A cardiac valve comprises a plurality of flexible trapezoidal membranes, each having an edge joined to an edge of another of the membranes to form an unsupported frusto-conical body. The body has an oval end portion and a plurality of flexible flap portions integral with and extending from the end portions,...http://www.google.es/patents/US5344442?utm_source=gb-gplus-sharePatente US5344442 - Cardiac valve
