Generation of Simulated Calcific Lesions in Valve Leaflets for Flow Studies

Calcific aortic valve disease (CAVD) is the most common valvular disorder. While fluid stresses are presumed to play a role in disease progression, the valvular hemodynamic changes experienced over the course of CAVD remain largely unknown. The study aim was to develop a laboratory protocol for the fabrication of tissue valve models mimicking mild and moderate calcific stenosis, for future use in flow studies.

Different hydroxyapatite (HA)-agarose mixtures were injected into porcine valve leaflets. Micro-computed tomography (micro-CT) was used to quantify HA deposition volume, area fraction and regional distribution, while von Kossa staining was performed to assess tissue mineralization. Particle image velocimetry measurements were carried out in intact and injected valves subjected to in vivo-like hemodynamics to characterize the degree of valvular stenosis in terms of geometric orifice area (GOA) and peak systolic velocity.

The 5% HA-1% agarose solution (solution 1) and the 5% HA-0.5% agarose solution (solution 2) maximized the HA deposition volume. Leaflet injections with solution 1 resulted in a significant 1.9-fold increase in HA area fraction relative to solution 2 injections. While solution 1 injections generated multiple sites of high HA concentration, solution 2 injections produced smaller, discrete spots. Injections of both solution 1 and solution 2 into whole valves generated significant 47% and 32% reductions, respectively, in GOA and 1.8-fold and 1.5-fold increases, respectively, in peak systolic velocity, relative to untreated valves.

Tissue valve models were generated that recapitulated the structure and hemodynamics of mild and moderate valvular calcification. Those models may be used for future investigations of the native valvular hemodynamic alterations that occur during CAVD.