History of the pacemaker
In the 1950s, electrical engineer Wilson Greatbatch was working at Cornell University when he put the wrong resistor into a circuit he was developing for an oscillator, generating an electrical pulse.
By chance, some five years earlier, two surgeons visiting Cornell had happened to sit next to him at lunch. They had talked about a condition called ‘heart block.’
Greatbatch recognised the potential of his pulsing circuit to restore the natural rhythm of the beating heart and this insight gave rise to the first generation of implantable pacemakers.
His pacemaker was first implanted in humans in 1960 after extensive animal testing. The first 77-year-old patient lived for 18 months after this device was implanted.
The first pacemakers in the UK comprised an external battery compartment powering a magnetic coil taped over another coil under the skin. Electrodes branched from this to the outside of the heart. The patient controlled their heart rate manually and the device gave a reassuring ‘tick’ as it pulsed.
The Greatbatch pacemaker was an improvement on this with a mercury battery that lasted for two years and a smaller size that could be implanted under the skin – usually just below the shoulder-blade. These batteries drove a circuit embedded in epoxy resin to withstand implantation into the body. The output was taken by electrodes to the heart. In the 1970s Greatbatch acquired the rights to a newly developed lithium-iodine battery, which proved even more effective.
Improvements in battery technology and electronic sensor and circuit design have allowed pacemakers to become ever smaller and more responsive. Standard pacemaker batteries today might last eight or more years and their sensors respond to the physical demands being made on the body. The electrodes are fed through blood-vessels to the heart to make better connections with heart muscle.
Currently different models of tiny wire-free pacemakers are being trialled. These pill sized pacemakers take their power from an ultrasound beam. The ultrasonic signal comes from a pacemaker-like box implanted in the chest above the ribs. The box contains an array of ultrasonic transducers that steer and focus the beam towards the receiver. The receiver picks up the signal and converts it into an electrical signal that regulates the heart.
If all goes well, these could be the standard types used within a year or two.
Ultimately electro-mechanical devices might be replaced entirely by ‘heart-repair’ where cells are grown and placed in the heart, or cells within the heart are induced to repair the damage that has led to the ‘heart-block’ in the first place.
It is said that fortune favours the prepared mind. Now, thanks to Wilson Greatbatch’s prepared mind, hundreds of thousands of people receive and benefit from pacemakers every year.