[Coronary sinus defects: rare form of interatrial communication]

A coronary sinus defect results in a communication of variable size between the coronary sinus (CS) and the left atrium (LA). It is in most cases associated with a persistent left superior vena cava (l-SVC) and an atrial septal defect of the coronary sinus type and often part of a more complex cardiac malformation. If the CS to LA fenestration is the single cardiac defect, this anomaly provides the basis of an unusual form of interatrial communication, which may cause diagnostic difficulties. Two patients with this rare anomaly are reported. A 9-year-old boy presented with history of mild cyanosis pronounced after physical activity (SaO2 < 90%) since the age of 3. Comprehensive pulmonary and cardiological diagnostic procedures in the referring hospital yielded normal findings. Finally, a 1-SVC draining into a mildly dilated coronary sinus could be demonstrated echocardiographically. Contrast echocardiography revealed a right-to-left-shunt at atrial level. Diagnosis of a partially unroofed coronary sinus was subsequently confirmed during cardiac catheterization. The second patient was primarily diagnosed echocardiographically to have an atrial septal defect of the primum type (ASD I) in the first year of life. After pulmonary vascular markings on chest-x-ray had increased, she was assigned to our hospital for cardiac catheterization. Slight arterial desaturation (SaO2 88%) was present due to a large l-SVC anomalously draining into the LA, the innominate vein was missing. The roof of the coronary sinus was predominantly absent. Combined with a large atrial septal defect of the coronary sinus type, this resulted in significant left-to-right-shunt and right-to-left-shunt at atrial level due to a pure unroofed coronary sinus.

A coronary sinus defect with partial or complete unroofing of the CS and a persistent l-SVC should be considered in the differential diagnosis of an otherwise unexplained systemic desaturation and in patients with both left-to-right-shunt and right-to-left-shunt at atrial level.