Case Presentation. A 33-year-old female with Down syndrome and complex congenital heart disease was admitted to the hospital with progressive cyanosis and fatigue. She had a history of a complete atrioventricular canal defect with a double-outlet right ventricle and severe pulmonary stenosis. A Waterston-Cooley and a modified Blalock-Taussig (BT) with a 6 mm PTFE graft shunt procedures were performed at 16 months and 10 years, respectively. She had presented with a stroke with residual right hemiparesis 2 weeks previously. Angiography showed an eccentric and severe stenosis at the mid-segment of the left-sided BT graft (Figure 1A). Intravascular ultrasound (IVUS) showed a laminar organized thrombus with areas of calcification and a mobile component protruding into the lumen of the BT graft (Figure 1B). Due to the high risk in the current clinical situation involving a recent stroke, surgery was delayed and the thrombotic stenosis was treated with direct implantation of a 4.5 x 12 mm bare-metal stent. After stent placement, IVUS demonstrated incomplete apposition, and postdilatation with a 5 x 12 mm noncompliant balloon was performed at high pressure. Finally, IVUS showed symmetrical expansion and complete apposition of the stent to the graft wall (Figure 2B). The patient’s oxygen saturation increased from 66% to 80% after stent implantation. Six months after discharge, her clinical condition had improved. Discussion. Progressive stenosis of palliative conduits in congenital heart disease could be caused by shrinkage of the walls, neointimal proliferation, calcification or thrombosis. This case illustrates the important role IVUS played in characterizing the graft stenosis, which allowed for optimal treatment to be chosen.