Atrial Fibrillation
Atrial fibrillation is an irregular heart rhythm that affects the normal contraction of the right and left atria. The atria lose their normal ability to contract and essentially "quiver". It may occur in association with valvular heart disease or other heart problems or it may occur in a normal heart. Over two million people in the United States have atrial fibrillation.
Symptoms
- Palpitations: The chief symptoms of atrial fibrillation are related to the heart rate and the heart rhythm. It is not uncommon for patients to develop heart rates that race up and down, and with a very high or very low heart rate the patient may feel dizzy, lightheaded, weak, or short of breath.
- Fatigue or heart failure: Although it is the ventricles that pump blood out to the body, the lack of contraction of the atria reduces the blood flow into the ventricles and there is a loss of cardiac function or output.
- Emboli: One of the biggest threats to a patient with atrial fibrillation is blood clots. With a loss of contraction of the atria, the blood within the atria tends to pool and stagnate, and blood clots can form. The most serious of these occur within the left atrium. These clots can then break loose and travel to the brain (causing a stroke) or to other vital organs or limbs. The risk of stroke for a patient with atrial fibrillation is 5% per year. One of every six strokes in the United States occurs in patients with atrial fibrillation.
Diagnosis
The diagnosis of atrial fibrillation is usually made on the electrocardiogram. For patients who have atrial fibrillation that comes and goes and is not seen on a single electrocardiogram, outpatient monitoring may be performed.
Many different classifications of atrial fibrillation have been proposed, but the most common system describes three categories:
- Paroxysmal: Episodes that last less than 7 days
- Persistent: Episodes that last longer than 7 days
- Permanent: Always having atrial fibrillation
For paroxysmal and persistent atrial fibrillation, if the patient has two or more episodes it is called recurrent paroxysmal or recurrent persistent atrial fibrillation.
Medical Treatment
Rate
and rhythm control
The medical treatment for atrial fibrillation
is complex and there have been many different approaches for controlling
the heart rate or rhythm or both, and these also are determined by
the category of atrial fibrillation (paroxysmal, persistent, or permanent)
and whether or not the episodes are recurrent. In certain instances
where the atrial fibrillation is not yet permanent, an electrical
shock known as cardioversion may be applied to break the atrial fibrillation
and restore a regular rhythm.
In some patients where the rate cannot be controlled with medication, the electrical conduction system of the heart can be interrupted with a procedure known as a nodal ablation. Although the atria continue to fibrillate, the electrical impulses are not conducted to the ventricles, and the heart rate slows down significantly. Because the heart rate gets very low, a patient having a nodal ablation will usually require a pacemaker. You must be very careful not to confuse nodal ablation with atrial fibrillation ablation; it is unfortunate that the word “ablation” is used with both procedures, because it does confuse things.
Prevention
of emboli
The other major goal of medical treatment is
to prevent blood clots from forming and breaking loose, and this
is done with blood thinners such as warfarin. Some patients
cannot take warfarin, and this can be a serious problem. In
addition, taking warfarin can cause bleeding problems, especially
if the patient has another problem such as a fall or an ulcer. Patients
on warfarin must have their blood checked regularly to make sure
it is not too thick or too thin. If the patient must have a
surgical procedure performed, the warfarin must be stopped in advance,
and this places the patient at risk.