Chapter 23. Pathological Calcification of Heart Valve Bioprostheses

Summary

Improvements in healthcare yields a rise in numbers of elderly people, which in turn increases the demand for healthcare among this population. Today, some 300 000 heart valve replacements are carried out worldwide each year, with about 40% of the prostheses being tissue-based. In the aortic position, these bioprostheses are the valves of choice in patients aged more than 65–70 years. Although these valves are advantageous in terms of their hemodynamics, thrombo-genicity, low risk of bleeding and minimal need for anticoagulants, they suffer from limited and unpredictable durability. Valve failure is mainly due to tissue calcification, caused by multiple factors [1]. In this chapter we demonstrate that it is possible to mimic, induce, and investigate this pathological process in vitro by the choice of an appropriate model, whilst neglecting possible host factors such as unphysiological calcium and phosphate levels or missing inhibitory proteins. The local sites of calcification can be predicted in advance by using a nondestructive, holographic method. Multiple parameters such as the valve tissue origin, valve design, glutaraldehyde fixation, and alternative chemical and irradiation treatments, have been identified as influencing calcification. Non-destructive evaluation of the calcific deposits is possible using microradiography (m̈-X-ray), clinical and industrial computed tomography (CT) and m̈-CT (Synchrotron). In this way, the degree of calcification can be determined with computer image analysis.