Atrial Fibrillation

Atrial fibrillation is the most common arrhythmia, affecting about 2 million Americans, primarily the elderly. In atrial fibrillation, the electrical signals in the atrial (upper) chambers of the heart are chaotic. In addition, the atrial electrical impulses that reach the ventricles (lower heart chambers) often arrive at irregular intervals. An irregular and, often, rapid heart rate results.


Diagnosis

In atrial fibrillation, the electrical signals in the atria (upper chambers of the heart) are chaotic and the electrical impulses reach the ventricles (lower heart chambers) often at irregular intervals, causing a fast and irregular heartbeat.

To diagnose atrial fibrillation, the patient may be asked about or tested for conditions that may trigger the fibrillation, such as heart disease or a thyroid gland problem. Several tests may be given to better understand the cause of the arrhythmia.

Stress Test
Atrial fibrillation may be triggered or worsen when the patient is exercising. During a stress test, the patient may exercise on a treadmill or stationary bicycle, with close monitoring by an ECG of heart activity. The test is intended to actively induce an irregular heartbeat while the patient is being monitored. The test may involve use of a drug to stimulate the heart instead of exercise. This may be particularly helpful to patients who have difficulty exercising. The stress test can also be used to detect coronary artery disease.

Electrocardiogram (ECG)
In this test, electrodes (sensor patches with wires attached) are placed on the patient's skin to measure the electrical impulses given off by the heart. The ECG measures the timing and duration of each electrical phase in the heartbeat.

Echocardiogram (Doppler Echocardiogram)
This test uses sound waves to produce detailed images of the patient's heart. Through a handheld device (transducer) on the patient's chest, sound waves bounce off the heart and are reflected to produce video images of the heart's size, structure and motion. The echocardiogram can also be used to measure the heart's blood volume and the speed and direction of blood flow through the heart.

Blood Tests
These may help rule out thyroid problems or other blood chemistry abnormalities that may lead to atrial fibrillation.

In addition, the heart may be monitored during regular activity.

Holter Monitor
A Holter monitor is a portable ECG device that the patient wears for a day or more to record the heart's electrical activity during the patient's daily routine.


Treatment

Nonsurgical Procedures

Cardioversion
To correct atrial fibrillation — reset the heart to its regular rhythm (sinus rhythm) — the physician will often perform cardioversion. This can be done with drugs or electrically.

Cardioversion with drugs
Medications (anti-arrhythmics) are used to stop the atria's quivering and restore normal (sinus) rhythm. The medications effectively maintain sinus rhythm for at least one year in 50 percent to 65 percent of people. However, they can cause side effects such as nausea and fatigue, as well as some long-term risks. In rare cases, the medications may actually increase the heart rate.

Electrical cardioversion
A patient under light anesthesia receives an electrical shock through paddles or patches on the chest. The shock stops the heart's electrical activity for a split second. When the heart's electrical activity resumes, the rhythm may be normal.

Cardioversion is not always effective. It may successfully restore regular heart rhythm in more than 95 percent of patients, but more than half of patients eventually go back into atrial fibrillation. In many instances, anti-arrhythmic medications are needed indefinitely.

Catheter Radiofrequency Ablation
For atrial fibrillations caused by abnormal heart tissue, catheter radiofrequency ablation can be used to destroy the abnormal tissue. In the procedure, catheters (thin, flexible tubes) are threaded through the patient's blood vessels to reach the abnormal heart tissue. The cardiologist then uses a small cutter or radiofrequency energy to remove the abnormal tissue.

Types of ablation for atrial fibrillation include:

• Pulmonary vein isolation ablation (PVI ablation or PVA) — This procedure electrically isolates "hot spots" in the pulmonary veins that trigger atrial fibrillations. Pulmonary vein isolation eliminates atrial fibrillation in 60 percent to 80 percent of patients who are treated. In addition, medications that did not help patients prior to ablation are now effective.
• AV node ablation with pacemakers — In AV ablation, a catheter is placed near the atrioventricular (AV) node (the electrical connection between the atria and ventricles). Radiofrequency energy is applied through the catheter to destroy a small area of tissue. The radiofrequency energy prevents the atria from sending too many electrical impulses to the ventricles. In 98 percent of patients, this procedure completely blocks the heart's electrical impulses and eliminates atrial fibrillation. Once the AV node is destroyed, doctors then implant a pacemaker to establish normal rhythm. Anticoagulation medication (blood-thinning medication) is required after the procedure to reduce the chance of developing blood clots.

Surgical Procedures

Pacemakers
A pacemaker is a medical device that helps regulate the heartbeat. The device, smaller than a matchbox, is placed under the skin near the collarbone. A wire extends from the device to the heart. If a pacemaker detects an abnormally slow heart rate or no heartbeat, it emits electrical impulses that stimulate the heart to speed up or start beating again. A pacemaker is used most often if medications to prevent atrial fibrillation or control the heart rate result in excessively slow heartbeats, and after AV node ablation.

Open-Heart Maze Procedure
For surgical Maze procedures, surgeons create multiple cuts into the muscle of the atria and then stitch them together. These incision lines interfere with stray electrical pathways and circuits. The lines reduce the size of atrial tissue sections needed to maintain atrial fibrillation. Due to its complexity, only a few medical centers in the United States perform the surgical Maze procedure.