Atrial Fibrillation

Also known as A-fib, AF
Atrial fibrillation is one of the most common types of arrhythmias, which are irregular heart rhythms. Atrial fibrillation causes your heart to beat much faster than normal. Also, your heart’s upper and lower chambers do not work together as they should. When this happens, the lower chambers do not fill completely or pump enough blood to your lungs and body. This can make you feel tired or dizzy, or you may notice heart palpitations or chest pain. Blood also pools in your heart, which increases your risk of forming clots and can leads to strokes or other complications. Atrial fibrillation can also occur without any signs or symptoms. Untreated fibrillation can lead to serious and even life-threatening complications.

Sometimes atrial fibrillation goes away on its own. For some people, atrial fibrillation is an ongoing heart problem that lasts for years. Over time, it may happen more often and last longer. Treatment restores normal heart rhythms, helps control symptoms, and prevents complications. Your doctor may recommend medicines, medical procedures, and lifestyle changes to treat your atrial fibrillation.

Explore this Health Topic to learn more about atrial fibrillation, our role in research and clinical trials to improve health, and where to find more information.

Types - Atrial Fibrillation

Atrial fibrillation is a type of arrhythmia. There are four main types of atrial fibrillation—paroxysmal, persistent, long-term persistent, and permanent atrial fibrillation. The type of atrial fibrillation that you have depends on how often atrial fibrillation occurs and how it responds to treatment.

Paroxysmal atrial fibrillation
- Atrial Fibrillation

You may experience a brief event—a paroxysm—of atrial fibrillation. It may pass without symptoms, or you may feel it strongly. It usually stops in less than 24 hours but may last up to a week. Paroxysmal atrial fibrillation can happen repeatedly.

You may need treatment or your symptoms may go away on their own. When this kind of atrial fibrillation alternates with a heartbeat that is slower than normal, it is called tachybrady syndrome.

Persistent atrial fibrillation
- Atrial Fibrillation

Persistent atrial fibrillation is a condition in which the abnormal heart rhythm lasts for more than a week. It may ultimately stop on its own but probably will need treatment.

Long-term persistent atrial fibrillation
- Atrial Fibrillation

With this condition, the abnormal heart rhythms last for more than a year without going away.

Permanent atrial fibrillation
- Atrial Fibrillation

Sometimes atrial fibrillation does not get better, even when you have tried several times to restore a normal heart rhythm with medicines or other treatments. At this point, your atrial fibrillation is considered permanent.

Causes - Atrial Fibrillation

Changes to the heart’s tissue and to its electrical signals most often cause atrial fibrillation. To understand atrial fibrillation, it helps to know how the heart works. When the heart’s tissue or signaling is damaged, the regular pumping of the heart muscle becomes fast and irregular. Most often, damage to the heart is the result of other conditions such as high blood pressure and ischemic heart disease. Other factors can also raise your risk of atrial fibrillation.

Illustration of atrial fibrillation
Atrial fibrillation. This image shows the electrical system of the heart during atrial fibrillation. Normally, an electrical signal at the sinoatrial (SA) node in the upper right chamber of the heart causes the upper chambers to contract and pump blood into the lower chambers. The electrical signal travels down the heart and causes the lower chambers to contract. In atrial fibrillation, abnormal electrical signals in the upper chambers overwhelm the normal signal from the SA node and cause the upper chambers to beat irregularly. This image includes a graphical representation of the EKG (ECG) showing the electrical impulses illustrated within the heart. Medical Illustration Copyright © 2019 Nucleus Medical Media, All rights reserved.


Changes in heart tissue
- Atrial Fibrillation

Usually the cells of the heart fire and contract together. However, when aging, heart disease, infection, genetics, or other factors change heart tissue, that pattern breaks down. This can happen because of fibrosis, inflammation, a thinning or thickening of the heart walls, lack of blood flow to the heart, or an abnormal buildup of proteins, cells, or minerals in heart tissue.

Changes in electrical signaling
- Atrial Fibrillation

Usually, a trigger heartbeat sets off atrial fibrillation. Electrical signals from this trigger may then cause the heart to beat slower or faster than usual because of changes in heart tissue. Sometimes, the signals create an atypical loop, telling the heart to contract over and over. This can create the fast, chaotic beating that defines atrial fibrillation.

