Plastics & The Artificial Heart
July 7, 2017
Cohn said demand for heart transplants far outstrips the supply of hearts, so heart patients need a practical artificial heart — something that is an improvement over other artificial hearts that are designed to be a bridge to a transplanted human heart.
The rotor in the BiVACOR heart does not create any friction. The device is a continuous-flow pump. "They should last forever," he said.
"There's no mechanical wear. There's nothing to wear out. Just one moving part floating in a magnetic field," Cohn said at Antec.
Cohn recapped the history of artificial hearts and detailed the BiVACOR in a keynote speech May 9 at Antec, the Society of Plastics Engineers' conference in Anaheim. Cohn is an internationally renowned heart surgeon and medical device entrepreneur. Last fall he became the head of Johnson & Johnson's Center for Device Innovation at Texas Medical Center in Houston.
Johnson & Johnson has allowed him to continue his academic work as a professor at Baylor College of Medicine. And Cohn said Johnson & Johnson has no interest, financial or otherwise, in his work on the BiVACOR heart.
Surgeons have been frustrated in their search for a machine that does not wear out, fail or cause infections and blood clots.
"If you have seams anywhere, blood clots will form on them, little pieces of clot break off and go to the brain. It's a devastating stroke," Cohn said.
Previous artificial hearts have used air hoses feeding membranes of multisegmented polyurethane. Bacteria can travel up these hoses and infect the heart, he said.
Cohn said the multisegmented PUR "is very durable. But nothing's durable enough. If it's beating 100 times a minute, that's 52 million heartbeats a year. There's no man-made device, no polymer that we have now, that can take that kind of cyclic stress."
The flexible membranes would eventually tear and fail. Even so, about 80 percent of the patients survived long enough to get a heart transplant, Cohn said, as the average time in a patient for the artificial heart was 60 days.
Cohn said durability has presented a challenge in the world of mechanical hearts and a barrier to creating a permanent artificial heart.
"So limited durability. Air hoses. And the device inside the chest is going to fail capriciously. And because of those, because it's only a temporary device, it's approved for a patient who's been listed for a heart transplant," he said.
But Cohn spelled out the challenging math of heart disease, the No. 1 cause of death in the United States.
"Over 5 million Americans have some degree of heart failure, and about 50 percent of them die within five years of diagnosis. Four hundred thousand people die of heart failure every year," he said.
And they can't all get transplants.
"From the time a heart is useable to when we need to use it, has to be like that," Cohn said, snapping his finger. "So, the hearts that we get, the donor hearts, are from very special cases, which is, they have to be both dead and healthy. Big and strong. They have to be brain-dead. That only happens about 4,000 times a year, worldwide."
Surgeons transplanted about 2,000 hearts last year, Cohn said. "Those are all the donor hearts that were still beating strong. If it stops, even for 15 minutes, we can't use it.
"So, 2,000 heart transplants in the United States. Four hundred thousand dying of heart failure. We can only transplant about one in 200. So we really need a device — something we can take off the shelf and sew into a person with a desperate need," Cohn said.
And that's been the big hurdle for making an artificial heart that can last for decades: 52 million heartbeats a year. "We don't need an artificial heart that lasts a year and half. We need something you're going to have for the rest of your life," he said.
Cohn has been thinking about mechanical hearts since his elementary school classmates were handing out Valentine's Day cards.
"This BiVACOR artificial heart is my pursuit of a passion I've had since I was about 9 or 10 years old: to develop the world's first practical artificial heart and to work with people in that area," he said.