In some examples an implantable medical device may include a frame and a flexible tubular valve body. The frame may define a frame lumen and may be expandable from a compressed configuration to an expanded configuration. The flexible tubular valve body may extend between a downstream end and an upstream end. The valve body may define a valve lumen, a downstream opening at the downstream end, and an upstream opening at the upstream end. The valve body may be attached to the frame such that the frame lumen is in fluid communication with the valve lumen. The valve body may comprise a neck and may be configured to fold about the neck to at least partially close the valve lumen. The valve body may be configured to collapse in an absence of fluid flow through the valve lumen to at least partially close the valve lumen.