Variations in the heart’s electrical signaling can be due to differences in heart anatomy, premature or extra heartbeats, normal heart rate adjustments, patches of faster or slower tissue, and repeated stimulation of certain tissue patches.

Look for
- Atrial Fibrillation

  • Treatment will discuss medicines and procedures that your doctors may recommend if you are diagnosed with atrial fibrillation.

Risk Factors - Atrial Fibrillation

Age, family history and genetics, lifestyle, heart disease or other medical conditions, race, sex, and a history of surgery can all raise your risk of developing the structural and electrical anomalies that cause atrial fibrillation. Even in a healthy heart, a fast or slow heart rate—from exercising or sleeping, for example—can trigger atrial fibrillation.

- Atrial Fibrillation

The risk of atrial fibrillation increases as you age, especially after age 65. Atrial fibrillation is rare in children, but it does occur, especially in boys and in children who have obesity.

Family history and genetics
- Atrial Fibrillation

If someone in your family has had atrial fibrillation, you have a higher risk of developing atrial fibrillation, too. Scientists have found some genes with mutations that raise the risk of atrial fibrillation. Some of these genes influence fetal organ development or heart cell ion channels. Sometimes these genetic patterns are also linked to heart disease. Some genetic factors may raise the risk of atrial fibrillation in combination with such factors as age, weight, or sex.

Lifestyle habits
- Atrial Fibrillation

Some lifestyle habits can raise or lower your risk of atrial fibrillation, including the following:

  • Alcohol. Drinking large amounts of alcohol, especially binge drinking, raises your risk of atrial fibrillation. Even modest amounts of alcohol can trigger atrial fibrillation in some people.
  • Illegal drugs. Some street drugs, such as cocaine, can trigger atrial fibrillation or make it worse.
  • Physical activity. Some competitive athletes and people—men, in particular—participating in endurance sports or exerting themselves at work may have a higher risk of atrial fibrillation. At the same time, moderate physical activity can have a protective effect. Physical fitness appears to be linked to a lower risk of atrial fibrillation.
  • Smoking. Studies have found that smoking increases the risk of atrial fibrillation. The risk appears to be higher the longer you smoke and decreases if you quit. Exposure to secondhand smoke, even in the womb, can increase a child’s risk of developing atrial fibrillation.
  • Stress. Stressful situations, panic disorders, and other types of emotional stress may be linked to a higher risk of atrial fibrillation.

Other medical conditions
- Atrial Fibrillation

Many other medical conditions can increase your risk of atrial fibrillation, especially heart problems. As you age, having more than one condition may increase your risk. Conditions that raise the risk of atrial fibrillation include:

Race or ethnicity
- Atrial Fibrillation

In the United States, atrial fibrillation is more common among whites than among African Americans, Hispanic Americans, or Asian Americans. Although people of European ancestry are more likely to develop the condition, African Americans with atrial fibrillation are more likely to have complications such as stroke, heart failure, or ischemic heart disease.

- Atrial Fibrillation

You may be at risk for atrial fibrillation in the early days and weeks after surgery of the heart, lungs, or esophagus. Surgery to correct a congenital heart defect can also raise the risk of atrial fibrillation. This can happen years after a childhood surgery or when you have surgery as an adult to correct a lifelong condition.

Screening and Prevention - Atrial Fibrillation

Typically doctors screen for atrial fibrillation only when you have risk factors. However, your doctor may check for Signs of atrial fibrillation as part of your regular medical care. Screening tests include checking your pulse or recording your heart’s electrical activity. Your doctor may recommend healthy lifestyle changes to help you lower your risk of developing atrial fibrillation.

Screening tests and results
- Atrial Fibrillation

Screening may be part of your regular care if you are 65 or older or if you have other risk factors.

  • Your doctor may check your pulse. Even without symptoms, your heart may have an irregular speed or faulty rhythm that your doctor can detect.
  • If you have had a stroke and there is no clear cause, your doctor may recommend screening for atrial fibrillation with a Holter or event monitor or a loop recorder, which is a small monitor placed just under the skin of your chest.
  • Several devices are now available to detect and record your heart’s rhythm similar to an electrocardiogram (EKG). These devices may also email the data to your doctor.

