Abnormal communication between the left atrium and the coronary sinus. Presentation of 2 cases and review of the literature.

A large communication between coronary sinus and left atrium is a rare cardiac anomaly. Twenty-four cases from the literature and 2 of our own observations are presented. In most cases a considerable left-to-right shunt may exist on the atrial level that can be misinterpreted as an atrial septal defect. The anomaly may be isolated or in combination with an atrial septal defect or complex cardiac malformations. It is difficult to diagnose this abnormality by cardiac catheterization and even during surgery. Continuous oximetry during a fiberoptic catheter pull-back in the coronary sinus ensures the diagnosis in the case of atrial left-to-right shunt. The anatomy, hemodynamics, diagnostic procedures, and the therapy of the cases reported are discussed.