A valve assembly (10) for controlling a flow of fluid includes a housing (30) having a passageway (33), and a valve sheath (40) disposed interiorly of the housing, at least substantially along the housing passageway. The valve sheath includes a cylindrical valve body (42) having a pair of generally wedge-shaped voids (50A, 52A) formed along opposing longitudinal sides of the valve body. Each of the wedge-shaped voids comprises first and second inwardly-directed sides that converge to define a generally linear edge. The edges are disposed along the valve body in a generally diagonal orientation with respect to a longitudinal axis through the valve body. The respective linear edges are structured and aligned in the valve body to meet along a passageway through the valve body interior in a manner to selectively close the valve body interior passageway, and to yield to permit passage of an interventional device therethrough.
