A Rare Congenital Cardiac Defect: Isolated Coronary Sinus Septal Defect and the Challenges of Diagnosis in a Child

• Isolated coronary sinus defect without persistent left superior vena cava is a rare cardiac defect. • Diagnosis can be difficult in the absence of other defects in an asymptomatic child. • Missed or difficult cases to diagnose may be found incidentally in adulthood. • Surgical outcome in the absence of any other defects can be very good.