A pacemaker is a medical device that substitutes for the heart’s natural electrical system. This small, battery-powered unit monitors the heartbeat and delivers precisely timed electrical impulses to the cardiac muscle when necessary. These impulses ensure the heart contracts at a regular, healthy rate, allowing it to pump blood effectively. By regulating an abnormally slow or irregular rhythm, the pacemaker has become a standard intervention in modern cardiology, dramatically improving the quality of life for millions of people worldwide.
The Problem and Early Resuscitation Attempts
The pacemaker was developed to treat life-threatening conditions like bradycardia (a slow heart rate) and heart block (interrupted electrical signals). Before a reliable electronic solution existed, patients experiencing prolonged cardiac standstill, known as Stokes-Adams attacks, often faced death. Early 20th-century medicine lacked a consistent method to sustain a failing heart’s rhythm.
The idea of using electrical current to stimulate a stopped heart dates back to the 18th century, but the first rudimentary pacing machines appeared much later. In 1928, Australian anesthesiologist Mark Lidwell successfully used intermittent electrical stimulation to revive a newborn baby whose heart had stopped. However, this device was bulky, ran on alternating current, and required a needle inserted directly into the heart muscle.
In the early 1930s, American physiologist Albert Hyman developed a hand-cranked, spring-wound device he termed the “artificial cardiac pacemaker.” Although portable and delivering impulses through a transthoracic needle, Hyman’s device was not widely adopted by the medical community. These pioneering efforts established the link between electricity and muscle contraction but failed to produce a practical, long-term solution for chronic heart rhythm problems.
The Development of the External Pacemaker
The critical breakthrough proving cardiac pacing was viable occurred in the mid-20th century. The first functional, external electronic pacemaker was designed and built in 1950 by Canadian electrical engineer John Hopps. Hopps was working with a surgical team investigating ways to stimulate the heart after it had been intentionally cooled during experimental open-heart surgery.
Hopps’s device was a large, vacuum-tube-operated unit that delivered impulses via a catheter electrode inserted through a vein. While successfully tested on animals, the initial design was crude and delivered painful shocks when applied externally. Furthermore, the device required AC power from a wall socket, presenting a significant risk of failure during a power outage.
In 1952, American cardiologist Paul Zoll ushered in the modern clinical era with his tabletop external pacemaker. Zoll’s device successfully treated patients suffering from heart block by stimulating the heart across the closed chest. His method utilized two large metal discs placed on the chest to deliver the current, requiring approximately 100 volts to capture the heart rhythm.
Zoll’s work demonstrated that external electrical stimulation could reliably control the heart rate in humans. However, the high voltage caused muscle twitching and skin burns, requiring patients to be sedated. While these mains-powered devices provided life-saving therapy in a hospital setting, they were impractical for a patient’s daily life, driving the need for a portable and eventually implantable device.
The Transition to Internal Devices
The limitations of bulky, AC-powered external units highlighted the need for a fully internal device that could operate independently. This challenge was first met in 1958 by a Swedish team: surgeon Åke Senning and engineer Rune Elmqvist. They developed a fully implantable pacemaker featuring a transistorized circuit powered by rechargeable nickel-cadmium batteries.
On October 8, 1958, Senning implanted this device into the first patient, Arne Larsson, in Stockholm. Although the first unit failed after only three hours, a second device was immediately implanted that lasted two days. Larsson lived for many more years, receiving 22 different pacemakers throughout his lifetime, proving the long-term viability of the implantable concept.
A parallel and significant development occurred when American engineer Wilson Greatbatch accidentally discovered the correct circuit for a small, battery-powered implantable device in 1958. Greatbatch was working on a heart rhythm recorder when he mistakenly used a resistor with the wrong value, causing the circuit to produce a perfectly timed electrical pulse. He quickly miniaturized this design.
Greatbatch’s first commercially viable implantable pacemaker, developed with surgeon William Chardack, was successfully implanted in 1960. This device utilized a zinc-mercury battery, which offered a longer lifespan of over two years compared to the rechargeable nickel-cadmium units. However, the need for frequent battery replacement surgeries remained a significant drawback.
The final piece for a truly long-lasting internal device was the introduction of the lithium-iodine battery in the early 1970s. This primary, non-rechargeable power source offered superior reliability and longevity, extending battery life to around 10 years. The shift to lithium technology, combined with miniaturization and improvements in lead design, transformed the pacemaker from a temporary life-support measure into the durable device used today.