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An abnormally fast heart rhythm, or
tachycardia can prove dangerous because
the racing interferes with the heart’s ability
to contract properly. As a result, a victim
may suffer a range of symptoms, from lightheadedness
to sudden cardiac death.
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Each heart has it own normal
rhythm brought about by the
seamless flow of electrical
impulses that begins in the heart’s
natural “pacemaker” (sinus node).
The electricity flows through the
upper chambers (atria), crosses the
bridge between upper and lower
chambers (atrioventricular node) and
travels to the lower chambers (ventricles).
This passage of electricity
culminates in a carefully coordinated
contraction of heart muscle that pushes
blood throughout the human body.
Each day, a normal heart contracts
about 100,000 times, at a rate anywhere
from 60 to 100 times a minute.
Changes in rate brought about by
variations in activity, diet, medication
and age are normal and common.
During intense exercise, a heart may
speed up to 160 to 180 or more beats
a minute. Running up a flight of stairs
or being startled by a noise account for
normal increases in heart rates as well.
The rapid-fire contractions in all these
situations are faster than the “normal”
resting range, yet they pose no danger.
When a heart begins to race for no
apparent reason, however, it can be
a sign of an abnormality in the
electrical pathway and is cause for
evaluation. Abnormal rapid heart rates
can range from 100 beats a minute up
to 400 beats a minute and can be relatively
harmless or life threatening.
Symptoms
When the heart beats too quickly, the
ventricles do not have enough time to
fill with blood and cannot effectively
pump blood to the rest of the body. The
lack of oxygen can prove deadly and
gives rise to the following symptoms:
| Heart skipping a beat |
Beating out of rhythm |
| Palpitations |
Rapid heart action |
| Shortness of breath |
Chest pain |
| Dizziness |
Lightheadedness |
| Blackouts |
Temporary blind spots |
| Fainting or near fainting |
Chaotic, quivering or irregular rhythm |
| Death |
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MOST DANGEROUS RAPID HEART RHYTHMS
Sudden rapid heartbeats originating in the ventricles are the most dangerous
arrhythmias. Ventricular tachycardia, a rapid yet steady beat is dangerous
in its own right. Worse, it can turn into ventricular fibrillation, or VF, which is
characterized by irregular and chaotic rapid heartbeats. Because the fibrillating
ventricular muscle cannot contract and pump blood to the brain and vital
organs, VF is the number one cause of sudden cardiac death. Without
immediate emergency treatment of an electric shock to restore normal rhythm,
an individual loses consciousness within seconds and dies within minutes.
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Types of Arrhythmias
Understanding some common terms
in the language of cardiac arrhythmias
helps sort through the types of rhythm
problems. An arrhythmia is any abnormality
in heart rhythm. Arrhythmias
are categorized in three main ways:
Rate
If the heart rate is rapid, or greater
than 100 beats a minute, it is considered
a tachycardia. Alternatively, a slow
heart rate, below 60 beats a minute, is
known as a bradycardia.
Location
The location of the problematic
electrical circuit helps define the
arrhythmia. For instance a rhythm is
called supraventricular if it originates
above the ventricles (lower chambers).
So, the problem is most likely in the
upper chambers (atria). It follows
that a ventricular arrhythmia is the
result of a problem in the lower
chambers (ventricles).
Irregular
The nature of the heartbeat, whether
it is steady or chaotic, is another
key to categorizing an arrhythmia.
A rapid beat that is irregular and
chaotic may be a type of fibrillation,
or quivering beat.
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MOST COMMON RAPID HEARTBEAT
More than 2 million people in the United States experience atrial fibrillation,
making it the most common heart rhythm disorder. In AF, or A Fib, the
heartbeat is irregular and rapid. The upper chambers, or atria, may beat as
often as 400 times a minute, about four times faster than normal. Although it
isn’t life threatening, A Fib can lead to other rhythm problems, chronic fatigue
and congestive heart failure. Chances of having a stroke are five times higher
for those with A Fib than for those without A Fib.
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Who develops rapid heartbeats?
Anyone can develop a rapid heartbeat,
even someone young without
a previous heart problem. However,
problems are more common in those:
| With previous heart trouble |
| Over 65 years of age |
| Who have suffered damage
caused by a heart attack, cardiac
surgery or other conditions |
| With rare, inherited heart defects |
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