Over the course of a normal lifespan, the heart will beat 2 to 3 billion times, rhythmically contracting nonstop to pump blood throughout your body. When it’s working well, you might not give the heart much thought. But when something’s amiss, it can have serious implications for your health.

Heart problems often trigger a common set of symptoms: shortness of breath, feeling tired, difficulty performing everyday activities, and palpitations—which feel as if the heart is pounding in the chest. These symptoms can be caused by a number of cardiac conditions, one of which is called atrial fibrillation, or AFib.

AFib is the most common type of irregular heart rhythm (also called arrhythmia). It affects an estimated 2.7 to 6.1 million people in the U.S., and causes about 450,000 hospitalizations each year.

AFib can affect people of any age, though it mostly occurs in people over 60. As the population grows older, the number of cases is expected to rise; experts estimate there will be 12.1 million cases in the U.S. by 2030.

While AFib is a serious condition, various treatments, including lifestyle modification, medications, and medical procedures can help.

“Atrial fibrillation is increasingly common in the U.S., and has important consequences for patients, including symptoms like palpitations, fatigue, and shortness of breath, as well as a higher risk of stroke and mortality,” says James Freeman, MD, MPH, MS, director of the Yale Atrial Fibrillation Program. “The good news is that we have a growing number of very effective treatments, including health behavior changes, rhythm medications, blood thinners, ablation procedures, and left atrial appendage occlusion procedures.”

AFib is a cardiac arrhythmia that interferes with how effectively the heart pumps blood throughout the body.

In a healthy heart, its four chambers—two upper atria and two lower ventricles—work together, contracting and pumping blood at a carefully controlled pace and rhythm.

The heart’s contractions are regulated by electrical signals generated by the sinoatrial node (the SA or sinus node), a part of the right atrium, the upper right chamber of the heart. In a heart that is working normally, the SA node generates an electrical signal. That signal stimulates the atria to contract and pump blood into the ventricles. The electrical signal travels down the heart and stimulates the ventricles to contract, causing them to pump blood to the lungs and the rest of the body.

In atrial fibrillation, however, electrical signals are generated from multiple areas of the atria, rather than solely from the SA node. These abnormal electrical impulses cause the atria to twitch and quiver rapidly and with a disordered, irregular rhythm. As a result, the atria do not contract fully, preventing them from efficiently pumping blood into the ventricles. Blood can pool in the atria, increasing the risk of blood clot formation and stroke. And because the upper and lower chambers of the heart do not contract in a coordinated pattern, the pumping of blood throughout the body is significantly impacted.

AFib often begins with short episodes of rapid, irregular heartbeats that go away on their own after a few days. But over time, the condition progresses, and these episodes become more frequent and longer lasting.

There are four main types of AFib, based on how long the condition lasts:

• Paroxysmal atrial fibrillation develops suddenly and resolves within 7 days of onset.
• Persistent atrial fibrillation is when AFib episodes last for over 7 days.
• Long-standing persistent atrial fibrillation is AFib that persists for 12 months or longer.
• Permanent atrial fibrillation describes AFib in which the heart’s rhythm remains irregular in spite of previous attempts to restore or maintain normal heart rhythm. At this stage, the doctor and patient jointly decide to stop trying to control the abnormal heart rhythm and AFib is permanent. Treatment instead focuses on lowering the heart rate in these patients.

Several factors and medical conditions are known to cause or increase the risk for AFib, including:

• Increasing age
• High blood pressure
• Cardiovascular disease (heart failure, coronary artery disease, valvular heart disease, rheumatic heart disease, cardiomyopathy)
• Obstructive sleep apnea
• Obesity
• Diabetes
• Chronic kidney disease
• Excessive alcohol consumption, including binge drinking
• Cigarette smoking
• Hyperthyroidism
• Family history of AFib
• Male sex

Previous heart surgery (in particular, risk is increased in the first few days following surgery)

AFib can cause a number of symptoms, including:

• Palpitations (sensation that heart is pounding, fluttering, skipping beats, or beating rapidly)
• Fatigue
• Shortness of breath
• Light-headedness
• Dizziness
• Weakness
• Rapid heartrate (100–160 or more beats per minute)
• Chest pain or discomfort
• Exercise intolerance (feeling excessively fatigued during exercise)
• Irregular pulse

However, some people who have AFib do not have any symptoms.

To diagnose AFib, your doctor will assess your medical history, conduct a physical exam, and run one or more diagnostic tests.

To obtain a medical history, your doctor may ask about symptoms, when they began, and whether you have any risk factors for AFib.

During the physical exam, although your doctor will check your pulse to see if there is an irregular heartbeat, diagnosis almost always requires an electrocardiogram, also known as an ECG or EKG (a test that measures the heart’s electoral activity).

If you are diagnosed with AFib, your doctor may also order an echocardiogram, or ultrasound of the heart. This imaging study can detect structural irregularities in the heart. (It’s important to note that bloodwork is usually necessary to determine the exact cause of AFib.)

Though AFib is serious condition, millions of people in the U.S. live with it. Timely treatment, regular monitoring of the heart, and appropriate lifestyle changes can help people who have AFib manage symptoms and live longer, healthier lives.

“The Yale Atrial Fibrillation program is a nationally and internationally recognized center of excellence for the treatment of patients with AFib,” says Dr. Freeman. “Our team of physicians, nurse practitioners, physician assistants, nurses, and technologists takes a comprehensive approach to treating AFib that is state-of-the-art and tailored to the needs of each patient. Our team also leads and participates in cutting-edge research on AFib, leading the field and bringing the most advanced treatments to our patients.”