Prevention strategies
- Atrial Fibrillation

To help you lower your risk of atrial fibrillation, your doctor may recommend certain heart-healthy lifestyle changes, including aiming for a healthy weight, being physically active, controlling your blood sugar, limiting alcohol, lowering your blood pressure, managing stress, and quitting smoking.

In addition, some illegal drugs, such as cocaine, can trigger atrial fibrillation or make it worse. Ask your doctor for help avoiding these triggers to prevent arrhythmia.

If you are having heart surgery, your medical team will monitor you. To prevent arrhythmia, your doctor may recommend antiarrhythmic medicine or treatment to maintain or supplement electrolyte levels during or after the procedure.

Look for
- Atrial Fibrillation

  • Diagnosis will explain tests and procedures that your doctor may use to diagnose types of atrial fibrillation.
  • Living With will discuss what your doctor may recommend to prevent your atrial fibrillation from recurring, getting worse, or causing complications.
  • Research for Your Health will discuss how we are using current research and advancing research to prevent atrial fibrillation.
  • Participate in NHLBI Clinical Trials will explain our open and enrolling clinical studies that are investigating prevention strategies for atrial fibrillation.

Signs, Symptoms, and Complications - Atrial Fibrillation

You may or may not notice atrial fibrillation. It often occurs with no signs or symptoms. If you do have symptoms, you may notice something that occurs only occasionally. Or, your symptoms may be frequent or serious. If you have heart disease that is worsening, you may notice more symptoms of atrial fibrillation. If your atrial fibrillation is undetected or left untreated, serious and even life-threatening complications can arise. They include stroke and heart failure.

Signs and symptoms
- Atrial Fibrillation

The most common symptom of atrial fibrillation is Fatigue. Other signs and symptoms include:

Keep track of when and how often your symptoms occur, what you feel, and whether these things change over time. They are all important clues for your doctor.

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When it is undetected or untreated, atrial fibrillation can lead to serious complications. This is especially significant for African Americans. Even though whites have atrial fibrillation at higher rates, research has found that many of its complications—including stroke, heart disease, and heart failure—are more common among African Americans. Some complications of atrial fibrillation include:

  • Blood clots. With atrial fibrillation, the heart may not be able to pump the blood out properly, causing it to pool and form an abnormal blood clot in the heart. A piece of the clot—a type of embolus—can break off and travel through the blood to different parts of the body, blocking blood flow to the brain, lungs, intestine, spleen, or kidneys. Atrial fibrillation may also increase the risk of venous thromboembolism, which is a blood clot that forms in a vein.
  • cognitive impairment and dementia. Some studies suggest that impaired cognition, Alzheimer’s disease, and vascular dementia occur more often among people with atrial fibrillation. This may be due to blockages in the blood vessels of the brain or reduced blood flow to the brain.
  • Heart attack. The risk of a heart attack from atrial fibrillation is highest among women and African Americans and especially in the first year after atrial fibrillation is diagnosed.
  • Heart failure. Atrial fibrillation raises your risk of heart failure because the heart is beating fast and unevenly. The heart’s chambers do not fill completely with blood and cannot pump enough blood to the lungs and body. Atrial fibrillation may also make your heart failure symptoms worse.
  • Stroke. If an embolus travels to the brain, it can cause a stroke. For some people, atrial fibrillation has no symptoms, and a stroke is the first sign of the condition. If you have atrial fibrillation, the risk of a stroke is higher if you are a woman.
  • Sudden cardiac arrest. With atrial fibrillation, there is an increased risk that the heart may suddenly and unexpectedly stop beating if you have another serious heart condition.
Illustration of how stroke can occur during atrial fibrillation
Atrial fibrillation and stroke. The illustration shows how a stroke can occur during atrial fibrillation. A blood clot can form in the left atrium of the heart. If an embolus, or a piece of the clot, breaks off and travels to an artery in the brain, it can block blood flow through the artery. The lack of blood flow to the portion of the brain fed by the artery causes a stroke. Medical Illustration Copyright © 2019 Nucleus Medical Media, All rights reserved.


Look for
- Atrial Fibrillation

  • Diagnosis will explain tests and procedures used to detect signs of atrial fibrillation and help rule our other conditions that may mimic atrial fibrillation.
  • Treatment will discuss treatment-related complications or side effects.

