Pacemakers
The cardiac pacemaker is used to treat
bradyarrhythmia (a heart rate that is too slow). This device monitors
the heart's rate (how fast it beats) and rhythm (the pattern in which it
beats), and provides electrical stimulation when the heart does not beat or
beats too slowly.
The pacemaker system consists of three components. Select a link below to jump
down the page:
Pulse Generator
The pulse generator is the brains of the cardiac pacemaker system. The generator
has two main parts: a hybrid circuit and a battery. The hybrid circuit, a
miniature computer, is so small that it is assembled unde a microscope. This
circuit contains all the components necessary to operate a state-of-the-art,
sophisticated device. It can take several months to build a hybrid, as it
undergoes numerous tests to ensure proper operation every time a component is
added or changed.
The batteries for pacemakers are designed to be small and flat to fit into the
pacemaker case. Since the mid-1970s pacemaker batteries have been made of
lithium iodine, which gives St. Jude Medical pacemakers maximum power and a
life span of up to 10 to 12 years.
The pulse generator case is made of titanium, a metal that is 10 times as strong
as steel, but much lighter. In the United States, the National Aeronautics and
Space Administration (NASA) uses titanium to make rockets and satellites. To
assemble the pulse generator, the hybrid and battery are placed in the titanium
case in a specially designed clean room that has no static or dust. Highly
qualified technicians adhere to strict procedures in these clean rooms,
including wearing gowns and special shoes. Because the electronic circuitry of
the pacemaker is exposed during this phase of assembly, there must be no static
electricity or dust in the room, both of which could compromise the integrity
of the hybrid.
Once the hybrid and the battery are in the casing, the casing is welded shut
with a high-powered laser beam. This laser beam gives the pulse generator a
hermetic seal, which means that the device is airtight and liquid-tight.
After the casing is welded, the pacemaker's epoxy plastic top, or header, is
attached. The header has ports, allowing the lead to be attached.
A typical pulse generator is small in size, often less than an ounce in weight,
less than two inches wide and a quarter-inch thin. This means that the device
is roughly the size of two silver dollars (United States currency) stacked on
top of one another. Once implanted in the upper chest, just below the skin near
the collarbone, the pacemaker's presence is nearly invisible to the eye.
Pacing Lead
The pacing lead, which connects to the pulse generator header, is a flexible
insulated wire with an electrode tip. This tip, inserted through a vein into
the heart, carries impulses from the pulse generator to the heart, stimulating
the heart to beat. It also carries information from the heart back to the pulse
generator, which the physician accesses via a special programmer.
Unique wire coils make up the inside of the lead. Some leads have more coils
than others, making them less flexible. There are a variety of reasons why
physicians request leads of different thicknesses and levels of flexibility.
Programmer
A special tabletop computer, a programmer, enables a physician to talk to the
pacemaker, even after it is implanted. The physician can evaluate the
pacemaker's performance and change settings noninvasively (without surgery). A
telemetry wand is placed on your chest over the implanted device, enabling the
pacemaker to communicate with the programmer and vice versa.
To facilitate programming, the programmer software provides high-speed
processing and easy operation. At the touch of a button, the unique Automated
Follow-Up feature delivers customized information on pacemaker function and
cardiac activity to help provide therapy specifically tailored to you.
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