Why the title needs a note
An implanted defibrillator is covered elsewhere on this site in the story of the cardioverter-defibrillator. This article looks at what came before: the long development of external defibrillation, because the implanted devices were only possible once doctors knew how to stop a fibrillating heart with an electric shock and had learned when and how much energy to use.
Early observations
Scientists noticed in the nineteenth century that electricity could disturb the heart, a line of study that began with Galvani’s frog experiments and gained a steady source of current with the voltaic pile. In 1899, the Swiss physiologists Jean-Louis Prevost and Frédéric Batelli reported that a strong electric shock could stop fibrillation in the hearts of dogs, and that a second shock could sometimes restore a normal rhythm. Their work was a laboratory finding and had no immediate effect on medicine. Fibrillation was, in practice, an untreatable condition.
In the 1930s, researchers in the United States, including William Kouwenhoven at Johns Hopkins, studied electric injuries and the heart. Kouwenhoven’s group built a defibrillator for animal experiments, and their work, along with the experience of electrical utilities studying accidental shocks, strengthened the idea that defibrillation could be controlled.
The first human defibrillation
The first well-known human defibrillation was carried out in 1947 by the Cleveland surgeon Claude Beck. During an operation on a teenage boy, the heart went into fibrillation. Beck’s team applied shocks directly to the exposed heart using paddles, and the heart recovered its rhythm. This is generally reported as the first successful case of human defibrillation, although earlier attempts are sometimes mentioned. It showed the technique was possible, but it required an open chest, so its use was limited to the operating room.
Shocking through the chest
The next step was a closed-chest approach. In the early 1950s Paul Zoll in Boston used external electrical devices for heart rhythm problems, and in 1956 he is credited with defeating ventricular fibrillation using an alternating current shock delivered through the intact chest wall. Alternating current from the mains was effective but crude. It could cause burns and some risk of damage to the heart.
A safer approach was developed in the early 1960s by Bernard Lown and colleagues at Harvard, who worked with the engineer Barouh Berkovits. They moved to a direct current pulse, released from a charged capacitor, which was generally more reliable and caused less damage. Lown also studied timing the shock to the heartbeat for non-fibrillating fast rhythms, a process now called cardioversion. This synchronized approach is the origin of the term used in later devices.
Taking defibrillators out of the operating room
Early machines were large, heavy and tied to electrical sockets. Cardiac arrest, however, often happens outside the hospital. In the 1960s, Frank Pantridge in Belfast became known for building portable defibrillators powered by batteries and installing them in ambulances. His mobile coronary care unit is often described as a pioneer of the modern practice of treating cardiac emergencies at the scene. The same period saw hospitals set up coronary care units where monitoring and defibrillation were available around the clock, following the spread of the ECG machine as a standard monitor.
Advances in electronics, including transistors and later integrated circuits, shrank the equipment steadily. Automated external defibrillators appeared in the 1970s and 1980s with software that analyzed the rhythm and advised or delivered a shock, and public access programs in airports and other places followed later. Those devices are designed for use by people with little training, though their effects depend on prompt use and good emergency care.
What the external era taught
Several lessons from this period shaped the implanted devices that followed.
- Rhythm detection matters: A shock is only helpful if given for the right rhythm, which led to algorithms for recognizing fibrillation.
- Energy and waveform matter: Too little energy fails and too much can injure. Later designs moved to biphasic shocks, which can work at lower energy.
- Time matters: The chance of recovery falls with every minute, which is what justified the idea of a device that is always present.
These points explain why researchers began to ask whether a patient at high risk could carry the machine inside the body. Resistance came from the view that such a device would be impractical and would shock inappropriately, but the external experience supplied the evidence that shocks could work.
Caution on claims
Dates and credit for firsts in defibrillation are sometimes given differently in different sources, and several people contributed at overlapping times. This article is history only and is not guidance on emergency care. In an emergency, people should contact local emergency services.