September is National
Atrial Fibrillation Awareness Month
What is atrial fibrillation?
Atrial
fibrillation (AF) is the most common arrhythmia or irregular rhythm of the
heart. The human heart has four chambers; two upper chambers called the atria
and two lower chambers called the ventricles. Normally, the blood is pumped
from the atria into the ventricles and then to the lungs and the rest of the
body. The electric impulse that begins this heartbeat starts in the sinoatrial
(SA) node, which is located on the right atria. This electrical impulse spreads throughout the right and left
atria and causes the atria to contract and pump blood into the ventricles. The
electrical signal then spreads to the atrioventricular (AV) node and to other
fibers in the heart causing the ventricles to contract and pump blood out to
the lungs and throughout the rest of the body.
In atrial
fibrillation, however, the electric signals do not work properly and start
somewhere other than the SA node. This causes the atria to beat rapidly or
quiver, which may cause symptoms in some patients. Because the atria do not contract properly, blood cannot
be efficiently pumped into the
ventricles. When this happens, blood tends to pool in the atria. This could
lead to the formation of a blood clot, and if this clot breaks through from the
atria and travels to the brain, it can cause a stroke. For this reason,
patients with AF are at a particularly high risk for stroke.
How many people are affected by atrial
fibrillation?
Approximately
2.3 million Americans are affected by AF. In the general population, the frequency of AF is 0.4% to 1%
and increases with age. The frequency of AF, however, does not differ between
males and females. The
rate of stroke in those with AF is about 5% per year, which is 2 to 7 times higher
than those without AF.
What types of atrial fibrillation are there?
AF can be
classified as paroxysmal, persistent, or permanent. Paroxysmal AF is used to
describe AF that goes away on its own within 7 days, while persistent AF
describes AF that lasts longer than 7 days. Persistent AF that lasts for over 1 year is considered to be
longstanding. For longstanding AF,
if the heart’s rhythm cannot be returned to normal with treatment, it is called
permanent AF. Some cases of AF may not necessarily fall into just one of the
classifications. For example, a
patient can sometimes have paroxysmal AF, while at other times have persistent
AF or vice versa.
There is
also another term referred to as lone AF that describes people who are younger
than 60 years old and have AF, but do not have high blood pressure or any other
structural problems with their heart. Compared to the other types of AF, patients with lone AF are
not at a high risk for stroke.
What are the common signs and symptoms
associated with atrial fibrillation?
Symptoms
of AF vary, and some patients may not experience any symptoms at all. However, most patients complain of
palpitations or abnormal heartbeats, chest pain, shortness of breath, fatigue,
lightheadedness, and fainting.
What are common causes or risk factors for
atrial fibrillation?
There are
many causes of AF. AF can be related a temporary condition or to more permanent
medical disorders or genetics. Temporary causes of AF include alcohol use, exercise, surgery,
electrical shock, and hyperthyroidism. Medical conditions such as obesity are also associated with
AF as well as heart conditions such as high blood pressure, heart failure, and
valvular heart disease, which is a disease where the valves of the heart are
damaged. Those with a family
history of AF are also at risk for developing AF. In some patients, AF may not be associated with any of these
factors and the cause is unknown.
How is atrial fibrillation diagnosed?
Atrial
fibrillation is diagnosed based on the patient’s symptoms, physical exam, and
electrocardiogram findings. Electrocardiogram (ECG) is a machine that measures the
heart’s electrical activity. Other
tests done when evaluating someone with AF include thyroid, liver, and kidney function
tests.
Why is early diagnosis of AF important?
If AF is
not properly diagnosed and treated, it can progress. Patients with AF are at increased risk for stroke and disability
or death; therefore, early diagnosis and treatment is important so that proper measures
can be taken to help prevent or reduce the risk of complications.
What medications are used in the treatment of AF?
There are
3 goals in treating AF: to prevent blood clots with the use of anticoagulants
(blood thinners), to control the heart rate (rate control), and to restore the
heart’s rhythm to normal (rhythm control).
Anticoagulation
Patients
with AF are at risk of forming blood clots and are at increased risk of a
stroke. Anticoagulation is, therefore, necessary to help prevent the formation
of blood clots in the first place, especially in patients who are at high risk
of stroke. Patients who are at
high risk of stroke include those who have had a stroke before, are older than
75 years old, have high blood pressure, diabetes, and/or heart failure. Drugs such as warfarin or dabigatran,
which work by preventing the formation of blood clots, are used in these
patients to help reduce their risk of stroke. Those considered to have a low risk of stroke may only
require aspirin.
Rate
Control
Rate
control is done to help slow the contractions of the ventricles and the number
of beats of the heart per minute. Usually
drugs called beta-blockers (including metoprolol or propranolol) or calcium
channel blockers (specifically verapamil and diltiazem) are used. These drugs can help with some of the
symptoms experienced by patients with AF. Side effects of beta-blockers include low blood pressure
and/or heart rate, worsening of asthma, and heart failure. Some major side effects for calcium
channel blockers are similar to beta-blockers and include low blood pressure and heart failure. The
heart rate can be controlled without necessarily having to return the heart’s
rhythm back to normal.
Rhythm
Control
Rhythm
control, also called cardioversion, is done to restore the heart’s normal
rhythm. This can be done either with
medications or by other methods. Cardioversion
with medication is most effective when given within 7 days after an episode of
AF. Medications used to
achieve rhythm control include flecainide, dofetilide, propafenone, and
ibutilide. The side effects vary with these drugs and include heart effects and
stomach upset. Amiodarone is another medication that can be considered for
rhythm control and, although effective, this drug is usually not preferred due
to its potential to cause severe side effects. Therefore, the other agents are
generally preferred when considering rhythm control with medication.
Another
method of rhythm control is by electrical or direct current cardioversion, which
requires shocking the heart in order to get it back to normal rhythm. Sometimes this is done along with the
use of medications that control the rhythm of the heart. Use of both of these methods
(medications and electrical cardioversion) may be more successful for some
patients in achieving and maintaining a normal heart rhythm.
Another procedure
called catheter ablation can also be used to restore normal rhythm of the heart,
especially when the rhythm is not well controlled by cardioversion. This procedure involves inserting a
catheter into a vein in the leg and up into the heart. Radiofrequency or freezing is then used
to destroy the tissue that is causing the abnormal electrical signal. For many patients, catheter ablation can
result in a long-term cure of AF.
What can I do to prevent atrial fibrillation?
Avoiding
the triggers associated with AF and treating the underlying causes of AF can
help prevent AF. For example, since alcohol ingestion may trigger AF in some
individuals, avoidance of alcohol
intake can help prevent it. Also, managing a healthy weight and blood pressure
can also minimize one’s risk for AF. These are just some ways to help prevent
AF.
Where can I find information on atrial
fibrillation?
More
information on AF can be found from the following organizations:
American
Heart Association:
Heart
Rhythm Society: http://www.hrsonline.org/patientinfo/heartrhythmdisorders/afib/
National
Heart, Lung, and Blood Institute: http://www.nhlbi.nih.gov/health/health-topics/topics/af/
National
Library of Medicine: http://www.nlm.nih.gov/medlineplus/atrialfibrillation.html
Written
by: Yoradyl Bendebel, Doctor of Pharmacy candidate
University
of Illinois at Chicago
UIC Pharmacy
UIC Pharmacy
September
2012
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