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Atrial Fibrillation
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Related terms:  afib, a-Fib, arrhythmia

Arrhythmias (heart rhythm disorders) are generally divided into two categories: ventricular and supraventricular. Ventricular arrhythmias occur in the lower chambers of the heart, called the ventricles. Supraventricular arrhythmias occur in the area above the ventricles, usually in the upper chambers of the heart, called the atria. Fibrillation, the most serious form of arrhythmia, is fast, uncoordinated beats, which are contractions of individual heart-muscle fibers. Atrial fibrillation (also called AFib or AF) is the most common type of supraventricular arrhythmia with irregular beats that are too fast (tachycardia).

Anatomy of the conduction system

Any irregularity in your heart's natural rhythm is called an arrhythmia. Almost everyone's heart skips or flutters at one time or another, and these mild, one-time palpitations are harmless. But there are about 4 million Americans who have recurrent arrhythmias, and these people should be under the care of a doctor. 

In the news . . . Dec. 4, 2012
The Heart Problem You're Not Worried About
Atrial fibrillation is a growing epidemic . . . awareness and early diagnosis can save lives. Age is the biggest risk factor for afib (an irregular and often rapid heartbeat that causes poor blood flow). A person's chances of developing the irregular heartbeat increase after age 60 . . . "Many people develop afib in their later years," says Mohammad Saeed, MD, a cardiac electrophysiologist at THI. Full article and associated videos from everydayhealth.com.

Supraventricular Arrhythmias and Atrial Fibrillation

Supraventricular arrhythmias begin in the areas above the heart’s lower chambers, such as the upper chambers (the atria) or the atrial conduction pathways. Generally, supraventricular or "atrial arrhythmias" are not as serious as ventricular arrhythmias. Sometimes, they do not even require treatment. Like PVCs, atrial arrhythmias can happen in response to a number of things, including tobacco, alcohol, caffeine, and cough and cold medicines. The disorder also may result from rheumatic heart disease or an overactive thyroid gland (hyperthyroidism). Supraventricular arrhythmias can cause shortness of breath, heart palpitations, chest tightness, and a very fast pulse. 

Atrial fibrillation is a fast, irregular rhythm where single muscle fibers in your heart twitch or contract. According to the National Institutes of Health (NIH), about 2.2 million Americans have atrial fibrillation. It is a main cause of stroke, especially among elderly people. Atrial fibrillation may cause blood to pool in the heart's upper chambers. The pooled blood can lead to the formation of clumps of blood called blood clots. A stroke can occur if a blood clot travels from the heart and blocks a smaller artery in the brain (a cerebral artery). About 15% of strokes happen in people with atrial fibrillation.

For this reason, many patients with atrial fibrillation need antiplatelet therapy. These medicines can prevent blood clots from forming and causing a stroke.

What causes an arrhythmia?

In the news . . . April 2011 
The Link Between Atrial Fibrillation and Family History
"Having a family history of atrial fibrillation can increase your chances of developing this common but potentially dangerous type of irregular heartbeat (arrhythmia)." Dr. Mehdi Razavi, cardiologist at Texas Heart Institute, discusses causes and preventive measures in this article from everydayHEALTH.
Many factors can cause your heart to beat irregularly. Some people are born with arrhythmias, meaning the condition is congenital. Some medical conditions, including certain types of heart disease, high blood pressure, and hemochromatosis (iron build-up in the body), may be factors. Also, stress, caffeine, smoking, alcohol, and some over-the-counter cough and cold medicines can affect the pattern of your heartbeat.

What are the symptoms?

Whether you have symptoms and what those symptoms feel like depend on the health of your heart and the type of arrhythmia you have. Symptoms also depend on how severe the arrhythmia is, how often it happens, and how long it lasts. Some arrhythmias do not produce any warning signs. If you have AFib, you may 

  • Feel a strong pulse in your neck, or a fluttering, racing heartbeat in your chest.
  • Feel chest discomfort, weak, short of breath, faint, sweaty, or dizzy.

How is an arrhythmia diagnosed?

The following techniques are used to diagnose arrhythmias.

