Crimp Induced Leaflet Damage and Calcification of Transcatheter Heart Valves
Aditi Sinha1, Oleksandr Barannyk2, Arash Kheradvar1.
1University of California, Irvine, Irvine, CA, USA, 2ViVitro Labs Inc, Victoria, BC, Canada.
OBJECTIVE:There is increasing evidence regarding different complications arising from clinical implantation of transcatheter aortic heart valves (THV). However, little is known if crimp-induced damage increases tissue calcification thereby reducing the durability of THRs. We are addressing the association between tissue micro-damage and calcification under accelerated wear conditions.
METHODS:Self-expandable THVs with glutaraldehyde-fixed bovine pericardial leaflet were used. The valves were divided into (1) uncrimped, (2) 18-Fr crimped, and (3) 14-Fr crimped. The six THVs were tested in an accelerated wear testing (AWT) system for 50 million cycles, at 37ºC, and 800 cycles/minute. A calcifying solution was used with a final concentration of 55 mM (KCl), 1.5 mM CaCl2, 1.25 KH2PO4 and 20 mM Barbital. The solution was monitored for consistent pH 7.5 and was changed weekly within the test period to minimize fluctuation of Ca++ and HPO4-. The pressure difference across the valves was adjusted at 120 mmHg. After completion of the tests, the valves were retrieved, washed, photographed, imaged using micro-CT scan, and tissues were embedded for histological analyses including stains for calcium (Von Kossa), collagen (Trichrome), and elastin (VVG).
RESULTS:Our results indicate that, all the valves, regardless of crimping, exhibited severe tissue calcific lesions around the stent commissures. However, micro-CT revealed that only crimped samples had discrete regions of leaflet calcification in the central region (Figure E and F). Furthermore, histological stains of the tissue segments demonstrated severe and permanent microstructural damage to the tissue including fragmentation of collagen fibers (Figures H and I).
CONCLUSIONS:Our results indicate severe crimp-induced structural damage to leaflets and hydroxyapatite deposition in the belly region of crimped leaflets; a finding that was not obvious in uncrimped groups. Further analysis is underway to determine the quantity of hydroxyapatite deposition on tissues. 
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