An artificial heart valve comprises a support structure defining an aperture for blood flow and a flexible leaflet which is attached to the support structure along first and second at least partially straight lines of attachment and along a base line of attachment which is adjacent to the aperture. The aperture defines an axis. A convex portion of a first lateral cross-section taken through the leaflet in a first plane which is located axially closer to the base line of attachment is longer than a convex portion of a second lateral cross-section taken through the leaflet in a second plane which is located axially further from the base line of attachment, and a concave portion of the first lateral cross-section is shorter than a concave portion of the second lateral cross-section.
