The failure of the fontan-circulation has been subject in numerous studies for a few years. All complication and symptoms, which arise from the modification of the blood circulation of patients with natively only one functioning ventricle, are defined under fontan-failure. The most frequent form in this is the heart insufficiency. However, the usual therapeutic approaches for patients with heart insufficiency emerged to be less effective for fontan-patients. The use of mechanical support system led only in isolated cases to success and until now no suitable therapeutic method for the treatment of fontan-failure could be found.
The individual adaptable fontan-prosthesis in combination with a cardiac support system represents a new and innovative therapeutic option. Therefore not only the position and size of the prosthesis is relevant but also the fluidic aspects of the pulsatile support form by the Berlin Heart EXCOR® systems. High flow velocities in too narrow dimensioned geometries result in shear forces, which cause cell damage of the blood. Low Velocities lead over a longer period to blood stagnation (stase), which supports the formation of thrombus. These negative influences are to be avoided and as a result have to be fundamentally studied. So far, there are no investigations, focusing on an optimal flow control in combination with this innovative therapeutic approach.
A simulation model for fluid dynamic optimization of an individual adaptable prosthesis geometry for the fontan-circulation with the use of a cardiac support system will be developed and with the help of experimental data validated. Subsequently, relevant parameters for anatomy, production and flow control should be discussed regarding to an optimal geometry.
The group for this project consists of three partners. The investigation of blood flow inside of the prosthesis is done by the RWTH.
The development of an optimal individual adaptable prosthesis geometry with the help of a numerical analysis can consider a variety of relevant patient, running and design parameters. Studies focusing on the flow control for a fontan circulation adjusted prosthesis in connection with a support system are so far not known.
The considered flow model includes a three-dimensional flow simulation of the prosthesis in a one-dimensional lumped-parameter circulation model. Hereby, a simulation platform is built, which allows a flexible view on the different parameters. The combined simulation model should be investigated within an extensive parameter analysis according to the individual patient parameters. Especially the diameter and the length of the used prosthesis geometry, as well as the position and the design of the connection to the pump device are implicated. Therefore, statements and criteria should be made for a stagnation free and blood gently flow control inside the prosthesis with a low-pressure loss. Therefore, a flow movement simulation of a number of pump cycles inside the prosthesis is necessary.
The significance of the flow model should be reinforced by a validation of the simulation results with the help of particle image velocimetry (PIV) measurements in lab tests. The model validation is an important part of this subproject.
The different flow, anatomy and production requirements should be evaluated with a suiting algorithm and joined in one optimal design.
New findings in regard to this project are used in the final characterization of the demonstrators. Parameter sensitivities and partly contrary optimization criteria should be discussed by means of an evaluation scheme. Consequently, the results will lead to new findings and individual approaches, which are transferable to other fields of application.
|This research project is funded by Federal Ministry of Education and Research (BMBF)