The pacemaker is a medical device that uses carefully timed electrical impulses to regulate an irregular or slow heart rhythm. The invention of the fully functional, implantable pacemaker was a complicated, multi-decade process involving contributions from multiple scientists and engineers. Its history is defined by a steady evolution from bulky external machines to the miniature, life-saving devices used today.
The Foundational Science and Early Concepts
The foundational science for cardiac pacing began centuries before the first machine was built, rooted in the study of bioelectricity. In the late 18th century, Italian physician Luigi Galvani demonstrated that electrical currents could cause muscle contraction in animals, establishing the concept of “animal electricity” that is fundamental to cardiac electrophysiology. This early work confirmed that the heart’s rhythm was controlled by electrical signals, not just nerves. However, it took nearly 150 years for this understanding to be translated into a functional medical device.
The first external devices appeared in the late 1920s and early 1930s, proving the concept of artificial cardiac stimulation. In 1928, Australian anesthesiologist Mark Lidwell used an electrical device to successfully revive a stillborn infant. Working independently, American cardiologist Albert Hyman developed an electromechanical instrument powered by a hand-cranked motor. Hyman popularized the term “artificial pacemaker,” but the medical community largely dismissed the concept at the time.
The next significant advancement came in the 1950s with the development of larger, clinically effective external devices. In 1958, Engineer Earl Bakken, co-founder of Medtronic, created a transistorized, battery-powered external pacemaker. This was a vast improvement over earlier devices that required a connection to wall current. While these external models established the practicality of pacing, they were temporary solutions that carried a high risk of infection where the leads entered the skin.
The First Implantable Device
The quest for a fully implantable device was pursued simultaneously in Sweden and the United States. In 1958, Swedish physician-engineer Rune Elmqvist and surgeon Åke Senning achieved the world’s first implantation of a fully internal pacemaker in Stockholm. They implanted a device using a transistorized circuit and a rechargeable nickel-cadmium battery into patient Arne Larsson. The first device failed after only three hours, but a second implant lasted for several weeks, proving a self-contained system was possible.
The first commercially viable design came from American electrical engineer Wilson Greatbatch. In 1958, Greatbatch accidentally selected the wrong resistor while building a heart rhythm recorder, resulting in a circuit that perfectly mimicked a heartbeat: an electrical pulse followed by a one-second pause. He spent two years refining this transistorized pulse generator, which surgeon William Chardack successfully implanted in a dog. In 1960, the Greatbatch-Chardack device, using mercury-zinc batteries, was implanted in the first human patients in the U.S. and became the foundation for the modern pacemaker industry.
Engineering the Transition to Permanent Power
The initial limitation of implantable pacemakers was the power source, as early batteries required frequent replacement surgery. The rechargeable nickel-cadmium and mercury-zinc cells offered a lifespan ranging from a few hours to about two years. Mercury-zinc batteries were particularly problematic because they released hydrogen gas, which could cause the device casing to fail. This instability and short lifespan threatened the long-term practicality of the device.
Greatbatch, recognizing the engineering challenge, shifted his focus to battery technology in the early 1970s. He championed the adoption of the lithium-iodide cell, a technology adapted for medical use. This non-rechargeable solid-state battery revolutionized the field because it produced no gas, allowing the pacemaker to be hermetically sealed in a corrosion-free titanium case. The lithium-iodide battery extended the device life to approximately ten years, transforming the pacemaker from a temporary fix into a permanent solution.
Modern Pacemaker Technology and Applications
Modern pacemaker technology has evolved far beyond delivering a fixed-rate electrical pulse. Devices today are externally programmable and feature sophisticated algorithms for rate-responsive pacing. This means the heart rate adjusts automatically based on the patient’s physical activity and metabolic needs, often achieved using built-in sensors like accelerometers that detect body movement.
A significant contemporary advancement is the development of leadless pacemakers. These tiny, self-contained units are implanted directly into the heart’s right ventricle via a catheter, eliminating the need for transvenous leads, which were a main source of complications like infection and mechanical failure. Modern devices are also often MRI-conditional, allowing patients to undergo magnetic resonance imaging. Primary applications treat bradycardia and heart block, and many pacemakers now include dual-chamber pacing to synchronize the atria and ventricles, improving cardiac output.