Download What is Atrial Fibrillation?

What is Atrial Fibrillation?
Atrial fibrillation is a common abnormal heart rhythm that is characterized by
abnormal beating of the upper heart chambers. The atrium or upper chamber of
the heart does not contract effectively during atrial fibrillation because it is going
too fast, usually 300-600 beats per minute.
Because the atrium is going so
fast, the blood tends to pool and
can form a blood clot. This blood
clot can go to other parts of your
body including your brain and
cause a stroke. The bottom
chambers of the heart, the
ventricles, may try to keep up
with the atrium and beat at a
faster rate than normal. If the
heart continues to race for a long
period of time the heart muscle
becomes worn out and may begin
to fail.
How common is Atrial Fibrillation?
Atrial Fibrillation occurs in over 2 million Americans. It is estimated that more
than 5 percent of individuals over 69 years of age have atrial fibrillation.
What causes Atrial Fibrillation?
In most cases there is not just one cause. There are several individual factors that
increase the risk of developing atrial fibrillation. These risks are congestive heart
failure, mitral or aortic valve disease, hypertension (elevated blood pressure),
advanced age, enlarged left atrium, obesity, sleep apnea, and thyroid disease.
Atrial fibrillation caused by thyroid disease may be reversible if it is caught and
treated in a timely manner.
What are the risks of Atrial Fibrillation:
The main risk of atrial fibrillation is stroke and the development or worsening of
heart failure. Nearly 25 percent of all strokes caused by a blood clot to the brain
are secondary to atrial fibrillation. Each individual may have different risk of
developing a stroke. If a person is young, healthy, and has only atrial fibrillation,
their stroke risk is around 1 percent. However, the majority of individuals have
multiple risk factors and the risk of stroke on average is about 4 percent per year
or greater. The risk of stroke determines how best to prevent the stroke. If the
risk of stroke is low usually 2 percent or less, then aspirin is usually enough. If the
risk of stroke is higher, then Coumadin (warfarin) is the recommended treatment.
Within the last year, two other drugs, Pradaxa and Xarelto, have been approved
to prevent stroke in non valvular atrial fibrillation. In some cases your health care
provider may recommend one of these drugs in place of Coumadin. Please note,
these two options are not for everyone and these options should be discussed
with your health care provider at length.
As we discussed earlier, during atrial fibrillation the bottom chamber of the heart
may go faster than usually. This can cause the heart muscle to become weak and
start to fail. To prevent this from happening, your health care provider may
prescribe various medications to control your heart rate. These medications are
usually beta blockers (metoprolol), calcium channel blockers (diltiazem), and\or
digoxin. Please note this is not an extensive list of medications and anywhere
from one to all three medications may need to be used for heart rate control.
What are the symptoms of Atrial Fibrillation?
Common symtpoms of atrial fibrillation include shortness of breath, chest
discomfort, feeling of palpitations or the heart racing, fatigue, leg swelling,
dizziness, or possible passing out. Some individuals do not realize their symptoms
or do not have any symtpoms. Unfortunately,the way atrial fibrillation is
discovered in some cases is after a stroke or mini stroke.
What tests may be ordered for Atrial Fibrillation?
Usually a 12 lead EKG is the first tests completed. For further detection or
monitoring of the rhythm, a 24 or 48 hour Holter monitor may be ordered for you
to wear.
If a longer monitor period is needed, an Event monitor may be ordered as this
monitor can be used for up to 30 days. An echocardiogram is done to measure
the size of the left atrium and other chambers of the heart. This tests also
evaluates the heart valves and the function of the heart. Depending on symtpoms
and risk factors, other tests may be needed such as a stress test, a sleep study, or
a CT of the chest or heart. Laboratory studies are routine to decide what
medications you can take and also to make sure there is not a reversible cause for
the atrial fibrillation (thyroid disease, electrolyte imbalance etc.).
What is the treatment for Atrial Fibrillation?
Treatment is aimed at preventing strokes, preventing heart failure, and
controlling symptoms. In order to prevent strokes a blood thinner is ordered. In
low risk patients, aspirin is usually enough. However, in many cases, the risks of
stroke are higher, especially if there are risk factors such as high blood pressure,
diabetes, heart failure, advanced age etc. and a stronger blood thinner will be
needed. There previously was only one strong blood thinner and that was
Coumadin (warfarin). However in the last year or so, some newer blood thinners
have come to market. Currently Pradaxa (Dabigatran) and Xarelto (Rivaroxaban)
are also currently available. In the near future, Eloquis (Apixaban) may come to
market if approved by the FDA as a fourth choice. Each of these drugs have
positives and negatives and a long discussion with your healthcare provider is
needed to decide which one is right for you. The newer agents are not for
everyone and currently are only indicated for patients with atrial fibrillation at
this point.
After the proper blood thinner has been prescribed, further treatment or need of
treatment is decided. As stated earlier, if the heart rate is too fast, it can cause
weakening of the heart muscle or heart failure. The next step is usually aimed at
controlling the heart rate. Medications such as beta blockers, calcium channel
blockers, or digoxin may be used long term or temporarily to get the heart rate
down. If the heart rate is not able to be controlled, an electrical cardioversion or
shock to the heart is then completed to restore normal rhythm. If there is still
difficulty controlling the heart rate or there are symtpoms from the atrial
fibrillation, new medications may be started called antiarrythmics. These are
stronger medicines that help keep the heart in normal rhythm. Several of these
medicines are on the market and include: Rhythmol (Propafenone), Flecainide
(Tambocor), Multaq (Dronederone), Sotalol (Betapace), Tikosyn, Amiodarone
(Pacerone, Cordarone). These medications require close monitoring by your
cardiologist and may even require a hospital admission to be started on the
medication for safety reasons.
If despite the medications, atrial fibrillation continues to occur , a procedure
called an ablation may be recommended. Atrial fibrillation ablation or pulmonary
vein isolation is a catheter based procedure that is completed by an
electrophysiologists to help maintain normal rhythm. Not everyone is a candidate
for this procedure due to the risks involved but may be an option for some
individuals. The most aggressive approach for atrial fibrillation is a surgical
approach called a MAZE procedure. It is done through the chest wall much like
open heart surgery and usually reserved for patients after an ablation has failed.
Finally, if the other procedures fail or patients are not a candidate for the other
procedures, and the heart rate continues to be too fast, an AV nodal ablation is
completed and a pacemaker is placed. This is not a cure for the atrial fibrillation,
nor does it prevent it. In some patients, this is the only way the heart rate can be
controlled.
These procedures are mainly aimed at patients that are highly symptomatic with
their atrial fibrillation. Many patients do not have any symptoms and it does not
hinder their life in any way. For those patients, these procedures are usually not
needed and the risks may outweigh the benefits. Please discuss all treatment
options with your healthcare provider so you can make the best most informed
decision.
References:
1. Libby, P., Bonow, D., Zipes, D. & Braunwald, E. (Eds). (2008). Braunwald’s Heart Disease:
A Textbook of Cardiovascular Disease Medicine. Philadelphia, PA: Saunders Elsevier.