BackgroundCoronary artery fistula (CAF) is a congenital anomaly of the coronaries that can lead to significant intracardiac shunting and myocardial ischaemia.Case summaryWe describe the case of a 15-year-old male with an incidentally documented precordial cardiac murmur. An evidently dilated coronary sinus (CS) on transthoracic echocardiography prompted further investigation. A computed tomography (CT) revealed the presence of a large CAF from the left circumflex coronary artery to the CS. No other structural heart defects were detected. A haemodynamically significant intracardiac shunt was confirmed during cardiac catheterization, and it was decided to close the fistula. This was successfully performed using a ventricular septal defect (VSD) occluder (Konar 10-8, Lifetech Scientific) that was deployed through a 6 Fr right coronary guiding catheter. A partial thrombotic occlusion of the CS behind the closure device was noted during follow-up which led to anticoagulation in a higher target INR range and concomitant start of low dose carbasalate calcium to reduce further retrograde thrombus extension. Patient is doing well at over 1 year of follow-up, and no further thrombotic extension into the CS was seen on a recent CT.DiscussionThis report illustrates the diagnostic workup and a percutaneous treatment strategy of a CAF using a VSD occluder. We also describe a not previously reported complication, thrombotic CS occlusion. Improving transcatheter techniques and marketing of novel devices with a broad spectrum of applications can offer new opportunities for treating CAF and avoiding surgical correction often involving cardiopulmonary bypass, reserving this option for patients with complex anatomy or failed transcatheter closure.