A series about people, products and discoveries that changed the world.
The most futuristic of the pacemakers that Vancouver cardiologist Matthew Bennett tucks into the lower chambers of his patients’ hearts are about the size of a bullet.
The capsule-like innovations are called leadless pacemakers because they don’t have the insulated wires or “leads” that connect a traditional pacemaker’s implanted pulse generator to a faulty heart.
Heart-rhythm specialists such as Dr. Bennett insert these modern pacemakers through the leg, thread them up through the body and into the right ventricle, where the devices provide computer-guided electrical pulses that keep the heart ticking in time.
“That’s been the biggest recent advance,” said Dr. Bennett, a clinical assistant professor at the University of British Columbia’s medical school who inserts pacemakers at Vancouver General Hospital. “It’s all within the heart.”
The modern pacemakers that Dr. Bennett and his cardiologist colleagues implant today all have their roots in a Canadian invention that bears little resemblance to a bullet, but that nonetheless acted as a starting gun on decades of development in cardiac pacing.
The world’s first artificial pacemaker, about the size and shape of a four-slice toaster, was built by a Winnipeg-born engineer named John “Jack” Hopps whose work using radiofrequency to heat food brought him to the attention of a pair of surgeons at the University of Toronto.
It was the late 1940s, and Wilfred Bigelow and his young research fellow, John Callaghan, were studying how hypothermia might make open-heart surgery possible.
The doctors were searching for a way to keep blood from circulating through the heart while they operated on the organ. There existed a crude early version of the heart-lung machine that cardiac surgeons rely on today, but Dr. Bigelow considered it too cumbersome and experimental.
Hypothermia, he believed, was a tantalizing alternative.
By anesthetizing mongrel dogs and wrapping them in ice-filled blankets, Dr. Bigelow found that blood flow would stop when the dogs’ body temperatures plunged below a certain level. Encouraged by that discovery, Dr. Bigelow and his colleagues at Toronto General Hospital’s Banting Institute turned their to attention to “the problem of rewarming.”
“We were in need of help from electrical engineering to test the possibility of rapidly rewarming animals, and later patients, with a high frequency diathermy machine,” Dr. Bigelow later wrote in his book, Cold Hearts: The Story of Hypothermia and the Pacemaker in Heart Surgery. “It would be more practical and esthetically more acceptable than plunging them in warm water after surgery.”
Dr. Bigelow and Dr. Callaghan asked for help from the National Research Council (NRC) in Ottawa, the research hub where Mr. Hopps had experimented with radiofrequency rewarming to pasteurize beer.
Mr. Hopps, who joined the NRC in 1941 as a 22-year-old fresh out of university, was part of a cadre of promising technologists who flocked to the NRC during the Second World War, when Canada and its allies and enemies were competing to master radar technology.
“After the war,” Dick Bourgeois-Doyle, the secretary-general of the NRC, said, “the insights into radar led people to do research into things like radiofrequency and heating, work we would associate with microwaves now.”
The NRC seconded Mr. Hopps to the U of T, “but it wasn’t to do a heart defibrillator or a pacemaker by any means,” said Steven Leclair, the archives officer for the NRC. “That was actually a byproduct of his work.”
Travelling back and forth between Ottawa and Toronto, Mr. Hopps worked away on the rewarming dilemma. Dr. Bigelow, meanwhile, stumbled on another problem that he thought the “brilliant” electrical engineer might be able to crack.
One day in 1949, as Dr. Bigelow experimented on a hypothermic dog in Room 64 in the basement of the Banting Institute, the canine’s exposed heart stopped unexpectedly.
Desperate to revive the animal, Dr. Bigelow “gave the left ventricle a good poke,” with his forceps. The dog’s heart squeezed a beat, then halted again. “I poked it regularly every second,” Dr. Bigelow later wrote. “It resembled a normal beating heart.”
The successful resuscitation of the lab mongrel gave Dr. Bigelow an idea: Perhaps an electrical pulse, such as a poke from his forceps, could jump-start the heart and keep it beating during surgery? He asked Mr. Hopps to create a machine that would make it possible.
Mr. Hopps returned to the NRC engineering lab, where he built the prototype of an external pacemaker stimulator.
Mr. Hopps’s original device resembles an old-time mantel radio. There are two large dials on the front – one labelled “heart rate,” the other labelled “volts.” There is a smaller, “voltage multiplier” between the two, and a foot-pedal to control some of the electrical-pulse delivery. The machine plugged into a wall outlet.
Mr. Hopps designed a catheter with a bipolar electrode on the end that could be applied directly to the organ during open-heart surgery, or intravenously when the chest was closed.
In experiments on dogs and rhesus monkeys, the machine worked – both as a defibrillator that could shock the heart back into a regular rhythm, and as a pacemaker that could hold that rhythm steady.
Dr. Callaghan presented the team’s findings at a meeting of the American College of Surgeons in Boston on Oct. 23, 1950. The New York Times picked up the story.
But Mr. Hopps was in no hurry to patent his creation. In his writings, “he doesn’t actually say why,” said Mr. Leclair, the NRC archives officer. “He just says that they were reluctant to do so, and they didn’t see the purpose in it, really. They didn’t see it as being anything new or different. While in the [United States] it was the exact opposite. It was patented right away. They loved it.”
The leap from an external pacemaker for heart surgery to an implantable pacing device came in the late 1950s and early 1960s, as small transistors supplanted the vacuum tubes in the original pacemaker.
Mr. Hopps, who went on to become the father of biomedical engineering in Canada, had a pacemaker implanted in 1984, 14 years before his death.
In the decades since, pacemakers have not only become tiny and “leadless,” but the devices now have batteries that can last as long as 15 years and sophisticated software that can be reprogrammed from outside the chest. In 2014-15, nearly 21,000 pacemakers were implanted in Canada alone.
“All these great innovations in science are some form of somebody standing on the shoulders of giants,” Mr. Bourgeois-Doyle said. “Sometimes the giants are Canadians.”