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Blood Lubricated Bearings in Cardiac Assist Devices

Excerpt

Ventricular assist devices are divided into two types: paracorporeal and implantable. The paracorporeal devices reside outside the body with percutaneous blood flow lines. Most of these devices are based on centrifugal pumps. The implantable devices are segregated into three distinct design generations, delineated mostly by their bearing design. The first generation of mechanical circulatory assist devices was based on positive-displacement type pumps and avoided the need for blood contacting bearings. These devices are larger in volume, require greater input power and have more moving parts compared to their newer rotary counterparts. The positive displacement pumps were the only option available for many years, in large part, due to the tremendous challenge of designing blood immersed bearings for rotary pumps. The rotary pumps are divided into two types: the second generation devices that use blood lubricated bearings, and the third generation devices that replaced the mechanical bearings with magnetic bearings. The rotary pumps are further divided into axial and radial pumps. Whereas the axial pumps generate high flow against low pressures, the radial or centrifugal pumps are capable of producing high pressures and low flows. In this section the types of bearings used in the different VAD designs are described. It is generally difficult to find accurate published information describing the bearings used in specific devices due to the confidentiality of such information.

4.1Bearings in Paracorporeal Devices
4.2Bearings in the First Generation VADs
4.2Blood Lubricated Bearings in Second Generation VADs
4.3Bearings in the Third Generation VADs
Topics: Bearings, Blood

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