Atrial Fibrillation and Stroke

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What are atrial fibrillation and stroke?

Atrial fibrillation (AF) describes the rapid, irregular beating of the left atrium or upper chamber of the heart. These fast contractions of the heart are weaker than normal contractions. This results in slow flow of blood in the atrium. The blood pools and becomes sluggish and can lead to the forming of blood clots. If a clot leaves the heart and travels to the brain, it can cause a stroke by blocking the flow of blood through the arteries of the brain. Some people with AF have no symptoms, but others may feel:

  • Fluttering in the chest above the heart
  • Chest pain
  • Lightheadedness or fainting
  • Shortness of breath
  • Fatigue

How are atrial fibrillation and stroke diagnosed and treated? 

Diagnosing AF

AF is diagnosed by an electrocardiogram (ECG), a device that records the heart's electrical activity. Other tests are often done to rule out such causes as:

  • High blood pressure
  • An overactive thyroid gland
  • Heart failure
  • Faulty heart valves
  • Lung disease
  • Stimulant or alcohol abuse

Some people will have no identifiable cause for their AF.

Treating AF

Within a few hours after the start of a stroke, treatment with drugs or devices that dissolve or break up the clot can restore blood flow to the brain and lead to a better recovery. To prevent strokes related to AF, doctors often give drugs to prevent clots from forming in the heart, which can travel to the brain and cause stroke.

Immediately after a stroke, doctors may temporarily give heparin by injection, while starting a drug by mouth for long-term protection from clots. Warfarin is the most commonly used drug to prevent clots. People taking warfarin must be closely watched to make sure their blood is thin enough to prevent clots, but not so thin as to promote bleeding. Since some foods, vitamin supplements, and medications can affect warfarin action, keeping the blood just thin enough can be tricky. More recently, a number of new blood thinners, including dabigatran, rivaroxaban, and apixaban, have been shown to be as effective as warfarin in stroke prevention. These newer drugs do not require regular blood test monitoring and may be less likely to cause bleeding due to making the blood too thin. Some people with AF may have a lower risk of stroke and may be treated with aspirin, either alone or with another drug. Other treatments for AF include:

  • Medications such as beta blockers or calcium channel blockers to slow the heartbeat
  • Anti-arrhythmic drugs or electrical cardioversion, which delivers an electrical shock to the heart to return the heartbeat to normal

Treating people with warfarin or new blood thinners reduces the rate of stroke for those who have AF by about one-half to two- thirds. People with AF can have multiple strokes, including silent strokes. Silent strokes don't show physical symptoms but show up on a brain scan that, over time, can cause dementia. This makes prevention very important. 

Learn About Clinical Trials
Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

How can I or my loved one help improve care for people with atrial fibrillation and stroke?

Consider participating in a clinical trial so clinicians and scientists can learn more about atrial fibrillation and stroke. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with atrial fibrillation and stroke at

Where can I find more information about atrial fibrillation and stroke?

The following resources may help individuals, families, friends, and caregivers of people living with atrial fibrillation and stroke:

MedlinePlus for Atrial Fibrillation

MedlinePlus for Stroke

Order publications from the NINDS Catalog
The NINDS Publication Catalog offers printed materials on neurological disorders for patients, health professionals, and the general public. All materials are free of charge, and a downloadable PDF version is also available for most publications.