Cleveland, OH —Leonard Golding, a former heart surgeon, is leading a team at the Cleveland Clinic Foundation developing a new left ventricular assist device (LVAD). The CorAide prevents hemolysis and thrombosis problems by eliminating the seal and reducing the pump to only three main components.
Designers of LVADs must be careful that the pump does not cause hemolysis—damage of red blood cell membranes from fluid shear and frictional forces. Hemolysis leads to anemia and eventually to kidney failure.
Developers must also avoid thrombosis, the development of blood clots within the vascular system that result from poor wash-over on an LVAD's blood contacting surfaces, and can result in strokes.
As the blood enters the CorAide's inlet, it passes into the main chamber. Inside the chamber, centrifugal force from the primary impeller pushes blood through the space between the volute housing and the rotating assembly. Blood then exits the pump through the outlet.
CorAide avoids these problems with its new three-component design. It includes a one-piece cast titanium volute housing, a stator housing containing the motor windings, and a cylindrical rotating assembly (the only moving part) containing a permanent magnet.
The main pumping end of the rotating assembly has a primary impeller, while the opposite end has a secondary impeller that allows a balance of axial hydraulic forces. The configuration uses an inside-out motor along with an inside-out radial bearing. The inside out motor combines the magnetic drive and bearing into one feature, and eliminates the need for a dynamic seal.
The bearing uses a unique non-circular profile on the inner stationary element that stabilizes the hydrodynamic forces and allows an axial tunnel through the center of the pump for blood circulation. As the rotating assembly spins, it develops a hydrodynamic lift and essentially waterskis on a film of blood. With the rotor suspended in this cradle of blood, there is normally no surface contact in the bearing.
"The shaft seal was the essential engineering problem, both with regard to reliability and formation of deposition," says CCF mechanical engineer Dave Horvath. The hydrodynamic bearing and inside-out motor eliminate the shaft seal, and provide a blood compatible bearing of very large area.
"The average pump flow for studies of the most recent design was 6.0 (liter)/min with no incidence of mechanical or motor controller failure," says Horvath. "The results in the animal model suggest that the CorAide pump design is ready to begin pre-clinical qualification for use in humans."
In April, Arrow Int'l. Inc. announced it signed an agreement with The Cleveland Clinic Foundation for the exclusive license of the CorAide patents.
For more information about heart pumps from Cleveland Clinic Foundation: