Gigantic arteriovenous fistula between left coronary cusp and coronary sinus draining into the right atrium

Coronary arteriovenous fistulas (CAF) are infrequent anatomic anomalies that establish a direct connection between coronary arteries and cardiac chambers. The reported incidence is extremely low and estimated at 0.002% in the general population. We report a rare case of CAF in a middle-aged man, who was asymptomatic but incidentally found to have a gigantic CAF on a low-dose Computed Tomography scan of his chest. The case was presented to cardiothoracic surgeons. Since the patient was asymptomatic, they recommended medical management and continued close surveillance. The Left Coronary Artery or its branches are extremely uncommon site for CAF. With the advances in technology, the network of veins including coronary sinus has gained further clinical relevance. While technology has helped elucidate many aspects of these rare anomalies, mysteries still remain. With continued research, we can expect more cost-effective and less invasive interventional therapies to be developed in the near future.