Diagnosis - Atrial Fibrillation

A doctor will diagnose atrial fibrillation based on your medical and family history, a physical exam, the results from an electrocardiogram (EKG), and possibly other tests and procedures. If you have atrial fibrillation, your doctor will also look for any disease that may be causing it and assess your risk of developing dangerous blood clots. This will help him or her plan the best way to treat you.

Medical history
- Atrial Fibrillation

To help diagnose atrial fibrillation, your doctor will ask about your eating and physical activity habits, family history, and other risk factors for atrial fibrillation and heart disease. Your doctor may ask whether you have any other signs or symptoms. This information can help your doctor determine whether you have complications or other conditions that may be causing you to have atrial fibrillation.

Physical examination
- Atrial Fibrillation

Your doctor will do a complete examination of your heart and lungs, including:

  • Checking for signs of too much thyroid hormone, such as a thyroid gland that is larger than normal
  • Checking for swelling in your legs or feet, which could be a sign of heart failure or a heart that is larger than normal
  • Checking your pulse to find out how fast your heart is beating
  • Listening to the rhythm of your heartbeat
  • Listening to your lungs to check for signs of heart failure or infection
  • Measuring your blood pressure

Diagnostic tests
- Atrial Fibrillation

To diagnose atrial fibrillation, your doctor will likely do an EKG first to record your heart’s electrical activity. Data from a pacemaker or implanted defibrillator may also be helpful. If the diagnosis is unclear from the EKG or your doctor would like more information, your doctor may order additional testing:

  • Blood tests to check the level of substances in the blood, such as potassium and thyroid hormone. This can help find the cause of your atrial fibrillation and show how well your liver and kidneys are working, which can help your doctor decide which medicines are most appropriate.
  • Echocardiography to show areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow. It may also identify harmful blood clots in the heart’s chambers.

Other tests
- Atrial Fibrillation

Your doctor may order other tests to record abnormal heart rhythms that happen under specific conditions or outside of the clinic, confirm whether you have atrial fibrillation or another arrhythmia, and figure out which treatment is best. These tests may include:

  • Chest X-ray to look for signs of complications from atrial fibrillation, such as fluid buildup in the lungs or a heart that is larger than normal.
  • Electrophysiology study (EPS) to record your heart’s electrical signals if your doctor wants more detail about what is causing a particular EKG reading or to distinguish among possible types of arrhythmias.
  • Holter and event monitors to record your heart’s electrical activity over long periods of time while you do normal, day-to-day activities. These portable EKG monitors can help assess the cause of symptoms, like palpitations or feeling dizzy, that happen outside the doctor’s office. Most portable monitors will send data directly to your doctor.
  • Loop recorder to record the heart’s electrical activity. Some loop recorder models are worn externally and some require minor surgery to place the device under the skin in the chest area. Implanted devices can record data for months and are used to detect patterns in abnormal heart rhythms that do not happen very often.
  • Sleep study to see if sleep apnea is causing your symptoms.
  • Stress test or exercise stress test to look at changes in your heart’s activity that occur with increase in heart rate, and recovery after exercise. If you cannot exercise, you may be given medicine to make your heart work hard and beat fast.
  • Transesophageal echocardiography (TEE) to detect blood clots that may be forming in the heart’s upper chambers because of atrial fibrillation. It uses sound waves to take pictures of your heart through the esophagus.
  • Walking test to measure your heart activity while you walk for six minutes. This can help determine how well your body can control your heart rate under normal circumstances.

- Atrial Fibrillation

Treatment - Atrial Fibrillation

Atrial fibrillation is treated with lifestyle changes, medicines, and procedures, including surgery, to help prevent blood clots, slow your heart beat, or restore your heart’s normal rhythm.

Your doctor may also treat you for an underlying disorder that is raising the risk of atrial fibrillation, such as overweight or obesity, sleep apnea, or an overactive thyroid gland.

