How long does afib last?

How Much Atrial Fibrillation Does It Take to Cause Stroke?

One question that I often receive from patients as well as their referring doctors is, “How much atrial fibrillation is required for a blood clot to form?”

How Atrial Fibrillation Leads to Stroke

Atrial fibrillation is an abnormal, fast electrical rhythm in the upper chambers of the heart. During atrial fibrillation the upper chambers do not contract fully. In small areas in the upper chamber, in particular a pouch called the left atrial appendage, blood flow can become impaired. When blood becomes stagnant to any degree the mechanisms that form a clot are activated. When you cut your hand, the injury itself and the rapid slowing of blood work together to quickly form a clot to stop the bleeding. In the heart, clot formation is slower as there is still some amount of blood flow and no injury. Unfortunately blood clots that form in the heart can have devastating consequences if they become dislodged and go the brain causing a stroke or the heart causing a heart attack.

Treatment to minimize risk of stroke in patients with atrial fibrillation depends on what other risk factors for stroke are present. General risk factors for stroke include: age >75, high blood pressure, diabetes, heart failure, and stroke. Prior stroke is such a strong risk factor it is counted as two or twice the risk. If you have no risk factors or only 1, then we often use aspirin or aspirin and a medication called clopidogrel (Plavix). If you have 2 or more then we use a blood thinner called warfarin (Coumadin) or one of the new agents recently approved that have lower stroke rates compared to warfarin in people with atrial fibrillation . Which blood thinning agent to use is a complex question I covered in a prior column.

How Much Atrial Fibrillation Does It Take?

How long does atrial fibrillation have to last to cause a blood clot that can result in a stroke? The best answer is we don’t fully know. What we do know is that if you have atrial fibrillation that requires an electrical shock to the heart, called a cardioversion, to make the heart beat normal again, then your risk of having a stroke is higher immediately afterward and for the next 2-4 weeks. This higher risk we believe occurs because as the heart beats normally again, clots that were already formed can become dislodged by the return on heart contractions and cause a stroke.

This observation led to a standard approach to restoring the heart rhythm to normal after atrial fibrillation starts. A cardioversion can be performed right away if the atrial fibrillation episode is less than 48 hours long or if a blood thinner has been used, such as fully effective warfarin on one of the new blood thinners for at minimum 3 weeks so the presence of clot is less likely.

If we don’t want to wait 3-4 weeks to allow a blood thinner to work, then an ultrasound examination of the heart called a transesophageal echocardiogram can be performed to look for a clot within the heart. If the imaging study is normal, a cardioversion can be performed.

Most episodes of atrial fibrillation are less than 48 hours, particularly when the disease starts. Some atrial fibrillation episodes can cause significant symptoms of chest pain, shortness of breath, lightheadedness, energy loss, and heart palpitations. Other episodes may occur at night and not be felt or occur in the day will lesser symptoms.

Many questions arise with these short afib episodes:

  • Do they also cause stroke?
  • Is there a certain amount of time in a day, week, or month of atrial fibrillation that is needed to cause stroke?
  • Finally, if there is a certain amount of time of atrial fibrillation that is required to cause a stroke?
  • If you experience less than this amount, is it okay not to take a blood thinner?

Pacemakers Monitor the Heart

The challenge in answering these questions is most of us don’t know what is happening with our hearts on a beat-to-beat basis. However, there are some people in which we can understand their heart on this level of detail, with a pacemaker. A pacemaker is a small device surgically inserted under the skin just below your collarbone. Small wires called pacemaker leads are threaded through a vein just under the collarbone into the upper and lower heart chambers. Pacemakers are designed to pace your heart if the heart rate goes too slow. Pacemakers are also continuous monitors of the heart recording on a daily basis any abnormal heart rhythms. In people with pacemakers the answers to these atrial fibrillation patients may be found.

