How Does a Pacemaker Work?
A pacemaker consists of a battery, a computerized
generator, and wires with electrodes on one end. The battery powers the
generator, and a thin metal box surrounds both it and the generator. The wires
connect the generator to the heart.
The pacemaker's generator sends the electrical
pulses that correct or set your heart rhythm. A computer chip figures out what
types of electrical pulses to send to the heart and when those pulses are
needed. To do this, the computer chip uses the information it receives from the
wires connected to the heart. It also may use information from sensors in the
wires that detect your movement, blood temperature, breathing, or other factors
that indicate your level of physical activity. That way, it can make your heart
beat faster when you exercise.
The computer chip also records your heart's
electrical activity and heart rhythms. Your doctor will use these recordings to
set your pacemaker so it works better at making sure you have a normal heart
rhythm. Your doctor can program the computer in the pacemaker without having to
use needles or directly contacting the pacemaker.
The wires in your pacemaker send electrical pulses
to and from your heart and the generator. Pacemakers have one to three wires
that are each placed in different chambers of the heart.
- The wires in a single-chamber pacemaker usually
carry pulses between the right ventricle (the lower right chamber of your
heart) and the generator.
- The wires in a dual-chamber pacemaker carry
pulses between the right atrium and the right ventricle and the generator. The
pulses help coordinate the timing of these two chambers' contractions.
- The wires in a triple-chamber pacemaker are used
for heart muscle weakness and carry pulses between an atrium and both
ventricles and the generator. The pulses help coordinate the timing of the two
ventricles with each other.
Cross-Section of the Chest With a
Pacemaker
The illustration shows a
cross-section of the chest with a pacemaker. Figure A shows the location and
general size of a double chamber, or double lead, pacemaker in the upper chest.
The wires with electrodes are inserted into the right atrium and ventricle of
the heart through a vein in the upper chest. Figure B shows the electrode
electrically stimulating the heart muscle. Figure C shows the location and
general size of a single chamber, or single lead, pacemaker in the upper chest.
The wire with the electrode is inserted into the right ventricle of the heart
through a vein in the upper chest.
Types of Pacemaker Programming
There are two main types of programming for
pacemakersdemand pacing and rate-responsive pacing.
A demand pacemaker monitors your heart rhythm. It
only electrically stimulates your heart if its beating too slow or if it
misses a beat.
A rate-responsive pacemaker will speed up or slow
down your heart rate depending on how active you are. To do this, the
rate-responsive pacemaker monitors your sinus node rate, breathing, blood
temperature, or other factors to determine your activity level. Most people who
need a pacemaker to continually set the pace of their heartbeat have
rate-responsive pacemakers. |