Lifestyle changes
- Atrial Fibrillation

Your doctor may recommend adopting heart-healthy lifestyle changes, such as the following:

- Atrial Fibrillation

Your doctor may consider treating your atrial fibrillation with medicines to slow your heart rate or to make your heart’s rhythm more even:

  • Beta blockers, such as metoprolol, carvedilol, and atenolol, to help slow the rate at which the heart’s lower chambers pump blood throughout the body. Rate control is important because it allows the ventricles enough time to fill with blood completely. With this approach, the abnormal heart rhythm continues, but you may feel better and have fewer symptoms. Beta blockers are usually taken by mouth, but they may be delivered through a tube in an emergency situation. If the dose is too high, it can cause the heart to beat too slowly. These medicines can also make COPD and arrhythmia worse.
  • Blood thinners to prevent blood clots and lower the risk of stroke. These medicines include edoxaban, dabigatran, warfarin, heparin, and clopidogrel. You may not need to take blood thinners if you are not at risk of a stroke. Blood-thinning medicines carry a risk of bleeding. Other side effects include indigestion and heart attack.
  • Calcium channel blockers to control the rate at which the heart’s lower chambers pump blood throughout the body. They include diltiazem and verapamil.
  • Digitalis, or digoxin, to control the rate blood is pumped throughout the body. It should be used with caution, as its use can lead to other arrhythmias.
  • Other heart rhythm medicines to slow a heart that is beating too fast or change an abnormal heart rhythm to a normal, steady rhythm. Rhythm control is an approach recommended for people who continue to have symptoms or otherwise are not getting better with rate control medicines. Rhythm control also may be used for people who have only recently started having atrial fibrillation or for highly physically active people and athletes. These medicines may be used alone or in combination with electrical cardioversion. Or your doctor may prescribe some of these medicines for you to take as needed when you feel symptoms of atrial fibrillation. Some heart rhythm medicines can make arrhythmia worse. Other side effects include effects on the liver, lung, and other organs, low blood pressure, and indigestion.

Your doctor may recommend treatments for an underlying cause or to reduce atrial fibrillation risk factors. For example, he or she may prescribe medicines to treat overweight and obesity, an overactive thyroid, lower high blood pressure, manage high blood cholesterol, control or prevent diabetes, or help you quit smoking.

Procedures or surgery
- Atrial Fibrillation

Your doctor may recommend a procedure, especially if lifestyle changes and medicine alone did not improve your symptoms. Typically, your doctor will consider a surgical procedure to treat your atrial fibrillation only if you will be having surgery to treat some other heart condition.

  • Catheter ablation to destroy the tissue that is causing the arrhythmia. Ablation is not always successful and in rare cases may lead to serious complications, such as stroke. The risk that atrial fibrillation will reoccur is highest in the first few weeks after the procedure. If this happens, your doctor may repeat the procedure. In some cases, your doctor will place a pacemaker at the time of the procedure to make sure your heart beats correctly once the tissue causing problems is destroyed.
  • Electrical cardioversion to restore your heart rhythm using low-energy shocks to your heart. This may be done in an emergency or if medicines have not worked.
  • Pacemaker to reduce atrial fibrillation when it is triggered by a slow heartbeat. Typically, a pacemaker is used to treat atrial fibrillation only when it is diagnosed along with another arrhythmia. For example, if you are diagnosed with a slow heart rate or sick sinus syndrome, a pacemaker implanted for that condition can also prevent atrial fibrillation. If you have surgery for a pacemaker, you will need to take blood-thinning medicines.
  • Plugging, closing, or cutting off the left atrial appendage to prevent clots from forming in the area and causing a stroke, if you cannot take blood thinners. Your doctor may do this at the same time as surgical ablation. It can be difficult to close off the appendage entirely, and leaking can contribute to ongoing clotting risk.
  • Surgical ablation to destroy heart tissue generating faulty electrical signals. The surgeon usually does surgical ablation at the same time as surgery to repair heart valves, but in some cases, surgical ablation can be done on its own.

Look for
- Atrial Fibrillation

  • Living With will explain what your doctor may recommend, including lifelong lifestyle changes and medical care to prevent your condition from recurring, getting worse, or causing complications.
  • Research for Your Health will explain how we are using current research and advancing research to treat people with atrial fibrillation.
  • Participate in NHLBI Clinical Trials will discuss our open and enrolling clinical studies that are investigating treatments for atrial fibrillation.

Living With - Atrial Fibrillation

If you have been diagnosed with atrial fibrillation, it is important that you continue your treatment. Follow-up care can help your doctor check your condition and talk to you about how to prevent repeat events and what to do in an emergency. Sometimes, atrial fibrillation may go back to a normal heart rhythm without treatment.

