Flexible radiopaque filaments coupled to and extending from a distal end of a guide catheter are disclosed that aid a clinician in locating an ostium of a branch vessel. The filaments are at least partially formed of a radiopaque material and are designed to move with the blood flow. In a method of locating an ostium of a branch vessel or a fenestration of an implanted graft, at least some of the filaments enter the ostium or fenestration when the distal end of the guide catheter is placed proximal thereto. The filaments provide an accurate and quick indication of the ostium location without the need for a contrast agent.
