What is Atrial Fibrillation/Atrial Flutter (AF/AFL)?
AF occurs when the electrical signals that control muscle contractions in the upper chambers (atria) of the heart become rapid sometimes causing these upper heart chambers to beat at a rate greater than 300 beats per minute. When the atria beat this fast, the heart muscle in the atrial walls can only quiver, so the atria cannot effectively pump blood to the lower chambers (ventricles). In atrial fibrillation, because the electrical activity is ever-changing and chaotic, the heart beat (pulse), which is controlled by the bottom chambers (ventricles), is usually irregular. Not every electrical signal from the top chambers travels down to the ventricles, which is why the pulse that is heard in the chest or felt in the wrist or neck is not as fast as the activity in the top atrial chambers. An irregular heartbeat usually is not a symptom of atrial flutter because the electrical activity in the atrial chambers is more regular, but still very fast.
How Common is AF?
AF is the most common heart rhythm disorder. An estimated 2.2 million people in the United States have AF, and approximately 160,000 new cases are diagnosed every year.
Who is Most Likely to Develop AF?
AF is uncommon among young people, and the likelihood of developing the condition increases with age. After age 65, between 3 percent and 5 percent of people have AF. Approximately 9 percent of people age 80 or older have the condition.
What Causes AF?
In many people, there is no apparent cause for AF. These individuals have what is called "lone" or idiopathic AF. In others, AF may be related to other medical conditions, such as: coronary artery disease (CAD), thyroid disease, high blood pressure (hypertension), structural defects of the heart and its valves, lung disease and other medical conditions.
What Is the Function of the Atria?
The right atrium receives returning blood that has circulated through the body and the left atrium receives oxygenated blood from the lungs. The atria act as priming pumps to send the blood to the lower chambers (ventricles). The ventricles are the main pumping chambers that pump the blood out of the heart and back to the lungs and the body.
What Are the Different Types of AF?
AF may occur from time-to-time and stop on its own (paroxysmal AF), or it may occur constantly (persistent or permanent AF).
How Serious is AF?
AF is usually not dangerous or life-threatening if it is properly diagnosed and treated. In younger people who have no other disease that affects the heart, AF usually is not considered serious. In some people, however, AF increases the risk of stroke, congestive heart failure or cardiomyopathy. According to the Framingham Heart Study, people with AF have a 3 to 5 times greater risk of stroke, especially individuals who are older than 65, have already had a stroke, or have high blood pressure, diabetes or congestive heart failure. These risks can be reduced by the careful use of medications, including blood thinners such as coumadin
Over time, AF also can lead to microscopic changes in the heart muscle, alter the normal electrical signals of the heart and change the patterns of contraction and relaxation of heart muscle. This is known as electrical remodeling.
What is the Relationship Between AF and Stroke?
During an episode of AF, the upper chambers of the heart do not contract as they normally do to force blood out of the atria, and through the heart valves into the ventricles. Instead, the heart valves open passively with each heartbeat, but some blood may not move forward into the ventricles as it should. Instead, blood tends to pool in certain parts of the atria, particularly in the nooks and crannies, increasing the risk that clots will form in the stagnant blood. Even small blood clots can cause problems if they leave the heart and are released into the general circulation. They may clog arteries in the body and disrupt the blood supply to vital organs. Stroke happens when a clot interrupts the blood supply to part of the brain.
How is AF Diagnosed?
The simplest way for your doctor to diagnose AF is a combination of feeling your pulse and recording an electrocardiogram (ECG). If your pulse is faster than 100 beats per minute and irregular, AF is suspected. The diagnosis is then confirmed with an ECG - a simple, painless test that records the electrical activity of the heart through electrodes that are pasted temporarily to the skin of the chest, arms and legs. An ECG often is performed in your doctor's office, using a machine that prints out a graph showing electrical activity of different parts of the heart.
Sometimes, the patient may be asked to wear a small portable device with electronic memory to record a series of ECGs over time. These devices include Holter monitors and event recorders. A Holter monitor runs continuously, and usually is worn for 24 to 48 hours. An event recorder is switched on by the patient to record an ECG whenever he or she senses an irregular heartbeat.
How is AF Treated?
