In vitro function and durability of a polyurethane heart valve: material considerations

Area of Science:

• Biomaterials Science
• Cardiovascular Engineering
• Polymer Chemistry

Background:

• Flexible trileaflet polyurethane heart valves show promise for in vitro hydrodynamic function.
• Selecting suitable polyurethanes is critical, as minor structural differences significantly impact long-term fatigue resistance.
• Short-term mechanical properties may not predict long-term durability.

Purpose of the Study:

• To compare the functional characteristics of two different polyetherurethane heart valves before and after long-term fatigue testing.
• To identify structural features contributing to polyurethane heart valve durability.

Main Methods:

• Two types of flexible trileaflet polyetherurethane valves were tested: one chain-extended with butanediol (PEU) and another with ethylene diamine (PEUE).
• Six valves of each type, with similar leaflet thickness, underwent long-term fatigue testing.
• Hydrodynamic function and failure modes were analyzed.

Main Results:

• Both valve types exhibited hydrodynamic function comparable to porcine aortic valves.
• PEU valves showed higher mean pressure drop, while PEUE valves had greater closure energy losses.
• PEU valves failed by 307 million cycles due to calcification-related leaflet damage; PEUE valves exceeded 450 million cycles, with three reaching over 800 million cycles without failure.

Conclusions:

• Superior performance of PEUE valves is attributed to better phase separation and rubbery characteristics.
• These findings indicate suitable polyurethane structures for heart valve fabrication.
• Results have implications for developing novel, durable polyurethanes for artificial heart valves.