Smart blood micro-pumps improve cirrhotic liver perfusion

Brussels 26 November 1997 Alcohol abuse is the major cause of liver cirrhosis in the western world whereas the infection with hepatitis B and C viruses affect the livers of about 800 million patients in the underdeveloped countries. This development of fibrous tissue in the liver causes an important decrease of portal blood flow amounting to portal hypertension. Thus, an unstable network of blood vessels is created. These varices in turn are the cause of uncontrollable bleeding of which a patient can die without swift intervention. Researchers now have designed an implantable blood micro-pump to go inside the hepatic portal veins and by driving blood through the liver reduce the intra-portal pressure. The people responsible for this IMALP project hope to prolong the active lives of liver patients until a transplantation can be offered.

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Alcohol abuse is the major cause of liver cirrhosis in the western world whereas the infection with hepatitis B and C viruses affect the livers of about 800 million patients in the underdeveloped countries. This development of fibrous tissue in the liver causes an important decrease of portal blood flow amounting to portal hypertension. Thus, an unstable network of blood vessels is created. These varices in turn are the cause of uncontrollable bleeding of which a patient can die without swift intervention. Researchers now have designed an implantable blood micro-pump to go inside the hepatic portal veins and by driving blood through the liver reduce the intra-portal pressure. The people responsible for this IMALP project hope to prolong the active lives of liver patients until a transplantation can be offered.

The Implantable Microsystem for Augmented Liver Perfusion, residing under the Esprit program, comprises a fully implantable electric micro-pump that incorporates 'smart' flow capability by using pressure and temperature sensors based on CMOS technology. Two pressure sensors are integrated in the pump, one in front and the other at the back, both fixed with different assemblies. Wireless power is transferred through an inductive link from a lithium rechargeable battery using bi-directional data communication. Since the micro-pump will be implanted in the bloodstream, the motor has to be hermetically sealed from its harsh environment so as not to suffer from eddy currents.

A Smart Battery System is introduced in order to control its own charging cycle. The battery charger adjusts its output to match the Smart Battery's requirements. It is even possible to send information on critical events such as alarms for over-charge, over-voltage and over-temperature. The battery is energised from an RF antenna or low-frequency magnetic loop implanted in the subcutaneous tissue. At present, it is not yet clear whether the best route for implantation of the pump will be transcutaneously near the liver or by passing the pump down the jugular vessels and across the liver under radiological control.

The IMALP project is associated with another project, residing under BIOMED and called ILIAS which stands for Implantable Liver Assist System. Researchers from both teams will try to implant the micro-pumps first in living normal pigs and consequently in pigs with cirrhotic livers so as to test the minimum operational lifetime for the IMALP system. Finally, human patients in three European centres will be selected to undergo the implant operation of the appropriately packaged blood micro-pumps. The eventual target is set at one year of continuous operation. Both the IMALP and ILIAS people hope that a successful outcome will save many lives through this new and superb intravascular pump.


Leslie Versweyveld

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