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McKesson Clinical Reference Systems: Women's Health Advisor 2002.2
Tachycardia
What is tachycardia?
Tachycardia means a fast heart rate. The normal adult heart
rate, or pulse, ranges from about 50 to 100 beats per minute. A
heart rate that stays above 100 beats per minute
is called tachycardia.
A fast heart rate can occur naturally. For example, your
heart rate may increase when you are exercising, but it
returns to normal when you rest. A fast heart rate can also
be caused by serious, life-threatening heart problems.
How does it occur?
Your heart rate normally increases in several situations,
such as when you:
- exercise
- have a fever
- are anxious or excited.
Hyperthyroidism (too much thyroid hormone in your body) can
cause a fast heartbeat. Problems with the heart that can
also cause tachycardia are:
- Paroxysmal atrial tachycardia (PAT) and supraventricular
tachycardia (SVT): These forms of tachycardia are caused
by changes in the natural electrical impulse that causes
your heart to pump. If you have PAT or SVT, it usually
means that you do not have a serious heart problem.
- Atrial fibrillation: This is an abnormal rhythm pattern
where the right and left atria (upper heart chambers) are
contracting irregularly and making the heart beat faster.
- Ventricular tachycardia: This is a less common, but more
dangerous kind of tachycardia. The heart beats in a
regular rhythm but very fast. This abnormality is
usually caused by heart disease. In a few cases it can
be due to medication you are taking. The problem starts
in your ventricles (lower heart chambers). The most
serious aspect of ventricular tachycardia is that it can
become ventricular fibrillation.
- Ventricular fibrillation: This is the most serious type
of tachycardia. Your heart beats in an irregular rhythm
and very fast. Your ventricles contract (squeeze)
chaotically, which prevents the heart from pumping. When
this happens, blood circulation stops (cardiac arrest).
Sometimes the episodes are brief and suddenly go away.
Most often, however, ventricular fibrillation requires
immediate medical treatment to prevent brain damage or
death.
What are the symptoms?
The main symptom is the sensation of a fast heartbeat.
Other symptoms of tachycardia that may require medical
treatment are:
- lightheadedness or fainting
- nausea
- cold sweat
- shortness of breath
- chest pain.
These symptoms may be caused by any type of tachycardia,
mild to severe. Contact your health care provider if you
are having any of these other symptoms in addition to the
fast heartbeat.
How is it diagnosed?
Your health care provider will ask about your medical
history, including your symptoms. He or she will examine
your heart and lungs. You may have blood tests to check for
metabolic diseases, such as thyroid disease. You may have a
chest x-ray. You will have an electrocardiogram (ECG),
which measures the electrical activity of your heart.
Your health care provider may want you to wear a Holter
monitor for 1 to 3 days, or to carry another type of monitor
with you for several weeks. The Holter monitor is a
portable ECG used to detect heart rhythm disturbances. If
your tachycardia seems related to exercise, you may need to
have an ECG while exercising on a treadmill.
How is it treated?
The treatment depends on which type of tachycardia you have.
Treatment may range from exercise conditioning to control of
anxiety symptoms. It may include medication.
Electrical shock may be necessary with atrial fibrillation,
and especially with ventricular tachycardia and ventricular
fibrillation. Implantable electroshock units are now being
used for some people with a high risk of having ventricular
fibrillation. In cases of life-threatening heart rhythm
problems, these units could provide instant, life-saving
electrical shock before medical help arrives.
What can I do to help prevent tachycardia?
The best prevention is to have a heart-healthy lifestyle:
- Maintain a healthy weight.
- Eat a healthy diet.
- Get regular exercise, as recommended by your health care
provider.
- Don't smoke.
- Seldom use other stimulants, for example, caffeine.
- Have regular medical checkups after age 40.
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