Japanese Researchers Advance Artificial Heart Design

Takashi Isoyama says the kind of engineering he does is a little like watching TV.

But it isn’t entertainment; it’s deadly serious. Isoyama is in an international race to develop the next generation of artificial hearts.

Isoyama and his team at the University of Tokyo Graduate School are using three-dimensional software to precisely model the heart, complete with animation that can show the way blood will flow through it—done with CAE software.

The most common kinds of pumps used in artificial hearts are turbo pumps, and “you can imagine that designing a turbo blade by two-dimensional CAD is difficult,” Isoyama says. “Three-dimensional models accelerate the process of designing the blades.”

Isoyama has made so much progress with his design that the heart has already been implanted into a goat, and he says the final model for animal use could be ready as early as 2016, a human model following five or more years down the road.

That’s key in the global competition to find the next generation of a permanent replacement artificial heart.

In the United States, Abiomed, whose AbioCor is the market-leading total artificial heart, is developing the AbioCor II. The French company Carmat is already testing its new total artificial heart in a human patient. BiVACOR in Australia has a titanium heart in the animal-experiment stage, and a team in South Korea is also in the running.

The demand is huge. Heart disease is the planet’s leading cause of death, according to the World Health Organization, killing 7.4 million people annually. That has sent the need for donor hearts skyrocketing, even as the Registry of the International Society for Heart and Lung Transplantation reports that the number of hearts available is flat and falling.

Some 4,000 people in the U.S. and 3,400 in the European Union are waiting for donor hearts, the U.S. Department of Health & Human Services and the European Commission Department of Health estimate.

Yet artificial hearts so far have been used sparingly, and almost exclusively as a bridge to keep patients alive until a human heart become available. Since viable artificial hearts were first invented 45 years ago, only 1,413 have been implanted, or barely 30 per year.

Among the problems: artificial hearts are often rejected by host bodies, or impede blood flow and can cause strokes. They’re also very expensive—the AbioCor heart costs a quarter of a million dollars—and typically is more than twice as big as a human heart.

The risk of infection too is high, and the more elements implanted the higher the risk.

For these and other reasons, doctors have come to prefer ventricular assist devices—which can help the patient’s own heart pump blood—over full-scale artificial hearts, says William Wagner, director of the McGowan Institute of Regenerative Medicine at the University of Pittsburgh Medical Center.

For an artificial heart to compete with that, “it would have to do very well to justify taking out a patient’s own heart,” Wagner says.

But advances in artificial hearts could help reduce disputes between clinicians who want to install heart pumps before patients are too far gone to tolerate them, and cardiologists who prefer to wait, avoiding the risks of stroke or infection, Wagner says.

That’s the idea behind the Helical Flow Total Artificial Heart being developed in the University of Tokyo as a challenger to the Abiomed and Carmat versions.

Although the power source is still outside the body, the University of Tokyo heart is lubricated with blood instead of oil, with the idea of extending its life (Carmat’s uses hydraulic fluid.)

This helped keep a goat alive with the heart for a record 100 days*.

It also required precision engineering.

The Tokyo team used PTC Creo software to design a non-contact rotary pump that consists of a shaft and a bearing. The 3D models sped up the process, Isoyama says, and made it easier to export the plans to computer-aided engineering software such as ANSYS for the next step: precision-machining the parts.

The technology also lets the group conduct “numerical fluid dynamics simulations”—animate the flow of blood, which Isoyama likens to watching it on TV—averting the kinds of eddies that can give it time to clot and cause strokes.

Such modeling, which other artificial heart researchers have also adopted to varying degrees, “has really advanced this,” Wagner says. Predicting the flow previously “would take a lot of number crunching.”

Isoyama says it’s been “essential.”

“At the research and development stage, animation is effective to show the intention of the designer and to discuss in the development team,” he says.

Not only that, Isoyama says, in the clinical stage, the animated models can be shown to the patients themselves—whose human hearts are about to be replaced with mechanical copies—“to give them a sense of security.”

*In addition to the Helical Flow Total Artificial Heart, the Tokyo team also holds a record 532 days of life with a paracorporeal total artificial heart using displacement-type blood pumps.

Photo courtesy of the University of Tokyo

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