Parametric finite element modeling of reinforced polymeric leaflets for improved durability

Abstract

Hyaluronic acid-enhanced polyethylene polymeric TAVR shows excellent in vivo anti-calcific, anti-thrombotic, and in vitro hydrodynamic performance. However, during durability testing, impact wear and fatigue cause early valve failure. Heart valve durability can be improved by strengthening the leaflet with fiber reinforcement. A thin plastic sheet is assembled into a cylindrical form by welding two ends, which never fails during accelerated wear testing (ISO 5840-2005). The weld at the commissure post region of the leaflet (ROI) is mechanically stronger than the rest of the leaflet, which protects this region. Braided polyester fibers are embedded on the leaflet regions of the commissure post perpendicular to the valve circumference, mimicking the weld but at a much higher strength. Leaflet durability skyrockets from a few million cycles to 73 million and comparable hemodynamics performances. The entire cardiac cycle of the heart valve with embedded fibers of varying angles, lengths, and numbers is simulated in Finite Element Analysis (FEA) to study their effects on leaflet maximum principal stress and leaflet opening dynamics. Horizontal fibers wrap the leaflet 360° to relax the leaflet completely during peak diastolic. However, the leaflet has a higher coaptation gap and lower geometric orifice area (GOA). The heart valve with embedded horizontal fibers is physically manufactured and tested in an in vitro flow loop and wear tester, which shows improved durability but compromised hemodynamics. The parametric study further predicts that 12 mm long fibers covering only the commissure post region of the leaflet have low principal stress, maximum GOA, and fastest opening as the spring-like fibers help leaflet opening.