Cardiac Pacemaker | The Canadian Encyclopedia


Cardiac Pacemaker

In 1950, one of Canada’s greatest medical innovations was developed at the University of Toronto’s Banting Institute. Cardiac surgeon, Dr. Wilfred Bigelow and research fellow, Dr. John Carter Callaghan were trying to understand how hypothermia (see Cold-Weather Injuries) could slow the beating of an animal’s heart before surgery. They were also looking for a way to stimulate the heart when it faltered as it cooled. This largely unknown area of research could have tremendous applications for humans. The doctors partnered with Dr. John A. Hopps from the National Research Council of Canada, who created a portable artificial external pacemaker. It was designed to send electric pulses to the heart, which caused the heart to contract and pump blood to the body. The device was successfully tested on a dog in 1950. This landmark discovery paved the way for the use of implantable pacemakers in humans.

Image of an experimental external cardiac pacemaker-defibrillator

Early research

Electrical pacing of the heart — the stimulation of the heart through electric currents — was studied for many years before the cardiac pacemaker was invented. In 1880, German physician Hugo von Ziemssen received a patient, Catharina Serafin, who had undergone surgery to remove an enchondroma, a noncancerous bone tumour, which left her heart exposed through a delicate layer of skin. During a time when cardiac research was gathering momentum, von Ziemssen used this opportunity to experiment. He delivered an electric current to the heart, revealed by an electrocardiogram, a test that measures the electrical activity of the heart. In 1928, Mark Lidwell, an anaesthetist from Sydney, Australia, saved the life of a baby by stimulating the heart sporadically with an electric current. The event was reported to the 3rd Congress of the Australasian Medical Society. Another exciting development occurred in 1932 when New York cardiologist, Albert S. Hyman documented the use of a hand-operated artificial pacemaker that could revive a stopped heart by delivering an electric current through a needle inserted into the right atrium.

Wilfred Bigelow

Portrait of Dr. Wilfred Gordon Bigelow

Cardiac pacing continued to be explored through the 1940s. The next major achievement came about unexpectedly when one Toronto doctor pursued his interest in hypothermia (see Cold-Weather Injuries). Dr. Wilfred Bigelow, the son of a rural Manitoba doctor, was a resident surgeon at Toronto General Hospital in 1941 when he had to amputate a patient’s fingers that had turned gangrenous from frostbite. Bigelow wondered about the possibility of avoiding gangrene, and amputation, by allowing blood to keep circulating. As an army surgeon in England during the Second World War, Bigelow’s curiosity and frustration grew when observing that limbs were amputated when the primary artery had been cut, even though the limb itself was in good condition. He wondered if lowering temperature temporarily could save a limb until surgery could be performed.

After the war, Bigelow served as a surgical fellow at Johns Hopkins in Baltimore. Bigelow observed that infant heart surgery was limited by the inability to cease the fast circulation of blood in the heart. One night in the late-1940s, he awoke from sleep with an idea: “Cool the whole body, reduce the oxygen requirements, interrupt the circulation, and open the heart.”

John C. Callaghan

Portrait of Dr. John Carter Callaghan

Bigelow returned to Toronto and began working in the cardiovascular surgical experimental laboratory at the Banting Institute, known as Room 64. Among the scientists was Dr. John Carter Callaghan. Born in Hamilton, Ontario, Callaghan graduated from the University of Toronto and had recently worked as a government medical officer in Aklavik, Northwest Territories.

Bigelow and Callaghan were trying to determine why an animal’s heart sometimes stopped when it was being cooled. During one experiment in 1949, an anaesthetized dog’s heart stopped unexpectedly at 21°C when it was cooled to prepare for surgery. Bigelow nudged the left ventricle of the dog’s heart, which jump-started contractions. For Bigelow, this confirmed that the heart could beat on its own and indicated “that these were real contractions, that the heart was not only beating but forcibly expelling blood in a normal manner.” Bigelow wondered if a pacemaker could replicate the beating heart. To further their research, Callaghan and Bigelow sought assistance from the National Research Council of Canada (NRC), based in Ottawa.

John A. Hopps

Portrait of Dr. John A. Hopps

The NRC recommended John A. (Jack) Hopps for the project. At the time, Hopps was studying the utilization of radio frequency rewarming to pasteurize beer. In Room 64, Hopps worked with Callaghan to determine the most effective method of delivering an electrical stimulus to the heart of a dog.

Hopps returned to the NRC and designed a portable pacemaker. The device had a catheter electrode that could be put in through a dog’s exterior jugular neck vein, and then into the right heart. In 1950, at the Toronto General Hospital, Bigelow and Callaghan performed the landmark experiment using Hopps’ pacemaker. When a dog’s heart stopped at 20 degrees during the cooling process, Hopps’ pacemaker took over and replicated the normal beating of the heart. In his book, Cold Hearts: The Story of Hypothermia and the Pacemaker in Heart Surgery (1984), Bigelow described the device as “the first pacemaker for continuous human use with a controlled physiological electrical stimulus.”


On 23 October 1950, Bigelow and Callaghan described their findings to the American College of Surgeons in Boston. The next day, the Sun newspaper in Baltimore reported, “Electric Machine Successfully Used On Dogs To Get Heart Beating Again.” The team at the Banting Institute had made a discovery that laid the groundwork for the use of implantable cardiac pacemakers in humans. This breakthrough also redefined the significance of using electronic devices in the medical field. This trailblazing work would lead to saving lives around the world, and it happened in Toronto.

Despite attempts by Dr. Hopps to receive a patent from the NRC, his application was turned down. Around the same time, the Toronto team suspected that many aspects of Dr. Hopps’ design were reused by American cardiologist Dr. Paul Zoll, who was credited for the design of an external pacemaker, described in 1952.

The codevelopers of the cardiac pacemaker went on to have outstanding careers and all were made Officers of the Order of Canada. Dr. Bigelow initiated the opening of the Toronto General Hospital Cardiovascular Investigation Unit, known colloquially as Bigelow’s Bungalow. Bigelow was also a pioneer in the development of open- and closed-heart surgeries. Dr. Callaghan performed the first successful open-heart surgery in Canada. Dr. Hopps continued to work on the pacemaker design and in 1951, along with Dr. Bigelow, he released the Model 3 Stimulator-Defibrillator pacemaker, which was used in a clinical setting on humans in 1951. Hopps, later known as the Father of Biomedical Engineering in Canada, founded the Canadian Medical and Biological Engineering Society in 1965.

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