Subclavian arteriovenous fistulas are a rare but known complication of catheterisation procedures, pacemaker and internal cardioverter-defibrillator (ICD) implantation and surgery. These fistulas typically become apparent few days after procedure through clinical signs of a high output circulation. However, small fistulas can remain asymptomatic. We describe a case of a chronic Subclavian Arteriovenous Fistula (AVF) complicating an otherwise straightforward ICD device implantation procedure. The patient required urgent endovascular treatment to close the fistula.