Misdiagnosis of persistent left superior vena cava with unroofed coronary sinus as a coronary sinus‐type atrial septal defect

KEY CLINICAL MESSAGE: Awareness of persistent left superior vena cava (PLSVC) with unroofed coronary sinus is crucial. Pre‐ and perioperative evaluation of this association is necessary for surgical plan. Creating an intra‐atrial tunnel to divert LSVC to right atrium without obstructing the mitral valve or the pulmonary veins is the safe surgical approach. ABSTRACT: Unroofed coronary sinus syndrome is a rare congenital heart defect representing less than 1% of all atrial septal defect (ASD) types, and may be associated with persistent left superior vena cava (PLSVC) which may be missed during preoperative diagnosis. Herein, we present a case of a 2‐year‐old patient who underwent an operation for repair of a coronary sinus‐type ASD; however, PLSVC was detected intraoperatively. An antra‐atrial tunnel has created to divert the flow of PLSVC into the right atrium along with the repair of the ASD.