Research Trials Show the Afib-Stroke Link

In a study called the ASSERT trial, 2,580 patients with pacemakers were studied. Over a 2.5 year period, an atrial fibrillation episode of 6 minutes or greater was found in over 40 percent of people. In only 15 percent of people was the atrial fibrillation noticed by the patient or their doctor. Unfortunately, even with brief episodes of 6 minutes of atrial fibrillation there was a 2.5 times greater risk of stroke.

If brief episodes of atrial fibrillation raise stroke risk, then perhaps early detection of these may help in guiding who to treat with blood thinners. In the TRENDS trial, 2,486 patients with pacemakers were studied. In this study, atrial fibrillation was detected in 50 percent of the patients. Also, 73 percent of the strokes occurred with essentially no atrial fibrillation immediately before the stroke. This second study showed us that relying on episodes of atrial fibrillation to start a blood thinner might not be a reliable approach. It also challenges the traditional concept that a blood clot forms due to a period of atrial fibrillation and then a forceful contraction from the upper heart chamber dislodges it.

These two studies bring us to the latest trial, published this month. In another analysis of the ASSERT trial the investigators tried to determine if there is a correlation between when atrial fibrillation occurs and when a stroke develops. This is an important study since by tradition we assume an episode less than 48 hours may not be as risky as one that is longer. Unfortunately, in only 8 percent of patients was atrial fibrillation within the 30 days before the stroke. In only 35 percent of the patients was atrial fibrillation detected at any time before the stroke. Then in 16 percent of patients, atrial fibrillation was diagnosed only after the stroke had occurred. The 16 percent of patients that were later diagnosed with atrial fibrillation show us that risk factors for developing the abnormal heart rhythm such as high blood pressure, diabetes, heart failure, and sleep apnea are also important contributors in stroke risk.

What do these studies teach us? First, we can’t use the timing and pattern of atrial fibrillation episodes to guide use of blood thinner medications. The use of these medications needs to be based on traditional stroke risk factors until we fully understand the mechanisms of stroke. Next, atrial fibrillation occurs more often than both physicians and patients realize, so trying to use how much atrial fibrillation that you feel or experience as a guide to use blood thinner medications is also not a good option. Finally, if you have risk factors of atrial fibrillation and experience a stroke, it is very important to use long-term monitors to detect if you have atrial fibrillation that may be present even if you are not experiencing symptoms.

Duration of atrial fibrillation and risk of stroke

Research we’re watching

Published: August, 2018

Episodes of atrial fibrillation (afib) — a chaotic, irregular heart rhythm — can last for minutes, hours, days, or much longer. The condition encourages blood clots to form in the heart; the clots can then escape and lead to a stroke. New research suggests that even intermittent bouts of afib (which were previously considered to be low risk) may increase a person’s risk of stroke.

The study included nearly 2,000 people who wore a small skin patch that continuously monitored their heart rates for 14 days. All of them had paroxysmal (intermittent) afib and were not taking anti-clotting medications. Researchers then tracked the participants’ incidence of stroke over the following five years. They found that afib that lasted more than 11% of the total monitoring time was associated with a threefold increase in stroke risk.

The findings suggest that the amount of time spent in afib (known as afib burden) is related to the risk of stroke. Measuring that burden may help doctors to assess better a person’s need for stroke prevention strategies, say the authors. The study was published online May 16 by JAMA Cardiology.

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Butterflies in the stomach can signal excitement or nervousness. But fluttering in the chest can signal a short circuit in the heart’s natural electrical wiring, or arrhythmia. Atrial fibrillation (A-fib), the most common arrhythmia in the United States, is an off-speed rhythm in the heart’s upper chambers.

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A-fib may be linked to conditions such as high blood pressure (hypertension), coronary artery disease, heart valve disease, heart failure, chronic lung disease or a clot in the lung (pulmonary embolism), among others. But in 10% of cases, A-fib isn’t associated with any other disease.

A-fib can cause the following symptoms:

  • Heart palpitations.
  • Dizziness.
  • Fatigue.
  • Chest discomfort.
  • Shortness of breath.

