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The pacemaker’s journey begins in 1932 with American physiologist Albert Hyman. Hyman dubbed his invention the “artificial pacemaker,” a moniker that has stuck with the device to this very day. The behemoth was operated by a hand crank and a spring motor, which turned a DC current generator. The electrical impulses generated were controlled by an interrupter disc, and electrode-laden, insulated needles inserted into the right atrium stimulated the heart.

Not hard to see why the public didn't embrace Hyman's invention - perhaps it was a little too "Frankenstein" to digest.

Hyman only tested his pacemaker on animals, and he never published the results of any tests on humans. Unfortunately, the device wasn’t publically or medically accepted at the time. Back then artificial heart stimulation was pretty controversial, as many people likened it to reviving the dead. (I would hazard a guess that the initial distaste for the device had something to do with the immense amount of casualties in World War 1 being in recent memory.)

The pacemaker didn’t became portable enough to be considered wearable until 1958, designed by engineer and Medtronic founder Earl Bakken. About the size of a few decks of cards, Bakken’s battery-powered and transistorized pacemaker (notably, the first one that didn’t require plugging into the wall!) was housed in a small plastic box and included controls to adjust pacing heart rate and output voltage. It was connected to electrode leads that passed through the skin, culminating in electrodes connected to the myocardial surface of the heart.

Now we're getting somewhere - at least you could carry this one around. (Credit: University of Minnesota - Lillehei Heart Institute)

The first fully implantable pacemaker followed not far after that in 1958, developed by Karolinska Institute’s Rune Elmqvist and Åke Senning. It was 52.5mm in diameter, 17.5mm thick and weighed 64.3 grams. Implanted by thoracotomy, a quite painful chest surgery, this pacemaker only functioned for about three hours after implantation - and a second version lasted only about two days. Both were powered by nickel-cadmium batteries, rechargeable outside of the body.

Greatbatch with his pacemaker. Why can't my mistakes be this innovative? (Credit: AP Photo)

What followed in 1960 is possibly one of the happiest accidents in medtech history. While attempting to build an oscillator, Wilson Greatbatch discovered that he had used the wrong transistor – but the resulting “mistake” produced a pacemaker with the longest battery life yet, using a mercury battery as the energy source. His design (Greatbatch's pacemaker was about the size of a large coin at this point) led to Medtronic’s manufacture and continued development of pacemakers. But Greatbatch didn’t stop there – his frustration with the limitations of battery technology prompted him to develop the lithium-iodide battery in 1972. With enormous energy potential at a low weight, low amperage, and the capability of hermetically sealing the circuit, this battery was an ideal pacemaker power source.

Continued improvements in battery technology, sensor, and circuit design have led pacemakers to become smaller and more responsive. Pacemaker batteries today last about eight years, their sensors respond to physical demands on the body, and the electrodes are fed through blood vessels to the heart. Most recently, pacemakers are being developed with wireless connectivity capabilities, and Medtronic’s most recent design (which received the CE mark yesterday!) is only about the size of a large vitamin, with a ten year battery life.

Here’s to hoping that design engineers continue to put their hearts into designing smaller and more efficient pacemakers! Hopefully one day (though it may seem like a stretch) they’ll be tiny enough to be injectable, and have a battery that lasts a lifetime!

What would you like to see covered in my next MedTech Memoir? Contact me at sam.brusco@advantagemedia.com with your ideas!

 

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