stent placement in an superior vena cava obstruction with a decreased gradient documented by TEE (Fig. 2). In 2 patients with multilevel LVOT obstruction, TEE confirmed transthoracic echocardiographic and angiographic findings but was superior to both in defining the nature of the stenoses. A 13-year-old girl had a gradient of 50 mm Hg in the LVOT at catheterization; TEE alone detected the presence of a muscular tunnel. In a 7-year-old girl with recurrent LVOT obstruction with a gradient of 40 mm Hg at catheterization, TEE demonstrated a fibromuscular ridge, a discrete membrane, and recurrent growth of atrioventricular valve tissue after complete atrioventricular canal repair. On the basis of these findings, no interventions were performed at the time of catheterization in these two patients. Conclusions. In this study, TEE performed in conjunction with cardiac catheterization provided crucial information regarding the atrial septum, postsurgical intraatrial obstructions of systemic and pulmonary venous connections, and the LVOT. This information may not be obtainable by transthoracic echocardiography or angiography. Our findings support the use of TEE to monitor the performance and success of these selected interventional catheterization procedures.