Impact of Calcification on Hemodynamic Performance of Tubular Heart Valves

Background: The number of aortic valve replacements has increased in Germany in recent years, with a particular rise in the use of biological heart valve prostheses. However, biological aortic valve prostheses have a limited durability due to calcification-related stenosis, which is why research is increasingly focused on the development of durable alternatives with an emphasis on design modifications. The aim of this study is to investigate the influence of calcifications on the hemodynamic properties of different heart valve geometries.

Methods: A newly developed tubular aortic valve prosthesis (AVP) was compared with a conventional tricuspid AVP. The tricuspid AVP was made from a 3D-printed scaffold sewn with bovine pericardium, while the tubular AVP consisted of a 3D-printed stent and a flexible tube of bovine pericardium. Both valves had a 21.5-mm diameter. Calcification was simulated by stiffening the pericardium using adhesives, with 3D-printed templates creating 15 and 40% calcification on the leaflets and 30% on the commissures. Mechanical properties were investigated through tensile tests and histological analyses were performed. Hemodynamic properties were evaluated using a pulse duplicator.

Results: The tests were successfully completed, and visual as well as histological evaluations confirmed the stenotic nature of the calcifications. The moduli of elasticity for untreated pericardium were measured at 45.94 ± 27.5 MPa, while calcified tissue exhibited values of 5.57 ± 0.87 MPa for cyanacrylate and calcium phosphate, and 6.51 ± 1.51 MPa for BioGlue. Pulse duplicator measurements showed a 19 ± 3% less increase of the mean pressure gradient across the tubular valve compared with the tricuspid valve. The effective orifice area (EOA) of the calcified tubular valve decreased from 2.5 ± 0.02 cm² to 2.1 ± 0.11 cm² compared with the untreated valve, whereas the tricuspid valve showed a reduction from 2.4 ± 0.07 cm² to 1.92 ± 0.15 cm².

Conclusion: Given the limitations of current biological aortic valve prostheses, particularly in terms of calcification-induced degradation, these results suggest that alternative valve geometries, like the tubular design, could offer significant benefits. The tubular valve demonstrated a more favorable response to calcification, both in terms of pressure gradients and EOA. However, further in vitro and in vivo studies are essential to confirm the long-term viability of this approach.

Publication History

Article published online:
11 February 2025