Problem: artificial heart pumps need power but running wires through the skin leads to infection. Solution: invent device to transfer power without wires.
It sounds like science fiction, but reality is not far away. Texas-based heart pump maker MicroMed Cardiovascular has this month signed a licensing deal with a supplier of wireless power technology New Zealand company TetCor, a subsidiary of Telemetry Research run by Auckland University bio-engineering specialist Simon Malpas.
The technology has been years in development and has so far been used to power wireless transmitters in laboratory animals. Using it to power devices in humans is a big step, said Malpas.
“If you look at medical devices that can be implanted in humans, this is probably at the most extreme edge because with most other devices, if they fail, or don’t quite work right, you’re not generally going to die. Pacemakers are intermittently on, and it’s very important for a defibrillator that it kicks in and works, but this is pumping blood 10 litres a minute, it’s got to work for the rest of your life. That’s like starting a car and never turning it off and expecting it to work for years and years. That’s pretty high-end technology.
“I don’t know of anything in terms of pump technology that’s more complicated than this, and I don’t know of another medical device that New Zealand’s been involved in that’s more complicated than this.”
MicroMed’s heart pumps are a triumph of engineering in their own right, emerging from a combination of medical expertise and space technology after heart surgeons Michael DeBakey and George Noon performed a heart transplant on Nasa engineer David Saucier in 1984.
Saucier was able to bring Nasa’s skills to bear on the surgeons’ problems with pumping blood artificially, particularly how to prevent coagulation and damage to red blood cells. Using techniques adapted from the space shuttle’s main engine turbopump, the group developed a machine that could be implanted in the human body to help support heart function pending a transplant. Their first “ventricular assist device” was implanted in a patient in Berlin in 1998.
While VADs have been used successfully many times since then, even in children, the biggest problem remains the infection risk from the power cable running through the skin. TetCor solves the problem by using magnetic coils to transfer power with no direct contact.
“What our technology is doing is sending the right amount of power between two coils with the skin in between, so there will be nothing piercing the skin to cause an infection,” said Malpas. “The interior coil’s about 5cm in diameter, that will communicate with a battery and also a power management system that we’re developing as well. And of course, there’s the heart pump as well.
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“The internal battery will be there as back up so you’ll be able to take the whole lot of the external parts off and have a shower and for that period be completely unencumbered.”
The outer coil, the same size as the inner, would normally be worn in a specially positioned pocket in a lycra vest underneath the normal clothing.
After extensive bench testing and prototypes, said Malpas, “we know it can transfer power, we know it does it efficiently, and we know it doesn’t cause heating. The next phase is integrating that technology and making it specific to the MicroMed requirements”.
A device for clinical trial could be ready in 18 months to two years.
