What Is Atrial Fibrillation?

An irregular heartbeat can be a very confusing idea to understand; however, it is key to describing one of the most common heart rhythm abnormalities called atrial fibrillation.

Atrial fibrillation is a condition where your heartbeat doesn’t follow a set rhythm, beating in a manner that seems to be random. This is a result of abnormal muscular contraction in a part of your heart called the atria. It is associated with very significant complications such as increasing your risk of strokes so it is not a condition to be taken lightly.

Please continue reading to find out more about atrial fibrillation.


Very tight coordination is extremely important for your heart to function appropriately and pump blood around the body. Cardiac muscle is very distinct from all the muscles in your body, and this is all under the control of a very complex system of nerves that ensures your heartbeat stays in rhythm and only beats as fast as your body needs it to within a safe range of 60-100 beats per minutes, normally only above this when you’re very physically active.1 However, some conditions result from an abnormality or disruption to this tightly controlled system, leading to abnormal heart rhythms. Cardiac arrhythmias and atrial fibrillation are the most common.2

The heart has four chambers. The two chambers at the top are called atria, and the 2 at the bottom are called ventricles. The blood flows into the right and left atria and pumps blood down into the ventricles. There is then a slight delay between the atria contracting and the ventricles contracting and this is so that there is enough time for the blood to completely fill the ventricles. The ventricles then contract and pump blood out of the heart, with the right ventricle pumping blood to the lungs, where they receive oxygen, and the left ventricle pumping blood to the rest of the body, where that oxygen is then unloaded all over the body to give your body energy.

In atrial fibrillation, there is a problem with the nerves responsible for controlling the contraction of the atria. This is typically a result of previous damage to the heart. This loss of coordination makes the atria beat rapidly and out of control. This then causes your ventricles to beat rapidly and out of control. Hence, the description of irregular heart rhythm. A heart rhythm is where your heartbeats are spaced out in a way where there is no discernable pattern.

Atrial Fibrillation is the most common heart arrhythmia, affecting over 1 million people in the UK, with many living with the condition entirely undetected. It affects the individuals assigned male at birth (AMAB) slightly more than the individuals assigned female at birth (AFAB) and is heavily associated with those who have heart failure or have had a previous heart attack.2

Causes of atrial fibrillation

There are many causes of atrial fibrillation. They are:3

  • Heart failure – a condition where your heart is no longer able to pump blood around your body well enough to supply your body with the nutrients it needs
  • Previous heart attack
  • Heart valve abnormalities, in particular mitral stenosis – When your heart chambers contract, your blood flows through valves, which prevents blood from flowing backwards. Your mitral valve is the valve between your left atria and left ventricle, and in mitral stenosis, this valve narrows, making it harder for blood to flow from your atria to your ventricles
  • Congenital heart disease – encompasses a wide spectrum of conditions that are inherited
  • Myocarditis – inflammation of the heart
  • Pericarditis – inflammation of the pericardium, which is a sac that encloses the heart
  • Hyperthyroidism – a condition where your thyroid gland produces increased amounts of thyroid hormones which cause your heart to beat rapidly and can lead to atrial fibrillation
  • Pulmonary embolism – this is where a blood clot forms somewhere in your blood vessels and gets stuck in one of the arteries in your lungs.

Signs and symptoms of atrial fibrillation

Atrial fibrillation is not always noticed because it often occurs without any symptoms. If you have heart disease, you are more likely to notice symptoms. Occasionally in some cases, you might notice symptoms like 

  • Palpitations
  • Chest pain
  • Dizziness or fainting 
  • Low blood pressure
  • Difficulty in breathing
  • Finding it more difficult to exercise 

Management and treatment for atrial fibrillation

How atrial fibrillation is generally managed depends on a few factors. One important factor is when atrial fibrillation begins to occur and whether they are exhibiting serious signs or symptoms. Anyone who has atrial fibrillation that is less than 48 hours long and shows symptoms of a rapid pulse above 150, low blood pressure, fainting, dizziness, and chest pain must immediately have an emergency admission to the hospital where they will have a procedure called cardioversion. This involves electric shocks and can be thought of as a way of rebooting the heart so that it can re-establish a normal rhythm. Emergency admission to a hospital will also be urgently required if you’re showing signs of a different severe disease such as a heart attack, a pulmonary embolism, stroke, or chest infection that could also have caused your symptoms. If you are someone who hasn’t shown symptoms but has had atrial fibrillation, you may be referred to the hospital but you might only need to be managed by your GP, depending on the severity. 

