Information for patients with an abnormal heart beat

Before you have your electrical cardioversion it is important that you understand your condition. This leaflet explains what causes an abnormal heart beat, the possible symptoms, and the treatment we recommend and why.

If there is anything that you feel the leaflet does not explain in enough detail or you have any further questions, then you will have the opportunity to discuss these with the cardioversion nurse when you attend the hospital for a pre-assessment appointment. 

Which type of abnormal heart beat do I have?

There are two types of abnormal heart beat that can be treated by electrical cardioversion, atrial fibrillation (AF for short) and atrial flutter. Both of these heart beats are caused by a disturbance in the electrical activity within the heart.

Atrial fibrillation is the most common. It is an irregular heart beat which can be fast or slow. Atrial flutter is far less common. It can be irregular or regular and can also be fast or slow. 

Your nurse will be able to tell you which one you have. 

Why do I have an abnormal heart beat?

We are not always able to tell what has caused this disturbance in electrical activity. Common causes are:

  • Infection
  • Drinking too much alcohol 
  • Drinking too much tea and coffee 
  • Problems with your thyroid gland 
  • High blood pressure 
  • Problems with the blood supply to your heart 
  • Problems with your heart valves
  • Raised body mass index (BMI)

Your nurse may be able to tell you the most likely cause. However, it may be that all your tests to investigate the cause were normal and there is no apparent cause.

What are the symptoms?

Your abnormal heart beat may have caused you to have symptoms of palpitation (a pounding or fluttery feeling in the chest), dizziness, chest pain or breathlessness. Symptoms are more likely to occur if your heart beat is fast. Quite often it is these symptoms that alert the doctor to the fact that there may be a problem with your heart beat. The symptoms can be quite mild or they can be severe, affecting your ability to lead a normal life.

Some people don’t have any symptoms and don’t even know they have an abnormal heart beat.

How can it be treated?

Your abnormal heart beat may already have been treated with tablets. These tablets are usually given to slow your heart rate and reduce your symptoms, or to try and put your heart beat back to normal and try and prevent further episodes. Tablets do not always work for everyone. Some people are unable to take certain tablets because of the side effects they can cause. In these cases we would usually recommend electrical cardioversion.  

Is treatment always required?

With or without symptoms, these abnormal heart beats can cause problems if left undetected or untreated. The main problem is a possible blood clot. Both of these heart beats are caused by a disturbance in the electrical activity within your heart muscle. This disturbance affects the way the top chambers of your heart squeezes blood through to the bottom chambers. This can interfere with the flow of blood through the heart and can cause blood clots to form within the heart. Even if you do not suffer symptoms from your abnormal heart beat and you feel well, you may still require treatment to prevent blood clots.

Why do I need to an anti-coagulant?

You will be taking an anti-coagulant to thin your blood and prevent clots from forming within your heart. This is important for two reasons. Firstly, if a clot develops within your heart it could get into your blood stream and cause a blockage which could result in a heart attack or stroke. Secondly, if there is a clot within your heart when you come to have your electrical cardioversion, the procedure itself could increase the risk of the clot getting into your blood stream and causing a blockage. 

You need to be on this medication for at least 4 weeks prior to the procedure.

If your electrical cardioversion is successful, you will still need to continue taking the anticoagulant until you are seen at the nurse-led follow up clinic 3 months later. This is to ensure you are protected from possible blood clots. If your heart beat remains normal at your follow up you may be able to stop taking the anti-coagulant.

If your abnormal heart beat comes back at any point, you will need to take the anti-coagulant again until you see your consultant/arrhythmia nurse.

If your electrical cardioversion is not successful you will need to continue taking the anticoagulant until you are seen again by your consultant/arrhythmia nurse. Your nurse will give you more information about this after the procedure before you go home.

Contacts numbers:


Cardioversion Nurse 0191 445 2408
Secretary 0191 445 3594

For further advice / support contact:

Arrhythmia alliance 

Arrhythmia alliance offer information and support to individuals with cardiac arrhythmia (abnormal heart beat).

NICE (national institute for health and clinical excellence) offer information for people who use NHS services. On their website you can find information about the care and treatment which should be offered to people with AF.