This is a prospective, randomized, controlled trial comparing two strategies for optimizing stent implantation during bifurcation stenting of the left main coronary artery (LM): an intravascular ultrasound (IVUS)-guided approach versus a "IVUS-trained eye" approach based on angiographic assessment and operator experience. All patients receive the same stent brand and procedure steps to minimize variability. The primary objective is to compare the planimetric stent appearance between two strategies.