Regardless, key points of management are generally to take a medical history, as this will allow your physician to calculate your stroke risk using a scoring tool called CHA2DS2VASc. If your score passes the threshold, you will be started on anticoagulant medication. This is a medication that is commonly known as “blood thinners” and its role is to stop clots from forming as easily. However, it is important to note that this increases your risk of serious bleeding, so you will be constantly monitored. You will also be started on medications that will slow your heart rate, as atrial fibrillation commonly causes abnormally and dangerously high heart rates. If unsuccessful, you may be referred to the hospital for cardioversion to establish control of the rhythm. If doesn’t work, there is the option of catheter ablation. Catheter ablation is a procedure where tubes are passed through the blood vessels to the heart, where they are then able to monitor the electrical activity in the heart and pinpoint exactly where the faulty tissue causing havoc is located. This area is then destroyed to restore normal heart rhythm.

Diagnosis of atrial fibrillation

Your healthcare provider can diagnose if you have atrial fibrillation by

  • Screening for the causes and risk factors helps healthcare providers decide whether diagnostic testing is needed
  • Checking your medical and family history
  • Conducting physical examination
  • Carrying diagnostic tests like blood tests, electrocardiograms, echocardiography, cardiac MRI, etc

Sometimes additional tests like chest X-rays, sleep tests, stress tests, walking stress, electrophysiology study, transesophageal echocardiography etc, might be required as well. 

Risk factors

These can be divided into modifiable and non-modifiable risk factors. Modifiable risk factors are things that can be prevented or changed, and these include: 2

  • Alcohol abuse
  • Excessive caffeine intake
  • Obesity
  • Smoking

Non-modifiable  risk factors are risk factors you can do nothing about, and these include :

  • Age over 65
  • Being an AMAB
  • Racial differences such as atrial fibrillation appear to be more common in those of caucasian ethnicity


  • Stroke blood clots forming in your heart make it difficult for your heart to contract properly and completely empty with each heartbeat. This allows blood to pool in the heart, forming blood clots that can then directly travel to the vessels in the brain. 
  • Heart failure
  • Heart attack 


How can I prevent atrial fibrillation?

You can prevent atrial fibrillation by managing your modifiable risk factors. Examples of how you could do this are: 

  • Improving your diet by eating fewer fatty foods
  • Increasing physical activity
  • Stopping smoking
  • Reducing your alcohol intake

How common is atrial fibrillation?

It affects 2.5% of the UK population or 1.5 million people.

When should I see a doctor?

Seek medical advice if you have experienced symptoms of palpitations, lightheadedness, dizziness, or chest pain. 


Atrial fibrillation is a condition where the heartbeat is irregular. This happens when there is a defect in the electrical signals sent by the nerves between the atria and ventricles. They mostly occur without any symptoms, but if you experience symptoms like palpitations, chest pain, breathlessness, dizziness etc, please visit your GP immediately. In conclusion, atrial fibrillation is the most common cardiac arrhythmia, which requires urgent management to prevent further complications.


  1. Van Weerd JH, Christoffels VM. The formation and function of the cardiac conduction system. Development [Internet]. 2016 Jan 15 [cited 2023 Oct 25];143(2):197–210. Available from: https://journals.biologists.com/dev/article/143/2/197/47400/The-formation-and-function-of-the-cardiac
  2. Staerk L, Sherer JA, Ko D, Benjamin EJ, Helm RH. Atrial fibrillation: epidemiology, pathophysiology, and clinical outcomes. Circ Res [Internet]. 2017 Apr 28 [cited 2023 Oct 25];120(9):1501–17. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC550087 4/
  3. Nesheiwat Z, Goyal A, Jagtap M. Atrial fibrillation. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Oct 25]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK526072/ 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jeandy Mibanzo-Ilamu

Master of Research Biology of Cancer - MRes University of Liverpool

Jeandy is a final year medical student which has allowed him to acquire strong clinical knowledge and familiarity with general health and wellbeing.His master's degree focused on the Biology of Cancer, a keen area of interest and allowed him to develop a lot of the skills he uses in writing his articles.

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