However, up to 30% of A-fib episodes cause no symptoms at all. Below, electrophysiologist Walid Saliba, MD, addresses some common myths about A-fib:

Myth #1: If you have just one or two episodes of atrial fibrillation, it probably won’t come back.

Fact: Atrial fibrillation is almost always a chronic disease. Lifelong treatment is needed to minimize symptoms and to avoid stroke and heart failure. Early on, episodes of A-fib tend to be sporadic. This is called paroxysmal atrial fibrillation. Over time, episodes usually become more frequent and last longer. Up to 30% of A-fib episodes cause no symptoms at all, but treatment is still needed to prevent stroke.

Myth #2: Cardioversion can stop atrial fibrillation for good.

Fact: Electrical cardioversion can “shock” the heart back to normal rhythm, but it does not guarantee that normal rhythm will be maintained. Medication may be needed to maintain normal heart rhythm and prevent stroke. “One to three types of medication are used in combination: those that control heart rate, such as beta blockers; anti-arrhythmic drugs to maintain normal rhythm; and anticoagulants to prevent blood clots,” says Dr. Saliba.

Myth #3: Your medicine isn’t working if you still get episodes of A-fib.

Fact: “Medication will not cure A-fib, but it will relieve symptoms by decreasing the frequency and duration of episodes,” says Dr. Saliba. Reducing a patient’s episodes from frequent to occasional is considered adequate treatment as long as the symptoms don’t trouble the patient. However, medications tend to become less effective over time, he notes. When that happens, catheter ablation is more likely to help.

Myth #4: Catheter ablation won’t help you if it doesn’t ‘take’ the first time.

Fact: Catheter ablation uses radiofrequency energy or cryoenergy (intense cold) to interrupt faulty electrical pathways in the heart. Sometimes more than one catheter ablation procedure is needed to get the best result. The cure rate of 70 to 80% after one catheter ablation goes up to 90% after a second or third one if there is no underlying heart disease. When A-fib is chronic or when there is underlying heart disease and the heart’s upper filling chambers (atria) are severely enlarged, maze surgery may be recommended.

Myth #5: If ablation works, you can stop taking Coumadin®.

Fact: “The decision to continue or stop Coumadin, an anticoagulant that requires frequent blood tests, depends upon the risk factors for stroke rather than on the success of the ablation,” says Dr. Saliba. Doctors calculate stroke risk in patients with A-fib using a formula called the CHADS2 score, based on the following risk factors:

  • Congestive heart failure.
  • Hypertension.
  • Age over 75.
  • Diabetes.
  • A past stroke.

Myth #6: If you take medication for A-fib and no longer have symptoms, you’re cured.

Fact: “A-fib cannot be cured, but ablation or surgery offers the closest possible symptom relief. There is no rush to undergo ablation if you are doing well on medication,” says Dr. Saliba. Ablation is safe even for patients in their 60s and 70s.

Episodes of A-fib can be triggered by stress, exercise, sleep apnea and hot flashes. Talk to your cardiologist about any concerns. Meanwhile, to minimize symptoms of A-fib and to improve heart health, Dr. Saliba advises patients to:

  • Quit smoking.
  • Drink in moderation.
  • Ask about exercise guidelines.
  • Limit caffeine use.
  • Read labels on cough and cold medicines to avoid those containing stimulants.
  • Seek treatment for sleep apnea.

Atrial Fibrillation Blood Clots: Symptoms and Prevention

Many cases of AFib are caught during a routine electrocardiogram (EKG). This is a simple test that your doctor can use to assess your heart’s electrical activity. It can help them spot irregularities, including AFib.

AFib isn’t always life-threatening. You can potentially go your entire life without experiencing complications from AFib. To lower your risk of complications, follow your doctor’s recommended treatment and management plan. This can help you prevent blood clots from forming.


If you’ve been diagnosed with AFib, your doctor might prescribe blood thinners to lower your risk of blood clots. They may also prescribe other medications to help restore your heart’s normal rate and rhythm.

