Discuss
UCSS is rare and often associated with LSVC. There are 62.9% (100/159) patients with LSVC in our series. The hemodynamic changes of UCSS depend on: (1) the presence of LSVC; (2) whether the CS opening is expanded, constricted or occluded; (3) whether there is a communication between the CS and the LA; (4) whether there are associated malformations such as the blood flow obstruction in the left or right atrioventricular system[3]. In our series, only 18 cases were sole UCSS, the remaining 141 cases were associated with other intracardiac malformations, the most common ones were associated ECD (40.9%, 65/159). Most clinical manifestations of UCSS should be analyzed comprehensively in combination with other associated cardiac malformations.