Polyurethane heart valves - current development and technical challenges - Essay Example

Download file to see previous pages Recently, a polyurethane tri-leaflet valve has been developed. This valve has three, thin polyurethane leaflets of approximately 100µm thickness, which are suspended from the inside of a flexible polyurethane frame. In the closed position, the valve is elliptical in the radial direction and hyperbolic in the circumferential direction.
Hydrodynamic tests have shown that the polyurethane valve exhibits pressure gradients similar to those for a bioprosthetic valve, and lesser regurgitation and leakage than a bileaflet mechanical valve or the bioprosthetic valve.
Accelerated fatigue tests have shown six consecutively manufactured polyurethane valves to have exceeded the equivalent of 10 years function without failure, and three valves have reached 527 million cycles (approximately 13 years equivalent). The only failure occurred after the equivalent of approximately 12 years cycling (González, et al., 2003). A new family of polymers, called the segmented polyurethane elastomers display high flexure endurance, strength, and inherent non-thrombogenic characteristics (González, et al., 2003).
polyurethanes, EV3.34 and EV3.35, to manufacture a flexible trileaflet heart valve. This valve was implanted in 12 young adult (18 month) sheep in the mitral position. At 6 months, six valves were electively explanted while the remaining six valves were explanted at 9 months follow-up. Surface Fourier transform infrared spectrometry (ATR/FTIR) and scanning electron microscopy (SEM) were used to examine the leaflet material. The leaflet was also put through cyclic mechanical testing and was compared with non-implanted control material, to see if there was any change in mechanical properties during implantation. There was no degradation of functional groups. The study also observed that EV3.35 might have superior long-term fatigue properties.
It has a two-phase microstructure of hard ...Download file to see next pagesRead More