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In western nations such as Germany, heart disease is a main cause for morbidity and mortality. The treatment of patients with end stage heart failure can be conducted by medication, by transplantation and by mechanical cardiac replacement or assistance. However it has been proven that the optimal medications for cardiac therapies lead to higher mortality when compared to cardiac assistance . Heart transplantation is a well established and preferred treatment, unfortunately the demand of donor hearts significantly exceeds the available number. In spite of this, the uptake of blood pumps as ventricular assist devices (VADs) has been slower as could have been expected by the market potential. The total number of implantations of VADs in 2005 in Germany has been in the same range as the transplantation of donor hearts (roughly 300-500 implantations) . Reasons for that are stated as form and size of devices, manufacturing costs and overall price, problems with blood damage and thrombus formation as well as extensive operations. These challenges justify and demand research and technical innovation in the field of mechanical heart assistance.
In the framework of international collaborations, the Helmholtz research group of cardiovascular engineering is currently working on four projects dealing with the development of mechanical heart assist devices. Goals are to conduct basic research and development in this field as well as push products towards clinical trials and the market. Modern VADs are implantable rotary blood pumps. During the development, many of the present tools at the institute are being employed such as CAD/CAM, PIV, CFD, experimental mock circulation loops and blood tests.
The MIRVAD (Minimally Invasive Right Ventricular Assist Device) project focuses on the research and pilot development of the mechanical assistance for the right ventricle. Right heart failure contributes to high mortality and is especially commonly induced after cardiac surgery, such as heart transplantation and left ventricular assist device (LVAD) implantation. However, the assistance of the right heart has been neglected compared to the left ventricle. It has been observed that using LVADs to assist the failing pulmonary circulation can be an overkill as the demand of the pulmonary circulation is lower. Current right heart support devices are either limited to short-term acute support or restricted to critically ill patients due to the invasive surgery. This effectively delays the use of RVADs in heart failure patients thus retards the possibility of cardiac recovery. This project is to develop a minimally invasive right ventricular assist device (MIRVAD) for long-term use.
In clinics today, VADs are used only to support one ventricle. A system currently under development pursuits the idea to employ one rotary blood pump to support both ventricles at the same time. This system can also be used as a rotary total artificial heart (TAH). In the framework of an international collaboration, parts of this research and development project are conducted in the institute. The BiVACOR is comprised of only one movable part. This rotor is levitated by magnetic and hydrodynamic forces. The active control of the flow balance between both sides is conducted via the axial position of the rotor as can be observed here.