In a workshop at the Chronic Disease Research Institute at the University of Buffalo, it was May 1958, and Wilson Greatbatch, a 39-year-old electrical engineer, was meticulously assembling an oscillator. This device was intended to drive a recording apparatus for cardiac sounds, capturing the rhythmic noises a heart makes as it contracts, for a research project on heart-rhythm disorders. The circuit he was constructing called for a 10-kilohm resistor, a seemingly innocuous component that would help generate a continuous oscillation. As Greatbatch reached into a drawer of resistors, he retrieved what he believed was the correct component and carefully soldered it into place. Upon powering up the circuit, however, the oscillator did not perform as expected. Instead of continuous oscillations, it emitted regular pulses. The resistor was not 10 kilohms but 1 megohm — 100 times the intended value. This mistake resulted in a circuit that produced brief electrical spikes, followed by pauses, at a rate of approximately one per second — a pace mirroring the pulse rate of a human heart. Greatbatch paused, recognising that this error had inadvertently demonstrated something profound: a miniature device that could potentially be used in cardiac care. Existing external pacemakers of the time were cumbersome, requiring mains electricity and invasive connections through the chest wall. This small, battery-powered pulse generator hinted at the possibility of an implantable device, challenging Greatbatch's previous assumptions about the limits of technology.

What had existed before

The notion of electrically stimulating the heart was not novel by the mid-20th century. As early as 1928, Australian physician Mark Lidwill had demonstrated electrical cardiac stimulation in animal experiments. By 1932, American physiologist Albert Hyman had developed a hand-cranked external pacemaker, although its practical use was limited. Progress continued in 1950 with Canadian engineer John Hopps, whose transistor-based external pacemaker was clinically tested by cardiac surgeon Wilfred Bigelow. Despite these advancements, the device's substantial size impeded its portability. In the United States, Paul Zoll's external pacemaker in 1952 set a standard for emergency cardiac stimulation but remained tethered to mains power and external electrodes. By 1957, C. Walton Lillehei and Earl Bakken of Medtronic had created a more portable transistor-based pacemaker, yet it still required external connections and carried the risk of infection. The fundamental challenge remained unsolved: creating an implantable pacemaker that was small, reliable, and safe. This required technological components that had only recently become available in the late 1950s, such as early commercial silicon transistors and miniature mercury batteries. Greatbatch's serendipitous circuit completed the picture, demonstrating a pulse-generating device small enough to fit within the body.

The development

Realising the potential of his accidental discovery, Greatbatch dedicated the following months to refining the design. He utilised miniature mercury-zinc batteries and sealed the components in epoxy resin, rendering them impervious to body fluids. This design ensured a stable pulse rate and sufficient electrical output to stimulate heart muscle contractions. By summer 1958, Greatbatch had produced a prototype the size of a button. He presented this innovation to William Chardack, a cardiac surgeon at the Buffalo Veterans Administration Hospital, who agreed to conduct tests. On 7 May 1958, Chardack implanted the device in a dog whose heart rhythm had been artificially disrupted. Remarkably, the dog's heart synchronised to the pacemaker's pulse, and the animal survived. Encouraged by this success, Chardack and Greatbatch conducted further tests on ten more dogs, all of which survived for varying durations, affirming the device's reliability and biocompatibility. The pivotal moment arrived on 6 April 1960, when the first human implantation took place. Henry Hannafin, a 77-year-old patient suffering from complete heart block, became the recipient. His heart rate stabilised from a perilously low 30 beats per minute to a healthy 60, and he lived an additional 18 months. Subsequent patients experienced even longer extensions of life, cementing the implantable pacemaker's place in medical history.

