Assertion: mechanical valve | /r/MadeOf | metal
Facets:
Source sentences:
text: Mechanical valves are made of metal and have evolved over time ("ball and cage", "bileaflet").
text: A mechanical valve made of metal, which requires you to take *blood thinners but is very durable; A valve made from biological tissue, which requires no blood thinners but may not last as long and may need to be replaced later; A homograft or valve from a donated human heart and preserved in special solutions may be use.