Effect of Arched Leaflets and Stent Profile on the Hemodynamics of Tri-Leaflet Flexible Polymeric Heart Valves

Abstract

Polymeric heart valves (PHV) can be engineered to serve as alternatives for existing prosthetic valves due to higher durability and hemodynamics similar to bioprosthetic valves. The purpose of this study is to evaluate the effect of geometry on PHVs coaptation and hemodynamic performance. The two geometric factors considered are stent profile and leaflet arch length, which were varied across six valve configurations. Three models were created with height to diameter ratio of 0.6, 0.7, and 0.88. The other three models were designed by altering arch height to stent diameter ratio, to be 0, 0.081, and 0.116. Particle image velocimetry (PIV) experiments were conducted on each PHV to characterize velocity, vorticity, turbulent characteristics, effective orifice area (EOA), and regurgitant fraction. This study revealed that the presence of arches as well as higher stent profile reduced regurgitant flow down to 5%, while peak systole downstream velocity reduced to 58% and Reynolds Shear Stress values reduced 40%. Further, earlier reattachment of the forward flow jet was observed in PHVs with leaflet arches. These findings indicate that although both geometric factors help diminish the commissural gap during diastole, leaflet arches induce a larger jet opening, yielding to earlier flow reattachment and lower energy dissipation.

In vitro Assessment of the Impacts of Leaflet Design on the Hemodynamic Characteristics of ePTFE Pulmonary Prosthetic Valves

“…The results from the current study showed that the highest RSS occurs at the ejection peak for each valve, at which point the streak-like high RSS regions appeared adjacent to the leaflets and developed along the central jet boundary. Similar RSS distribution patterns downstream the bioprosthetic and polymeric aortic valves have been reported by several in vitro studies under aortic conditions (Leo et al, 2006;Yousefi et al, 2017;Davis, 2018), and the RSS magnitude levels of both valves are within the physiological range under pulmonary conditions (Stein et al, 1982).…”

“…where t p1 to t p2 is the period of different phases within a cardiac cycle. RSS: The RSS is a term derived from the Reynolds decomposition of Navier-Stokes equations and indicates the turbulence level (Yousefi et al, 2017). Based on the velocity fields captured by PIV, the RSS fields in the immediate vicinity of the pulmonary valve prostheses could be calculated from Eq.5.…”

“…It has been well recognized that the RSS level in the vicinity of the valves plays a vital role in the development of thrombosis and valve degradation (Stein et al, 1982;Wheatley et al, 2001;Leo et al, 2006). One of the major mechanobiology mechanisms involved in this progress is the hemolysis and blood damage that occurred in high RSS environments (Yousefi et al, 2017). However, the RSS threshold for hemolysis and blood damage varies, whose range could be between 100 and 5000 Pa (Leo et al, 2006;Jhun et al, 2018).…”

Novel Polymeric Valve for Transcatheter Aortic Valve Replacement Applications: In Vitro Hemodynamic Study

“…9 A Hyaluronan-Polyethylene SAVR valve showed good potential in terms of material properties, valve hydrodynamics, hydrophilicity, blood clotting, and platelet and leukocyte adhesion. 26,38 The Triskele (UCL TAV™, University College London, London, UK) TAVR valve utilizes urethane (POSS-PCU) leaflets and skirt, demonstrated in vitro testing comparable hydrodynamic performance to other, clinically-used, tissue TAVR valves. 27 Foldax Inc. (Salt Lake City, UT, USA) utilizes an elastomer in their prosthetic heart valve products, 10,11 which include aortic and mitral surgical valves, and a transcatheter valve.…”

The Pursuit of Engineering the Ideal Heart Valve Replacement or Repair: A Special Issue of the Annals of Biomedical Engineering

“…While the article by Bark Jr. et al focuses on overcoming the limitations of mechanical heart valves through the incorporation of superhydrophobic materials in order to eliminate the need for anticoagulation therapy, 2 the articles by Yousefi et al focus on novel tri-leaflet synthetic heart valves made from polymeric or textile (fabric) heart valves. 14,15 Both approaches tackle the issue of developing a non-biological alternative valve which would be both durable and free from anticoagulation therapy. Bark et al's study shows that by making the mechanical heart valve's surface superhydrophobic, the physical contact area between blood and the valve's surfaces can be dramatically reduced effectively relaxing the no-slip fluid boundary condition resulting in reduced skin drag and wall shear stresses.…”