What Is a Pacemaker?
A pacemaker is a small device that's placed under
the skin of your chest or abdomen to help control abnormal heart rhythms. This
device uses electrical pulses to prompt the heart to beat at a normal rate.
Pacemakers are used to treat heart rhythms that are
too slow, fast, or irregular. These abnormal heart rhythms are called
arrhythmias
(ah-RITH-me-ahs). Pacemakers can relieve some symptoms related to arrhythmias,
such as fatigue (tiredness) and fainting. A pacemaker can help a person who has
an abnormal heart rhythm resume a more active lifestyle.
The Heart's Electrical System
Your heart has its own internal electrical system
that controls the speed and rhythm of your heartbeat. With each heartbeat, an
electrical signal spreads from the top of the heart to the bottom. As it
travels, the electrical signal causes the heart to contract in an organized
manner and pump blood.
Electrical signals normally begin in a group of
cells called the sinus node. As these signals spread from the top to the bottom
of the heart, they coordinate the timing of heart cell activity. First, the two
upper chambers of the heart, called atria (AY-tree-uh), contract. This
contraction squeezes blood into the lower chambers of the heart, which are
called ventricles (VEN-trih-kuls). The ventricles then contract and send blood
to the rest of the body. The combined contraction of the atria and ventricles
is a heartbeat.
For more information about the heart's electrical
system and how a healthy heart works, see the Diseases and Conditions Index
article on
How
the Heart Works.
Overview
Faulty electrical signaling in the heart causes
arrhythmias. A pacemaker uses low-energy electrical pulses to correct faulty
electrical signaling. Pacemakers can:
- Speed up a slow heartbeat
- Help end an abnormal and fast rhythm (only in
implantable cardioverter defibrillator/pacemaker combination devices)
- Make sure the ventricles contract normally if the
atria are quivering instead of beating in a normal rhythm (a condition called
atrial fibrillation)
- Coordinate the electrical signaling between the
upper and lower chambers of the heart
- Coordinate the electrical signaling between the
ventricles (cardiac resynchronization therapy used in
heart
failure)
Pacemakers also can monitor and record your heart's
electrical activity and the rhythm of your heartbeat. Newer pacemakers can
monitor your blood temperature, breathing rate, and other factors and adjust
your heart rate to changes in your activity.
Pacemakers can be temporary or permanent. Temporary
pacemakers are used to treat temporary heartbeat problems, such as a slow
heartbeat due to
heart
attack, heart surgery, or an overdose of medicine. Temporary pacemakers are
used in emergencies until a permanent pacemaker can be implanted or until the
temporary condition goes away. A person with a temporary pacemaker will stay in
the hospital as long as the pacemaker is in place.
In this article, "pacemakers" refers to permanent
devices, unless stated otherwise.
Doctors also treat arrhythmias with another device
called an implantable cardioverter defibrillator (ICD). An ICD is like a
pacemaker in some ways, but it can use higher energy electrical pulses to treat
certain dangerous types of arrhythmia. For more information on ICDs, see the
Diseases and Conditions Index article on
Implantable
Cardioverter Defibrillator.
May 2008
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