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Electrodyne PM-65 Pacemaker
Paul Zoll et al, c. 1955
The accompanying photo from 1958 shows a patient walking for exercise, pushing a hospital cart with a PM-65 pacemaker on top. (The patient was using the first catheter electrode.) The pacemaker was line-powered and heavy. A cart was needed, and it could only go as far as the extension cord would allow. This was acceptable as long as the pacemaker was considered emergency apparatus for post-surgical care. But the patient in this picture needed pacing for months, and whenever doctors tried to wean him off the machine, his heartbeat dropped dramatically. Likewise, Dr. C. Walton Lillehei was using the PM-65 to maintain heart action in young children he'd operated on for "blue baby" heart defects. Sometimes their heart would not beat normally after surgery, and the pacemaker would be used to keep it beating while it healed. But the children started feeling good long before their heart was ready to beat on its own - with their heart repaired, they had more energy than they'd ever had in their young lives, and they wanted to get up and about. Being tethered to a massive PM-65 kept them alive, but made them unhappy. Because of a power failure, Dr. Lillehei asked Earl Bakken to "make something that runs on batteries". Bakken's pacemaker was not only battery-powered, but dramatically smaller and lighter than anything else on the market. It still was external, but people could have a life while wearing it. We have both a functional PM-65 and Bakken's first pacemaker on display; the PM-65's provenance is unknown beyond the local Ax Man Surplus store. |
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The
PM-65 was designed by Paul Zoll et al so that it could both
monitor and pace the heartbeat. On top, it had an electrocardiograph;
below was an electrical pulse generator. The pulses could be powerful
enough to pace the heart from external electrodes, but this was very
uncomfortable for any length of time. Normally electrodes were led
directly to the heart, and a smaller pulse was used.