Receive routine follow-up care
- Atrial Fibrillation

How often you need to see your doctor for follow-up care will depend on your symptoms and treatment.

  • Keep all your medical appointments. Bring a list of all the medicines you are taking to every doctor and emergency room visit. This will help your doctor know exactly what medicines you are taking.
  • Take your medicines as prescribed. If you are taking medicines to treat your atrial fibrillation, your doctor will monitor their effects, including the dose, your body’s electrolyte levels, and the medicines’ effect on other organs.
  • Tell your doctor if your medicines are causing side effects, if your symptoms are getting worse, or if you have new symptoms.
  • Ask your doctor about physical activity, weight control, and alcohol use. Find out what steps you can take to manage your condition. If you use illegal drugs, ask your doctor for help stopping.
  • Check with your doctor before taking over-the-counter medicines, nutritional supplements, or cold and allergy medicines. Some of these products can trigger rapid heart rhythms or interact poorly with other medicines. In addition, medicines to treat arrhythmia can make the effect of blood thinners stronger.
  • If you have had an ablation, your doctor will want to see you regularly for three months to check on the healing process, to check for the reappearance of atrial fibrillation events, and to make adjustments to blood thinning medicines as needed. You will continue to take blood thinners for several months and maybe much longer. Report any lasting pain—for example, at the site of the incision—or any other signs of a complication. Your doctor will want to see you at least once a year after the initial follow-up period.
  • If you are taking warfarin, it is important to monitor the dose by measuring how quickly your blood clots. Your doctor will do blood tests every week at first, then monthly once the level has stabilized. You may be able to do this yourself at home. You will need to avoid certain other medicines and watch what you eat. Some foods, such as leafy green vegetables, may interfere with warfarin.

Return to Treatment to review possible treatment options for your atrial fibrillation.

Monitor your condition
- Atrial Fibrillation

Regular visits to the clinic give your doctor a chance to see how well medicines are controlling your atrial fibrillation, monitor your ongoing risks of clotting or bleeding, and see how well you are healing from any procedures. Your doctor may also ask you to wear a heart rhythm monitor and send data in between visits to see how well your treatment is working and to detect any repeat events.

  • Electrocardiogram (EKG). Regular EKG monitoring can help your doctor detect a repeat atrial fibrillation event or assess your response to changes in dose or medicine, or to ending treatment with medicines. Your doctor may record an EKG during your regular visits or recommend a portable monitor. A band that can record a 30-second EKG has also been approved by the U.S. Food and Drug Administration.
  • Stress tests or a six-minute walking test can help your doctor see whether your medicine prevents atrial fibrillation while you are doing typical everyday activities.
  • Blood tests to check the effect of certain heart rhythm medicines on your thyroid, kidneys, or liver. The blood thinner warfarin also requires regular testing to make sure the dose is correct. In some cases, your doctor may talk to you about devices available for monitoring your blood thinning medicines at home. Blood thinners can be stopped or adjusted if you are going into surgery.

Prevent repeat atrial fibrillation
- Atrial Fibrillation

To help prevent a repeat episode of atrial fibrillation, your doctor may recommend the following:

  • Medicine that you can take at home as needed to correct your heart rhythm. Before giving you this medicine, the doctor will ask you to take a dose and try to trigger an event to see if the medicine prevents it effectively. You can take this medicine if you start feeling symptoms of atrial fibrillation.
  • Treatment for an underlying condition, such as sleep apnea, high blood pressure, and diabetes.
  • Heart-healthy lifestyle changes, including aiming for a healthy weight. Combining weight loss with physical activity and the management of other risk factors, such as high blood pressure, diabetes, alcohol use, and smoking, can improve symptoms more than weight loss alone.

