UC Irvine

Introduction: Previous studies suggest that crimping causes permanent structural damage to the leaflet tissues of transcatheter heart valves (THV). However, this damage is not yet known to facilitate calcification process. Hypothesis: Our hypothesis is to test whether crimp-induced damage promotes valvular calcification. Methods: Self-expandable THVs with Glutaraldehye-fixed bovine pericardial leaflets was used. The valves were divided into two groups; crimped and uncrimped, and each group was split into two to be exposed either to a calcifying solution or to a control -normal phosphate buffered saline- solution. For the crimped group, the valves were carefully crimped with a standard crimper at 14Fr and held crimped for 20 minutes. The calcifying solution contains ionic concentrations corresponding to normal human plasma. All groups were maintained at pH 7.5, 37°C, on an orbital shaker at 400 rpm for 7 weeks. At the end, each tissue sample was individually embedded, sectioned and stained for calcium stain (Von Kossa), Verhoff’s Van Geison (VVG) stain for elastin and collagen stain (trichrome III). Results: Fig 1A show the normal bovine pericardium with arranged collagen layers in blue whereas intermittent striations are seen across the collagen fibers in the crimped group (Fig 1B). VVG stains show similar results with continuous elastin fibers (black) in the uncrimped group (Fig 1C) versus fragmented elastin fibers in the crimped group (Fig 1D). Of most significance are the results from the von kossa stains where crimped samples in saline show minimal hydroxyapatite deposition (Fig 1E) while crimped samples in calcifying buffer show brown deposits of hydroxyapatite along the crimped regions (Fig 1F). No hydroxyapatite deposition was observed in uncrimped group exposed to calcifying solution. Conclusions: Our results indicate that severe structural changes due to crimping are associated with greater levels of calcium deposition along the crimped sites.