A minimally invasive system for the evaluation of prosthetic heart valves.

摘要

The Bjork-Shiley Convexo-Concave (BSCC) heart valve employs a pyrolytic carbon disc, held in place by two struts, as an occluder to prevent retrograde flow of blood in the heart. The strut on the inlet side is integral to the suture ring while the strut on the outlet side is welded to the suture ring. In some cases, for reasons yet unclear, the weld at one of the two sites fractures after several years of use. This results in a single-leg separation (SLS) of the strut. The fracture causes the load on the weld at the other end of the strut to increase, thereby setting the stage for it to fail eventually. A complete fracture of the outlet strut would cause the disc to escape resulting in mortality. This thesis describes a minimally invasive electromagnetic approach, called the gradiometer-based method, for detecting SLS failures. The feasibility of the method is investigated using three dimensional finite element analysis techniques. A clinical scale gradiometer-based examination system is constructed and in vitro studies of the system have shown 100% accuracy in detecting SLS cases.