Learn the warning signs of serious complications and have a plan
- Atrial Fibrillation

Atrial fibrillation can lead to serious complications such as sudden cardiac arrest and stroke. Risks of treatment with blood thinners include severe bleeding in the brain. If you suspect any of the following in you or someone else, call 9-1-1 right away:

  • Bleeding in the brain, digestive system, or urinary tract. This can happen if you take a dose of blood-thinning medicines that is too high. Signs and symptoms may include bright red vomit; bright red blood in your stool or black, tarry stools; blood in your urine; severe pain in the abdomen or head; sudden, severe changes in your vision or ability to move your arms or legs; or memory loss. A lot of bleeding after a fall or injury, or easy bruising or bleeding, may mean that your blood is too thin. Excessive bleeding is bleeding that will not stop after you apply pressure to a wound for 10 minutes. Call your doctor right away if you have any of these signs.
  • Heart attack. Signs of heart attack include mild or severe chest pain or discomfort in the center of the chest or upper abdomen that lasts for more than a few minutes or goes away and comes back. It can feel like pressure, squeezing, fullness, heartburn, or indigestion. There may also be pain down the left arm. Women may also have chest pain and pain down the left arm, but they are more likely to have less typical symptoms, such as shortness of breath, nausea, vomiting, unusual tiredness, and pain in the back, shoulders, or jaw. Read more about the signs and symptoms of a heart attack.
  • Stroke. If you think someone may be having a stroke, act F.A.S.T. and do the following simple test:

    F—Face: Ask the person to smile. Does one side of the face droop?
    A—Arms: Ask the person to raise both arms. Does one arm drift downward?
    S—Speech: Ask the person to repeat a simple phrase. Is their speech slurred or strange?
    T—Time: If you observe any of these signs, call 9-1-1 immediately. Every minute matters.

    Read more about the signs and symptoms of a stroke.
  • Sudden cardiac arrest. Usually, the first sign of sudden cardiac arrest is fainting. At the same time, no heartbeat can be felt. Some people may have a racing heartbeat or feel dizzy or light-headed just before they faint. Within an hour before cardiac arrest, some people have chest pain, shortness of breath, nausea, or vomiting. Call 9-1-1 right away if someone has signs or symptoms of sudden cardiac arrest. Look for a defibrillator nearby and follow the instructions.

Research for Your Health

The NHLBI is part of the U.S. Department of Health and Human Services’ National Institutes of Health (NIH)—the Nation’s biomedical research agency that makes important scientific discovery to improve health and save lives. We are committed to advancing science and translating discoveries into clinical practice to promote the prevention and treatment of heart, lung, blood, and sleep disorders including atrial fibrillation. Learn about current and future NHLBI efforts to improve health through research and scientific discovery.

Improving health with current research
- Atrial Fibrillation

Atrial fibrillation research is a major focus of NHLBI funding and the source of findings with important consequences for clinical care. Learn about the following ways the NHLBI continues to translate current research into improved health for people with atrial fibrillation. Research on this topic is part of the NHLBI’s broader commitment to advancing heart and vascular disease scientific discovery.

  • Studying Innovations to Improve Heart and Vascular Disease Outcomes. The Cardiothoracic Surgical Trials Network (CTSN) is an international network that studies heart valve disease, arrhythmias, heart failure, coronary heart disease, and the complications of surgery. CTSN researchers have studied the success of treatments for people with atrial fibrillation who need heart valve surgery and compared rate control and rhythm control as a first treatment after surgery.
  • Uncovering Disparities in Atrial Fibrillation Outcomes. Findings from the NHLBI’s Atherosclerosis Risk in Communities (ARIC) study linked obesity and other risk factors to the development of atrial fibrillation. For example, the study found that atrial fibrillation increased patients’ risk of venous thromboembolism (VTE) and that VTE is a risk factor for atrial fibrillation, especially for African Americans. ARIC researchers also showed that African-American participants in an atrial fibrillation study tended to have higher rates of heart complications—including stroke, heart failure, and coronary heart disease—even though white participants were more likely to develop atrial fibrillation. African Americans with atrial fibrillation were also twice as likely as whites to die prematurely.
  • Investigating the Genetic Basis of Atrial Fibrillation. The NHLBI-supported Candidate-gene Association Resource (CARe) study discovered gene variants that are more common in people who have atrial fibrillation. In addition, investigators in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium leveraged data from NHLBI’s longstanding population and epidemiology studies to identify new genetic variants linked to atrial fibrillation. Understanding the genetics involved may help researchers develop new treatments for atrial fibrillation and identify people who would benefit most from screening and prevention strategies.
  • Testing Varied Approaches to Treatment. The Catheter Ablation versus Antiarrhythmic Drug Therapy for Atrial Fibrillation (CABANA) trial compared catheter ablation with medicine to treat atrial fibrillation. Read Surgery no better than medication at preventing serious complications of atrial fibrillation for more information.
  • Establishing a Foundation for the Understanding of Atrial Fibrillation Risk. The Framingham Heart Study established a link between atrial fibrillation and risk factors such as obesity, age, diabetes, and heart disease. The study also documented the link between atrial fibrillation and its health outcomes and found that risk for atrial fibrillation can be inherited.
  • Investigating Women’s Experience of Atrial Fibrillation. The Women’s Health Study demonstrated that weight gain, especially obesity, can raise a woman’s risk of atrial fibrillation and that weight loss can lower it. The study also found that high blood pressure and two or more drinks of alcohol daily can increase women’s risk of atrial fibrillation. The study found that the top number in a blood pressure reading—systolic blood pressure—better predicted which women would develop atrial fibrillation than the bottom, or diastolic, number.
  • Identifying Characteristics of Atrial Fibrillation in Women. Researchers for the Women’s Health Initiative specifically examined the effects of hormone treatment on a participant’s risk of developing atrial fibrillation. In addition, physical activity was linked to a lower risk of atrial fibrillation, compared with women who did not exercise.
  • Expanding Understanding of How Atrial Fibrillation Appears in Diverse Populations. Researchers with the Multi-Ethnic Study of Atherosclerosis (MESA) helped document how common atrial fibrillation is in Hispanic and Asian communities in the United States.

