TMC PULSE

t m c » p u l s e | f e b r u a r y 2 0 1 9 29 rare cases, the device helps a heart recover to the point that the patient no longer requires a transplant, and in even rarer instances, it can be used as a permanent therapy for a failing heart. What sets the Jarvik 2015 apart is that it is the first and only implant- able ventricular assist device with a continuous flow designed specifi- cally for small children. The continuous flow is key: Rather than pumping like the heart, it pushes blood through an impeller with the help of an agitator blade attached to the rotor—technology that has been associated with significantly improved outcomes in adults. But designing a simi- lar technology tiny enough to be implanted in a small child's chest— like Hickman's—proved nearly impossible. The team behind the Jarvik 2015, which is approximately the size of a AA battery, has been working on its design for more than a decade, watching each competitor give up and move on to a new, per- haps more attainable challenge. After the U.S. Food and Drug Administration (FDA) rejected the device twice in 2014, Adachi came on board to test the current iteration that had undergone substantial design modifications, including the shape of the blade. That final modifi- cation would prove to be the charm. "The main problem was that the previous iterations caused the red blood cells to break because it was spinning too fast," explained Adachi, who continued his involve- ment in the project as the principal investigator of preclinical testing. "So they changed the design of the blade and they also increased the size of the pump slightly so it didn't have to spin so quickly, which reduced damage to the red blood cells. But it had to stay small, which is the challenge in making a pump for kids versus adults. The pediatric pump has to be smaller, despite the fact that the red blood cells are nearly the same size regardless of age." The waiting game As a result of extensive testing in the Texas Medical Center, the latest prototype of the Jarvik 2015 has been approved by the FDA for a clinical trial. Because it has not yet been approved for commer- cialization, Adachi had to obtain expanded access use from the FDA for Hickman's procedure. He was able to do so because Hickman was too small to be a candidate for a VAD made for adults, which, while not ideal, is what Texas Children's typically uses on patients in heart failure. All other options are external devices, which are hooked up to the heart through cannulae (tubing) and remain on the outside of the body. They carry with them increased risks of side effects, espe- cially strokes. "The Jarvik 2015 is an internal device, and the only other device we have for this sized population is on the outside of the body, but it's very clear that the outcome of the outside device is much worse than an inter- nal device," Adachi said. "That has been clearly shown in the adult pop- ulation—internal devices are better in general than the external devices. There is no question about it." The Jarvik 2015 turned out to be perfect for Hickman. Not only did the tiny device keep her alive as she waited for her heart transplant, but it actually improved her blood flow so much that her visceral organs recov- ered dramatically in the weeks lead- ing up to her surgery. Hickman was stronger and healthier and in much better shape overall to undergo major surgery and rehabilitation. "One of the most significant benefits of this ventricular device's support is that we can make the patient stronger so that they can be a better candidate for the next operation, which is usually a heart transplant," Adachi said, adding that the practice aligns with Texas Children's Heart Center's clinical philosophy in general. ➟ One of the most significant benefits of this ventricular device's support is that we can make the patient stronger so that they can be a better candidate for the next operation, which is usually a heart transplant. — IKI ADACHI, M.D. Congenital heart surgeon at Texas Children's Hospital

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