“Implantable blood pumps can last for over a year,” says Behr. “That’s long enough for people to find a transplant donor. But our ambition is to make it viable as a permanent replacement.”
Behr directs the Chair for Computational Analysis of Technical Systems (CATS) at the RWTH Aachen University. His team of engineers receives CAD models of the DeBakey VAD from MicroMed Cardiovascular Inc. of Houston, Texas, and subjects them to engineering analysis. The DeBakey VAD is already a medical and commercial success — it has been implanted in nearly 400 patients. But MicroMed and CATS continue to look for ways to improve it.
The pump may be small, but it takes major computing muscle to run the FEA flow studies that Behr and his team are using to refine its design. CATS chose a 44-processor Xserve cluster to power the program.
“We convert the MicroMed CAD models to a finite element mesh,” says Behr, “and we use the mesh to simulate a fully developed flow field on the Xserve cluster using our own computational fluid dynamics (CFD) software. Each simulation is a series of about a thousand time steps, each step with five to ten million finite elements. We needed massive compute power for this process, and once we made our comparisons it was easy to choose the Apple cluster.”
CATS uses these compute-intensive simulations to explore the potential of each design modification, running a variety of flow profiles, flow rates, and impeller speeds to find the best way to improve the flow pump’s biocompatibility. Could it be reduced in size to make it more suitable for young patients? Would a change in the geometry of the impeller blades or the stators reduce hemolysis? Hemolysis — the release of hemoglobin into the bloodstream — can result from damage to red cells. It is a potential danger to internal organs and can be life-threatening in extreme cases.
The MicroMed DeBakey Ventricular Assist Device (VAD), an axial flow blood pump, implanted in the patient’s chest could bypass his ailing heart.