Magnetic Bearings for Mechanical Cardiac Assist Devices

According to the American Heart Association, approximately 5 million Americans have congestive heart failure (CHF) and more than half a million new cases are reported every year. It is estimated that at least 40,000 of these patients are candidates for heart transplantation; however, only 3,800 donor hearts are made available each year worldwide. While effective pharmacologic therapies have improved outcomes for mild to moderate CHF, the need for mechanical circulatory support is well defined and growing. Most current mechanical circulatory cardiac devices, however, do not allow for hospital discharge of patients. If fully implantable and wearable devices-using magnetic bearings and other related MEMs devices--were available, at least 100,000 patients annually could benefit from this technology. This book introduces magnetic bearings--mechatronic devices that produce contact-free electromagnetic force to support a load, such as a moving train or a spinning rotor. Compared to traditional bearings, magnetic bearings offer several advantages: no friction, low heat generation, no required lubrication, quiet operation, and fast and stable rotation. For these reasons, magnetic bearings have been used in rotary ventricular assist devices (VADs) to increase design life, reduce or eliminate material wear and bearing maintenance, as well as to increase biocompatibility by eliminating high fluid stresses and heat generation, both of which are associated with hemolysis, platelet activation and aggregation, and thrombus growth. The book covers the principles of these bearings, how they are used in integrated control and electronics systems, and useful information on several major brands of current assist devices.