On this page
Your heart has its own timer. When the electrical signal from that timer cannot reach the lower chambers, the heart can slow to a dangerous rate. Today a small device under the skin fixes that. Its inventor was an electrical engineer who first heard about the problem from visiting surgeons over lunch. Here is Wilson Greatbatch's story, the circuit idea behind the pacemaker, a worked energy calculation from his patent, and what you can learn from how he worked.
Who was Wilson Greatbatch?
The US National Inventors Hall of Fame records that Greatbatch was born in Buffalo, New York, on 6 September 1919 and died on 27 September 2011. He served in the US Navy during the Second World War, leaving as an aviation chief radioman in 1945. He then earned an electrical engineering degree from Cornell University in 1950 and a master's from the University at Buffalo in 1957. He held over 300 patents.
What problem did the pacemaker solve?
The heart's natural pacemaker is the sino-atrial node. The NCERT Class 11 Biology chapter on Body Fluids and Circulation explains that it generates 70 to 75 action potentials a minute, and that the heart beats about 72 times a minute on average.
Greatbatch's patent describes what goes wrong in heart block. The signal normally passes from the upper chambers to the ventricles after about a 0.1 second delay. If that path fails, the ventricles fall back to a much slower rhythm of their own. The patent notes that below 40 beats a minute patients usually suffer fainting spells, and below 30 brain damage or death may follow.
In his IEEE oral history, Greatbatch recalls first hearing about heart block from visiting surgeons around 1949 to 1951, while building instruments for animal research at Cornell. He saw it as a communication fault, which an engineer could fix. But external pacemakers of the time were large boxes plugged into the wall, and the vacuum tubes of the day could not be sewn inside a body.
How did a wrong resistor help?
The Lemelson-MIT Program describes the moment. Greatbatch was building an oscillator to record heart sounds and fitted a resistor with the wrong value. Instead of recording, the circuit gave out a steady train of electrical pulses, and he saw that such a circuit could drive a heart.
Transistors made it practical. In the oral history he explains that he built the first transistor pacemaker for an animal implant in 1958, then quit his jobs and made pacemakers in a barn behind his house. Working with surgeons William Chardack and Andrew Gage in Buffalo, the team's first successful human implant came in 1960. He filed his patent on 22 July 1960 and it was granted on 9 October 1962.
Worked example: how much energy does one beat take?
The patent says the circuit "generates a square pulse of approximately 10 volts amplitude and approximately one millisecond duration" and can deliver over three milliamperes. Take 3 mA as an estimate.
Power during the pulse. P = V × I = 10 × 0.003 = 0.03 W.
Energy per pulse. E = P × t = 0.03 × 0.001 = 3 × 10⁻⁵ J, or 30 μJ.
Pulses per day at 72 a minute. 72 × 60 × 24 = 103,680.
Energy per day. 103,680 × 3 × 10⁻⁵ = 3.11 J.
That is tiny, which is why a small battery could run the device for years. The oral history adds that battery life became the real limit, and Greatbatch later turned to lithium batteries in the 1970s.
What mistakes do students make with these problems?
Forgetting milli. 3 mA is 0.003 A and 1 ms is 0.001 s. Missing either changes the answer a thousandfold.
Using rate per minute as rate per second. Convert beats per minute before multiplying by time in seconds.
Confusing energy and power. Power is joules per second; energy is power multiplied by time.
Our post on RC circuits and charging explains why a resistor and capacitor set a time scale, and Willem Einthoven and the ECG shows how the heart's electrical signal was first recorded.
When an RC timing problem goes wrong and you cannot see where, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer.
What can a student learn from Greatbatch's way of working?
Notice what a mistake does. A wrong resistor is usually just an error. He asked what the new behaviour could be used for.
Wait for the right tool. He knew the problem years before transistors made a solution possible, and kept it in mind.
Go and find the expert. He talked to surgeon after surgeon until one, Chardack, took the idea seriously.
Find the real bottleneck. Once the circuit worked, the battery was the weak point, and he worked on that next.
Next step: redo the energy calculation for a heart paced at 60 beats a minute and compare the daily total with the 72-beat answer.
