Anomalous coronary sinus communication to the left atrium.

This report highlights an unusual anatomical finding with serious implications in clinical cardiac care. We present a case of a fistula or bridging vein originating from the left atrium (LA) and inserting into the coronary sinus (CS) which courses posteriorly to the right atrium and inserts near the superior vena cava, essentially serving as a left to right shunt in a 64-year-old woman presenting with chest pain. The coronary venous system serves as a vital access point in the placement of cardiac pacemakers and defibrillators. Coronary sinus anomalies are rare and often occur in isolation or in association with other vascular anomalies. The described conduit serves as a functional interatrial shunt, though likely with minimal hemodynamic significance given the low pressure state of the left and right atria. This case highlights the importance of understanding the coronary venous anatomy and its variations in terms of anatomic course, valves, diameter, angulation, relationship to coronary arteries. <Learning objective: Coronary CT angiography can provide detailed anatomical information for diagnosis and treatment of anomalous coronary sinus communication to the left atrium. Coronary sinus ablation may be necessary in atrial fibrillation refractory to pulmonary venous isolation. An important differential diagnosis to this anomaly is unroofed CS. Anomalous coronary sinus communication to the left atrium demonstrates anomalous bridging vein indirectly communicating the CS to the LA. However, unroofed CS demonstrates a direct CS to LA communication through a wall defect; the CS is usually enlarged.>.