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The
Early Years
The Move Toward Manufacturing
Early Pacemaker Research
The Hunter-Roth Electrode
Expanding Use of External
Pacemakers
Success With Implantable
Pacemakers
Early Pacemaker Research
Dr. C. Walton Lillehei with
a child who received one of the early Medtronic external
pacemakers.
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In the mid-1950s, Earl Bakken
became acquainted with Dr. C. Walton Lillehei, a pioneer in
open heart surgery at the University of Minnesota Medical
School. At that time, Dr. Lillehei and other surgeons discovered
that heart block occurred after corrective heart surgery in
about 10 percent of their cases. Silk sutures used in patching
the defect interfered with the heart's electrical impulses,
causing abnormally slow rates that were not sufficient to
carry a patient through recovery.
For some time - in fact, since
1803 - physicians knew that electricity was effective in stimulating
heart activity. However, the pacemakers built in the late
1950s were bulky, relied on external electrodes, and had to
be plugged into a wall outlet. External electric shocks were
frequently too traumatic for young heart block patients, and
the AC-operated pacemaker could fail during a power blackout.
Dr. Lillehei and his colleagues set out to develop a better
system, and Medtronic engineers became closely involved in
their work. By 1957, the research team discovered that by
combining a pulse generator with a wire electrode attached
directly to the hearts of dogs, heart rates could be controlled.
A pacemaker system was then applied successfully to heart
block patients, but physicians still needed to tackle the
problems of size and the inconvenient and unreliable power
source. When a power failure occurred in the Twin Cities and
resulted in the death of one of Dr. Lillehei's young patients,
the surgeon turned to Earl and Medtronic for a battery back-up
for the AC pacemakers.
Over the next few weeks, Earl developed a new kind of pacemaker
that was not much larger than a paperback book. He borrowed
parts from other electrical devices that he had in the shop.
For the new device's circuitry, he relied on a design for
a transistorized metronome he had seen in a trade publication.
When finished, he had produced a pacemaker that was powered
by mercury batteries, provided a 9-volt DC pulse, and could
easily and comfortably be "worn" by young patients.
The original Bakken pacemaker was tested in the University
of Minnesota's laboratory. The following day, it was applied
to a pediatric heart block patient. The effect was instantaneous.
The pacemaker immediately restored the child's heartbeat to
near normal. Within days, the child's heart resumed a normal
rhythm on its own, and the pacemaker was removed.
The development of the wearable, external, battery-powered
pacemaker amounted to a leap forward in the treatment of heart
block and other cardiac problems. It also signaled the beginning
of a new era in the therapeutic application of electrical
technology for patients around the world.
The Hunter-Roth Electrode
Warren Mauston, first recipient
of the Hunter-Roth electrode.
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The next step in the development
of pacing was to improve the electrode system. Surgeons found
that not only did the single wire electrode occasionally dislodge
from the heart or break but also that the heart's demand for
current increased over time.
The first major improvement in
pacing electrodes was developed by Dr. Samuel Hunter of St.
Joseph's Hospital research laboratory in St. Paul, Minnesota,
and Norman Roth, an electrical engineer at Medtronic. They
designed a plastic patch with two imbedded needle-like electrodes,
which was sutured to the heart and concentrated the electrical
field where it was needed.
The system required about 70 percent less current than the
previous pacemaker system. The "Hunter-Roth" electrode
was first used in 1958 in a patient who recovered and lived
an additional and active seven years.
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