To Prevent Stroke. Aspirin and warfarin (Coumadin®) are drugs that may be prescribed to prevent the formation of blood clots that can lead to stroke. These medications, called anticoagulants, must be carefully regulated so that the body maintains its ability to form clots that will stop bleeding in the event of injury. The decision to prescribe these medications - and which to prescribe - is based on patient age and risk factors. Warfarin usually is prescribed for patients who are over age 65, or who have had a prior stroke or have other health problems such as heart failure, coronary artery disease, diabetes or hypertension. Aspirin (or no medication) is the standard treatment for people under age 65 who do not have any risk factors that increase the likelihood they will develop blood clots associated with AF. Every patient is different, and the physician will help decide what type of blood thinner to use in each individual situation.
To Treat Arrhythmias. There are a number of short-term and long-term treatments aimed at preventing or controlling the abnormal heart rhythm associated with AF.
Short-Term Treatments
Oral medications that slow the heart rate during AF include drugs such as beta blockers (metoprolol, atenolol, propranolol, carvedilol), calcium antagonists (verapamil, diltiazam) and digitalis. (digoxin) These slow the transmission of electrical signals from the atria to the ventricles, slowing down the pulse rate.
Electrical Cardioversion. For most individuals with chronic AF or those whose symptoms are not improved with medications, the heart's normal rhythm can be restored by delivering a controlled electric shock to the heart. This breaks the pattern of abnormal electrical signals. This procedure is performed under careful medical supervision and short-acting sedatives are used so that patients do not feel any pain or discomfort. While this small procedure can restore a normal rhythm, it does not affect the chances of whether the heart will go back into AF at some point afterward.
Drug Cardioversion is when drugs such as ibutilide are given to restore the heart's normal rhythm instead of using an electrical shock.
Long-Term Treatments
The goal of long-term treatment may be to maintain the heart's normal sinus rhythm and prevent future episodes of AF. Sometimes the goal is simply to control the heart rate, in which case the medications mentioned above can be used indefinitely. Treatments to try to keep the heart in normal rhythm may include:
Oral medications: Medications to control heart rhythms are called "anti-arrhythmics". A number of different drugs with different characteristics may be used to convert or prevent AF. Antiarrhythmic drugs need to be tailored specifically to the individual patient. Unfortunately, medications are not always effective in controlling AF, or cannot be used in some patients because of undesirable side effects. When medications do not work or are not an option because of side effects, catheter ablation (CA) may be effective in some patients.
Catheter Ablation (CA): In this procedure, flexible, thin wires (catheters) are introduced into blood vessels and directed into the heart under x-ray guidance. Bursts of radiofrequency energy can be delivered at different sites in the left and right atrium to destroy small areas of heart muscle that give rise to abnormal electrical signals. If most or all of the abnormal spots can be eliminated with the ablation procedure, then the initiation of AF may be prevented. When medications are not effective to prevent AF and rapid heart rates remain difficult to control, a different type of CA may be used to permanently cut the electrical connection between the atria and ventricles (called an “AV node ablation”). This requires implantation of a pacemaker and does not eliminate the need for blood thinners, but does restore a regular heart rhythm and many people feel much better after undergoing this procedure.
Pacemakers are devices permanently implanted under the skin to regulate the rhythm of the heart to reduce the frequency of paroxysmal AF in some patients, especially in those with slow heart rhythms that result from abnormalities of their own natural pacemaker or from medications.
Low-energy internal atrial defibrillators (atrial ICDs) automatically (or on command) deliver a controlled electric shock to restore the heart's normal rhythm when they detect an episode of AF, although these devices are not used often.
In many patients the decision may be made to allow atrial fibrillation to persist. Therapy is then focused on adequate rate control with medications (to make sure the pulse rate never goes too fast) and protection from the formation of blood clots with blood thinner medications, as outlined above.
Atrial Fibrillation & Flutter - What to Ask Your Doctor If you have been diagnosed with atrial fibrillation (A-Fib) or atrial flutter (AFL), or suspect that you may have the condition, here are some questions that you may want to ask your physician.
- What is the cause of my atrial fibrillation or atrial flutter?
- How can I be sure I have A Fib or AFL and not a more serious heart rhythm problem?
- Will my condition go away on its own?
- What are the risks that it will become worse? (more symptomatic)
- Am I at increased risk of having a stroke?
- What are my treatment options?
- What are the risks and side effects of medications to control my condition, or to reduce the risk of stroke?
- What are the risks/benefits of other treatment options?
- Should I see an electrophysiologist (a specialist in heart rhythm disorders)?
