a heart attack 
  • taking certain medicines
  • other diseases, such as Lyme disease
  • having heart surgery

Babies are more likely to have congenital heart block if they're born with a heart defect, or if their mother has an autoimmune condition, such as lupus.

Treatment of heart block

Heart block normally only needs to be treated if it's causing symptoms.

Depending on the cause of heart block and your symptoms, you may need to have a small device called a pacemaker fitted in your chest. A pacemaker is a small battery-operated device inserted under the skin of your chest. It sends frequent electrical pulses to keep your heart beating regularly.

Read more about how a pacemaker is fitted.

Treatment for heart block usually works well. Most people live a normal active life with a pacemaker.

Diagnosing heart block

Unless you're experiencing symptoms, heart block is often diagnosed during routine tests for other conditions.

An electrocardiogram (ECG) is the main test used to diagnose heart block. It measures the electrical activity of your heart.

An ECG can be carried out at rest or while you're exercising. Your doctor may ask you to wear a portable ECG monitor to get a reading over time. It provides a useful overall assessment of how well your heart is working.

The results of an ECG can also sometimes indicate the type of heart block you have.


Who can get it

Heart block can be present from birth (congenital) or develop later in life (acquired).

Babies are more likely to have congenital heart block if they're born with a heart defect, or if their mother has an autoimmune condition, such as lupus.

Acquired heart block

Acquired heart block can affect people of any ages, but older people are more at risk.

There are several causes, including:

  • heart surgery – thought to be one of the most common causes of complete heart block
  • being an athlete – some athletes get first-degree heart block because their hearts are often bigger than normal, which can slightly disrupt their heart's electrical signals
  • a history of coronary heart disease, heart attack or heart failure – this can leave the heart tissues damaged
  • some diseases – such as myocarditis, cardiomyopathy, Lyme disease, sarcoidosis, Lev's disease, diphtheria or rheumatic fever
  • exposure to some toxic substances
  • low levels of potassium (hypokalaemia) or low magnesium (hypomagnesemia) in the blood
  • high blood pressure (hypertension) that isn't well controlled
  • cancer that's spread from another part of the body to the heart
  • a penetrating trauma to the chest – such as a stab wound or gunshot wound

 Certain medications can also cause first-degree heart block, including:

  • medication for abnormal heart rhythms – such as disopyramide
  • medications for high blood pressure – such as beta blockers, calcium channel blockers, or clonidine
  • digoxin – a medication used to treat heart failure
  • fingolimod – used for treating certain types of multiple sclerosis 
  • pentamidine – used to treat some types of pneumonia
  • tricyclic antidepressants  – such as amitriptyline

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website nhs.uk
Last Updated: 02/09/2021 14:45:56