The Effect of the Physiological Environment on the Mechanical Properties of Biomaterials in Cardiovascular Applications

Abstract

The long-term biocompatibility and physical performance of polymeric materials in the physiological environment depend both on adsorption and absorption processes. While the former has received significant attention in the literature, the latter has not been sufficiently appreciated. Accelerated testing of prosthetic devices in the wrong media and temperatures yield misleading information as exemplified by pumping bladders of heart assist devices and heart valves. Although glutaraldehyde-treated porcine heterograft heart valves performed better than expected in humans over a period of several years, physical degradations that have been observed may be associated with the breakdown of the cross-links. Appropriately selected smooth-surfaced biomaterials and hydrogels are far better suited for temporary blood contacting prosthetic applications such as left ventricular heart assist devices (LVADs) than polyester flocked fibril surfaces that result in the deposition of a thick layer of fibrin/cellular mesh with clot-like morphology with inherent dangers of loss of polyester fibrils, and the shedding of clots as the result of cyclic flexing of the pump bladders. With the proliferation of various medical devices, the possibility of increased litigations with secondary and tertiary liabilities involving not only physicians, surgeons, and device manufacturers, but also suppliers of materials and components, it is essential to select pertinent rather than complex test procedures.