What Is Atrial Fibrillation (AFib)?

Atrial fibrillation, or "AFib," is the most common type of serious arrhythmia, affecting about 2.2 million Americans, with 160,000 new cases diagnosed annually.

AFib is a very fast and irregular rhythm originating in the atria (upper chambers of the heart). AFib occurs when the heart’s electrical signal begins in a different part of the atrium other than where it is supposed to begin, the sinoatrial (SA) node, which is known as the pacemaker of the heart.

When this happens, the electrical signal does not travel through the normal pathways in the atria, but instead may spread throughout the atria in a fast and disorganized manner. This causes the walls of the atria to quiver very fast (fibrillate) instead of beating normally. As a result, the atria are not able to adequately fill with blood or pump blood in sufficient amounts.

AFib and other supraventricular (originating above the ventricles) arrhythmias can occur for no apparent reason. Most of the time, however, supraventricular arrhythmias are caused by an underlying condition that interferes with the heart's ability to conduct electrical impulses. These conditions include high blood pressure (hypertension), coronary artery disease, heart failure or rheumatic heart disease. Other conditions also can lead to AFib, including overactive thyroid gland (too much thyroid hormone produced) and heavy alcohol use. AFib also becomes more common as people get older.

AFib Awareness

Types of AFib

AFib is divided into different categories, based on the cause and duration of irregular-heartbeat episodes. Although symptoms may be the same across multiple types of AFib, the treatment options may be different. It is important to remember that all types of AFib increase the risk of stroke, even if no symptoms are present.

Paroxysmal Fibrillation

AFib episodes are inconsistent and unpredictable, and symptoms may come and go. Episodes can occur frequently, or they may only occur a few times a year. Each episode may last only a few minutes or could persist for hours or even days. Some people with paroxysmal fibrillation do not require treatment if the episodes resolve on their own, while others may need consistent treatment. It is not uncommon for AFib to begin as paroxysmal fibrillation and progress to a more permanent form of the condition over time.

Persistent AFib

When an irregular heartbeat lasts for more than seven days, it is called persistent AFib. This type of arrhythmia does not resolve on its own and requires ongoing treatment.

Long-standing, Persistent AFib

When the heartbeat is constantly irregular, lasting more than 12 months, it is called long-standing, persistent AFib. Medical or surgical treatment is necessary to regulate and maintain a healthy heartbeat.

Permanent AFib

With permanent AFib, an irregular heartbeat cannot be reset and maintained at a normal rate for an extended period of time, even with treatment. Physicians may recommend medication to help prevent blood clots.

Nonvalvular AFib

AFib that is not caused by a heart-valve problem is called nonvalvular. It may be caused by another condition, like high blood pressure, or the cause may be unknown.

Causes and Risk Factors of AFib

Causes and risk factors of heart arrhythmia include:

Symptoms of AFib

It is important to remember that AFib does not always cause symptoms. Patients who do experience symptoms may notice any of the following:

  • Irregular heartbeat (either too fast, too slow or skipping beats)
  • Heart palpitations (including fluttering or quivering)
  • Shortness of breath
  • Fatigue or weakness
  • Dizziness, lightheadedness or fainting
  • Difficulty with exercise
  • Chest pain or pressure

If you experience chest pain or pressure, it is important to call 911 or go to the nearest emergency room immediately.

AFib symptoms can be similar to symptoms of other conditions, including anxiety and panic. Because it can be difficult to determine if your symptoms are from AFib or from another condition, it is important to see your physician. If you need a physician referral, please call (713) 222-CARE (2273).

Diagnosing AFib

Tests to find underlying heart diseases, like atrial fibrillation, may include:

Heart Attack, Heart Failure and Stroke: Know the Warning Signs

AFib can lead to other serious cardiac and neurological conditions including heart attack, heart failure and stroke. Even when symptoms are mild or nonexistent, if you have AFib, you have an increased risk of these serious complications.

Heart Attack (myocardial infarction)

When the amount of blood flowing through the heart is reduced or blocked, a heart attack can occur. If you experience these symptoms, call 911 immediately:

  • Chest pain or discomfort (pressure, tightness or aching) that lasts more than a few minutes or that stops and reoccurs
  • Pain or discomfort that spreads to one or both arms, shoulders, back, neck or jaw
  • Shortness of breath
  • Heartburn or indigestion
  • Nausea, lightheadedness or dizziness
  • Cold sweat
  • Fatigue

Women may experience different symptoms that can include sharp pain in the arm, back or neck, instead of more severe chest pain.

Heart Failure

Heart failure is a serious, life-threatening condition where the heart cannot pump enough blood through the body. AFib can cause heart failure when the ventricles beat too fast and do not have enough time to fill with blood to pump out to the body. This condition gradually develops over time as the heart’s pumping action weakens. Heart failure does not mean the heart stops. The heart is still functioning, but not as well as it should to sustain the systems within the body. The most common warning signs of heart failure are:

  • Shortness of breath or trouble breathing
  • Fatigue
  • Swelling in the ankles, feet, legs, abdomen and veins in the neck


A stroke is a “brain attack” caused by a sudden interruption of blood supply to the brain. Patients with AFib have an increased risk of blood clots which increases the risk of stroke. In AFib, blood clots can form in the atria because some of the blood “pools” in the fibrillating atria instead of flowing into the ventricles. If a piece of a blood clot in the left atrium breaks off, it can travel to the brain, causing a stroke. Many people with AFib take blood thinners or other treatments to help prevent blood clots from forming.

Stroke is a life-threatening emergency, and getting treatment quickly is very important. Remember these warning signs for stroke: BE FAST.

BALANCE: Is there a sudden loss of balance or coordination?

EYES: Is there sudden double or blurred vision and/or sudden trouble seeing that persists?

FACE: Ask the person to smile. Is one or both sides drooping?

ARMS: Ask the person to raise both arms. Does one side drift downward? Weakness or numbness on one side?

SPEECH: Does the person have slurred/garbled speech? Can he/she repeat a simple phrase?

TIME: If you observe any of these signs, call 911 immediately and note the time symptoms began.

Finding Treatment

The innovative team at Memorial Hermann is here to help you find the treatment you need. For more information on diagnostic procedures to minimally invasive treatments for your thoracic condition, fill out the form below or call to schedule an evaluation.

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