Coronary Sinus Ostial Obstruction in Single-Ventricle Congenital Heart Disease

Coronary sinus ostial obstruction is an exceedingly rare anomaly that is particularly important to diagnose in patients with single-ventricle heart disease before surgical palliation. We present 2 cases, an infant and an adult, diagnosed with coronary sinus ostial obstruction, with different clinical outcomes due to timing of diagnosis. (Level of Difficulty: Intermediate.)