There are three fundamental issues that need to be addressed in anyone with atrial fibrillation: heart rate control, prevention of blood clot formation and stroke, and conversion back to normal rhythm.
Heart rate control
As previously described in the section What is atrial fibrllation?, heart rate control is critical in all patients who are in atrial fibrillation to prevent the development of heart failure. Heart failure can have life-threatening consequences in addition to severly diminishing a patient's quality of life. Most commonly, heart rate control can be adequately achieved through the use of medications which help control the speed at which atrial fibrillation is allowed to spread to the lower chambers of the heart (the ventricles). These medications may include a beta blocker, a calcium channel blocker, or digoxin. In addition, there are several other medications primarily used for regulating the heart rhythm (antiarrhythmics) which may also be used to control the heart rate.
In many patients, the use of these medications leads to the heart being too slow when not in atrial fibrillation. This is a common problem as rapid atrial fibrillation often goes hand-in-hand with slowly responding sinus node, the body's natural pacemaker. This condition is known as tachy-brady (or fast-slow) syndrome. In such patients, if a medication cannot be properly dosed to prevent rapid heart rates, implantation of a pacemaker may be necessary to prevent the heart rate from going to slow so that increasing dosages of these medications may be used.
In other patients in whom rate control is unsuccessful, other options include catheter ablation of the atrial fibrillation itself, as described below, or catheter ablation of the AV node. Catheter ablation of the AV node is a relatively straightforward procedure where an ablation catheter is advanced to the area of the AV node by way of the lower extremity veins.
Usually only a few lesions are required with the ablation catheter to irreversibly damage the AV node to the point that there is no more conduction through the AV node of atrial fibrillation occurring in the atria. This procedure requires that a patient also have a pacemaker implanted to stimulate the ventricles to activate. After an ablation of the AV node, the ventricles are dependent on the pacemaker to support the heart rate but there is no worry of rapid heart rates as a result of ongoing atrial fibrillation.
Prevention of blood clots
People with atrial fibrillation have an increased risk for stoke as a result of blood clots that can form in the heart due to the sluggish flow of blood in the atria. To lower the risk of the development of blood clots, it is critical that people with atrial fibrillation take a blood thinner. Depending on an individual person's risk of forming a blood clot, a person may be advised to take aspirin or warfarin (Coumadin). Although aspirin is effective at reducing blood clots, it is only an option for people who are at a low risk for clots. For everyone else, warfarin is the most effective treatment for preventing blood clots. Unfortunately, the major problem with warfarin is that it can lead to excessive bleeding. Anyone who takes warfarin must be carefully monitored with periodic blood test to be sure the dose of the warfarin is adequate to prevent stroke but not lead to excessive bleeding. The proper dose varies from person to person and must be individualized.
To determine whether one is at a low or high risk for forming blood clots, a calculator based on certain risk factors for forming blood clots is used:
|Risk Category||Recommended Therapy|
|No risk factors||Aspirin|
|One moderate-risk factor||Aspirin or Warfarin|
Any high-risk factor or more than 1
|Less Validated or Weaker Risk Factors||Moderate-Risk Factors||High-Risk Factors|
Age greater than or equal to 75 years
Previous stroke, TIA, or embolism
Conversion to normal rhythm
In many people, an episode of atrial fibrillation will revert back to normal rhythm. However, in some people atrial fibrillation does not return to normal rhythm on its own. The likelihood of atrial fibrillation returning to normal rhythm and the likehood that it will recur if does return to normal rhythm is dependent on a number of factors, some of which are unknown. Clearly, however, the presence of underlying heart disease makes the likelihood of staying in atrial fibrillation higher. This highlights the concept that atrial fibrillation is not the same in any individual. There is a spectrum of disease and each person must be approached on an individual basis.
If atrial fibrillation does not return to normal rhythm and there is a desire to revert to normal rhythm, most commonly a person will undergo an electrical cardioversion. Electrical cardioversion involves the use of an electrical shock from a cardioverter delivered through pads placed on the chest. This is a relatively straightforward procedure done on an outpatient basis. During this procedure, a person is sedated with anesthetics given through an interavenous line. Once a person is adequately sedated, instantaneous current is delivered through the pads by the cardioverter. There is a very high (>90%) likelihood of success of a cardioversion in returning a patient to normal rhythm.
When a person undergoes electrical cardioversion, it is important first to know that there is no blood clot in the heart because the early period after a cardioversion is a time when a blood clot located in the heart may dislodge and migrate to another blood vessel, possibly causing a stroke. It is important, therefore, that a patient either be treated with warfarin for several weeks to eliminate any blood clot that may be in the heart. If this is not possible, a procedure called a transesophageal echocardiogram may be performed to exclude the presence of a blood clot in the heart while blood thinners are being started. During this procedure, a small ultrasound device is swallowed while a person is sedated (similar to an "endoscopy" procedure), and the heart is directly visualized to exclude the presence of a clot.
Maintenance of normal rhythm
As described above, the likelihood that atrial fibrillation will recur depends on a number of factors, some of which are unknown. Some known factors that influence whether atrial fibrillation will recur include:
- The presence of a reversible or treatable cause such as hyperthyroidism, recent surgery, or sleep apnea
- The presence of a family history of atrial fibrillation
- A person's age
- The length of time atrial fibrillation has been present
- The presence of underlying heart disease other than atrial fibrillation such as coronary heart disease, high blood pressure, or heart failure
If a person is quite symptomatic when in atrial fibrillation, it may be desirable to maintain normal rhythm. In discussion with your electrophysiologist, there are several options for maintaining normal rhythm:
- After a successful cardioversion, one could just take and wait-and-see approach to see if atrial fibrillation recurs. This may be appropriate if it is a person's first episode of atrial fibrillation and there are few, if any, risk factors for recurrent atrial fibrillation as outlined above. In some people, atrial fibrillation doesn't recur for years.
- If a person has recurrent atrial fibrillation or risk factors that increase the likelihood of recurrence, to maintain normal rhythm it is usually necessary to make an intervention. Usually, the first intervention is to take an antiarrhythmic medication. That is, a medication specifically designed to prevent the electrical instability that leads to fibrillation. There are many different types of these medications, including flecainide (Tambocor), propafenone (Rythmol), sotalol (Betapace), dofetilide (Tikosyn), and amiodarone (Cordarone). Each medication has it's particular effectiveness and side effects. In addition, some of these medications cannot be given in a person with underlying heart disease (see chart below). In discussion with your electrophysiologist, a trial of a particular medication could be started.
- If a person has recurrent atrial fibrillation despite an attempt of one or two antiarrhythmic medications to maintain normal rhythm, a third option is catheter ablation for atrial fibrillation. Since the late 1990's, catheter ablation has transformed the care of atrial fibrillation. In selected patients, catheter ablation can be very effective at maintaining normal rhythm with a low risk of complications. For more information on catheter ablation of atrial fibrillation, click here.