Cardiac pacemakers are a useful treatment for certain
heart diseases. The most frequent are an abnormally slow pulse rate
(bradycardia) associated with symptoms such as dizziness,
fainting (syncope), or heart failure. These may arise from
a problem with the SA node (sick sinus syndrome) or with
the conduction system (heart block). One of the first uses
of pacemakers was to treat complete or third degree heart block. The SA node and the atria fire at a normal rate but the
wave front cannot pass through the conduction system. The
AV node or some other part of the conduction system then
begins firing and driving the ventricles at its own, pathologically
slower rate…. A pacemaker stimulating the ventricles can be used to restore a
normal ventricular rate.
The myocardial pacing wire was the first electrical device ever to be implanted
in the human body and left there for a period of time. Surgeons at
Minnesota were now able to pace children for days or weeks after heart
surgery. By October 1957, they had used the technique with 18 patients.
But Lillehei now grew uneasy about the Grass stimulator because it was
bulky and plugged into the electrical system. The surgeon wanted to get his
heart patients out of bed and moving around, but the stimulator had to
accompany them on a wheeled cart. The electrical cord was a further nuisance.
‘‘Many of these [patients] were kids. They wanted to wander around
and get active. Well, they were active. They couldn’t go any further than the
cord. We had to string wires down the hall. . . . And then, if they needed an
X ray or something that couldn’t be done in the room, you couldn’t get on
the elevator so you had to string them down the stairwells. It seemed that
almost everything you wanted was on a different floor. We needed something
battery-operated.’’
From Machines In Our Hearts.
The plug-in stimulator was more than an inconvenience, for by introducing
the myocardial pacing wire, Lillehei and his associates had connected
the hearts of their surgical patients to the 110-volt electrical system
of the hospital. Everyone in the program knew that an electrical surge
might send patients into ventricular fibrillation or that a power outage
could leave them without pacemaker support. On October 31, 1957, an
equipment failure at a large Twin Cities power plant caused an outage
lasting nearly three hours in Minneapolis. The University hospital had
auxiliary power in its surgical suites and recovery area, but not in patients’
rooms. None of his heart patients died—but Lillehei viewed the event as a
warning. Lillehei…turned to Earl Bakken…a young engineer who owned a small medical electronics business
called Medtronic and repaired and serviced equipment for the Department
of Surgery.
Bakken…realized that he could simply build a stimulator that used
transistors and small batteries. ‘‘It was kind of an interesting point in history,’’
he recalled—‘‘a joining of several technologies.’’ In constructing the
external pulse generator, Bakken borrowed a circuit design for a metronome
that he had noticed a few months earlier in an electronics magazine
for hobbyists. It included two transistors. Invented a decade earlier, the
transistor was just beginning to spread into general use in the mid-1950s.
Hardly anyone had explored its applications in medical devices. Bakken
used a nine-volt battery, housed the assemblage in an aluminum circuit box,
and provided an on-off switch and control knobs for stimulus rate and
amplitude.
At the electronics repair shop that he had founded with his brother-in-law
in 1949, Bakken had customized many instruments for researchers at
the University of Minnesota Medical School…When Bakken delivered the
battery-powered external pulse generator to Walt Lillehei in January 1958,
it seemed to the inventor another special order, nothing more. The pulse
generator was hardly an aesthetic triumph, but it was small enough to hold
in the hand and severed all connection between the patient’s heart and the
hospital power system. Bakken’s business had no animal-testing facility, so
he assumed that the surgeons would test the device by pacing laboratory
dogs. They did ‘‘a few dogs,’’ then Lillehei put the pacemaker into clinical
use. When Bakken next visited the university, he was surprised to find that
his crude prototype was managing the heartbeat of a child recovering from
open-heart surgery.
The Bakken Museum. From wikipedia.
Russ Hobbie is retired from the University of Minnesota, and still lives in the area, so he is particularly familiar with Earl Bakken. He served on the board of the Bakken Museum, which is devoted to bioelectricity (my kind of museum). Russ say he ‘‘was impressed by Bakken's vision, energy, and desire to help people. The Bakken Museum has an extensive outreach program which does a lot of good things.’’ They recently posted a statement honoring their founder.
Medtronic is one of the largest medical device companies. I had a job interview there years ago, but I didn’t get the position. I came away impressed by the company, and wish I had bought stock.
Bakken is a member of the dwindling greatest generation; he was an airborne radar maintenance instructor during World War II. He had a long, full life, and we will miss him.
Below are a couple of videos about Earl Bakken. Enjoy!
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