Scaling up

The success of the early pacemaker prototypes led Greatbatch and Chardack to license their design to Medtronic, a burgeoning medical-device company in Minnesota, which had been crafting external pacemakers since the early 1950s. Under Medtronic's stewardship, the design underwent significant improvements. Advances included more efficient batteries, such as lithium-iodide cells that extended lifespan to 10-15 years, and programmable pulse rates, allowing non-invasive adjustments to suit individual patient needs. Innovations like demand pacing, which activated only when the patient's intrinsic heart rhythm faltered, and dual-chamber pacing, which coordinated atrial and ventricular contractions, further refined the technology. By the mid-1970s, implantable pacemakers became the standard treatment for a variety of cardiac conditions. Their impact has been profound. By 2000, approximately 600,000 pacemakers were being implanted annually worldwide; this number doubled by 2020, with a cumulative total of about 30 million devices implanted. The medical community recognises that pacemakers have added approximately 50 million life-years between 1960 and 2020, transforming conditions like complete heart block and severe bradyarrhythmias from death sentences to manageable chronic issues.

Greatbatch's later career

Wilson Greatbatch's journey from a radio operator in the United States Army Air Forces during World War II to a pivotal figure in biomedical engineering is remarkable. After earning an engineering degree from Cornell University, he worked in various electronics roles before joining the research staff at the University of Buffalo in the mid-1950s. The pacemaker breakthrough marked the beginning of his lifelong commitment to biomedical innovation. In 1970, he founded Wilson Greatbatch Ltd., focusing on developing the lithium-iodide battery, which became the standard power source for pacemakers. His prolific career spanned over 350 patents and earned him numerous accolades, including the National Medal of Technology in 1990. Greatbatch's humility was as notable as his technical prowess. He consistently attributed the pacemaker's invention to a simple mistake in component selection, resisting the urge to embellish the discovery narrative. He passed away in 2011 at the age of 92. His autobiography, 'The Making of the Pacemaker: Celebrating a Lifesaving Invention', remains a testament to his modesty and ingenuity. The wrong resistor, a testament to the serendipitous nature of discovery, is now housed in the Smithsonian Institution.

The continuing development

The evolution of the implantable pacemaker has been relentless. Modern devices are miniaturised to the size of a fingertip and operate entirely wirelessly, eliminating the need for leads that once connected through the chest wall. The introduction of implantable cardioverter-defibrillators (ICDs) in the 1980s marked a significant advancement, providing both pacing and the ability to deliver corrective shocks for life-threatening arrhythmias. Cardiac resynchronisation therapy (CRT) devices have further enhanced treatment options by coordinating contractions in failing hearts. The availability of leadless pacemakers, introduced in 2016, represents a leap forward in device implantation, simplifying the procedure and reducing complications. These advancements extend to the sophistication of pulse-generation circuits, which now include rate-responsive pacing, adjusting pulse rates based on the patient’s activity level. Remote monitoring capabilities allow clinicians to receive device data in real-time over home wifi networks, enabling proactive patient management. The horizon of cardiac care is bright with the ongoing development of biological pacemakers, which aim to restore natural cardiac rhythm through gene therapy. Although these remain experimental as of 2026, the potential to replace electronic devices with biological solutions represents a significant future shift. However, the tried and tested electronic pacemaker continues to underpin cardiac treatment and is unlikely to be supplanted in the near term.

As we reflect on the wrong drawer incident, it's astonishing to consider that approximately 1.2 million individuals receive a pacemaker each year. Each of these devices, a small titanium-cased pulse generator, contains a battery designed to last over a decade, mirroring the function Greatbatch accidentally achieved in 1958. Whether through traditional leads or in newer leadless designs, each pacemaker performs the same fundamental task: delivering a steady electrical pulse to maintain a heart's rhythm. The original device Greatbatch built was no larger than a button; today's versions are even more compact, reliable, and sophisticated, yet they operate on the same basic principle. The fortuitous error of reaching for the wrong resistor redirected Greatbatch's career trajectory, culminating in one of the most successful medical-device innovations of the 20th century. The wrong resistor, a humble component, resides in the Smithsonian, symbolising the power of serendipity in scientific progress. Meanwhile, the right resistor, which never created an oscillator, remains a footnote in history. Over 30 million people, whose lives have been touched by this technology, owe their heart's continued operation to a simple mistake.