• What Causes Atrial Fibrillation (Afib or AF)?


    Atrial fibrillation (also known as Afib or AF) is an irregular heartbeat caused by an abnormal heart rhythm. Normally the heart sends regular electrical signals from one section to another. In Afib, irregular signals are sent down from the top heart chambers (the atria). This results in quivering (or fibrillation) of the atria. This quivering prevents the heart from pumping blood through its chambers as it should, allowing blood to collect in the heart, where it can form clots. The clots may then travel throughout the body, including to the brain, where they can cause a stroke. This is why Afib patients are at risk for stroke.

    Afib is the most common heart irregularity, or cardiac arrhythmia. The American Heart Association estimates that 2.7 million people are living with Afib. Some people experience symptoms such a fluttering in their chest or the sensation that their heart is racing. Others describe dizziness, weakness or nausea. Others don’t feel any symptoms; they may be diagnosed with Afib during a regular medical checkup.

    Risk Factors for Atrial Fibrillation

    While the root cause of Afib is the misfiring of electrical signals in the heart, certain risk factors heighten the chance that atrial fibrillation will occur. These include the following:

    High Blood Pressure

    High blood pressure, also known as hypertension, is the leading risk factor for stroke. Blood pressure is defined as the force with which blood presses against the artery walls as it circulates through the body. High blood pressure means the heart has to pump harder in order to circulate this blood. This can weaken the walls of the arteries and cause problems with circulation. Hypertension also causes changes in the chambers of the heart itself. The muscle of the heart’s pumping chambers (the ventricles) thickens in response to the increased pressure. The upper chambers of the heart also dilate in response to high blood pressure. Enlarged, dilated atria are more likely to develop atrial fibrillation. If you have Afib and high blood pressure, then you will are at greater risk for stroke. High blood pressure can be controlled by medications and lifestyle changes, including diet and exercise. Learn more about your blood pressure and about hypertension here.

    Coronary Artery Disease (CAD)

    Coronary artery disease, or CAD, is a build-up of fat and cholesterol in the arteries that supply blood to your heart. These deposits (called plaques) grow slowly, clogging the heart arteries. If a heart artery is severely blocked, it reduces blood flow to the heart and can cause chest pain or even a heart attack. Coronary artery disease is something that occurs over time and can be hereditary, although there are various risk factors that can play a role in its development. Learn more about coronary artery disease here.

    Heart Valve Problems

    Heart valve problems (valvular heart disease) are a risk factor for Afib. Your heart’s valves are essential for proper circulation because they regulate the direction that your blood flows. The heart valves play an important part in delivering necessary oxygen to your body. Heart valves that don’t work the way they should can put your heart and other organs at risk. In general, heart valve disease falls into two categories: congenital valve disease, meaning it is present at birth (though some people may have no symptoms until adulthood); and acquired valve disease (which develops throughout life). Just as valve disease is a risk factor for Afib, there are many things that can increase a person’s risk of acquired valve disease. Learn more about the various types of valve disease, as well as complications, risk factors, treatments and more, here.

    Heart Attack

    Heart attack is another risk factor for Afib. A heart attack is the result of a sudden and complete blockage an artery that supplies blood to your heart. Blockages are caused by a disease process throughout the arteries in your body called atherosclerosis, in which a fatty substance (plaque) builds up in the arteries. This plaque narrows the arteries, leaving less room for blood to flow. Heart attacks are caused by coronary artery disease, which is the leading cause of death in both men and women in the United States. According to the American Heart Association, every year in the United States roughly 785,000 people will have their first heart attack. And approximately 470,000 who have had a heart attack before will have another one. Learn more about heart attacks here.

    Lung Disease

    Lung disease is one of the risk factors for Afib; however, lung disease is a general term for a number of medical problems relating to the lungs. These can include the following:

    • Asthma, in which the airways are often inflamed, leading to shortness of breath
    • Chronic obstructive pulmonary disease (COPD), a form of lung disease that includes chronic bronchitis and emphysema. It is characterized by the inability to exhale normally.
    • Cystic fibrosis, a genetic condition that results in a buildup of mucus in the lungs, and chronic lung infections as a result.
    • Pneumonia, an infection of the lungs that may be viral or bacterial
    • Tuberculosis, also known as TB, is a bacterial infection that can spread throughout the body.
    • Pulmonary edema, in which fluid leaks from blood vessels, into the air sacs
    • Lung cancer
    • Acute respiratory distress syndrome (ARDS), caused by a sudden injury or trauma to the lungs
    • Pneumoconiosis, a result of inhalation of substances harmful to the lungs
    • Pulmonary hypertension, which is high blood pressure in the arteries of the lung
    • Pulmonary embolism, when a blood clot forms in a vein in the leg (this is referred to as deep vein thrombosis) and travels through the body to the lung

    These are not the only forms of lung disease; according to the American Lung Association, there are multiple forms, all with various causes, treatments and symptoms.


    In general, anything that stimulates the heart to beat more rapidly can increase the risk of Afib. Alcohol, caffeine, certain medications (including over-the-counter cold medicines) and tobacco are all substances that can increase your heart rate and bring on episodes of arrhythmia. Illegal drugs, such as amphetamines, methamphetamines and cocaine (among others) may also produce Afib.

    Sleep Apnea

    Sleep apnea is a risk factor for Afib. In fact, sleep apnea affects many people who have cardiovascular disease. If you have sleep apnea, your breathing may pause and then restart several times while you are sleeping. Sleep apnea is caused by temporary blockage of your breathing airway. These pauses in breathing tax the cardiovascular system. In addition to keeping you from getting restful sleep and contributing to exhaustion and difficulty concentrating during the day, sleep apnea can contribute to the misfiring of the electrical impulses in the heart and to episodes of atrial fibrillation. Learn more about sleep apnea and its risks here.


    Cardiomyopathy, another risk factor for Afib, is a general term that includes diseases of the heart muscle. In cardiomyopathy, the heart becomes enlarged, thick or tough, meaning it does not beat as well. It is less able to pump blood effectively and more prone to arrhythmias, including atrial fibrillation. There are several types of cardiomyopathy:

    • Dilated cardiomyopathy, in which the chambers of the heart enlarge, leading to heart failure if left untreated
    • Hypertrophic cardiomyopathy, in which the heart walls are thicker and less flexible, meaning the heart is less able to beat effectively
    • Restrictive cardiomyopathy, in which the ventricles progressively grow stiffer and more rigid
    • Arrhythmogenic right ventricular dysplasia (ARVD), a rare form of cardiomyopathy, in which the walls of the right ventricle die are replaced by scar tissue

    As with heart valve disease, cardiomyopathy can be congenital or acquired. Acquired cardiomyopathy has several risk factors. Learn more about cardiomyopathies here.

    Learn More

    SecondsCount includes in-depth information about many of the medical conditions and other risk factors that contribute to atrial fibrillation and may also increase the risk for stroke. To learn more about the following conditions, follow these links:   

    To learn more about how atrial fibrillation is diagnosed and the options for treatment, visit the SecondsCount Atrial Fibrillation Center.