Well-Flushed Hydrodynamic Bearing for Miniature Blood Pumps

Perfusion Solutions, Inc., South Euclid OH

Investigators

Abstract

Ventricular assist devices (VAD?s) clearly have a role in cardiac medicine; how to precisely define that role is still subject to research and debate, considering the possibilities of destination therapy, bridge to transplant, bridge to recovery, bridge to definitive therapy and possibly other variants one might specify. Certain VAD features are emerging as required: 1) adequate output to truly make a difference to the patient, realizing that an unloaded ventricle will frequently show significant restoration of function, 2) reliability through the period of use, however long that might turn out in reality to be after support is instituted; 3) ease of use; 4) minimal morbidities associated with use, such as those resulting from major surgical invasion, bleeding, or thrombosis, and; 5) high costs resulting from hardware complexity or demanding post-operative care. Large devices can result in extensive tissue/organ displacement and large pockets, further weakening already very ill patients, providing locations for bacterial and fungal colonization, and result in extensive adhesions impeding later surgeries. High shear stresses can shorten red cell life and disturb both platelet and leukocyte function. Thrombosis on the foreign surfaces of the pump can form and later embolize, and/or systemic coagulation pathologies occur. Aggressive pump anticoagulation protocols limit a clinician?s ability to respond to other patient issues. Perfusion Solutions, Inc. (PSI) has a new bearing technology which promises to address these issues. Small hydrodynamic bearings are located before and after the rotor, in the main flow stream. The unload side of the bearing is open to the blood flow. Magnetic radial loading ensures proper rotor positioning. Unlike similarly sized pivot supports, these bearings are not only continuously washed by blood flow but also have the surfaces separated by a hydrodynamically generated, wear-free fluid film. Complexity and costs are much lower than new generations of magnetic bearing pumps. The PSI hydraulic design approach has demonstrated low bench hemolysis and baseline free hemoglobin in 30-day lamb implants. The PSI design configuration is readily adaptable to many surgical approaches; our initial packaging of the core hardware is directed to suit an intrathoracic implant via port surgery for medium term to permanent support. Phase I will use bench tests to demonstrate hydraulic performance, low hemolysis, acceptable surface temperatures and initial freedom from axial or radial wear. During phase II, additional pump prototypes will be built and used for 30, 60 and 90 day in vivo studies, while the Phase I pumps continue on long term endurance testing. Phase II will also explore anti-coagulation free pump surfaces.