What is it?
Atrial fibrillation (AF) is a type of abnormal heart rhythm. It is characterized by fast and irregular beating. It often has no symptoms, and starts as short and infrequent episodes that become longer and more frequent over time. When there are symptoms they often include heart palpitations, fainting, shortness of breath, and chest pain.
AF is the most common serious abnormal heart rhythm. In Europe and North America it affects 2-3% of people. It gets more common with age and is less common in developing countries.
What causes it?
Many other cardiovascular problems, such as high blood pressure and coronary artery disease, are associated with AF. Problems with breathing, obesity, excessive alcohol consumption, and problems with the thyroid gland are thought to play a role. Genes can also increase the risk of developing AF.
What happens during it?
The contraction of the heart begins when the sinoatrial node near the right atrium sends an electrical signal.. This happens in a regular pattern. AF happens when these regular electrical signals are overwhelmed by disorganized signals that often mostly come from the roots of the veins that come from the lungs. The signal sent by the sinoatrial node is supposed to cause the atria to contract, but in this case the muscle cells start contracting in whatever disorganized manner the other signals tell them to.
In AF some of the muscle tissue of the atria is replaced by fibrous tissue. Most of the diseases known to increase the risk of AF do so because they lead to this process called fibrosis. This, in turn, is thought to lead to changes in conductivity that makes it easier for the muscle cells to take irrelevant signals seriously, although it is not entirely clear how or even if this happens.
How can it be treated?
The main goals of treatment are to keep the blood flow as steady as possible and to prevent strokes. Medications can be used to control the pace of heart beats, and anticoagulants can be used to prevent blood clots, the main cause of strokes.
Sources: https://en.wikipedia.org/wiki/Atrial_fibrillation, https://www.ncbi.nlm.nih.gov/pubmed/21633248