In a representative embodiment, an implantable prosthetic heart valve device comprises an elongated body having first and second end portions, the body being configured to be implanted around a native leaflet of a heart valve such that the first end portion is on an atrial side of the leaflet and the second end portion is on a ventricular side of the leaflet and such that the body can coapt with and move away from an opposing native leaflet during operation of the heart valve. The device can further comprises a fastener configured to be mounted on a suture that extends from one of the first or second end portions, through the native leaflet and through the other of the first or second end portions such that the body is secured to the native leaflet.