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The Warsaw Voice » Other » September 16, 2009
Medicine
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Helping Children With Heart Disorders
September 16, 2009   
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Researchers at the Foundation for Cardiac Surgery Development (FRK) in the southern city of Zabrze have built a prototype device to help children with severe heart problems.

The device, modeled after a similar product for adults, gives time to an ailing heart to regenerate and, if regeneration is impossible, extends the life of the patient while he or she waits for a heart transplant.

The ventricular assist system for adults has been used successfully for over a decade and has helped more than 200 patients, the researchers say. The device for children is intended for pint-sized patients with severe circulatory failure and weighing from 20 to 40 kilograms.

The foundation's Artur Kapis, who heads the project to build a heart assist device for children, says it is not enough to reduce the size of the device already used in adults. The device intended for children also needs to be adapted to pumping a smaller volume of blood, for example.

If they have enough money to press ahead with their project, the researchers say they will soon make laboratory tests on the prototypes they have built. Later this year or early next year, they plan to start experimenting with the use of real blood and then launch tests on animals.

Small but mighty
The POLVAD-PED pediatric device built in Zabrze was developed to supplement the POLVAD heart assist device for adult patients, which has been in successful clinical use since 1996. It is used by six Polish cardiac surgery centers, and has helped 207 patients so far.

Encouraging treatment results in adults led the foundation's engineers to start working on a smaller device. Most diseases where heart assist devices are used, such as myocarditis, also occur in children and teenagers. A pediatric system was requested specifically by doctors from the centers that use the adult version.

The experience gathered while working with the device for adult patients helped speed up work on the prototype of a pediatric device. The Foundation for Cardiac Surgery Development started the project in 2008; the prototype for children was ready in February this year. Specialist laboratory tests and experimental testing on animals will last until January 2010. The designers hope that the pediatric heart assist device can be used as a standard method in treating extreme cardiovascular problems from the end of 2010.

"Building a device for children does not mean a simple reduction of the adult device," says Roman Kustosz, head of the foundation's Artificial Heart Laboratory. Apart from its smaller size, which enables it to be connected properly to a child's vascular system, the pump also has to have a smaller capacity. In adults, it pumps about 5 liters of blood per minute, in children this has to be 2.5-3 liters. The pump is designed for a certain nominal flow at which it operates safely, meaning that all the pump's parts are optimally washed with blood and the blood flows through safely, ensuring minimal risk of clotting in the device, Kustosz says. Clotting is the greatest hazard faced by patients with a heart assist device. For smaller patients, the pump has to be different not only anatomically but also functionally.

The POLVAD-PED device, like the adult heart assist device, can be implanted as a left-, right- or bi-ventricular device, the researchers say. It is made wholly from biocompatible polyurethane and is fitted with two one-disk mechanical valves. It is powered pneumatically, by a drive that is also the foundation's original project-the same kind that is used in the adult device.

Engineering work on the prototype was conducted using advanced CAD methods and computer flow simulations. It involved three stages. In the first stage, the device's parts were designed in several versions, the best of which was then chosen in blood flow simulation tests.

A range of devices
The POLVAD-PED device is meant for children aged 7 to 12 and weighing between 20 and 40 kilograms. Younger children, including infants, would need an even more complicated device, and though the Foundation for Cardiac Surgery Development does not rule out such a project in future, there are no official plans as yet. Even so, expanding the range of Polish heart assist devices to include an even smaller version seems to be a natural continuation of the current work, the researchers say.

"Heart surgeons keep asking about an assist device for very small patients, even babies," Kustosz says. "There's no question that such devices are needed clinically. German-made pumps of this kind exist, but they are unimaginably expensive. Meanwhile, our team has the know-how and the potential to develop a device for infants that would be unique in Europe and beyond. I think if funds could be found, the foundation could relatively quickly design a whole range of heart assist devices, starting with one for newborns."

At present the foundation is working on its own design for a valve for heart assist devices. The idea came from Dr. Jacek Moll from a heart surgery clinic in £ód¼; the designers from Zabrze have been working with him for many years. "This project has been in the pipeline for some time, but the technology enabling it to be implemented surfaced only recently," Kustosz says. "After recent progress in materials engineering we can now return to this idea. Once we outfit the heart assist devices with the new valve, they will gain a competitive edge on the global market."

Clinical practice
The devices built at the Artificial Heart Laboratory are part of the POLCAS heart assist system designed by the foundation. This includes not only building heart assist devices but also supporting their clinical application. The device's designers train medical personnel, run clinical projects to develop increasingly better treatment methods and effectively eliminate the risk linked to clotting within the devices. All this means continual development of treatment methods involving heart assist devices. As a result, heart assist devices are used today both as an aid in heart transplants and, increasingly often, as assistance in heart regeneration; that means they stay implanted in the patient for a long period of time. A few years ago, the average time a heart assist device implant stayed in a patient was three to four weeks. Today the typical period is two to six months; the longest time it has operated in a patient is 204 days. Today heart assist devices are used to treat the heart-by giving it time to regenerate, which often means that a transplant can be avoided.

Today, about 100 POLVAD devices for adult patients are manufactured per year. The maker is a technology company established by the Foundation for Cardiac Surgery Development; the company also deals with distribution and maintenance of heart assist systems. All the output goes to the domestic market and meets the needs of Polish clinics. The foundation has plans to increase production with a view to entering foreign markets as well.

The design work on the POLVAD device-from project commencement to the first implant-took eight years. Work on the prototype for the POLVAD-PED pediatric device lasted just one year. Kustosz says that production and then experimental clinical application of the latter device will be launched in 2010. In addition to Kustosz, the team that developed the pediatric device comprises Artur Kapis, who is the project's manager, Maciej Dar³ak, Wojciech Bujok, Agnieszka Szuber as well as Bogdan Stolarzewicz and Sebastian Stolarzewicz from Plastmed company.

Work on the POLVAD-PED device has been financed from the Foundation for Cardiac Surgery Development's own funds and from a public collection for projects involving heart assist devices.
Ewa Dereñ
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