Abstract
BACKGROUND: Unroofed coronary sinus (UCS) is a rare subtype of atrial septal defect. It is frequently associated with a persistent left superior vena cava and is often part of a more intricate cardiac malformation. CASE SUMMARY: This report describes a rare case of an adolescent patient with UCS featuring atrial situs solitus, absence of the right superior vena cava and a persistent left superior vena cava draining into the left atrium consistent with total unroofing of the coronary sinus. This was associated with concurrent severe mitral insufficiency secondary to redundant and prolapsing leaflets, and a substantial left-to-right shunt across the coronary sinus orifice. A comprehensive examination of the existing literature is included, shedding light on the diagnostic challenges of UCS and describing the available surgical options within the context of mitral valve surgery. CONCLUSION: UCS is a complex condition requiring careful consideration of associated anomalies and a tailored surgical approach.