Cardiac procedures

In some cases, your doctor may recommend electrical cardioversion to restore your heart’s rhythm. Your doctor will use paddles or patches to apply an electrical current to your chest.

Sometimes, your doctor may not be able to control your heart rate with medication. Atrial fibrillation tends cause your heart rate to be very high. Rate control medications usually help keep your rate normal but, occasionally, an adequate dose to keep your rate normal may also result in a very low heart rate. A low heart rate or fluctuating heart rate can occur without medications as well. This condition is known as tachy-brady syndrome. In this case, you may be a candidate for catheter ablation. During this procedure, your doctor will thread a thin catheter through one of the veins in your heart. Electricity is then used to destroy either the area that is firing too fast or the pathway that allows the electrical impulses to travel from the atria where the impulses originate to the ventricles.

Treating underlying conditions

Your doctor may also recommend treatment for underlying conditions that might be contributing to your AFib. For example, heart defects, heart disease, electrolyte abnormalities, drug and alcohol use and abuse, pulmonary emboli, thyroid problems, and infections can cause AFib and increase your risk of blood clots. Your recommended treatment plan will vary, depending on your specific diagnosis.

Diet and lifestyle changes

Healthy lifestyle choices can help you prevent AFib, other forms of heart disease, and the formation of blood clots. For example:

  • Get regular exercise, such as walking, running, biking, and swimming.
  • Eat a well-balanced diet, while limiting your intake of sodium, saturated fat, and cholesterol.
  • Restrict your consumption of caffeine and alcohol.
  • Avoid smoking.

Know Atrial fibrillation

Atrial fibrillation (AFib) is a common type of arrhythmia, or irregular heartbeat. Because the heart beats and contracts irregularly, blood flow may slow or pool and cause the formation of a clot. A blood clot that forms as a result of AFib is an example of arterial thromboembolism. If that clot breaks free, it can lodge in an artery, travel to the brain and result in a stroke. Persons with AFib are at greater risk for stroke and are estimated to account for 15 percent of the 15 million strokes that occur worldwide every year.12,13 AFib-related stroke can be particularly dangerous. Patients are twice as likely to be bedridden and more likely to die compared to patients with non-AFib-related stroke.14 Just as every person being admitted into hospital has the right to a VTE risk assessment, everyone has the right to be evaluated for AFib. As a first step, have your pulse checked for an irregular heartbeat. An electrocardiogram (EKG or ECG) may be ordered to detect or confirm AFib. AFib is often present without any signs or symptoms. That’s why early identification and management is critical.

Risk Factors for afib
  • Congestive heart failure
  • High blood pressure
  • Age of 65 or older
  • Diabetes
  • Stroke (prior), TIA, or thromboembolism
  • Vascular disease
  • Sex category (female > risk)
Take Action
  • Talk with a healthcare professional about AFib and ask to have your pulse checked for an irregular heartbeat.
  • If you are a healthcare professional, take initiative and evaluate your patients for AFib/arrhythmia risk.

* Based on the CHA2DS2VASc prediction score which estimates risk of stroke in patients with AFib

AFib Resources

Atrial Fibrillation Association
Offers a suite of patient and provider resources about AFib through multiple consumer education campaigns, including AF Aware Week and Know Your Pulse.

Act Against AFib
Encourages patients to ‘ACT’ against AFib by: Assessing risk, consulting a doctor, and treating their AFib. Posters, palm cards and videos reinforce the ACT model.

American College of Physicians
This ‘What You and Your Family Should Know’ booklet provides helpful information about AFib, including risk factors, blood clot prevention, and questions to ask your healthcare professional.

American Heart Association
The AFibFive is a comprehensive e-zine developed to help adults with AFib understand their diagnosis and learn how to lead a healthy life. The resource includes videos, audio instructions and an interactive quiz.

European Society of Cardiology (ESC)
ESC created, an educational website designed by health professionals and patients for people suffering from AFib, as well as their families and caregivers. The site offers information about proper detection and management of AFib.

