Fatigue analysis of clinical bioprosthetic heart valves manufactured using photooxidized bovine pericardium.
Keywords
Abstract
OBJECTIVE
Recent reports have given details of early clinical failures of bioprosthetic heart valves manufactured using dye-mediated photooxidized bovine pericardium. These failures were attributed to abrasion of the inflow surface of the leaflets against the cloth-covered inner face of the outer valve frame. These failures had not been detected during preclinical testing of such valves. The aim of this study was to determine if such failure modes could be replicated during fatigue testing of the photooxidized valves, and whether lining of the inflow face of the outer frame with pericardium could eliminate these failures.
METHODS
The fatigue properties of six lined and six unlined PhotoFix(R) alpha valves was determined using two Rowan Ash fatigue testers which were cycled at 15 Hz for a maximum of 210 million cycles. The closing pressure within in each chamber was 110+/-10 mm Hg. Each valve was inspected every 40 million cycles for any signs of fatigue failure. All valves were tested to at least 210 million cycles.
RESULTS
In all six lined PhotoFix alpha valves there was no evidence that wear, tear or abrasion of the inflow aspect of the leaflets adjacent to the inflow face of the outer frame had occurred. Only one unlined valve showed any signs of damage adjacent to the outer frame, as evidenced by loss of loose connective tissue, but this did not have the imprint of the cloth covering, which would have suggested actual wear. Effectively, after 200 million cycles, no fatigue failures of either the lined or the unlined PhotoFix alpha valves had occurred. Moreover, the leaflet tears that had been observed clinically were not replicated in this study.
CONCLUSIONS
Previous studies have shown a good qualitative, quantitative association between fatigue failure in Rowan Ash accelerated fatigue testers, and clinical experience in glutaraldehyde-treated bovine pericardial valves. The accelerated fatigue tester did not provide an adequate model for the prediction of clinical failure for the photooxidized pericardial valves.
