An implantable medical device has an outer stent with a tubular body disposed about a longitudinal axis. The outer stent includes members defining openings which are in fluid communication with a flow path. At least one opening is larger than adjacent openings when the outer stent is in an expanded state, and is positioned between the ends of the outer stent. The at least one larger opening is a side branch opening having a perimeter. The device also has an inner stent with a tubular body disposed within the outer stent and about a longitudinal axis. The inner stent has a branch portion with deployable petals positioned adjacent to the side branch opening of the outer stent. The petals are biased against the perimeter of the side branch opening such that the petals are restrained from opening outward when the outer stent is in an unexpanded state.