For many reasons, the "best" treatment for atrial fibrillation is controversial. The most obvious approach to treatment -- and the one most doctors and patients at least initially believe to be the correct one -- is to restore and maintain a normal heart rhythm. As we will see, however, there are problems with this approach that make it difficult or inadvisable for many patients with atrial fibrillation.
First, How Is a Normal Heart Rhythm Restored?
Two general methods are used: antiarrhythmic drugs, and cardioversion. But since antiarrhythmic drugs will restore a normal rhythm only 50 - 60% of the time, and because using these drugs exposes the patient to side effects, cardioversion is usually the treatment of choice in stopping an episode of atrial fibrillation.
Cardioversion involves first placing the patient in a light anesthesia-induced sleep for a few minutes, and then, while the patient is asleep, administering an electrical discharge to the patient's chest.
In the vast majority of cases, the electrical discharge "wipes out" the atrial fibrillation, and allows the normal heart rhythm to resume. When performed by trained individuals, cardioversion is very safe and effective.
The most dreaded complication of cardioversion has more to do with the atrial fibrillation than with the cardioversion itself. As we have noted, atria that have been fibrillating for more than 24 to 48 hours tend to form blood clots. If fresh blood clots are present and then the atria begin contracting again (because atrial fibrillation has now been terminated), the action of the beating atria can dislodge the fresh clots from the heart, and a stroke can result. The risk of this complication - post-cardioversion stroke - can be greatly diminished by placing the patient on anticoagulation with coumadin (a drug for clots) for 4 - 6 weeks prior to cardioversion. (Another alternative is to perform a transesophageal echocardiogram to look for clots in the atria. If none are seen, many cardiologists consider it relatively safe to proceed with cardioversion without taking the step of anticoagulating.)
Second, How Is a Normal Rhythm Maintained Over Time?
The real problem with restoring and maintaining a normal heart rhythm is with the maintaining part. This is because maintaining a normal rhythm most often requires the use of antiarrhythmic drugs - and these are among the most toxic drugs used in medicine.
For many patients, atrial fibrillation tends to come back, and unless aggressive steps are taken after cardioversion, the patient finds him/herself back in atrial fibrillation after some period of time. For these patients to have any realistic chance of staying in a normal rhythm, antiarrhythmic drugs must be used. Here, I must stress that each individual with atrial fibrillation is different. Some have only rare and short-lived episodes of atrial fibrillation (also known as paroxysmal atrial fibrillation), while others tend to return to atrial fibrillation quickly, and to stay there until cardioversion is again performed (i.e., chronic or persistent atrial fibrillation). Often, the doctor initially will not know how likely it is that a particular patient will develop AF again.
Many doctors therefore will simply cardiovert patients when they first develop atrial fibrillation, then watch to see what happens. If atrial fibrillation returns, the cardioversion can be repeated, this time using antiarrhythmic drugs.
When Is it Important to Restore and Maintain a Normal Rhythm?
Despite the drawbacks, for some patients with atrial fibrillation it is important to make the effort to stop the arrhythmia and maintain a normal heart rhythm. Such patients include:
- People who have a lot of symptoms from atrial fibrillation, even if the rapid rate can be controlled
- People with certain cardiac disorders (such as hypertensive cardiac disease and aortic stenosis) in which the loss of normal coordination between the atria and the ventricles causes special problems
- People with "lone" atrial fibrillation or certain other forms of atrial fibrillation in whom, if a normal rhythm can be restored, are likely to remain in a normal rhythm for an appreciable period of time, often without antiarrhythmic drugs
- People with recent-onset atrial fibrillation who have never had an attempt at cardioversion.
How the Process Works for Different Patients
Once the decision has been made to restore and maintain a normal rhythm, the patient should be scheduled for cardioversion, following 4-6 weeks of anticoagulation, unless the atrial fibrillation has been present for less than 24 hours.
If this is the first episode of atrial fibrillation, many doctors will withhold antiarrhythmic drugs, in the hope that the normal rhythm, once restored, will maintain itself.
But if the atrial fibrillation recurs, then after the second cardioversion, antiarrhythmic drugs normally are given. Drug selection is generally trial and error. If a drug does not work or causes unacceptable side effects, then another drug is chosen (or the decision to use antiarrhythmic drugs is reconsidered).
In most cases, patients should be monitored in the hospital for at least a day or two whenever starting antiarrhythmic drugs, since the drugs can cause significant problems.
Success Rates
With these aggressive measures, a little more than 50% of patients will achieve good control of their atrial fibrillation after one year. This success rate leaves much to be desired, obviously. This is why much work is being done to develop alternative therapies for atrial fibrillation, including ablation procedures aimed at eliminating the arrhythmia altogether.
Sources:
Fogoros, RN. Treatment of Supraventricular Arrhythmias. In: Fogoros, RN. Antiarrhythmic Drugs - A Practical Guide. Blackwell Publishing, Malden, MA: 2007.