Learn about some of the pioneering research contributions we have made over the years that have improved clinical care.

Advancing research for improved health
- Atrial Fibrillation

In support of our mission, we are committed to advancing atrial fibrillation research in part through the following ways.

Learn about exciting research areas that the NHLBI is exploring about atrial fibrillation.

Participate in NHLBI Clinical Trials

We lead or sponsor many studies on atrial fibrillation. See if you or someone you know is eligible to participate in our clinical trials.

Did you develop atrial fibrillation after coronary artery bypass graft (CABG) surgery?

This study will examine whether adding oral anti-blood clotting medicines to anti-platelet medicines (such as aspirin) helps prevent stroke and other complications in people who develop atrial fibrillation after CABG surgery. To participate in this study, you must be at least 18 years old and have been diagnosed with atrial fibrillation after having CABG surgery. The study is located in 63 places in 22 states, the District of Columbia, Canada, and Germany.

Do you have paroxysmal or persistent atrial fibrillation?

This study aims to confirm whether autoimmune disorders have a role in the onset of atrial fibrillation. Researchers also hope to identify immune proteins in the blood that could help identify patients at an increased risk of developing atrial fibrillation. To participate in this study, you must be between 18 and 99 years old and have either paroxysmal or persistent atrial fibrillation. This study is located in Rochester, Minnesota.
View more information about Autoimmunity in the Pathogenesis of AF.

Do you know someone who will be having heart surgery?

This study aims to identify what genetic patterns might cause atrial fibrillation and other adverse events that happen after heart surgery. To participate in this study, you must be between 20 and 90 years old. The study is in three locations in Massachusetts and Texas.

Are you a Minnesota resident with hypertrophic cardiomyopathy?

This study aims to find out how common it is for people with hypertrophic cardiomyopathy to also have sleep apnea. Hypertrophic cardiomyopathy is a disease that causes the heart muscle to thicken. Participants will also wear a heart rhythm monitor to help researchers learn whether sleep apnea is linked to arrhythmia. The study seeks healthy volunteers as well as participants in the Hypertrophic Cardiomyopathy Registry. To participate in this study, you must not have had a catheter ablation procedure to treat atrial fibrillation, had surgery to replace your heart valves, or been treated for sleep apnea. The study is located in Rochester, Minnesota.

Are you being treated for atrial fibrillation?

This study aims to compare two types of ablation treatment for patients who continue to have symptoms of atrial fibrillation despite treatment with medicines. The two ablation procedures treat different areas of tissue. To participate in this study, you must be at least 21 years old. The study is located in Palo Alto and San Diego, California.

More Information

After reading our Atrial Fibrillation Health Topic, you may be interested in additional information found in the following resources.

Non-NHLBI resources
- Atrial Fibrillation