A device for determining a physical parameter of a tissue opening is provided. The device includes an expandable member which is designed for positioning within a tissue opening such as a valve annulus. The expandable member is capable of expanding while applying an inward radial force indicative of a diameter thereof. When the expandable member is positioned within the tissue opening and expanded, an increase in the inward radial force induced by contact between the expandable member and tissue surrounding the opening can be utilized to derive information relating to the physical parameter of the tissue opening.
