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Atrial
Fibrillation
What
is atrial fibrillation?
Atrial fibrillation is the most common cardiac arrhythmia, or
abnormal heart rhythm seen today. Approximately 2.2 million Americans
suffer from this disorder. On average, there are 160,000 new cases of
diagnosed each year. Atrial fibrillation is a
disorder in which the upper two chambers of the heart no longer beat in a
normal, synchronized fashion. Rather, electrical impulses move about both
atria in a chaotic, or circus-movement pattern, resulting in activation
of the atria at somewhere between 400 and 600 times per minute. The
impulses coursing through the atria traverse through a structure called
the A-V node to reach the ventricles. The hallmark of atrial
fibrillation is an irregular rhythm where the ventricles, or bottom
pumping chambers of the heart, beat in a very chaotic fashion.
What
are the warning signs and symptoms of atrial
fibrillation?
Individuals
with atrial fibrillation may have heart rates
that are too slow, too fast, or within the normal range. Individuals with
atrial fibrillation may experience no symptoms,
limited symptoms in the form of palpitations, or catastrophic symptoms
such as loss of consciousness due to rates which are either too fast or
too slow . A major risk of atrial
fibrillation is stroke, with the incidence of stroke approximately five
times that of similar-aged individuals who do not have atrial fibrillation. The risk factors which appear to
increase the risk of stroke in individuals with atrial
fibrillation include age greater than 65 years, presence of diabetes
mellitus, presence of hypertensive heart disease, congestive heart failure,
mitral stenosis (tight mitral valve), or
history of prior stroke or near-stroke (Transient Ischemic Attack). The
risk of stroke in individuals with atrial
fibrillation may be significantly reduced by use of anticoagulant therapy
in the form of Warfarin.
What
are the treatment options for atrial
fibrillation?
Treating atrial fibrillation varies by individual. Your doctor
will take a thorough history and perform a comprehensive physical
examination to determine if your atrial
fibrillation is due to another problem, such as hypertension, coronary
artery disease, valvular heart disease, or
thyroid dysfunction. Oftentimes, these primary problems may be treated
with resolution of the atrial fibrillation. If
the atrial fibrillation is not corrected by
resolution of the primary problem, the patient is oftentimes anticoagulated for three to four weeks, and
subsequently cardioverted back to normal
rhythm. Cardioversion may occur in the form of
an antiarrhythmic medication either orally or
intravenously, or by the administration of electric shock therapy through
patches placed on the chest. Electrical cardioversion
occurs in a hospital setting, with the patient under brief general
anesthesia for two to three minutes. Following cardioversion,
patients are frequently kept on anticoagulant therapy for a minimum of
three to four weeks to prevent a stroke that may occur up to that period
of time following cardioversion. At times, atrial fibrillation is allowed to persist, without an
attempt at cardioversion. In that case, the
main concern, aside from anticoagulation, is to control the rate of the
ventricles, and that is typically done with either
medical therapy or with use of a pacemaker in combination with A-V Nodal
Ablation (see below).
Other
Treatment Options
At times,
medications do not adequately control the ventricular rate in atrial fibrillation. In these cases, a commonly
performed procedure today is to place a pacemaker, either single or
dual-chamber, followed by catheter ablation of the A-V Node. While this
does not abolish the atrial fibrillation
itself, or the need for anticoagulant therapy, it does abolish the slow
or rapid ventricular response that may occur, and allows the patient to
have a regular, normalized heartbeat.
One of the
newer procedures for atrial fibrillation
involves placing catheters into the left atrium near the pulmonary veins,
which are the vascular channels that drain blood returning from the lungs
to the heart. Atrial fibrillation today is
thought to originate from small islands of tissue within the pulmonary
veins, and catheter-ablation at the entrance of the vein into the left
atrium may abolish the atrial fibrillation from
occurring.
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