Global Atrial Fibrillation Alliance
Provides tools, resources and news to help patients around the world talk with healthcare providers about the treatment and management of AFib. The Alliance also hosts World AF Day, which occurs annually on the second Saturday of September.

Heart Rhythm Society
The Society’s Atrial Fibrillation Awareness webpage provides educational resources for patients and providers about AFib, including symptoms and risk factors.

National Blood Clot Alliance
The Alliance’s AFib webpage provides an overview of AFib-related blood clots and clot-provoked stroke.

National Heart, Lung, and Blood Institute
A detailed overview of AFib, including an animated video of irregular heartbeat and the impact on the rest of the body.

Preventive Cardiovascular Nurses Association
Educational information for adults with AFib, including detection tests, symptoms, and instructions on how to conduct a self-pulse test.

Sign Against Stroke
A global patient charter to make AF-related stroke prevention a priority and to create a unified voice to improve the care and treatment of individuals with AFib.

Society of Cardiovascular Patient Care
Resources for healthcare professionals, hospitals and health systems, including a pocket guide for the evaluation and management of AFib patients, articles and abstracts, and guidelines and recommendations.

Stop Afib
The latest news and resources about AFib, including treatment and management options, and caregiver tools. Includes an international listing of AFib services.

Stroke Association
Offers a resource library on stroke and stroke-related issues, including AFib. Leaflets, factsheets and FAQs are available for download.

An Atrial Fibrillation Health Center offers tools and resources for adults with AFib, including the causes, symptoms, procedures and treatment options and helpful lifestyle changes.

World Stroke Organization
World Stroke Organization established a Global Atrial Fibrillation Patient Charter, designed to bring a worldwide, unified voice to improving the care and treatment of AFib. The charter contains recommendations for policymakers, healthcare providers and governments.

World Heart Federation
The Global AF Action campaign is dedicated to increasing recognition for AFib as a major international public health concern. Provides steps to conduct a do-it-yourself pulse test and multi-language care resources.

12 Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation: a major contributor to stroke in the elderly. The Framingham Study. Arch Intern Med 1987;147:1561-4.

13 Kannel WB, Benjamin EJ. Status of the epidemiology of atrial fibrillation. Med Clin North Am 2008;92:17-40.

14 Paciaroni M, Agnelli G, Caso V, et al. Atrial fibrillation in patients with first-ever stroke: frequency, antithrombotic treatment before the event and effect on clinical outcome. J Thromb Haemost 2005;3(6):1218-23. PMID: 15892862.

Q: I’m 69, female and an avid runner. Must I take a blood thinner for my AFib?

A: Because atrial fibrillation (AFib) increases your risk of blood clots forming in the left atrium, anticoagulation — taking blood thinners — can reduce your risk of stroke.

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Your CHA2DS2Vasc score helps determine your stroke risk. Most guidelines recommend that patients with atrial fibrillation and a CHA2DS2Vasc score of 2 or more are usually better off with anticoagulation, unless they have a high risk profile for bleeding.

CHA2DS2Vasc awards points in this way:

  • Congestive heart failure = 1 point.
  • Hypertension = 1 point.
  • Age of 75 or more = 2 points; age over 65 = 1 point.
  • Diabetes = 1 point.
  • Stroke or transient ischemic attack (TIA) in the past = 2 points.
  • Vascular disease (any type, including coronary artery disease) = 1 point.
  • Sex, female = 1 point (but only if you have at least 1 other point on the scale).

You already have 1 point for being over 65 years, and 1 point for being a female, and you’ll get a third point when you turn 75.

So overall, your risk/benefit ratio would likely be in favor of anticoagulation — especially if you do not have any previous history of bleeding or predisposition toward bleeding. (For example, liver, kidney or platelet problems must be factored in, as they increase your risk of bleeding.)

The decision to take blood thinners is an individual one, so talk it over with your doctor, who knows your health history.

— Cardiologist Mandeep Bhargava, MD

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