The Heart of a Child

For some manufacturing sectors, pursuing the easiest means of production is an acceptable goal. For manufacturers of sensitive medical devices, such an approach is rarely possible, let alone preferable. Jarvik Heart Inc. of New York defines its goal as pursuing the best solution, and then working to make it possible. A recent installation of a GF AgieCharmilles wire EDM machine demonstrates the company's constant commitment to excellence, even when it is far from easy to accomplish.

Dr. Robert Jarvik possesses more than 30 years of experience in the field of medical device design and production. Working with a team of researchers at the University of Utah in the 1970s, he developed the Jarvik-7, the world's first totally-artificial heart designed to provide lifelong support. Since 1987, he has continued his efforts to develop devices for people with severe heart failure at a facility occupying four floors of a building in Manhattan. Recently, this unique location presented a significant hurdle in implementing the best available production solution.

In April 2004, Jarvik Heart was awarded a $5 million contract from the National Institutes of Health (NIH). The goal was to develop a miniaturized version of the highly successful Jarvik 2000 VAD (ventricular assist device) for use in children and infants with congenital heart defects. At present, children with such conditions face extremely dire odds.

There is a cumulative 50% mortality rate for the multiple operations necessary in the first two years of life for children with some of the more serious heart defects. After that, only one in ten children receive a donor heart. Additionally, those lucky few may spend years waiting, with a reduced quality of life due to liver damage, fluid buildup in the abdomen, and other associated complications. The development of a permanent VAD will have tremendously positive effects on these children born with the cards stacked against them.

Miniature Design

For nearly four years, Jarvik and his team worked tirelessly to reduce the size of the Jarvik 2000 to the point where it would be suitable for pediatric use. Unfortunately, smaller designs created a host of problems.

"We found that we could not just shrink the existing design," Jarvik says. "With a smaller pump, we continually had problems with thrombus formation within the device. This was a severe problem, as it would eventually lead to premature pump failure. A small thrombus would form around the bearings and cause enough friction to stop the rotor from spinning. The tiny motors do not have enough torque to overcome this binding force."

Late in 2007, Jarvik made a breakthrough in the concept of a pediatric VAD. While the exact details are confidential, it can be said that the turning point involved a redesign of the bearings used in the pump. Extensive calculations and initial prototype testing suggested that the solution had been found and the question became how best to machine the component. It would require several sharp angles and levels of accuracy and surface finish exceeding the capabilities of Jarvik Heart's existing equipment, so the team began examining its options.

Jarvik Heart's previous success is what drives its vision of the future.

"We found ourselves in a very tight spot," Jarvik explains. "Our annual review with NIH was just over two months away, and we felt it was imperative that we be able to prove the benefits of the new design in that time. Because of its size and requirements, we knew the part would need to be machined on a wire EDM. It was a matter of finding the right machine and proceeding with its installation as quickly as possible."

After some initial investigation into the capabilities of various makes and models of machines, Jarvik Heart requested test cuts from several EDM manufacturers. Based on the results, the company chose the AC Classic V2 from GF AgieCharmilles. The machine features the IPG-V generator that increases pulses' shape factor while shortening the pulse duration, allowing it to obtain high accuracy and surface finish. These areas are also bolstered by the machine's unique toroids, which activate during taper cutting, increasing the wire tensile force. The machine provided exactly the results Jarvik Heart needed and the next challenge was obtaining the machine in time to produce tangible results prior to the NIH review.

Making it Fit

Once the order had been placed, GF AgieCharmilles began preparations for an expedited delivery. This process uncovered a significant problem. The opening to the freight elevator in Jarvik Heart's building was approximately 4" narrower than the width of the AC Classic V2. Given the sensitivity of the project, GF AgieCharmilles immediately formed a team to address the challenge. Employees from the GF AgieCharmilles Refurbishment, Advanced Technical Support, and Northeast Regional Service departments came together to devise a solution.

While revolutionary in its own rite, the original Jarvik 2000 VAD is too large for use in infants and small children.

It quickly became clear that the only option was to disassemble a machine for delivery and then reassemble it onsite. An AC Classic V2 was delivered to GF AgieCharmilles' Lincolnshire, IL, facility, where it was immediately stripped of sheet metal and peripherals. A team of technicians then disassembled the machine, carefully identifying and marking every component, connection and fitting. The machine then made the journey to New York in six crates.

In January 2008, four engineers from GF AgieCharmilles traveled to Jarvik Heart to reassemble the machine. A special hoist was created to aid in the unconventional installation. After several days, Jarvik Heart had its new wire EDM, its condition indistinguishable from a machine fresh off of the production line.

To further aid in meeting the deadline imposed by Jarvik Heart, applications specialists from GF AgieCharmilles assisted in development of the complex programming needed to complete the prototype Jarvik had envisioned. In the end, the part was completed to the exact specifications required.

"The AC Classic V2 delivered the precision and surface finish demanded by the part," Jarvik says. "We have to hold steep angles within a 0.016° tolerance, while having the machine provide surface finish of around 0.15µm. It is a demanding application and we could not do it without the innovations found in GF AgieCharmilles' wire EDM."

Once reassembled, the appearance and performance of Jarvik Heart's AC Classic V2 were indistinguishable from a machine delivered via a more conventional process.

Jarvik Heart's 2008 NIH review went extremely well, with all parties impressed by the breakthroughs the team had made. While developed for infants, the new design has potential ramifications for all those who suffer from life threatening heart disease. To be effective, the pediatric VAD needed to be able to increase its output to match the growing body of its host. In an infant, it would require operation at 20,000rpm to achieve the necessary blood flow. As that child grows, the pump's rpm increases to drive a greater amount of blood. Initial evaluation of the new design indicates that the pump is capable of maintaining 70,000rpm, pumping enough blood for an adult. Due to its much smaller size, the new pump could considerably reduce the risks and complexity of the surgery necessary to implant a VAD.

Continuous Improvement

"The new model holds tremendous promise," Jarvik states. "The fit of the bearings is so perfect that the amplitude of radial vibrations possible is on the order of 10 to 20 millionths of an inch. When the pump is running at 70,000rpm underwater, it is nearly silent, and you can hold it and feel practically no vibration."

The pediatric VAD will soon be used in its first animal implants. If that produces the expected results, a long period of clinical trials will be necessary. As with all medical devices, full acceptance and integration of the product will be a lengthy process due to regulatory hurdles.

The early success of the Jarvik 2000 infant model is attributed to an innovative new bearing design.

"Each improvement to the design of a VAD becomes somewhat more difficult," Jarvik explains. "Once we had a device that proved effective for two years, people then wanted one that would last for five. Once we cleared that hurdle, people wanted one that would last for ten. And once one model receives those results, the regulatory bodies want every model to achieve those results. In effect, each success we achieve lengthens the time it will take to develop our next improvement."

That challenge does not faze the team of 40 employees working with Jarvik. They recognize that the road to improving people's lives will always have significant hurdles to overcome. For Jarvik Heart, the reward is worth making the effort to always strive for the best possible results.