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Introduction
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Fremont, CA 94538-7330
United States
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About Atrial Fibrillation
What is Atrial Fibrillation?
Atrial Fibrillation (AF) is a cardiac rhythm disorder caused by chaotic electrical impulses within the heart. It is a fast, irregular heartbeat originating in the atria. The heart is divided into four chambers, the upper two are the atria, and the lower two chambers are the ventricles.
The heart is an electromechanical pump. The pumping action of the heart relies on its electrical system to contract the muscles and pump blood throughout the body. The right side of the heart receives unoxygenated blood from the body and then delivers it to the lungs to be oxygenated. The left side of the heart receives oxygenated blood from the lungs and pumps it out to the rest of the body. The rhythmic contractions require electrical signals to reach each chamber in an organized, controlled manner.
The heart's electrical system is called the Cardiac Conduction System. It is made up of specialized cells within the heart muscle tissue. This conduction system carries electrical signals in a properly timed sequence to the muscle cells throughout the heart.
The normal electrical heart beat starts in the right atrium within a specialized group of cells called the Sino-Atrial (SA) node. The SA node is the heart's "natural pacemaker," regularly discharging an electrical signal that, under normal circumstances, is responsible for setting the heart rate. The normal heart rate is usually 60 to 100 beats per minute.
The signal generated in the SA node spreads throughout the atria until it reaches the Atrio-Ventricular (AV) node. After the atria contract and fill the ventricles with blood, the signal travels down the Bundle of His (pronounced "hiss").
The electrical signal is then distributed widely throughout both ventricles by the Purkinje Fibers. The ventricles contract at the same time. Since the ventricles pump blood to the lungs and the body, they are composed of a larger amount of muscle tissue than the atria. The left ventricle is the stronger of the two ventricles, generating higher pressure in order to pump oxygenated blood through the entire body. In the normal heart, the four chambers work in rhythm with each other to ensure that oxygenated blood is delivered throughout the body. The heart's conduction system must function properly to make the heart an effective pump.
When this conduction system is functioning properly, it is known as Normal Sinus Rhythm. When the electrical signals are fired in a chaotic uncontrolled manner AF can result.
The signs and symptoms of AF include:
- Rapid heart beat
- Palpitations
- Dizziness
- Shortness of breath
- Weakness
Risks associated with AF:
- Stroke
- Blood clots in the heart that may travel to other areas of the body
- Decreased functioning of the left ventricle
- Uncontrolled ventricular rate leading to:
- Enlargement of the heart
- Congestive heart failure
Diagnostic Procedures
AF is routinely diagnosed using an electrocardiogram (EKG or ECG), in which electrodes are placed on the skin to record the electrical signals of the heart. However, sometimes electrocardiograms are unable to locate the origin, or focus, of the AF.
Sometimes a longer recording is needed. A Holter monitor records EKG signals while the patient continues normal daily activities. A Holter monitor usually records for 24 hours.
An exercise EKG test may also be done. This involves recording the EKG while the patient is exercising either on a bicycle or treadmill. The activity may bring on arrhythmias (irregular cardiac rhythms) that may not be recorded during a resting EKG.
These tests diagnose the arrhythmia. An electrophysiology (EP) study may be required to identify the origination or focus of the arrhythmia. The EP study involves placing catheters with electrodes inside the chambers of the heart. These electrodes record the electrical signals generated and map the location of the focus.
Current Treatment Options
Current treatments for Atrial Fibrillation (AF) are directed at trying to reestablish a normal heartbeat and prevent stroke. They are primarily supportive and palliative; meaning they treat only the symptoms rather than offering a cure.
Antiarrhythmic and anticoagulant drugs are the most common treatment for AF. They are typically an attempt to control AF by restoring the heart's natural rhythm and limit blood clotting. However, antiarrhythmic drug therapy often becomes less effective over time, with approximately half of the patients eventually developing resistance to the drugs. In addition, antiarrhythmic drugs can have severe side effects, including pulmonary fibrosis and impaired liver function.
Another palliative procedure for AF is external cardioversion, or the application of strong electrical current under general anesthesia. This treatment is usually effective for a limited period of time as well.
Pacemakers are another treatment option. They are usually inserted in the Cardiac Catheterization Lab. Pacemakers control the heart rate, but do not treat the underlying disease process.
Internal Cardioverters/Defibrillators are implanted devices that are programmed to deliver a shock to the heart. They also do not offer a cure or improve the quality of life for someone who suffers from AF.
| Treatment Type | Curative | Invasive | Side Effects |
|---|---|---|---|
| Medication | No | No | High |
| Cardioversion | No | Low | No |
| Artificial pacemaker | No | Medium | No |
| Implantable cadioverter- defibrillator | No | Medium | Medium |
| Cox Surgical Maze | Yes | High | Low |
|
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The only clinically proven cure for AF is the Cox Surgical MAZE. This procedure has a success rate of over 90%. However, it is a highly invasive procedure requiring open heart surgery. The surgeon makes several slices through the wall of the atrium with a scalpel and then sews the cuts back together creating a scar pattern. The scars isolate and contain the chaotic electrical impulses. The heart does not develop AF because the path of conduction is controlled.
The REVELATION® Maze Procedure* mimics the Cox Surgical Maze, but it is much less invasive. Therefore there is less risk of complication and a shorter recovery time.
*Not available in the U.S.