External pacemaker

The external pacemaker emerged in 1950 Toronto from an unlikely collaboration between a surgeon, a trainee, and an electrical engineer solving a problem nobody had set out to address. Wilfred Bigelow at the University of Toronto was developing hypothermia for cardiac surgery—cooling patients to reduce metabolism during heart operations. But at 21°C, hearts stopped, and rewarming wasn't fast enough to restart them.

Bigelow and his trainee John Callaghan began experimenting with electrical stimulation to restart cooled hearts. They needed an engineer who could build the stimulating equipment, and the National Research Council of Canada assigned John Hopps to the project. Working in Room 64 of the Banting Institute, Hopps and Callaghan tested different methods of delivering electrical pulses to dog hearts.

The resulting device was roughly 30 centimeters long—large, clunky, but functional. It used a catheter electrode that could be inserted through the jugular vein into the right side of the heart. In 1950, they tested it on a dog whose heart had stopped during cooling. The pacemaker took over, replicating normal heartbeat until the animal could be rewarmed.

The invention's significance extended far beyond hypothermia surgery. Paul Zoll in Boston read the Toronto team's work and developed an external pacemaker that could be applied through the chest wall, demonstrating its use for heart block in 1952. The technology proved that electrical pacing could maintain life when the heart's natural pacemaker failed.

The path from Hopps' external device to modern pacemakers required two more decades of miniaturization. Transistors replaced vacuum tubes. Batteries became smaller and longer-lasting. By the 1960s, pacemakers could be implanted entirely within the body. In a remarkable twist, Hopps himself received an implanted pacemaker in 1984—saved by a descendant of the device he had created.

Hopps, later known as the Father of Biomedical Engineering in Canada, founded the Canadian Medical and Biological Engineering Society in 1965. His serendipitous solution to a hypothermia problem had opened an entire field of cardiac rhythm management.