Why does fibrillation occur

The AV node is then bombarded with signals trying to get through to the lower heart chambers ventricles. This causes a fast and irregular heart rhythm. The heart rate in atrial fibrillation may range from to beats a minute. The normal range for a heart rate is 60 to beats a minute. Problems with the heart's structure are the most common cause of atrial fibrillation.

Possible causes of atrial fibrillation include:. In atrial fibrillation, the chaotic heart rhythm can cause blood to collect in the heart's upper chambers atria and form clots.

If a blood clot in the left upper chamber left atrium breaks free from the heart area, it can travel to the brain and cause a stroke.

The risk of stroke from atrial fibrillation increases as you grow older. Other health conditions also may increase your risk of a stroke due to A-fib , including:. Blood thinners are commonly prescribed to prevent blood clots and strokes in people with atrial fibrillation.

Healthy lifestyle choices can reduce the risk of heart disease and may prevent atrial fibrillation. Here are some basic heart-healthy tips:. Atrial fibrillation care at Mayo Clinic. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview Atrial fibrillation Open pop-up dialog box Close. Atrial fibrillation In a typical heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal sinus node impulse.

Request an Appointment at Mayo Clinic. Share on: Facebook Twitter. Show references Atrial fibrillation. National Heart, Lung, and Blood Institute. Accessed July 6, Zipes DP, et al.

Catheter ablation: Technical aspects. Elsevier; Accessed Feb. Ferri FF. Atrial fibrillation. However, because atrial fibrillation tends to come and go, an office ECG may be normal. If this is the case, your doctor may give you an ECG monitor to wear at home that will record your heart rhythm over time. These include:.

Holter Monitor — a portable ECG you wear continuously for one to seven days to record your heart rhythms over time. Event Monitor — a portable ECG you wear for one or two months, which records only when triggered by an abnormal heart rhythm or when you manually activate it.

Implantable Monitor — a tiny event monitor inserted under your skin, worn for several years to record events that only seldom take place. Some people with atrial fibrillation will return to normal rhythm without treatment.

Otherwise, the first focus of treatment is to find and treat the underlying cause. If the cause is thyrotoxicosis, treatment may consist of medications or surgery. For most patients no specific reversible cause can be identified. Medications to slow the heart rate including the following classes of medications:. Medications to prevent blood clots , called anticoagulants or blood thinners.

The most important risk of atrial fibrillation is the development of a stroke, which can be lethal. Atrial fibrillation increases the risk of stroke fivefold.

Many patients with atrial fibrillation, especially those over the age of 65, require lifelong anticoagulation to prevent strokes and prolong life. Catheter ablation , to address the most common trigger for atrial fibrillation: cells in the pulmonary veins that produce their own electrical signal. This type of ablation creates a ring of scar tissue where the veins enter the heart, blocking electrical signals from the veins.

Left atrial appendage closure procedure , for patients who are unable to take blood thinners because of bleeding risks. Call immediately as you need immediate treatment in hospital.

When the heart beats normally, its muscular walls tighten and squeeze contract to force blood out and around the body. They then relax so the heart can fill with blood again. This process is repeated every time the heart beats. In atrial fibrillation, the heart's upper chambers atria contract randomly and sometimes so fast that the heart muscle cannot relax properly between contractions. This reduces the heart's efficiency and performance. Atrial fibrillation happens when abnormal electrical impulses suddenly start firing in the atria.

These impulses override the heart's natural pacemaker, which can no longer control the rhythm of the heart. This causes you to have a highly irregular pulse rate.

The cause is not fully understood, but it tends to affect certain groups of people, such as older people and people living with long-term chronic conditions such as heart disease, high blood pressure or obesity. It may be triggered by certain situations, such as drinking too much alcohol or smoking.

Atrial fibrillation can be defined in various ways, depending on the degree to which it affects you.