Look here for a more medically detailed discussion of the causes, clinical characteristics, and treatment of atrial fibrillation.

There are four issues that concern patients with atrial fibrillation:

1. control of the rate of the ventricular response,
2. conversion of the atrial rhythm to sinus rhythm,
3. maintenance of sinus rhythm following conversion, and
4. prevention of embolic stroke from thrombi that form in the fibrillating left atrium.

When a person has "ventricular preexcitation" (Wolff-Parkinson-White syndrome), the ventricles can beat so rapidly that they develop ventricular fibrillation, causing immediate death. This can occur because in this condition, the atrioventricular node is "bypassed" by one or more extra ways for electrical signals to get from the atria to the ventricles.

The treatment for the usual patient with atrial fibrillation with rapid heart rates can include:

1. medication to slow conduction through the atrioventricular node, so that the ventricles beat at a more normal rate,
2. conversion of the atrial fibrillation to a normal rhythm (see below) with medications or with surgery, or
3. in desperate cases, destruction of the atrioventricular node with radiofrequency ablation together with implantation of a permanent pacemaker.

1. The medications that keep the rate from being too high act by slowing conduction through the atrioventricular node. Often, these patients have disease in the atrioventricular node. Sometimes, the node conducts very rapidly (which is why the medications are given). Sometimes, however, it conducts normally or slowly. The reason for the changes is usually not apparent, although it is likely related to changes in the activity of the "sympathetic" and "parasympathetic" nervous systems. Whatever the reason, the medications cause the atrioventricular node to conduct even more slowly than it would have in the absence of the medications. The result can be a very slow heart rate.
2. In some patients, atrial fibrillation is not continuous. Instead, it starts and stops on its own. When it stops, the normal "sinus node" pacemaker of the heart is supposed to take over immediately and restore a normal heart rate. In some people, however, either the sinus node takes a long time (several seconds) to start functioning again, or it functions at such a slow rate that the person feels very poorly.

It is very important to realize that blood clots (thrombi, to be technically correct) form on the walls of the atria during atrial fibrillation. When normal sinus rhythm is restored, these can break off the walls and fly into the brain or elsewhere in the body, causing strokes or other catastrophic problems. The risk of such events is about 5% or less of all "unprotected" cardioversions, but the consequences are so awful that cardioversion is rarely performed in this country unless the patient has been taking a "blood thinner" (anticoagulant, for example heparin or warfarin) for two to three weeks. After cardioversion, anticoagulant medication should be continued for another two to three weeks because the atria sometimes don't contract mechanically for some time after the electrical abnormality has been corrected.

We do not want to frighten anyone with the above information. Right now, experts in atrial fibrillation do not know whether it is better to prescribe antiarrhythmic drugs or to prescribe Coumadin and drugs that keep the heart rate from going too high. This is the subject of an ongoing clinical study sponsored by the National Institutes of Health called the AFFIRM trial. We suggest that people who are faced with this decision talk with physicians they trust to decide what is best for them.

Whether a person should take antiarrhythmic drugs for prevention of atrial fibrillation is a decision that should be made by that person together with her or his physician.

There is a surgical procedure that can cure atrial fibrillation. It was developed by Dr. James Cox at Washington University - St. Louis. It requires open heart surgery, however, and is rarely used today. A variation that uses ablation energy (either heating or cooling or both) can be used with good success in patients who are having open chest surgery for another reason at the same time.

Techniques for curing atrial fibrillation with radiofrequency ablation using catheters passed through the veins are now well-developed enough to be clinically useful. These techniques are associated with complications that can be significant, however. The best candidates for the procedure are people who still have atrial fibrillation despite taking one or more antiarrhythmic medications, who are otherwise in fairly good health, and whose heart rhythm is not atrial fibrillation all the time. In this group, the success rate is up to about 80% although sometimes more than one ablation procedure is required to achieve this success rate. People who do not meet the above characteristics can still experience a success rate of about 50%.

An atrial defibrillator was developed that could detect and convert atrial fibrillation automatically. This device was implanted under the skin, just like an ordinary pacemaker. Unlike a pacemaker, however, it detected fast atrial rates rather than slow ones, and delivered a large shock rather than many tiny ones. There were two problems with the designs by InControl, Inc. (website no longer active) and Medtronic, Inc. First, the shocks hurt. It turned out that the amount of energy needed to convert atrial fibrillation with the current design was above the pain threshold for some people. On the other hand, many people who actually had these devices said that the shocks did not hurt, or at least that they did't hurt much for the immediate relief that they brought. Second, the shock could, in principle, cause ventricular fibrillation. Thus, it had to have enough energy to convert this rapidly lethal rhythm. The Medtronic model could do this, while the InControl device could not. On the other hand, InControl reported that no episodes of atrial shock-induced ventricular fibrillation had occurred in their clinical studies. While this type of device offered an exciting new approach to atrial fibrillation, it appears no longer to be available.

Whether a person should take such drugs and, if so, which ones, for reduction of risk of stroke during atrial fibrillation, is a decision that should be made by that person together with her or his physician.