  • A standard electrocardiogram (ECG or EKG) is the best test for diagnosing arrhythmia. This test helps doctors analyze the electrical currents of your heart and determine the type of arrhythmia you have.
  • Holter monitoring gets a non-stop reading of your heart rate and rhythm over a 24-hour period (or longer). You wear a recording device (the Holter monitor), which is connected to small metal disks called electrodes that are placed on your chest. With certain types of monitors, you can push a "record" button to capture your heart's rhythm when you feel symptoms. Doctors can then look at a printout of the recording to find out what causes your arrhythmia.
  • Event monitoring records problems that may not be found within a 24-hour period. The devices used for this type of test are smaller than a Holter monitor. One such device is the size of a beeper, and another is worn like a wristwatch. As with Holter monitoring, you wear the recording device. When you feel the symptoms of an arrhythmia, you can telephone a monitoring station, where a record can be made. If you cannot get to a telephone during your symptoms, you can turn on the device's memory function. Later, you can send the recorded information to a monitoring station by using a telephone. These devices also work during episodes of fainting.
  • Electrophysiology studies (EPS) are usually done in a cardiac catheterization laboratory. A long, thin tube called a catheter is inserted into an artery in your leg and guided to your heart. A map of electrical impulses from your heart is sent through the catheter. This map helps doctors find out what kind of arrhythmia you have and where it starts. During the study, doctors can give you controlled electrical impulses to show how your heart reacts. Medicines may also be tested at this time to see which will stop the arrhythmia. Once the electrical pathways causing the arrhythmia are found, radio waves can be sent through the catheter to destroy them. (See radiofrequency ablation in treatment section below.)
  • A tilt-table exam is a way to evaluate your heart's rhythm in cases of fainting. The test is noninvasive, which means that doctors will not use needles or catheters. Your heart rate and blood pressure are monitored as you lie flat on a table. The table is then tilted to 65 degrees. The angle puts stress on the area of the nervous system that maintains your heart rate and blood pressure. Doctors can see how your heart responds under carefully controlled times of stress.

How is arrhythmia treated?

Antiarrhythmic medicines, including digitalis, beta-blockers, and calcium channel blockers, are often the first approach taken for treating arrhythmia. Other treatments include percutaneous (catheter) interventions, implantable devices, and surgery (for severe cases).

  • Ventricular tachycardia and ventricular fibrillation can be treated by an implantable cardioverter defibrillator (ICD). This is a device that applies electric impulses or, if needed, a shock to restore a normal heartbeat. The device's power source is implanted in a pouch beneath the skin of your chest or the area above your stomach and connected to patches placed on your heart. Newer implantable devices are inserted through blood vessels, which means that you do not need open-chest surgery.
  • An electronic pacemaker is used in some cases of slow heart rate. Smaller than a matchbox, the pacemaker is surgically implanted near the bone below your neck (the collarbone). The pacemaker's batteries supply the electrical energy that acts like your heart's natural pacemaker.
  • Catheter ablation (radiofrequency ablation) is a procedure that uses a catheter and a device for mapping the electrical pathways of the heart. After you are given medicine to relax you, a catheter is inserted into a vein and guided to your heart, where doctors use high-frequency radio waves to destroy (ablate) the pathways causing the arrhythmia.

In some cases, these treatments may not work or they may not be right for you, and surgery may be needed to destroy the source of the irregular heartbeat.

  • Surgical ablation is like radiofrequency ablation. Using computerized mapping techniques, surgeons can find out which cells are "misfiring." A technique called cryoablation can then be used to eliminate tissue with a cold probe and destroy the "misfiring" cells.
  • Maze surgery may be recommended if you have atrial fibrillation that has not responded to medicines or electrical shock (cardioversion therapy) or to pulmonary vein ablation (a procedure similar to radiofrequency ablation). Surgeons create a number of incisions in the atrium to block the erratic electrical impulses that cause atrial fibrillation.
  • Ventricular resection involves a surgeon removing the area in the heart's muscle where the arrhythmia starts.

In other cases, no treatment is needed. Most people with an arrhythmia lead normal, active lifestyles. Often, certain lifestyle changes, such as avoiding caffeine (found in coffee, tea, soft drinks, chocolate, and some over-the-counter pain medicines) or avoiding alcohol, are enough to stop the arrhythmia.

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Atrial Fibrillation (AFib)  

National Heart, Lung, and  Blood Institute
What Is Atrial Fibrillation?

Updated October 2013
Texas Heart Institute Heart Information Center
Through this community outreach program, staff members of the Texas Heart Institute (THI) provide educational information related to the prevention, diagnosis, and treatment of cardiovascular disease. It is not the intention of THI to provide specific medical advice, but rather to provide users with information to better understand their health and their diagnosed disorders. Specific medical advice will not be provided and THI urges you to visit a qualified physician for diagnosis and for answers to your questions.
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