Jülich Magnetic Bearings in Cardiac Surgery
Research Centre Jülich provides key technology for cardiac pumps
[10. März 2004]
Roughly 15 million people worldwide suffer from chronic heart disease. Many of them can only hope for a transplantation in order to survive. Roughly 100,000 donor hearts are annually required - about 2,500 are available. The life-saving alternative is an implantable cardiac pump, which takes over the blood-transporting function of the heart. Scientists at Research Centre Jülich have developed a unique magnetic bearing for these cardiac pumps. With the Jülich key technology blood pumps operate in a non-contacting and almost non-wearing manner, are of lighter weight, transport the blood in a non-destructive manner and reduce the risk of thrombogenesis in the interior of the pump. The Research Centre has recently been granted European and American patents for these magnetic bearings inserted in cardiac pumps.
The Jülich technology is applied in heart supporting pumps developed by a German company, with which the Research Centre has concluded a licensing agreement defining the sales share in this novel type of artificial heart.
The blood pump is implanted next to the heart into the patient's body and directly transports the blood from the left ventricle into the aorta. It thus takes over the pumping function of the heart and helps the patient escape from a life-threatening situation which would otherwise require an immediate heart transplantation.
The novel supporting pump stands out from other artificial heart generations by the unique magnetic bearing technique of the Jülich scientists. The rotor in the interior of the pump rests on the non-contacting bearing and thus wear-free between two permanent magnets and provides the required pumping capacity with up to 12,000 revolutions per minute.
Due to the Jülich magnetic bearing the pump rotor is so light that it could also be operated at pulsating instead of constant speed so as to simulate the human heart pulse. Since the rotor is not in mechanical contact with the pump casing, no friction heat is produced and the blood is transported in a non-destructive manner. Moreover, the blood can flow unimpeded in any location - the risk of thrombogenesis in the pump interior is thus considerably reduced.
The heart supporting pump with the Jülich magnetic bearing is the first and so far only implantable blood pump worldwide with a rotor on a magnetic bearing licensed for clinical application. More than 100 pumps of this design have already been implanted at various heart centres in Europe and China. In several cases, it was even possible to remove the pump after the patient's own heart had recovered.
Headed by Dr Johan Fremerey, the magnetic bearing laboratory at the Research Centre's Central Department of Technology (ZAT) has been developing non-contacting bearings and drive systems for more than 25 years now. Wherever lubricants cannot be used - for example, at high speeds, in sensitive measuring instruments or in vacuum units - magnetic bearings are the solution. The drive shafts are supported by non-contacting permanent magnets as are known from magnetic panels. "In order to prevent the rotor shaft from sticking to the magnets, the pulling force of the magnets must be exactly balanced out at any moment" Johan Fremerey explains the technical difficulty. "This is achieved by electric coils, which are controlled by sensors and suppress any deviation of the rotor from its non-contacting position."
"Since we do not use continuously current-carrying electromagnets, the energy consumption of our magnetic bearings is very low", the physicist refers to a further advantage. "Moreover, only two pairs of magnets are needed." The novel heart supporting pump with a diameter of 30 millimetres thus only weighs 200 grams and can also be applied to small patients.
The Jülich know-how from the magnetic bearing laboratory is being successfully marketed by industry. With vacuum pumps based on Jülich magnetic bearing technology alone, the industry has achieved sales to the amount of several hundred million euros since the early 1990s. A US study from the year 2001 predicts a long-term potential of 6 billion US dollars per year for heart supporting systems.
Photo: Research Centre Jülich
Information on Research Centre Jülich:
Research Centre Jülich is the largest interdisciplinary research centre in Europe with an annual budget of 360 million euro (including special tasks) and a staff of 4200 (as of 2003). The partners of "Forschungszentrum Jülich GmbH" are the Federal Republic of Germany (90%) and the federal state of North Rhine-Westphalia (10%). The Research Centre, founded in 1956, is one of the 15 members of the Helmholtz Association of German Research Centres. In Jülich, scientists from the disciplines of physics, chemistry, biology, medicine and the engineering sciences work together on an interdisciplinary basis in the fields of matter, energy, information, life and the environment. The work comprises long-term contributions in basic research for science and technology as well as concrete technological applications for industry.
Research Centre Jülich
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