Fetal Echocardiography Practice Test

The key idea is using a distinctive internal structure to identify the right ventricle. The moderator band, or septomarginal trabecula, is a prominent muscular bundle that stretches from the interventricular septum to the anterior wall and papillary muscle inside the right ventricle. Its presence is a hallmark of the RV and helps the observer confirm the chamber you’re seeing, since the left ventricle lacks this band and has a different trabeculation pattern.

Other structures mentioned—coronary sinus (in the right atrium), sinus venosus (part of the right atrium), and pulmonary veins (drain into the left atrium)—do not serve as reliable markers of the right ventricle, so they’re less helpful for orientation in this context. Recognizing the moderator band provides a reliable cue to identify the RV and assess its function and outflow.