WASHINGTON -- An estimated 2 million Americans suffer from one
form or another of atrial fibrillation, the heart condition that
has several times briefly interrupted campaigning by Democratic
presidential hopeful Bill Bradley.
For many of them, the disorder amounts to little more than a
nuisance, although if not properly treated it can lead to a stroke,
according to the American Heart Association.
Cardiac electrophysiologists, the specialists who deal with the
way electric currents regulate the heartbeat, said Friday that
atrial fibrillation can be managed in several ways and should not
affect Bradley's ability to serve as president, should he be
elected.
Former President Bush experienced at least one episode of the
heart disorder while in office. In his case, the heart arrhythmia
apparently grew out of a thyroid condition.
Bradley said Thursday he has experienced four episodes of the
irregular heartbeat since disclosing Dec. 10 that he had the
condition. In all four incidents, his heart rhythm returned to
normal -- ``converted'' -- without treatment, his aides said.
``By working with a doctor to manage atrial fibrillation, people
can keep it under control and minimize its effects,'' heart
association said in a statement released Friday. ``When handled
appropriately, the condition normally doesn't interfere with
regular day-to-day function.''
Dr. Mina Chung, a cardiologist and cardiac electrophysiologist
at the Cleveland Clinic in Cleveland, Ohio, explained that the
disorder occurs when electrical currents that pulse through the
heart, causing its chambers to contract and push blood through the
arteries and veins, get out of whack.
Normally, these currents are regulated at two areas of the
heart.
The ``sinus node'' at an upper area of the right atrium manages
the pulses that flow through the two atria, causing the smaller
heart chambers to contract and force blood into the larger
ventricles.
The electrical pulses then must pass through an area known as
the atrioventricular node, the electrical gatekeeper to the
ventricles.
After a brief pause at the atrioventricular node, the impulses
spread through the ventricles, causing them to contract and push
the blood into the arteries.
In atrial fibrillation, the regulation of electrical current at
the sinus node is lost and impulses spread rapidly and repeatedly
through the atria. The uncontrolled impulses can range as high as
300 to 600 beats per minute.
The atrioventricular node usually re-establishes control over
the electric current before it passes to the ventricles, so that
the pulse rate rarely rises over 150 beats per minute.
However, the uncontrolled atrial action means the delivery of
blood to the ventricles is impaired and the heart's overall
efficiency often is reduced by 20 to 30 percent. In some cases,
drugs or electric stimulation is used to cause the heart to shift
back into normal gear.
That accounts for one of the main dangers of atrial
fibrillation, Chung explained. Because the blood is not flowing
smoothly through the atria, it is more likely to clot. Should a
clot dislodge and travel to the brain, it can cause a stroke.
The risk of stroke among persons with atrial fibrillation is
between 3 and 7 percent a year, or approximately five times higher
than the general population.
Depending on the seriousness of the fibrillation, persons with
the disorder may be required to take blood thinners -- ranging from
aspirin to warfarin -- to control the stroke risk, she said.
Chung, who said she would not hesitate to vote for someone for
president solely because he had atrial fibrillation, said the
condition can be managed with medication.
Causes of the condition can range from underlying cardiovascular
problems such as valve disease and coronary artery disease to
stress, hypertension, excessive caffeine, electrolyte or metabolic
imbalances, hyperthyroidism and even severe infections.
In some cases, the cause is never identified.
For more information on atrial fibrillation, see the American
Heart Association's Internet page, http://www.Americanheart.org,
and the Cleveland Clinic's page, http://www.clevelandclinic.org.
