Approximately 60,000 mechanical prosthetic or bioprosthetic heart valves (BHV) are annually implanted in the United States. BHV have excellent hemodynamics and generally do not require the anti-coagulation therapy necessary for mechanical heart valves. Our long-term goal is the development of rigorous engineering principals for improving replacement heart valves. However, BHV continue to fail 8-10 years after implantation from calcification and mechanical damage. Many studies have demonstrated that maintaining tissue structural integrity is a prime factor in extending durability. Nevertheless, while much research has focused on chemical treatment technologies to reduce mineralization, little work has been done on understanding the mechanisms underlying non-calcific mechanical damage.
The goal of this research will be to develop a better understanding of the mechanical fatigue damage behavior of bioprosthetic heart valve biomaterials. We will utilize a rigorous experimental testing protocol to evaluate of the onset, mode, and progression of chemically treated BHV tissue damage under cyclic loading conditions. Based on this data, we will develop a fatigue damage model to clarify and relate the relative impact of different structural changes, such as fiber debonding and fiber weakening, to changes in macro-level tissue mechanical properties. The fatigue damage model will ultimately serve as a guide for the development of key experiments for fatigue damage assessment of novel chemical treatment technologies. This will aid in the rational development, as opposed to the current ad-hoc approach, of novel chemically modified collagenous biomaterials for more durable cardiac valve bioprostheses.
During each year, one graduate student will spend four months at Baxter engaging in direct industrial collaboration with Baxter scientists. The goal of this interaction to gain insight on how the results of this study can be applied to BHV biomaterial development. Specifically, this student will 1) gain insight as to what critical fatigue damage issues need to be addressed by the heart valve industry, 2) begin utilization of our results toward solving these issues, and 3) improve Baxter's general core competence in biomechanical testing of BHV soft tissues. Next, a Baxter research scientist will spend approximately one month during each project year to visit our labs to consult with our team. This scientist will work closely to advise the theoretical/modeling work and provide guidance on how results can contribute most effectively to product improvements. In addition, during these visits this scientist will give lectures to engineering students on challenges facing the biomedical device industry.
