An implantable medical device includes a structural body made from a superelastic material and includes one or more marker holders integrally formed on the structural body. Each marker holder is designed to hold a radiopaque marker which has a level of radiopacity greater than the superelastic material. The radiopaque marker can be made from a nickel-titanium alloy which includes a ternary element. The ternary element can be selected from the group of elements consisting of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium. In one form, the marker holder includes a pair of projecting fingers connected together at a notched region to cooperatively create a particular-shaped opening. This opening, in turn, is adapted to receive a similarly shaped portion formed on the radiopaque marker. In one form, the radiopaque marker includes an inner core which is partially, or completely, encased by an outer layer. This inner core can be made from a highly radiopaque material while the outer layer is formed from a material that is easier to weld to the marker.