Atrial Fibrillation

Many patients are referred for a cardiology consultation because of a heart arrhythmia (a disturbance in the normal rhythm of the heart). There are many kinds of arrhythmias and atrial fibrillation is the most common.

Atrial Fibrillation and the Risk of a Stroke:

In this condition the upper chambers of the heart (the atria) receive their electrical stimulation in a chaotic fashion rather than the normal orderly sequence of electrical activation. This results in an inability of the atria to contract normally. Rather than a co-ordinated contraction where all of the muscle cells in the atria shorten at the same instant, the cells shorten at different times resulting in an ineffective atrial contraction. Because the atria do not contract normally, some blood is left behind in the atria rather than all of it being pumped out to the lower chambers. When blood is left behind it can become stagnant and clot in one of the little pockets of the left atrium called the left atrial appendage. If a piece of this clot were to break off, it would be pumped out of the heart with the blood and since the clot is solid, it would ultimately get stuck, like a cork, in a blood vessel it's own size. If the clot were to be pumped to the the head, it would lodge in a blood vessel in the brain and would prevent the blood behind it from getting through. This would result in that part of the brain being deprived of it's normal oxygen flow (the blood carries the oxygen) and that part of the brain tissue would be injured and die. A Stroke would result. In order to prevent this from happening, we need to place certain patients with atrial fibrillation on a blood thinning medicine called coumadin or warfarin. It turns out that not all patients with atrial fibrillation are prone to stroke and we only put those who are vulnerable on the blood thinning medicine (warfarin). You can learn more about blood thinning medicines by reading Anticoagulants.

Patients With Atrial Fibrillation Who Require Blood Thinners:

1. All patients over 75 years of age unless there is a good reason why they can't take the blood thinner. Some authorities believe all patients older than 50 should be on blood thinners. Please feel free to discuss this with your cardiologist or primary care provider.

2. Patients in whom their atrial fibrillation is associated with valvular heart disease.

3. Patients who are younger than 75 years of age but who have one of the following risk factors: high blood pressure, diabetes mellitus, prior stroke or TIA (transient ischemic attack, a temporary stroke which reverses), structural heart disease such as a weakened heart muscle (cardiomyopathy).

4. Patients who don't need the blood thinning medication (warfarin) or who can't take it for some reason should be on one adult Aspirin (325 mg) daily.

Heart Rate and Atrial Fibrillation:

Patients with atrial fibrillation often notice that their heart rates are increased. The atria commonly conduct electrical activity much faster in atrial fibrillation than they do when the heart is in a normal rhythm. It is often the rapid heart rate which first alerts the patient that something is wrong. There are a number of medications (beta blocking drugs like atenolol and metoprolol, amiodarone, digoxin, diltiazem, verapamil)which can slow the heart down to a normal heart rate (60-100 beats/minute)during atrial fibrillation. Not all patients will need medications to slow the heart down in this condition but many will. In addition to the rate racing, a person with atrial fibrillation may notice that their heart beats irregularly (the heart beats aren't spaced equally apart). Since the heart beats less efficiently, some patients will also notice that they have less energy or get short of breath when in atrial fibrillation.

Getting Patients Out of Atrial Fibrillation:

The decision whether or not to try to restore a normal heart rhythm depends on several factors such as how the patient feels in atrial fibrillation, how likely it is that normal rhythm can be maintained, how willing a patient is to continue longterm blood thinning medication and other factors. This is a decision that the patient and cardiologist should make together. If a decison is made to attempt to restore a normal heart rhythm several methods are available to try. These include medications like amiodarone and electrical cardioversion which means to shock the heart back into a normal rhythm. Generally, prior to attemting to restore a normal heart rhythm, a patient is given blood thinners for a month or a special test (TEE, transesophageal echo) is done to make sure that no clots are in the heart.

Electrical Cardioversion; Shocking the Heart:

This is a safe and painless procedure. The patient comes to the clinic having had nothing to eat for 8 hours. An anesthesiologist puts the patient to sleep with a very short acting medication and the patient receives a shock to the chest wall which generally restores normal rhythm. Blood thinning medicines are usually required for at least one month after a normal rhythm is restored. The patient goes home when fully awake, usually an hour or 2 after being shocked.

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